CHAPTER ONE
INTRODUCTION
1.1.
Background to the Study
Maize or corn (Zea mays L) belongs to the family of grasses (Graminaceae). It is
cultivated globally, being one of the most important cereal crops worldwide (IITA, 1991).
Maize is grown by both peasant and commercial farmers’ worldwide (Onwueme
and Sinha, 1991). It is ranked third in terms of both production and consumption,
following rice and wheat world –wide (Yayock et al, 1988). In Ghana, it is the first among
the cereal crops grown (Gounou et al., 1994; Yayock et al, 1988). The crop is cultivated
throughout the ecological zones of Ghana. Ashanti region, which is within the forest zone,
is one of the leading regions where the crop is cultivated twice in a year, i.e, the major
season from April – July and the minor season from August- November.
Maize is an important human nutrient, as well as a basic element of animal feed and
raw material for manufacture of many industrial products(Romains, 2001). The products
include corn starch, corn flakes, maltodextrins, corn oil, corn syrup and products of
fermentation and distillation industries. It is also being recently used for biofuel(Romains,
2001).
In industrialized countries, maize is largely used as livestock feed and as a raw
material for industrial products, while in developing countries, it is mostly used for human
consumption (IITA, 2007). About 66% of maize produced worldwide is used for feeding
livestock, 25% for human consumption and 9% for industrial and seed purposes (Romains,
2001).Maize is an important source of carbohydrate, protein, iron, vitamin B, and minerals.
1
Several improved maize varieties with different maturity periods have been
developed and released to farmers by the CSIR- Crops Research Institute(CSIR-CRI) of
Ghana to meet the needs of growers in the different ecological zones of Ghana (Twumasi –
Afriyie et al., 1992, 1997). These varieties includeOkomasa, Abeleehi, Obatanpa, Dadaba,
Mamaba,CIDA-ba, Golden Jubilee Maize.Dadaba, Mamaba, Golden jubilee, CIDA –
baandObatanpa are quality protein maize (QPM) varieties developed and released by
CSIR- CRI (Asiedu et al., 2001). Unlike normal maize, these QPM varieties have adequate
amounts of lysine and tryptophan. The QPM produces 70–100% more of lysine and
tryptophan than most modern varieties of tropical maize; their high yielding potential
coupled with their high nutritive value make them the best varieties to boost maize
production (Asiedu et al., 2001).
Constraints to maize production include the declining soil fertility, limited use of
nitrogenous fertilizers, and periodic drought caused by erratic rainfall distribution patterns.
These can reduce maize yields by an average of 15% each year (IITA, 2007).Maize
requires adequate supply of nutrients particularly nitrogen, phosphorus and potassium
(NPK) for good growth and high yield. Nitrogen and phosphorus are very essential for
goodvegetative growth and grain development in maize production. The quantity required
of these nutrients particularly nitrogen depends on the pre-clearing vegetation. Soil organic
matter content, tillage method and light intensity (Kang, 1981).
Nitrogen is the key element in increasing productivity. It is an integral component of
many compounds essential for plant growth processes including chlorophyll and many
enzymes (Sobulo, 1980). Nitrogen also mediates the utilization of potassium, phosphorus
and other elements in plants (David and Adams, 1985). Maize nitrogen requirement can be
as high as 150 to 200 kg per hectare. However, nitrogen requirement and utilization in
maize also depend on environmental factors such as irrigation, varieties and expected
2
yield. Hardas and Aragiaanne-Hrestous (1985) reported that N at 180 kg/ha was the
optimum for maize. Singh et al. (2000)also reported that application of N at 200 kg/ha
increased grain yield of maize. However, a substantial percentage of applied nitrogen is
lost due to volatilization, leaching, denitrification etc. Therefore, nitrogen should be
applied in such a way that would minimize its loss. Awuku et al. (1991) stated that a
farmer can use organic or chemical fertilizer on continuously or previously used land in
southern and central Ghana. Forest land fallowed for at least five years before planting
does not need any fertilizer application. They further stated that nitrogen is required by
maize in large quantities but because it easily leaches through the soil, it cannot be applied
at planting time but it should rather be applied as a side dressing in a split application two
weeks before tasselling or silking. Again, Ghana Grain Development Project Report (1990)
stated that if organic sources of nitrogen are not available in sufficient quantities, inorganic
fertilizers should be used in addition to whatever manure or compost applied. The
recommended rate depends on the soil type and cropping history of the field.
Many diseases also hinder maize production in Sub-Saharan Africa. These include
rust, leaf blight, downy mildew, stalk and ear rots, leaf spot, and maize streak virus. Insect
pests such as stem and ear borers, armyworms, cutworms, grain moths, beetles, weevils,
grain borers, rootworms, and white grubs are also serious challenges in Africa.
The problem of pests in general and maize stem borers in particular has been
reported to cause great damage to the crop.Across Africa, the most important field pests of
maize are lepidopterous stem and cob borers belonging to the families of Noctuidae and
Pyralidae (van Ransburg, et al.1988). WorldWide, lepidopterous stem borers cause
considerable yield losses of maize and sorghum (Davis and Pidigo, 1990; Morallo Rejesus,
et al. 1990; Van Rensburg, and Klopper,2004).
3
Yield losses due to stem borers range from 10 – 100% (Bosque-Perez and Mareck,
1990). Stem borers often attack maize in the major season and are especially devastating in
the minor season. They may destroy a whole field especially if the attack occurs within the
first month after sowing. Controlling these insect pests is difficult because most part of
their life cycles is spent inside the plant which serves as a physical protection to insecticide
application (CSIR, 2005).
1.2
Statement of the Problem and Justification
The lepidopterous stem borers seriously limit the potential of attainable maize yield in
Africa. These insects infest maize crop throughout its growth, from seedling stage to
maturity. Maize stalk borers are difficult to control with insecticides (Vitale et al.
2007), the reason presumably being that existing spray-based practices have been
found ineffective against the internal feeders and they are costly and hazardous
(Clieve, 2003).
In Ghana, studies on the role of nitrogen fertilizer on stem borer infestation in
maize have been very limited or non-existing. Relevant information on the most
appropriate rate of nitrogen fertilizer for the production of quality protein maize (Mamaba,
Obatanpa and Golden jubilee) in the Mampong Municipality in the Ashanti Region of
Ghana is not readily available. Most farmers in Ghana who plant maize in the minor season
have little or no knowledge at all on the effect of nitrogen fertilizer on stem borer
infestation. This has resulted in a reduction in maize grain yield up to 25% (Twumasi,
1994). The search for the most appropriate rate of nitrogen fertilizer in relation to maize
stem borer infestation that would give maximum yield with minimum loss prompted this
research to be carried out.
4
It is an undisputed fact that maize stem borer infestation is one of the major
production problems facing maize farmers across Africa and losses due to these insect
pests are estimated to be 20- 40% of the potential grain yield (Reddy and Walker, 1990).
Agricultural intensification often leads to higherpest pressure, and stem borers are
considered to be one of the most important pests in cereal production in Africa. There is
therefore the urgent need for new stem borer management technologies to enable farmers
reduce crop pest infestation and thus increase maize production to cope with the increasing
demand for maize, a major staple food crop in Africa.
According to Groote (1996), stem borers are a major problem in sorghum and
maize production. This author reported that significant maize losses, estimated at 400,000
tons representing 14% of total maize production and valued at more than US$72 million,
were registered annually in Kenya.
This present investigation is very crucial because an appropriate rate of nitrogen
fertilization for effective reduction of maize stem borer menace and the production of high
yields of quality protein maize in this ecological zone may be identified. It has been
observed that when recommended agronomic practices are followed, quality protein maize
could produce more dry grains per hectare (about 5000kg /ha or 5t/ha) (NARP, 1997).
Besides, the increase in productivity is likely to motivate some of the youth in the locality
to take up the production of quality protein maize.Moreover, kwashiorkor, a protein –
deficiency disease among children, could be reduced if more people have access to quality
protein maize.
Finally, the findings of the study are expected to be of an immense benefit to the
government and MOFA in particular, in the quest to reduce maize importation which is
costing the country huge sums of money.
5
1.3
Objectives of the Study
The main aim of this study was to determine the role of nitrogen fertilizer on stem
borer infestation in three varieties of maize in the transitional zone of Ghana and to
recommend the most appropriate rate that can be adopted by farmers in the area.
The specific objectives of the study were to:
i.
identify the stem borer species prevalent in the Mampong Municipality, a
transitional area in the Ashanti region
ii.
assess the effect of nitrogen fertilizer on the stem borer population density in the
three varieties of maize.
iii.
assess the effect of rates of nitrogen on stem borer infestation on growth, yield and
yield components in the three varieties of maize in the transitional area.
6
CHAPTER TWO
LITERATURE REVIEW
2.1.Origin and Distribution of Maize
Maize or corn (Zea mays L.) belongs to the family of grasses (Poaceae). It is
cultivated globally being one of the most important cereal crops worldwide (IITA, 1991).
Maize was domesticated in Central Mexico (Matsuoka et al. 2002) between 9,000
and 6,000 years ago (Benz, 2000). Zea mayswas introduced into Africa in the 16th century
from its native Mesoamerica, and now is one of the most widely grown cereal crops in
Africa. Its evolution in Mesoamerica led to diversification into approximately 55 races
(Sanchez et al. 2000). In 2000, North America accounted for nearly 50% of the world
maize production. The USA produced approximately 42%, China 18% and Europe 10%,
whereas Australia produced less than 0.1% (Farnham et al. 2003). Total land area planted
to maize in Africa is estimated at 21 million ha. Yields range between 800 and 1200kg/ha,
which is far below the world average of 3700kg/ha.
2.2
Botany of the Maize Crop
Maize is a coarse, annual grass. The root system consists of seminal, secondary or
coronal or crown and aerial or prop roots, the seminal roots, usually 3 – 5 in number grow
downwards at the time of germination. The secondary roots, which are about 15 – 20 times
as numerous as the seminal roots, develop from the first few nodes at the base of the stem.
The aerial roots grow from the nodes above the ground and help to anchor the plant firmly
(Onwueme and Sinha, 1991). The maize stem ranges in height from 0.6 – 4.5m and in
diameter from 1.4 – 5.0cm. The stem consists of 8-12 internodes and a leaf develops at
each node (Onwueme and Sinha, 1991). Tindall (1988) stated that the stems grow up to 3m
7
in height and from 3-4cm in diameter with several nodes and internodes. Raemaekers
(2001) stated that the maize stalk is herbaceous and sub-divided into internodes. The
number of internodes ranges from 6-20. The stalk varies from 1.0 – 3.5m in height. Most
maize types form only one stalk but there are types that form a number of side stalk or
tillers.
According to Onwueme and Sinha (1991), the number of leaves ranges from 8 –
14. A leaf may be 80cm long and 9 – 10cm wide. Raemaekers (2001) reported that the
leaves arise from the nodes and they alternate on opposite sides of the stalk. The female
flowers are borne on a receptacle, termed ear, which arises at leaf axils near the mid-point
along the stem. Normally one to three or more such ears develop. The flower organs, and
later the grain kennels, are enclosed in several layers of papery tissue, termed husks.
Strands of "silk", or the stigmas from the flowers, emerge from the terminals of the ears
and husks at the same time the pollen from the terminal tassels is shed. The pollen is wind
blown and comes in contact with the emerged silk or stigma. The pollen then germinates
and a pollen tube grows down through the silk to the egg cell of the female flower. The
male gamete fuses with the egg and from the fertilized egg the corn seed or kernel
develops. Maize is a crop par excellence for food, feed and industrial utilization.
Grain: The individual maize grain is botanically a caryopsis, a dry fruit containing
a single seed fused to the inner tissues of the fruit case. The seed contains two sister
structures, a germ which includes the plumule and radicle from which a new plant will
develop, and an endosperm which provides nutrients for that germinating seedling until the
seedling establishes sufficient leaf area to become autotrophic ( http://www.infonetbiovision.org last visited 13/09/ 2009)
The germ is the source of maize “vegetable oil” (total oil content of maize grain is
4% by weight). The endosperm occupies about two thirds of a maize kernel’s volume and
8
accounts for approximately 86% of its dry weight. The endosperm of a maize kernel can be
yellow or white. The primary component of the endosperm is starch, together with 10%
bound protein (gluten), and this stored starch is the basis of the maize kernel’s nutritional
uses. http://www.infonet-biovision.org.last visited13/09/ 2009.
2.3
Quality Protein Maize Varieties in Ghana
Quality Protein Maize (QPM) breeding began with the objective of improving the
nutritional value of maize grain protein. Normal maize protein, as a point of comparison,
has a biological nutritional value of 40% of that of milk (Bressani, 1991) and therefore
needs to be eaten with complementary protein sources such as legumes or animal products.
Unfortunately, many millions of people worldwide are overly dependent on maize as a
staple food. In Africa, maize supplies at least one fifth of total daily calories and accounts
for 17 to 60% of the total daily protein supply of individuals in 12 countries as estimated
by FAO food balance sheets (FAO, 2003). These values are average estimates per capita,
and specific groups within these countries such as weaning children, sick children or
adults, or all individuals during lean crop production cycles are even more dependent on
maize as the major source of dietary protein and are therefore more susceptible to risk of
protein or essential amino acid deficiencies.
Obatanpa maize; (Reg. no. CV-1, PI 641711), a tropically adapted, intermediate
maturing, open-pollinated maize cultivar was developed by the CSIR-Crops Research
Institute (CRI), Kumasi, Ghana in collaboration with the International Institute of Tropical
Agriculture (IITA), Ibadan; the International Maize and Wheat Improvement Center
(CIMMYT), Mexico; and the Sasakawa Global 2000.Obatanpa is a white dent and flint
endosperm Quality Protein Maize (QPM) with elevated levels of lysine and tryptophan and
was first released by CRI, Ghana in 1992 as Obatanpa to help improve the protein
9
nutritional status and the health of a large population of low-income groups in subSaharan Africa who depend on maize as a major component of their dietary protein intake.
Though, Obatanpa has about 10% protein just like any other maize variety, its
protein has higher levels of tryptophan and lysine. Apart from its superior quality protein,
Obatanpa was also superior comparable to the popular normal maize varieties in yield and
agronomic traits. For example, Obatanpa had a yield potential of 4.5 tonnes/ha similar to
improved intermediate and late maturing normal maize varieties while the local maize
variety (Landrace) yields 3.5 tonnes/ha (Sallah et al. 1997; Twumasi – Afriyie etal. 1992).
Obatanpa is a medium – maturing variety with a maturity period of 105 – 110 days. It
attains a maximum height of 175cm. Like all other maize varieties, Obatanpa responds to
good soil fertility and weed management (Sallah, et al. 1997). 1000-grain weight of
Obatanpa at 12% moisture content is 310g.
following
diseases:
maize
streak
virus,
Obatanpa is resistant or tolerant to the
rust
(Puccinia
pollysora),
blight
(Helminthosporium maydis), Fusarium ear rot and Aspergilius flavus (Asiedu et al., 2003).
Mamaba maize:Thisis a three-way cross QPM hybrid which has a maturity
classification of 105–110 days (Twumasi-Afriyie et al. 1997) and was released by CSIRCRI, Kumasi. Mamabahas superior nutritional quality compared to the normal maize
varieties. It contains nearly twice as much usable protein as other normal maize grown in
the country and yields more grain than traditional varieties of maize. This QPM maize
produces 70–100% more of lysine and tryptophan than most modern varieties of tropical
maize. Protein deficiency among children is common in northern Ghana where meat, fish
and eggs are beyond the means of the average family with low incomes. Thus, the adoption
and utilization of QPM may be a way of alleviating malnutrition, particularly in children.
The CRI of the Council for Scientific and Industrial Research (CSIR) has
developed four new Quality Protein Maize varieties to replace the old varieties, The
10
varieties are CSIR-CRI "Golden Jubilee" to commemorate the Ghana Golden Jubilee,
CSIR-CRI "Aziga", meaning big egg in Ewe, CSIR-CRI "Etuto-Pibi", meaning father's
child in Gonja and CSIR-CRI "Akposoe" in honour of Dr. M.K Akposoe, a former Senior
Maize Breeder of CRI for his contribution towards maize improvement work in Ghana.
The varieties contained lysine and tryptophan, the two essential amino acids are necessary
for the normal growth and development of humans and other monogastric animals such as
poultry and pigs.
2.4
Climatic and Soil Requirements
Maize needs a regular supply of water and suffers badly in times of drought. It
requires rainfall of about 600 – 1,200mm per annum and this must be well distributed
throughout the year (Awuku et al. 1991). According to these authors maize needs water
particularly at the time of tasselling and silking.
The best maize growing areas in West Africa have minimum rainfall of 1,000 1,300mm per annum, well – distributed during the growth period (Tweneboah, 2000).
According to this author, certain growth periods are particularly important if severe
reductions in yield are to be avoided. In particular, the tesselling – to – silking stage is
critical because grain formation is initiated during this short period. Availability of soil
moisture at the time of tasselling is therefore essential for the production of high yields
(Tweneboah, 2000).
Experiments in a number of countries have demonstrated that soil moisture
deficiency that causes wilting for 1 -2 days during tasselling can reduce yield up to 20%,
and 6 – 8 days of wilting at this stage can reduce yield by 50% which cannot be made up
by later availability of soil moisture either by precipitation or irrigation (Tweneboah,
2000). Maize has two periods in its growth when inadequate moisture availability can
11
disastrously affect yield. The first is during establishment, when stand can be substantially
reduced because of inability of seeds to imbibe water against the gradient of soil water
potential. Studies conducted by Rouanet (1987)have shown that maize is particularly
sensitive to a shortage of water 30 – 40 days either side of flowering. The stage of the plant
growth is also a critical period. To obtain high yields, it is most important that water
deficits do not occur just prior to tasselling till completion of grain filling. Of all the
growth stages, tasselling is the most sensitive period to water shortage as far as grain yield
is concerned (Adjetey, 1994).
Maize tolerates a wide range of environmental conditions but it is essentially suited
for warm climates with adequate moisture. Temperatures of 21 – 300 C are suitable
(Adjetey, 1994). High temperature and low moisture result in pollen being shed before silk
is receptive or death of tassel and drying of silk (Adjetey, 1994). Temperature strongly
influences the development of maize. After seedling emergence, high soil and air
temperatures accelerate leaf appearance (Tollenaar et al. 1979; Strulk, 1983) and also
advance tassel initiation. Maximum plant yields are obtained when temperatures of the
late vegetative and reproductive phases are relatively lower than 300 C (Adjetey, 1994).
According to Awuku et al. (1991), maize requires an average temperature of 250 to 300.
Tweneboah, (2000) stated that the optimum temperature for maize ranges from 18 – 21 C.
The minimum temperature for germination is 100 C.
Germination and especially emergence will be far more rapid and uniform at
temperatures above 160 C. At about 200 C, maize usually emerges 5-6 days after sowing
(Raemaekers, 2001). Reaemaekers, (2001) stated that the critical temperature affecting
yield is around 320 C. The aspect of light that influences maize growth substantially is the
amount of light (intensity) received during the growth period. Maize requires a lot of clear
sunshine (Adjetey, 1994).
12
Maize grows satisfactorily in a variety of soils but requires well-drained, deep
loams or silty loams with high to moderate organic matter and nutrient content and pH 5.5
– 8.0 for best production (Tweneboah, 2000).Adjetey (1994) stated that maize grows on a
wide variety of soils but it prefers deep, fertile, well – drained loam and silty loam soil
with the soil pH not less than 4.5.
Maize does not like water –logged or shallow soil. According to Baffour (1990),
maize normally does very well on moist soils and does badly on pure clayey or sandy soils.
The best soils for maize are normally loams and loamy soils rich in humus (Baffour, 1990).
Raemaekers (2001) stated that the ideal soil for maize is a deep, medium – textured, well –
drained, fertile soil with a high water – holding capacity. Clayey and sandy soils are not
conducive for its growth. However, maize is grown on a wide variety of soils and gives
high yields if the crop is well managed (Raemaeker, 2001). Maize is quite tolerant of salt
during germination; increasing salinity delays germination but, up to a point it has no
detrimental effect on the percentage of emergence (Raemaekers, 2001).On the whole,
maize is considered to be relatively sensitive to salinity and is not suited for growing in
saline soils or irrigation with saline water (Raemaekers, 2001).
2.5
Cultural and Management Practices
Maize seeds need a soil that is warm, moist, well aerated and only fine enough to
give contact between the seed and the soil. Therefore, the ideal field for maize is well
ploughed, with moderate packing in the row. Under traditional farming in tropical Africa,
maize is grown in ridges, but it does better on the flat land (Raemaekers, 2001). Minimum
tillage for field preparations has been more extensively tested and adopted for maize than
for any other crop. Minimum tillage for maize has generally given yields that were equal to
or even greater than those obtained from conventional tillage (Raemaekers, 2001).
13
According to Raemaekers (2001), the time of sowing maize is the critical factor
affecting maize yields. Timely sowing which costs the farmer little or nothing is the
cheapest and the most effective step towards ensuring satisfactory maize yields. As a
general rule, maize should be sown as near the beginning of the rains as possible. If sowing
is delayed, there is a decline in the yield of maize (Raemaekers, 2001).In parts of West
Africa, where there are two distinct rainfall peaks, two crop seasons of maize can be grown
in a year. The sowing date for early maize (major season) is March to April and for the late
(minor season) maize is August to September.
In the Northern sector of the country, there is only one rainy season (Raemaekers,
2001). Planting should therefore not be done too early or too late since either of these may
lead to about 40-50% loss in yield (Baffour, 1990).To obtain optimum yield, maize must
be planted early in the season to take advantage of the early rains (Tweneboah, 2000). In
Southern Ghana, maize is grown twice yearly. When grown as a sole crop, it may be sown
at a spacing of about 80 – 90cm between rows and 40 -60cm within rows with two plants
per hill to give stand population of 37,000 -62,500 plants per hectare (Tweneboah, 2000).
Baffour (1990) also stated that on commercial farms, the spacing should be about 90cm
between rows and 30cm within rows with two seeds per hill. According to Awuku et al.
(1991), the recommended spacing for maize cultivation is 90cm apart and 40cm between
plants, and 75cm x 40cm depending on the variety.
All plants require a certain amount of nutrients, water and space for growth, and
when crowded they cannot thrive well. If the space needed for their development is to
some extent occupied by weeds that rob the cultivated plants of nutrients, moisture and
sunlight, then returns from the crop must be correspondingly less. Ghana Grain
Development Project (G.G.D.P) (1990) stated that weeds have a competitive advantage
over young maize seedlings and therefore it is necessary to keep fields free from weeds at
14
least in the first 4 – 6 weeks after sowing. Yield losses of 40 -60% due to weeds have been
reported (Raemaekers, 2001). Weeds must never be allowed to out-grow maize plants
before being controlled. According to James et al.(2000), OMAFRA(2002) and Dogan et
al.(2004), the best time to minimize the effect of weeds on maize yields is within 4 to 8
weeks after planting when maize is in the 2 to 8-leaf stage.
Alternatively, application of a good contact or systemic herbicides prior to planting
will ensure that maize field is free from weeds during the critical growth stage of the crop
that is, up to four weeks after planting. There is the need to be followed up with light
slashing of weeds at six weeks after sowing James et al.(2000). Tweneboah (2000) also
stated that weeds may be controlled by hoeing 3 – 4 weeks after sowing.
Awuku et al. (1991) stated that a farmer can use organic or chemical fertilizer on
continuously or previously used land in southern and central Ghana. They again, stated that
50kg of nitrogen, 50kg of phosphorous and 50kg of potassium should be applied on one
hectare of land at planting time or a week after planting. Forest land left unused for at least
five years before planting does not need any fertilizer application
(Awuku et al.1991).
They further stated that nitrogen is required by maize in large quantities but because it
easily leaches through the soil, it cannot be applied at planting time but it should rather be
applied as a side dressing in a split application two weeks before tasselling or silking. G.
G. D. P Report (1990) stated that if organic sources of nitrogen are not available in
sufficient quantities, chemical fertilizers should be used in addition to whatever manure or
compost is applied. The recommended rate, however, depends on the soil type and
cropping history of the field.
15
2.6
Nitrogen Fertilizer on Maize Developmentand Yield
Nitrogen is the key element in increasing productivity. It is an integral component
of many compounds essential for plant growth processes including chlorophyll and many
enzymatic activities (Roth and Fox, 1990).Nitrogen is a component of a number of
compounds (proteins, nucleic acids, chlorophyll) and has an important role in many plant
physiological processes (Raven etal., 1999). In particular, it is important in the efficient
capture and use of solar radiation and therefore affects yield (Lafitte 2000; Birch et al.
2003). Nitrogen also mediates the utilization of potassium, phosphorus and other elements
in plants. The optimum amounts of these elements in the soil cannot be utilized efficiently
if nitrogen is deficient in plants. Therefore, nitrogen deficiency or excess can result in
reduced maize yields. Maize nitrogen requirement can be as high as 150 to 200 kg per
hectare. However, nitrogen requirement and utilization in maize also depends on
environmental factors like irrigation, varieties and expected yield. Application of nitrogen
fertilizer has also been reported to have significant effect on grain yield and quality of
maize (Lucas, 1986). Hardas and Aragiaanne-Hrestous (1985) reported that N at 180 kg/ha
was optimum for maize. Singh et al. (2000) also reported that application of N at 200 kg/ha
increased grain yield of maize. However, a substantial percentage of applied nitrogen is
lost due to volatilization, leaching, denitrification e.t.c. If water and temperature conditions
are ideal then productivity can only be limited by nonavailability of nitrogen (Purseglove
1972; Lafitte 2000; Birch et al. 2003).
Maize begins to rapidly take up nitrogen and other nutrients during the middle
vegetative growth period with the maximum rate of nitrogen uptake occurring near silking
stage (Hanway, 1971). Nitrogen deficiency is indicated by leaf yellowing first in the lowest
leaves that starts at the tip and then extends along the mid-rib, stunted plants, delayed
flowering and short, poorly filled ears Hughes 2006). Maize can utilize nitrogen in both
16
theammonium and nitrate forms but because of the ready conversion of ammonium to
nitrate by soil microbes, most nitrogen is taken up as nitrate (Farnhamet al. 2003). If
nitrogen is supplied via irrigation water, urea is the best source (Birch et al.
2003).Application of nitrogen had a significant effect on plant height, number of grains per
cob, 1000-grain weight and harvest index (Mahmood et al. 2001).
Increases in yield due to nitrogen application are supported by the findings of many
research workers who reported increases in grain yields of cereals with nitrogen (Buah et
al. 1998; Khosla et al. 2000; Workayehu, 2000; Yamoah et al. 2002; Aflakpui et al. 2005;
Conley et al. 2005).
According to Lafitte (2000) and Birch et al. (2003), if water and temperature
conditions are ideal then productivity can only be limited by non availability of nitrogen.
Eghball and Maranville (1993) found that the mean nitrogen influx of maize increased with
increasing soil nitrogen supply.With good agronomic practices, improved maize varieties
have the potential to produce 4–6 t/ha of grain (MOFA, 2002),
Increase in maize grain yield with an increased in the rates of nitrogen was also
observed by Luschinger et al. (1999), Sabir et al.(2000) and Younas et al.(2002), in their
investigations on nitrogen levels and maize grain yield.
Nunes et al. (1996) reported that biomass and grain yields of maize crop increased
with increasing N rate. Fedotkin and Kravtsov (2001) reported that grain and stover yield
increased significantly up to 240kg N /ha. Shivay and Singh (2000) reported that highest
plant height, leaf area index(LAI) and dry matter accumulation were recorded with 120kg
N /ha. Increased application of N reduced barrenness and increased the shelling
percentage. Gokmen et al. (2001) stated that plant height, 1000- grain weight and grain
weight per cob increased significantly with 100kg N/ hawhile tasseling period generally
decreased with increasing N rate.
17
2. 7
Insect Pests of Maize
Among the important constraints to maize production are field insect pests. Of the
130 insect pests that affect maize crop, stem borer, shoofly, armyworm, jassid, thrips,
white ant, pyrilla, grasshopper, grey weevil, hairy caterpillar, root worm, earworm and leaf
miner are more serious, though the spectrum varies in different agro-ecological regions.
Most of the research efforts have gone the breeding for resistance to European corn borer
(Ostrinia nubilalis), a pest of maize in the USA and Europe. Fall armyworm (Spodoptera
frugiperda) is another very important pest in tropical and subtropical areas. In India,
spotted stem borer (Chilo partellus) is the major pest throughout the country. Total crop
loss could occur if the insects are not controlled (Owusu – Akyaw and Afun, 1994).
Armyworms (Spodoptera spp) and grasshoppers (Zonocerus spp) may cause serious
damage to young maize by eating the soft vegetative parts.Sasamia spp, Busseola spp and
Eldana sp mostly attack both maize stem and cob whereas Mussidia nigrivenella and
Cryptophlebia attacks cobs of maize (Moyal, 1988).
2.7.1 Stem Borers
Maize stalk borers are difficult to control with insecticides (Vitale et al.
2007), the reason presumably being that existing spray-based practices have been
found ineffective against the internal feeders and they are costly and hazardous
(Clieve,
2003). The most notorious ones are Sesamia spp
Eldana
sp
(Lepidoptera:
Pyralidae)
and Busseola
(Lepidoptera:Noctuidae),
fusca
Fuller
(Lepidoptera:
Noctuidae) (Abu, 1986). Chilo partellus (Lepidoptera: Pyralidae) is of Asian origin
but it has been recently introduced into eastern Africa (Bosque-Perez, 1995).
Significant reduction in yield due to stem borers has been reported in the entire major
producing areas in Ghana ( Girling, 1980). The larvae of stem borers usually cause the
18
damage. Estimated yield losses caused by stem borers in West Africa range from 10-100%
(Usua, 1968). The situation is not different from other parts of Africa where most peasant
farmers do not plant maize during the minor season because of stem borers’ attacks
(Gounou et al. 1993). Chilo aleniellus (Strand)
2.7.2 Maize Stem Borers Worldwide
Several species of maize stem borers have been reported worldwide. The most
notorious ones are Sesamia calamistis (Lepidoptera:Noctuidae), Eldana saccharina
(Lepidoptera: Pyralidae) and Busseola fusca Fuller (Lepidoptera: Noctuidae) (Abu,
1986). Chilo partellus (Lepidoptera: Pyralidae) is of Asian origin but it has been
recently introduced into eastern Africa (Bosque-Perez, 1995) and is now the most
important species of stem borers in Kenya (Mulaa.1995). The European corn borer
(Ostiinia nabilalis) is one of the most important corn borers in Europe.
2.7.3 Stem Borer Species in Africa
Lepidopterous stem borer species which cause significant yield losses in maize in
Africa are follows:

the maize stalk borer, Busseola fusca Fuller (Lepidoptera: Noctuidae);

the pink stalk borer, Sesamia calamistis Hampson (Lepidoptera: Noctuidae);

the African sugarcane borer, Eldana saccharina Walker (Lepidoptera: Pyralidae);

andChilo aleniellus Strand (Lepidoptera: Pyralidae).

the spotted stalk borer, Chilo partellus Swinhoe (Lepidoptera: Pyralidae).
The first four are of African origin and are present in most countries of sub-Saharan
Africa, while C. partellus is Asian and only recently introduced into eastern
Africa.http://www.infonet-biovision.org.13/09/ 2009.
19
2.7.4 Stem Borer Species in Ghana
In Ghana, four species of stem borers namelySesamia calamistis Hampson
(Noctuidae), Bussela fusca Fuller (Noctuidae).Eldana saccharina Walter (Pyralidae), and
and Chilo aleniellus Strand (Lepidoptera: Pyralidae) have been identified as the common
species associated with maize. They are known to occupy different ecological niches
(Atkinson, 1980; Cochereau, 1982). The most predominant species across the ecological
zone was Eldana sp followed by Sesamia spp.(Gounou et al. 1994). Chilo aleniellus
Strand (Lepidoptera: Pyralidae) was found in the Central region. Like Eldana saccharina
Walter (Pyralidae), Chilo aleniellus, was found more on mature plants than younger plants
(Borkety-La, 1995).
2.7.5
Distribution and Brief Biology of Pink Stalk Borer(Sesamia species)
Geographical distribution: Sesamia sppoccurs in most of tropical Africa. Country
records include South Africa, Zimbabwe, Malawi, Uganda, Tanzania, Kenya, Zanzibar,
Madagascar, Mauritius, Angola, Nigeria, Cote d‟Ivoire, Cameroon, Gambia, Ghana, (Tams
and Bowden, 1953), Mozambique (Cugala et al. 1999), Ethiopia (Gebre-Amlak, 1989).
Host Plants: The following plants were recorded as hosts of Sesamia spp.
Maize, sorghum, finger millet, rice, sugarcane (Nye, 1960), Andropogon sp.,
Cenchrus ciliarus, Panicum maximum, Pennisetum purpuream, Sorghum arundinaceum,
Sorghum vulgare Cyperus distans, C. immensis, C.papyrus (Khan et.al. 1997).
In 3-5 days, the female lays up to 350 eggs, deposited in batches of 10-40. The eggs
are arranged in two to four contiguous rows and inserted between the lower leaf
sheaths and stem. Several hours after hatching, the larvae leave the ovipositor site to
penetrate the stems either directly or after feeding on the leaf sheath. The larval stage, lasts
30-60 days, depending on the climatic conditions, and usually involves five to six molts,
20
larvae may successively attack a number of young stems or tillers. Pupation generally takes
place in the stem, rarely between the sheath and stem. The pupal period lasts 10-12 days at
250C. Under tropical conditions five to six generations are completed in a year. S.
calamistis breeds throughout the year without diapauses. S. calamistis is considered to be
a very damaging pest in West Africa, whereas in the eastern and southern Africa it is only
of moderate importance (Bosque-Perez and Schulthess, 1998).
2.7.6 Distribution and Brief Biology of the African SugarcaneBorer(Eldana sp)
Geographical distribution: Eldana spis widely distributed in sub-Saharan Africa
including Burundi, Chad, Ghana, Kenya, Mozambique, Nigeria, Rwanda, Sierra Leone,
Somalia, South Africa, Tanzania, Uganda and Zaire (Maes, 1998).
Host Plants:The
saccharina:
Sugarcane,
following
maize,
plants
were
rice, sorghum,
recorded
Panicum
as
host
maximum,
of
Eldana
Pennisetum
purpureum, Phragmites sp., Rottboellia cochinchinensis, C. distans, C. immensis,C.
maculates and Papyrus (Khan et al., 1997).
Atkinson (1980) published a detailed account of the biology, distribution and
natural hosts of the species in Natal, South Africa, while Girling (1978) did the same in
Uganda, and Sampson and Kumar (1985) studied this species in Ghana. Females lay
batches of 50-100 eggs on dry leaves at the base of the plants, which may partly explain
the tendency of Eldana spto infest mature crops. Eggs hatch after about 6 days and the
young larvae feed externally on epidermal tissue before penetrating the stems. The length
of larval development is variable and may take up to two months. Larvae pupate within the
stems. Up to six generations may occur in a year and there is no larval diapause. In West
Africa, Eldana spis a pest of maize and sugarcane. Bosque-Perez and Mareck (1991)
found that even though Eldana spattacks maize plants late in the growing season
21
damage can be as high as 20%. In Southern Africa, Eldana spis considered to be a serious
pest of sugarcane (Atkinson, 1980). In eastern Africa, Eldana spattacks maize, but usually
towards the end of the growing season, and is generally not considered a serious pest.
2.8 Economic Importance of Maize Stem Borers
The initial damage of stem borers is caused by feeding on the leaf tissues, followed
by tunnelling and feeding within the stem, and sometimes the maize cobs (Swaine, 1957).
Infestation by stem borerson maize starts with oviposition on the leaves (Ajala and Saxena,
1994). After hatching, the first instars move into the leaf whorls where they feed and
develop on the bases of the leaves, causing lesions. The late third or early-fourth instars
bore into the stem, feeding on tissues and making tunnels. When the infestation is severe,
the larvae, either in the leaf whorl or in the stem, can cut through the meristematic tissues;
the central leaves than dry up to produce the ‘dead heart’ symptom, resulting in the death
of the plant. In Ghana, using the production function, crop loss was estimated at 14–17 %
in the savanna zones and 27 % in the rainforest zone (Gounou et al. 1994).
Feeding and stem tunneling by borer larvae on plants results in crop losses as a
consequence of destruction of the growing point, early leaf senescence, interference with
translocation of metabolites, and nutrients that result in malformation of the grain, stem
breakage, plant stunting, lodging, and direct damage to ears (Bosque-Perez and Mareck
1991).
Natural infestations by E. saccharina decreased maize yields by 16%, 15%, and
28% in the dry season and the first and second rainy seasons, respectively (Bosque-Perez
and Mareck 1991). Infested plots had significantly lower grain weight, indicating that E.
saccharina damage to the stems affects grain filling. In Ghana, a positive relationship
between the number of Sesamia spp. larvae and the extent of damage to maize stems, and a
22
negative relationshipbetween damage to maize stems and maize yield were shown by
(Gounou, et al.(1993). Thecalculated yield loss caused by Sesamia spp. to maize in the rain
forest and coastal regions in West Africa ranges from 20- 40% of the potential grain yield
(Reddy and Walker, 1990). Stem borer control in sorghum in the southern Guinea savanna
of Nigeria, where S. calamistis predominates, improved yields by 16–19%, whereas in the
northern Guinea savanna, where B. fusca predominates, yield losses of 49% in sorghum
were reported (Ajayi, 1987).
2.9 Rates of Nitrogen and Stem Borer Infestation
Studies in Cameroon have shown that soil application of nitrogen improved the
nutritional status of maize, which consequently enhanced its tolerance to the African maize
stem borer attack (Chabi-Olaye et al. 2005). However, if nitrogen is applied at rates greater
than required for maximum yield, plant biomass increases at the expense of yield. Studies
on several stem borers in Africa showed that an increase in the application of nitrogenis
related to higher pest loads and tunnel damage. However, soil nutrient levels, such as
nitrogen, greatly influenced the plant's tolerance to stem borer attack as well. This is due to
an increase in plant vigour, which is reflected in lower yield losses (Setamu et al.1995).
23
CHAPTER THREE
MATERIALS AND METHODS
3.1
Description of Site/ Location of Experiment
The experiment was conducted at the maize farm or cornbelt area of the University
of Education, Winneba,Mampong– Campus. The first season trial was undertaken during
the minor season of August, 2009 to January, 2010 (designated as 2009 minor cropping
season). The second season trial was carried out in the 2010 major season from April to
July (referred to as 2010 major cropping season). Ashanti Mampong is situated on latitude
070 04’N and longitude 010 024’W and 137.3m above sea level. (Asiedu, 2001).And lies
within the transitional zone of Ghana (i.e, between the rain forest of the south and the
Guinea savannah of the north).
The soil falls within the Bediesi series of the savannah ochrosol class, formed from
Voltaian sandstone of the Afram Plains. It is characteristically deep, yellowish red, sandy
loam and free from concretions and stones. It is well-drained and has satisfactory moisture
- holding capacity with a pH of 5.5 – 6.5 (Asiedu, 2001). It is easy to cultivate both by
hand and by machines. The soil also supports the cultivation of many crops such as cereals,
legumes, root, and tuber crops.
The rainfall pattern of the area is bimodal. The major season starts from March and
ends in July, with a peak rainfall in June, while the minor rains occur between August and
November with a peak rainfall in October. The mean annual rainfall and temperature are
1094.2mm and 30.80C., respectively (Asiedu, 2001). The mean daily temperature ranges
from 25°C to 37°C.(Asiedu, 2001).
24
The experimental site is one of the University’s main farms which is always put
under maize production. Other crops such as cowpea are sometimes grown in some parts
of the land. Both the major and the minor cropping seasons had been used over the years
for continuous maizecropping. Prominent weed species noted were Panicum spp,
Pennisetum speciesand Chromolaena odorata.
3.2
Experimental Design and Treatments
The experimental design used was 3 x 4 factorial trial arrangedin a Randomized
Complete Block Design (RCBD). With four (4) replications each plot size was 10m x 4m.
A total of 48 plots were used for the experiment with 1.0m path between plots and between
blocks. There were 12 treatment combinations comprising (i) three (3) varieties of maize
(Obatanpa, Mamaba and Golden Jubilee) and (ii) four (4) nitrogen levels (0, 45, 60, and
90) kgN/ha.
The seeds of the three varieties of maize were obtained from the CSIR-Crops
Research Institute, Fumesua - Kumasi. Three seeds were sown per stand and it was thinned
to two seedlings per stand two weeks after sowing. The planting distance used was 75cm
between rows and 40cm between plants. The seeds were sown at a depth of 3-5cm.
25
3.3
Cultivation and Management Practices
The experimental field was cleared and ploughed twice with a tractor. Later, the
field was leveled manually and the land divided into four (4) blocks and 48 plots before
planting. The total land area used for the experiment was 87m x 29m (2523m2) for both the
minor and the major cropping seasons.
The seeds of the three maize varieties were sown manually on the flat land on 12th
September, 2009 during the minor cropping season and 21st April, 2010 for the major
cropping season.Percentage emergence was determined seven days after sowing for each
treatment for both trials.
The traditional hoe as well as a post emergence herbicide(Caliherb + Atrazine) was
used to control weeds. The first weeding was carried out three (3) weeks after seedlings
emergence and the second weeding six (6) weeks after seedlings emergence. Earthing up
was carried out after the second weeding to provide support for plants against root lodging.
A compound fertilizer 15-15-15 NPK was basally applied at the rate of 7.5g/hill to
all treatments. The compound fertilizer was applied two weeks after seedling emergence.
The fertilizer was side placed 10cm away from the maize plants at a depth of 2-3cm. Top
dressing with sulphate of ammonia ((NH4)2SO4 )at the rates 0kgN, 7.5kgN, 22.9kgN and
53kgN was carried out on the 22
nd
of October, 2009 and 2nd June, 2010, respectively, for
both cropping seasons.
There was an armyworm outbreak on the 9th October, 2009. However, the situation
was brought under control by the use of Dursban during the minor cropping season.
Damage caused was, however, insignificant.
Harvesting for both trials was done manually 15 weeks after sowing. The plants
were harvested at physiological maturity stage. Signs of maturity considered included
toppling and drying of leaves and cobs. Yield components were taken from a quadrat
26
of2.1m x 1.2m (2.52m2) within the harvestable area of each treatment plot. All the varieties
were harvested 15 weeks after sowing.
3.4 Data Collected
3.4.1 Soil Sampling and Analysis
Before planting, for the first trial, a representative soil sample was taken at different
parts of the field. The soil augur was used to sample soil at a randomly selected site oneach
treatment combination plot. The samples were taken at a depth of 0-15cm. They were then
mixed thoroughly, air-dried and made to pass through a 2mm, and 0.5mm sieves for soil
texture and chemical analysis. The soil sample was later sent to Soil Research Institute at
Kwadaso- Kumasi for a routine analysis for both physical and chemical properties of the
soil. This was repeated during the major season. The results of the soil analysis are shown
in Table 4.1
3. 4.2 Plant Height
The heights of 10 randomly tagged plants were measured every two weeks from the
ground level to the tip of the terminal leaf with the aid of the meter rule. The mean height
was then computed. The plant height measurements were taken from the forth week of
seedling emergence to the tenth week of plant growth when the crop tasseled.
3.4.3 Plant Girth
The girth (diameter) of the plant stem was taken weekly at the base of each plant
about 5cm above ground level with the aid of a Vernier calipers. Ten (10) plants were
randomly tagged from the fourth week to the tenth week for the girth data. The mean girth
(diameter) was then calculated and recorded.
27
3.4.4 Leaf Area Index
A quadrat of 2m2 area was selected randomly at the 8WAP where optimum plant
growth was achieved in both cropping seasons from each plot. The measurement of length
and width at the broadcast point of each leaf in the quadrat was then taken. Each leaf area
designated as A was estimated by the formula A= L x B x 0.75, where L is the length of
the leaf, B is the maximum width of the leaf (cm) and 0.75 is the correction factor. The
summation of all leaf area in a quadrat was divided by the area of the quadrat to obtain the
LAI. Thus:
LAI = Total Leaf Area per quadrat
Ground area of quadrat
3.4.5 Days to 50% Tasselling and 50% Silking
The plants in the threemiddle rows in each plot was used to estimate days to 50%
tasselling and 50% silking. At the 6WAE to 8WAE, the number of maize plants which
were completely tasseled and silked were counted and recorded on daily basis. The total
number of plants recorded daily per plot was then converted into percentages.
Mathematically, the total number of tasseled and silked plants (x) recorded was than
divided by the total plant population (y) in the three middle rows and the results than
multiplied by 100. This is repeated till the day the number of days to 50% tesseling and
50% Silking per plot was achieved.
28
3.4.6
Number of Grains per Cob
Five (5) cobs were selected at random from each plot. The number of grains in 2-3
rows was then counted and an average calculated and multiplied by the number of rows on
the cob. The mean number of grains per cob for each treatment was then computed.
3.4.7 Shelling percentage
Ten (10) cobs selected at random from each plot were weighed. These were shelled
and the grains weighed. These were then used to compute the shelling percentage as
follows:
Shelling (%) = Maize grain weight
Weight of cobs
x 100%
3.4.8 Grain Moisture Content
The wet and the dry moisture content of the maize grains were measured by the use
of a moisture meter. After shelling, few grains were picked from each treatment and the
wet grain moisture content taken. The mean percent grain moisture was than computed.
After sun drying the maize grains for two weeks, the dry grain moisture content from each
treatment was again obtained using the moisture meter called procimeter; part of it was
used to grind the maize after which the moisture content was measured. The mean percent
dry grain moisture content was then computed.
3.4.9 1000-grain weight
Thousand grains from each plot were weighed at moisture content of 13 to14% and
the treatment mean computed.
29
3.4.10 Grain yield (kg) per hectare
The grain yield from each plot harvested from cobs in the harvestable rows was
calculated and the results were then used to compute the yield per hectare. The formular
for calculating grain yield per hectare is given as
Grain yield (kg) per hectare= 10000m2 x Q grain (kg)
Harvest area(m2)
3.4.11 Harvest Index
The harvest index was calculated as follows. One plant per hill was selected
randomly from each plot and the shoot with roots together with the cob weighed. The
cobwas then removed and weighed alone. The harvest index was then computed as the
ratio of the cob (c) weight to the weight of shoot (s) plus cob.
Thus Harvest index = Grain(wt)
Shoot + Grain
or
HI = G
S+ C
3.4.12 Stem Borer Damage
The sampling technique used in sampling stem borers was that of destructive
sampling. All plants in each plot were inspected for external signs of borer attack (dead
heart, leaf damage, frass and bored holes) and counted as damage and used to estimate
percent borer damage. Additionally, five (5) plants were randomly selected from each
quadrat and cut at ground level. Leaves of each plant were removed to check for the
presence of borer exit holes. The plants were then cut open longitudinally and examined
for stem borers in their bored holes (Bosque-Perez and Mareck, 1991). Percentage stem
borer infestation in plants per plot was then computed. The larvae of the stem borer species
obtained were stored in large glass jars in a solution made up of 20% alcohol. This was
30
done weekly beginning from the first week of stem borer sampling to the last week during
both cropping seasons. The purpose was to preserve the larvae for identification.
The key developed by Overholt et al. (2001) was the reference material used to
identify the species of stem borers which were sampled from the infested maize plants.
With regard to the percentage number of pupae, plant samples suspected to be infested
with stem borers were cut open and the number of pupae estimated at harvest.
3.5
Plant Lodging
The number of lodged plants in each plot was counted and the percentage of lodged
plants computed.
3.6
Data Analysis
The data collected were subjected to the analysis of variance(ANOVA) using SAS-
GLM procedures (SAS Institute, 1999). The treatment means were separated by the least
significant difference (LSD) at 0.05 probability level.
31
CHAPTER FOUR
RESULTS
4.1
Physical and Chemical Properties of the Soil
The results of soil sample analysis with regard to physical and chemical properties
of the soil prior planting are shown in Table 4.1. The soil was sandy clay loam in texture.
The soil had a pH of 5.4 in 2009 minor season and a pH of 4.9 in the 2010 major
season.This means the soil was moderately acidic. The soil available P was low and the
exchangeable cations (K, Na, Ca and Mg) were not also high in both cropping seasons. The
percentage nitrogen, organic matter and organic carbon were moderate. The micro
nutrients analyzed in both seasons were also not high.
Maize grows on a wide variety of soils but it prefers deep fertile, well – drained
loam and silt loam soil with the soil pH not less than 4.5. The best soils for maize are
normally loams and loamy soils rich in humus.
32
Table 4.1 Physical and chemical properties of the soil
Soil properties
pH 1:1(H2O)
Organic C (%)
Soil organic matter (%)
Total N (%)
P (mgkg G1)
2009 Minor
5.4
1.22
2.10
0.11
34.3
2010 major
4.9
1.03
1.78
0.08
15.62
Exchangeable cations (Cmol/kg G1)
Ca
Mg
Na
K
4.01
1.87
0.09
0.60
3.20
2.14
0.10
0.45
Particle size (%)
Sand
Silt
Clay
58.10
26.64
15.26
58.10
26.64
15.26
Micro Nutrients
Zn
Cu
Fe
Mn
1.4
0.9
21.9
52.85
1.2
1.05
24.6
42
33
4.2. Plant Establishment, Growth and Development of Maize
4.2.1 Percentage Plant Establishment/Emergence
During the 2009 minor season, significant (P<0.05) differences were observed
between the three maize varieties on their emergence or establishment. Maximum percent
emergence count was recorded inMamaba that was statistically at par with that of
GoldenJubilee. Minimum percent emergence was recorded in Obatanpa.
In the 2010 major season, there were no significant (P>0.05) differences. However,
maximumpercent germination count was recorded inGolden Jubilee whereas minimum
germination count was observed inObatanpa. No Significant (P>0.05) differences were
recorded between the levels of nitrogen which were applied to the varieties in the 2009
minor and 2010 major cropping seasons.
The interaction between maize varieties and levels of nitrogen showed significant
(P<0.05) differences in both cropping seasons.In Obatanpa, emergence was highest at
0kgN/ha and 60kgN/ha in 2010 and 2009 cropping seasons respectively. For Mamaba
emergence was highest at 90kgN/ha in 2009 and 45kgN/ha in 2010 cropping seasons. In
Golden Jubilee, the highest emergence was obtained at 60kgN/ha in 2009 and 45kgN/ha in
2010 cropping seasons.
34
Table 4.2 Percent Plant Emergence in the Three Varieties of Maize during 2009 Minor
and 2010 Major Seasons as Affected by Levels of Nitrogen.
TREATMENT
Obatanpa
N0
N45
N60
N90
Mamaba
N0
N45
N60
N90
Golden Jubilee
N0
N45
N60
N90
LSD Variety
LSD Nitrogen
LSD Variety x N.
2009 minor season
2010 major season
Emergence (%)
Emergence (%)
Variety X Nitrogen
85.7
88.0
89.0
85.0
93.0
91.8
93.0
89.0
92.8
92.5
90.3
93.8
89.9
94.2
91.1
91.8
90.3
87.8
92.3
87.0
3.94*
NS
5.57*
91.4
93.8
92.3
91.3
NS
NS
4.05*
* = significant at 5% probability level
NS= not significant at 5% probability level
35
4.2.2Plant Height
The results(Figure 4.1) showed that plant height increased across the treatments at
all stages of growth. At 4 and 6 weeks after planting (WAP), the varieties of maize did not
show any significant (P>0.05)differences in plant height during the 2009 minor season.
However, 8WAP and 10WAP, plant height in the maize varieties differed significantly (P<
0.05).Highest plant height was recorded in Obatanpa at 10 WAP during the minor season.
The height was not significantly different fromGolden Jubilee, but highly significant
(P<0.05) than Mamaba variety. The plots fertilized with 90kgN/ha produced the highest
plant height, which was statistically similar with plots fertilized with 60kgN/ha. The least
plant height was recorded on those plots fertilized with 45kgN/ha and 0kgN/ha.
Similarly in the 2010 major season, the maize varieties recorded significant
(P<0.05) differences in plant height. Maximum plant height was recorded in Obatanpa at
8WAP.This was followed by Golden Jubileeand Mamaba.The differences observed in
plant height during the 2010 major season showed no significant (P>0.05) difference
between Obatanpa and Golden Jubilee. However, both varieties recorded highly significant
(P<0.05) differences over Mamaba. Similar observations were recorded on the levels of
nitrogen applied to the maize varieties in the 2010 major season. The interaction between
varieties and nitrogen levels of plant height was significant (P<0.05) at the 8WAP in 2009
minor season and 4WAP to the 8WAP during the 2010 major season(Figure 4.1). Plots
which received 90kgN/ha produced the highest plant height. This was followed by plots
which received 60kgN/ha, 45kgN/ha and 0kgN/ha in that order (Figure 4.1)
36
Figure 4.1 The Defferent Rates of Nitrogen on Plant Height in the Three Varieties of
Maize During 2009 Minor and 2010 Major Seasons.
300
N
0
200
150
N
4
5
100
50
Plant Height (cm)
Plant Height (cm)
250
0
250
200
150
N0
100
N45
50
N60
0
4
6
8
10
250
6
7
8
200
200
N
0
150
100
N
4
5
50
Plant Height (cm)
Plant Height (cm)
5
Weeks After Planting (WAP)
Figure 4.1b Obatanpa 2010…
Wees After Planting (WAP)
Figure 4.1 a Obatanpa 2009…
0
4
6
8
150
N0
100
N45
50
N60
N90
0
10
4
Weeks After Planting (WAP)
Figure 4.1 c Mamaba 2009…
5
6
7
8
Weeks After Planting (WAP)
Figure 4.1d Mamaba 2010…
250
300
200
250
N0
200
N4
5
N
0
150
100
N
4
5
50
Plant Height (cm)
Plant ahaeight (cm)
N90
4
0
4
6
8
150
N6
0
100
50
0
10
4
5
6
7
8
Weeks After Planting (WAP)
Figure 4.1f Golden Jubilee…
Weeks After Planting (WAP)
Figure 4.1 e Golden Jubilee…
4.2.3 StemPlant Girth
37
The data presented in Figure 4.2 showed the effect of nitrogen application on the
plant girth of maize varieties at various growth stages after planting. In the 2009 cropping
season, there were no significant (P>0.05) differences in plant girth between Obatanpa and
Golden Jubilee. However, significant (P<0.05) differences were observed in Obatanpaand
Golden Jubilee over Mamaba. No significant (P>0.05) difference were observed between
the various nitrogen levels applied during the season, except at 8WAP. The interaction
between varieties and nitrogen levels on plant girth showed significant (P<0.05)
differences at 5 and 8WAP.Nitrogen applied at 90kgN/ha produced the biggest plant girth
in Golden Jubilee; while 0kgN/ha produced the smallest plant girth in Mamaba.
During the 2010 major season, maize varieties did not show significant (P>0.05)
differences in plant girth at 6, 7 and 8WAP. The biggest stem girth was recorded in
Obatanpa maize which was not significantly (P>0.05) different from that of the
GoldenJubilee maize. The smallest stem girth was observed in the Mamaba maize.With
regards to the various nitrogen levels, significant (P<0.05) differences in plant girth
occurred during 4 and 5 WAP. Interaction between nitrogen and the varieties of maize
significantly (P<0.05) affected plant girth.Plots which received 90kgN/haproduced the
biggest plant girth. This was followed by plots which received 60kgN/ha, 45kgN/ha and
0kgN/ha in that order (Figure 4.2).
Figure 4.2 The Defferent Rates of Nitrogen on Stem Girth in the Three Varieties of Maize
38
4
3.5
3
2.5
2
1.5
1
0.5
0
5
N
0
Stem Girth (cm)
Stem Girth (cm)
During 2009 Minor and 2010 Major Seasons.
N
4
5
4
3
N
45
2
N
60
1
0
4
4
5 6 7 8
Planting2009
(WAP)
FigureWeeks
4.2a After
Obatanpa
N
0
5
6
7
8
4
3
N
4
5
2
1
N0
5
Stem Girth (cm)
Stem Girth (cm)
5
Weeks
Planting
(WAP)
Figure
4.2bAfter
Obatanpa
2010
Major Season.
Minor Season.
N4
5
N6
0
N9
0
4
3
2
1
0
0
4
5
6
7
4
8
N
0
4
3
N
4
5
2
1
6
7
8
5
Stem Girth (cm)
5
5
Weeks
Planting
Figure
4.2dAfter
Mamaba
2010(WAP)
Major
Season
Weeks
Planting
Figure
4.2c After
Mamaba
2009(WAP)
Minor
Season.
Stem Girth (cm)
N
0
0
N
0
N
45
N
60
4
3
2
1
0
4
5
6
7
8
4
Weeks After Planting (WAP)
Figure 4.2e Golden Jubilee
2009 Minor Season.
5
6
7
8
Weeks
Figure
4.2fAfter
GoldePlanting
Jubilee (WAP)
2010
Major Season.
39
4.2.4 Leaf Area Index
No significant (P>0.05) differences in the leaf area index were observed among the
varieties during 2009 minor season (Table 4.3). However, during 2010 major season, the
largest leaf area index was significant (P<0.05) in Obatanpa (3.38). In both cropping
seasons, the varieties which received 90kgN/ha, 60kgN/ha and 45kgN/ha significantly
(P<0.05) showed the highest leaf area index.
The various levels of nitrogen significantly (P < 0.05) affected leaf area index in
both 2009 minor and 2010 major seasons. As the level of nitrogen applied was increased
the leaf area index also increased. (Table 4.3). Similarly, plots treated with the highest dose
of N (90kg /ha) and 60kgN/ha were significantly (P<0.05) different from plots with the
lowest dose of 45kgN/ha and 0kgN/ha applied in both 2009 minor and 2010 major
cropping seasons. Analysis of the data also showed that, interaction between nitrogen
levels and varieties of maize was significant (P<0.05) in both cropping seasons. The leaf
area index observed in the maize varieties was highest at the application rate of 90kgN/ha.
4.2.5Days to 50% Tasselling and 50% Silking.
Statistical analysis of the data indicated significant (P<0.05) differences in the days
to 50% tasselling between the varieties of maize in the 2009 minor cropping season (Table
4. 3). The 2010 major season on the contrary did not show any significant (P>0.05) in the
days to 50% tasselling. The highest significant (P<0.05) number of days to 50% tasselling
was observed in Obatanpa and the least number of days to 50% tasselling occurred in
Mamaba in the 2009 minor season (Table 4.3). Various levels of nitrogen applied did not
show any significant (P>0.05) effect on the days to 50% tasselling during both the 2009
minor and 2010 major seasons. On the contrary, the interaction between maize varieties
40
and levels of nitrogen showed significant (P<0.05) differences in both 2009 minor and
2010 major seasons.
With regard to the number of days to 50% silking, the varieties did not show any
significant (P>0.05) differences in the 2009 minor season. However, in the 2010 major
season, significant (P<0.05) differences were observed in the days to 50% silking. Mamaba
showed the least significant (P<0.05) number of days to 50% silking compared with
Golden Jubilee and Obatanpa. Significant (P <0.05) differences were observed between the
levels of nitrogen which were applied to the varieties in both the 2009 minor and 2010
major seasons. In both seasons, the varieties of maize which received 0kgN/ha
significantly (P<0.05) recorded the highest number of days to 50% silking. The interaction
between the varieties of maize and the levels of nitrogen with regard to 50% silking
showed no significant (P>0.05) during the 2009 minor season, but significant (P<0.05)
differences occurred during 2010 major season. In Obatanpa, days to 50% tasselling were
highest at 90kgN/ha in 2009 minor 60kgN/ha in the 2010 major seasons respectively. For
Mamaba and Golden jubilee, the highest number of days to 50% tasselling was observed at
both 90kgN/ha and 0kgN/ha during both cropping seasons. With regard to number of days
to 50% silking, Obatanpa and Mamaba were highest at 0kgN/ha in 2010 major season.
.
41
Table 4.3 Levels of Nitrogen on Leaf Area Index and Phenology in Three Varieties of
Maize during 2009 Minor and 2010 Major Seasons.
TREATMENT
Obatanpa
N0
N45
N60
N90
Mamaba
N0
N45
N60
N90
Golden Jubilee
N0
N45
N60
N90
LSD Variety
LSD Nitrogen
LSD Var. x N.
2009 Minor season
2010 Major season
Leaf Area Days to
Days to
Leaf Area
Days to
Index
50%
50% silking
Index
50%
8WAP
tasselling
8WAP
tasselling
Variety X Nitrogen
Days to
50% silking
2.57
3.05
3.46
3.60
49.75
49.75
49.75
50.00
51.00
50.75
50.50
50.75
2.62
3.09
3.84
3.96
47.50
48.75
49.00
48.50
51.25
51.00
50.25
50.75
2.53
2.87
3.14
3.53
48.25
48.25
48.00
48.25
51.00
50.50
50.5
50.25
2.46
2.69
3.19
3.48
48.25
48.00
48.00
48.25
50.75
50.25
50.25
50.50
2.50
2.84
3.30
3.72
NS
0.24*
48.25
48.75
48.75
49.25
0.43*
NS
51.00
50.25
50.75
50.25
NS
0.47*
2.39
2.93
3.51
3.88
0.19*
0.22*
48.75
48.75
48.50
48.75
NS
NS
50.75
51.00
50.50
51.00
0.37*
0.42*
0.42*
0.86*
NS
0.38*
0.93*
0.73*
* = significant at 5% probability level
NS= not significant at 5% probability level
42
4.2.6Dry Matter Content per Plant
Table 4.4 shows the summary of the results of the dry matter content per plant
obtained during the trials in 2009 minor season and 2010 major season. The results
indicated no significant (P>0.05) differences were recorded on the dry matter content of
the maize varieties at 6WAP and the 8WAP. However,the levels of nitrogen were found to
show significant (P<0.05) differences at 6WAP but not at the 8WAP. At 6WAP plots
treated with 90kgN/ha produced significantly (P<0.05) higher value of dry matter content
than plots treated with 0kgN/ha. No significant (P>0.05) differences were observed
between the nitrogen levels of 90kgN/ha, 60kgN/ha and 45kgN/ha. Observations from the
study indicated that the interaction between the nitrogen levels and the varieties of maize
significantly (P<0.05) affected dry matter content at 6WAP but not at 8WAP (Table 4.4).
In the 2010 major cropping season, the maize varieties and various nitrogen levels
as well as the interaction had significant (P<0.05) effect on dry matter content from 6WAP
to 10WAP. No significant (P>0.05) differences were observed at 4WAP.Observations
showed that the dry matter content increased as the maize plants received higher dose of
nitrogen and also as the maize plants grew older.
43
Table 4.4 Different Levels of Nitrogen on Dry Matter Content (g) in Three Varieties of
Maize during 2009 Minor and 2010 Major Seasons.
TREATMENT
2009 Minor Season
2010 Major Season
Dry matter
Dry matter
Dry matter
Dry matter
Dry matter
8WAP
4
WAP
6
WAP
8 WAP
6WAP
Variety X Nitrogen
Obatanpa
N0
19.25
52.75
N45
22.50
53.00
N60
21.50
55.50
N90
22.75
56.00
Mamaba
N0
21.25
48.75
N45
20.25
54.00
N60
21.50
55.25
N90
23.00
56.25
Golden Jubilee
N0
19.75
51.75
N45
22.25
49.25
N60
22.25
53.75
N90
23.00
55.25
LSD Variety
NS
NS
LSD Nitrogen
1.95*
NS
LSD Var.x N.
3.37*
NS
* = significant at 5% probability level
NS= not significant at 5% probability level
Dry matter
10 WAP
7.25
7.25
7.50
7.25
11.50
11.75
11.50
17.00
18.25
19.25
23.75
26.00
51.00
55.75
62.75
68.00
7.00
7.25
7.75
7.00
11.00
11.25
12.00
17.00
17.50
19.25
24.25
28.25
46.00
50.00
55.75
65.00
7.25
7.00
7.25
7.25
NS
NS
NS
10.75
11.25
15.50
17.75
0.64*
0.74*
1.28*
17.25
19.50
25.75
29.00
1.03*
1.19*
2.06*
45.50
49.25
60.25
64.50
3.48*
4.02*
6.97*
44
4.3
Yield and Yield Components of Maize
4.3.1Cob Length
The results oncob length for 2009 season are indicated in Figure 5.1There were
significant (P<0.05) differences in cob lengths among the three maize varieties.The mean
highest cob length was recorded in the Golden Jubilee maize. Various levels of nitrogen
also significantly (P <0.05) affected the cob lengths. Interaction between nitrogen and
maize varieties had significantly (P <0.05) affected the cob length. Plots with the nitrogen
levels of 0kgN/ha had the lowest cob length.
During the 2010 major season,cob lengths recorded in the maize varieties showed
significant (P<0.05) differences with Obatanpa maize producing the highest cob length.
Similarly, the various nitrogen levels showed significant (P<0.05) effect on the maize cob
length. Plots which received nitrogen level of 90kgN/ha produced the highest cob length.
The interaction between nitrogen and maize varieties significantly (P<0.05) affected cob
length. Plots with the nitrogen level of 0kgN/ha resulted in the production of the lowest
cob length (Figure 5.1)
45
Cob Length (cm)
Figure 5.1 Different Levels of Nitrogen on Cob Length in Three Varieties of
Maize during 2009 Minor and 2010 Major Seasons.
30
20
Cob Length 2009
10
Cob Length 2010
0
N0
N45of nitrogen
N60
Levels
Figure 5.1a Obatanpa
N90
Cob length (cm)
25
20
15
Cob length
2009
10
Cob length
2010
5
0
N0
N45
N60
Levels
of
nitrogen
Figure 5.1b Mamaba
N90
Cob length (cm)
30
25
20
15
10
Cob length 2009
5
Cob length 2010
0
N0
N45
N60
N90
Levels of nitrogen
Figure 5. 1c Golden Jubilee
46
4.3.2 Cob Width
The data on the cob width are summarized in Figure 5.2 In both cropping
seasons,significant (P<0.05) differences were observed on the cob width in the maize
varieties. The highest cob width was significantly (P<0.05) observed in the Obatanpa maize
variety. The cob width in Mamaba and Golden Jubilee were significantly (P<0.05) similar. No
significant (P>0.05) differences in the cob width were observed between the levels of nitrogen
applied during the 2009 minor season. During 2009 minor cropping season, the interaction
between nitrogen and maize varieties did not show any difference in the cob width (P >0.05).
During 2010 major season,cob width which were recorded in the maize varieties as
well as the nitrogen levels, showed significant (P<0.05) differences. The highest cob width
was observed in the Obatanpa maize variety followed by Golden Jubilee with Mamaba
recording the least cob width. The highest cob width was obtained on plots with the
application of 90kgN/ha and this was followed by nitrogen levels of 60kgN/ha, 45kgN/ha and
0kgN/ha in that significant (P<0.05) order. The interaction between nitrogen levels and maize
varieties also significantly (P<0.05) affected the maize cob width.
47
8
7
6
5
4
3
2
1
0
Cob Width 2009
Cob Width 2010
N0
N45
N60
N90
Levels of nitrogen
Figure 5.2a Obatanpa
6
COb width (cm)
5
4
Cob width 2009
3
2
Cob width 2010
1
0
N0
N45
Levels of nitrogen
N60
N90
Figure 5.2b Mamaba
6
5
Cob width (cm)
Cob width (cm)
Figure 5.2 Different Levels of Nitrogen on Cob Width in Three Varieties of
Maize during 2009 Minor and 2010 Major Seasons.
4
Cob width 2009
3
Cob width 2010
2
1
0
N0
N45
N60
N90
Levels of nitrogen
Figure 5.2c Golden Jubilee
48
4.3.3
Harvest Index
During 2009 minor cropping season, analyses of the data indicated that no significant
(P>0.05) effect on the harvest index was observed between the maize varieties (Figure 5.3).
The different levels of nitrogen significantly (P<0.05) affected the harvest index. The harvest
index recorded on plots which received 90kgN/ha was significantly (P<0.05) higher than that
on plots with 0kgN/ha. No significant (P>0.05) differences in harvest index were observed
between 90kgN/ha, 60kgN/ha and 45kgN/ha. However, the interaction between nitrogen and
maize varieties significantly (P<0.05) affectedharvest (Figure 5.3).
In the 2010 major cropping season, the harvest index which was recorded in the maize
varieties, the levels of nitrogen applied and the interaction showed significant (P<0.05) effect
(Figure 5.3). The harvest index was higher in Obatanpa followed by Golden Jubilee and
Mamaba in that significant (P<0.05) order.
In the case of nitrogen levels, 90kgN/ha produced the highest harvest index that was
statistically similar (P<0.05) with 60kgN/ha. Treatment with nitrogen level of 0kgN/ha
producedthe lowest harvest index.
49
Figure 5.3 Different Levels of Nitrogen on Harvest Index in Three Varieties of
Maize during 2009 Minor and 2010 Major Seasons.
0.7
Harvest index
0.6
0.5
0.4
0.3
Harvest Index 2009
0.2
Harvest Index 2010
0.1
0
Harvest index
N0
Levels N45
of nitrogen N60
Figure 5.3a Obatanpa
N90
0.54
0.53
0.52
0.51
0.5
0.49
0.48
0.47
0.46
0.45
Harvest index 2009
Harvest index 2010
N0
N45
N60
Levels of nitrogen
Figure 5.3b Mamaba
N90
0.7
Harvest index
0.6
0.5
0.4
0.3
0.2
Harvest index 2009
0.1
Harvest index 2010
0
N0
N45
N60
N90
Levels of nitrogen
Figure 5.3c Golden Jubilee
50
4.3.4 Shelling Percentage
During the 2009 minor cropping season, the shelling percentage in the maize varieties
did not show significant (P>0.05) differences. However, Golden Jubilee maize showed the
highest shelling percentage closely followed by Mamaba with Obatanpa producing the least
shelling percentage. With regard to nitrogen levels, shelling percentage was significantly
(P<0.05) high with the 90kg N/ha treatment and significantly (P<0.05) low with 0kgN/ha
treatment. The interaction between nitrogen and maize varieties significantly (P<0.05) affected
shelling percentage in both cropping seasons (Figure 5.4).
In the 2010 major cropping season, the varieties of maize and the levels of nitrogen
also significantly (P<0.05) affected the shelling percentage.
Significantly high (P<0.05)
shelling percentage was recorded in the Obatanpa and the least was recorded in Mamaba
maize variety. Plots which received 90kgN/ha significantly (P<0.05) produced higher shelling
percentage than plots which were treated with 45kgN/ha and 0kgN/ha
51
Figure 5.4 Different Levels of Nitrogen on Shelling Percentage in Three Varieties of
Maize during 2009 Minor and 2010 Major Seasons.
100
Shelling (%)
80
60
Shelling (%) 2009
40
Shelling (%) 2010
20
0
N0
N45
Levels of nitrogen
Figure 5.4a Obatanpa
N60
N90
Shelling (%)
80
Shelling (%)
2009
60
40
Shelling (%)
2010
20
0
N0
N45
N60
Levels of nitrogen
N90
Figure 5.4b Mamaba
90
80
Shelling (%)
70
60
50
40
Shelling (%) 2009
30
20
Shelling (%) 2010
10
0
N0
N45
N60
N90
Levels of nitrogen
Figure 5.4c Golden Jubilee
52
4.3.5Maize Grain Yield
The seed grains realized from the trials during the two seasons are shown in Table 4. 5.
During 2009 minor cropping season, the responses ofthe maize varieties under study as well
as the nitrogen levels to grain yield was significant (P<0.05). The Obatanpa maize variety
produced the highest grain yield per hectare which was significantly (P<0.05) similar to the
yield byGolden jubilee maize. The lowest (P<0.05) grain yield (t/ha) was obtained from
Mamaba.Maize grain yieldincreased significantly (P<0.05) withincreasein nitrogen level up to
90kg N/ha. The highest (P<0.05) grain yield was obtained from plots treated with 90kgN/ha
and the lowest (P<0.05) yield from plots which received 0kgN/ha. The interaction between the
maize varieties and the nitrogen levels was found to have significant (P<0.05) affect on grain
yield.
Again, in the 2010 major cropping season, the three maize varieties and the nitrogen
levels had significant (P<0.05) effects on the mean maize grain yield (Table 4.5).Obatanpa
maize variety significantly (P<0.05) produced the highest grain yield followed by Golden
jubilee and Mamabain that order. Maize grain yield was significantly (P<0.05) higher on plots
treated with higher nitrogen levels. The interaction between the maize varieties and the
nitrogen levels significantly (P<0.05) affected the grain yield. The highest (P<0.05) grain yield
was observed from plots with the nitrogen dose of 90kgN/ha and the lowest (P<0.05) yield
from plots treated with 0kgN/ha (Table 4.5).
53
Table 4.5 Levels of Nitrogen on Yield and Yield Components in Three Varieties of Maize
TREATMENT
2009 Minor Season
2010 major season
Maize
No of Grains 1000 Grain
Maize Grain
No of Grains
Grain Yield per cob
Yield t/ha
per cob
Weight (g)
t/ha
Nitrogen X Variety
Obatanpa
N0
4.68
549.65
N45
5.50
553.25
N60
6.50
577.67
N90
7.70
593.00
Mamaba
N0
3.85
526.40
N45
4.48
529.45
N60
4.93
591.40
N90
5.93
537.45
Golden Jubilee
N0
5.03
547.80
N45
5.70
549.75
N60
6.00
561.35
N90
6.70
561.20
LSD Variety
0.52*
NS
LSD Nitrogen
0.60*
NS
LSD Var x N.
1.04*
NS
* = significant at 5% probability level
NS= not significant at 5% probability level
1000 Grain
Weight (g)
272.00
293.50
314.50
311.00
4.73
5.63
6.70
8.23
504.73
549.65
610.15
626.95
271.50
293.50
314.50
315.25
264.00
271.75
297.00
290.00
3.95
4.18
5.30
6.00
499.53
545.80
602.70
672.03
264.00
271.75
309.25
325.50
277.00
287.25
309.00
310.00
NS
21.52*
37.27*
4.28
4.90
6.13
6.63
0.31*
0.36*
0.62*
499.73
551.95
606.60
658.13
NS
28.33*
49.06*
269.75
292.25
314.75
325.50
NS
16.77*
NS
54
4.3.6 1000- Grain Weight
The analyses of the data on the 1000-grain weight for 2009 minor and 2010 major
cropping seasons are summarized in Table 4.6No significant (P>0.05) differences were
observed in the maize varieties in both seasons. However,1000-grain weight was higher
inObatanpa followed by Golden jubilee maize variety and Mamaba variety. With regard to the
nitrogen rates, significant (P<0.05) effect was recorded in both cropping seasons.
Significantly (P<0.05) higher 1000-grain weight was recorded from plots treated with
60kgN/ha and 90kgN/ha than plots treated with 45kgN/ha and 0kgN/ha during the 2009 minor
and the 2010 major cropping seasons.Significant (P<0.05) weight differences were also
observed in the interaction between the maize varieties and the levels of nitrogen applied in
both cropping seasons.Minimum 1000-grain weight produced by 45kgN/ha was statistically
similar to treatment of 0kgN/ha.
4.3.7Number of Grains per Cob
In the 2009 minor cropping season, the results presented in Table 4.6 showed the effect
of different rates of nitrogen on the number of grains per cob. No significant (P>0.05)
differences between maize varieties were observed. Obatanpa however, produced the highest
number of grains per cob followed by Golden Jubilee and Mamaba in that order. The various
nitrogen levels as well as the interaction the between the levels of nitrogen and the maize
varieties did not show any significant (P>0.05) differences in the production of number of
grains per cob.
55
During 2010 major cropping season, data regarding thenumber of grains per cob are
summarized in Table 4.6. Statistical analyses of the data showed that the maize varieties did
not show any significant (P>0.05) effect on the number of grains per cob.The highest grains
per cob though not significantly different (P>0.05) from Obatanpa and Golden Jubilee was
recorded by Mamaba in the 2010 major season. On the contrary, there was significant
(P<0.05) effect on the number of grains per cob with regard to the different nitrogen levels as
well as the interaction between maize varieties and the nitrogen. Plots treated with 90kgN/ha
nitrogen rates produced the maximum number of grains per cob. This was followed by plots
treated with 60kgN/ha, 45kgN/ha and 0kgN/ha.
56
4.4
The Different Levels of Nitrogen on Maize Stem Borer Infestation in Three
Varieties of Quality Protein Maize
4.4.1 Species of Stem Borers in the Three Varieties of Maize
The species of stem borers identified in the maize plants in the study area were
Sesamia spp notablySesamiacalamistisHampson andSesamia botanephaga Tams and Bowden
(Lepidoptera: Noctuidae), and the African Sugarcane borer, Eldanasaccharina Walker
(Lepidoptera: Pyrallidae).
During the major and minor cropping seasons, Sesamia spp.were the first stem borers
which infested the maize plants. Infestation of Sesamia spp. was first observed at 3WAE
during the major season and 4WAE during the minor season. E.saccharinawas the last stem
borer which infested the varieties of maize. Infestation was first observed at 8WAE during the
major season and 6WAE during the minor season. It was observed that these stem borers
infested the plants in succession.
57
Plate 1.Eldana saccharinaon maize Leaf Plate 2.Sesamia botanephagainMaize Stalk.
4.4.2 The Different Levels of Nitrogen on the Population of Sesamia spp in the
Three MaizeVarieties.
Table 4.6 shows the effect of nitrogen application on the population of Sesamia
spprecorded in the varieties of maize at various growth stages after seedling emergence
during 2009 minor season. The maize varieties did not show any significant (P>0.05)
differences in the number of Sesamia spp at 4WAE, 5WAE, 9WAE and the 10WAE.
However, at 6WAE significant (P<0.05) differences were observed in the number of Sesamia
spp sampled. At 6WAE and 7WAE the levels of infestation was significantly (P<0.05) higher
in Obatanpa than in the Golden Jubilee. This observation was the reverse at 8WAE.
At various nitrogen levels, significant (P<0.05) differences in the number of Sesamia
sppwere observed except at 10WAE. The levels of infestation in plants on plots which
received 90kgN/ha was significantly (P<0.05) higher than on plots which received 0kgN/ha.
58
Similarly, the interaction between varieties and nitrogen levels was statistically significant
(P<0.05) in the numbers of Sesamia spp recorded at the 4 WAE, 5WAE, 6WAE, 7WAE,
8WAP and 9WAE but not significant (P>0.05) at 10WAE. It was observed that generally the
population of Sesamia sppdecreased as the maize plants became older in the field.
59
Table 4.6 Different Levels of Nitrogen on the Number of Larvae of Sesamia sppSampled
in three Varieties of Maizeduring 2009 Minor Season.
Weeks after Seedlings Emergence (WAE)
TREATMENT
4
5
Obatanpa
N0
1.35
2.15
N45
1.30
2.43
N60
1.35
2.73
N90
2.40
3.55
Mamaba
N0
0.85
2.28
N45
1.03
3.05
N60
1.58
3.63
N90
1.78
3.83
Golden Jubilee
N0
0.83
1.65
N45
1.25
1.83
N60
0.83
3.53
N90
2.30
4.03
LSD Variety
NS
NS
LSD Nitrogen
0.50*
0.75*
0.86*
1.29*
LSD Var. x N.
* = significant at 5% probability level
NS= not significant at 5% probability level
6
7
Variety X Nitrogen
8
9
10
1.88
2.58
3.60
3.65
1.65
2.13
2.80
3.18
1.03
1.35
1.23
1.55
0.95
1.28
1.03
2.20
0.70
0.70
0.70
0.90
1.45
2.28
2.95
3.83
1.25
2.08
2.23
3.60
1.25
1.45
2.53
2.73
1.15
1.45
0.95
1.15
0.70
0.70
0.83
0.85
0.83
1.58
2.43
3.55
0.58*
0.67*
1.16*
1.20
1.15
2.30
2.55
0.52*
0.60*
1.04*
1.33
1.68
2.35
2.38
0.42*
0.49*
0.84*
1.15
0.95
0.95
1.45
NS
0.35*
0.61*
0.83
0.83
0.83
0.90
NS
NS
NS
60
During the 2010 major season, no significant (P>0.05) differences on the number of
Sesamia spp were observed at 3WAE, 4WAE, 6WAE, and 7WAE in the various maize
varieties (Table 4.7). However, significant (P<0.05) differences were observed on the level of
infestation of the larvae of Sesamia spp with regard to the various maize varieties from the
8WAE to the 13WAE. Generally, infestation on Mamaba was significantly (P<0.05) higher
than Obatanpa and Golden Jubilee varieties. With regard to the levels of nitrogen, no
significant (P>0.05) differences on the population of Sesamia spp were detected at 3WAE and
4WAE. However, it was observed that 5WAE up to 13WAE significant (P<0.05) differences
in the number of Sesamia spp occurred. Similarly, significant (P<0.05) differences were
observed on the number of Sesamia spp from 5WAE to 13WAE when the interaction between
maize varieties and levels of nitrogen applied was assessed.
Significantly lower (P<0.05) numbers of Sesamia were sampled from plots which received
0kgN/ha than plots of 90kgN/ha.
61
Table 4.7 Different Levels of Nitrogen on the Number of Larvae of Sesamia spp
Sampled in three Varieties of Maizeduring 2010 Major Season.
Weeks after Seedlings Emergence (WAE)
TREATMENT
3
4
5
6
7
8
Variety X Nitrogen
9
10
11
12
13
Obatanpa
N0
1.00
1.40
1.20
1.65
0.70
0.70
0.70
0.70
0.70
0.90
0.70
N45
N60
1.33
1.40
1.10
1.30
1.40
0.90
1.30
1.45
0.90
1.20
0.70
1.93
1.00
0.90
0.70
0.90
0.70
0.70
0.70
0.70
0.70
0.70
N90
1.38
1.20
2.05
1.83
2.45
2.23
1.20
1.40
1.20
1.00
0.90
N0
1.40
1.10
1.20
1.08
0.70
0.70
0.70
0.70
0.70
0.70
0.70
N45
N60
1.50
1.70
1.48
1.10
1.10
1.68
1.75
1.85
0.90
1.85
1.10
2.25
0.70
1.20
0.70
1.40
0.90
1.60
0.70
1.20
0.70
1.20
N90
1.50
2.20
2.25
2.55
2.10
2.40
0.90
1.98
1.65
2.05
2.38
Golden Jubilee
N0
1.40
1.65
0.70
1.60
1.00
1.10
0.70
0.70
0.70
0.70
0.70
N45
1.50
1.30
1.00
1.68
0.70
0.90
0.70
0.70
0.70
0.70
0.70
N60
1.10
1.68
1.28
1.00
1.58
1.10
0.90
1.40
1.10
0.90
0.90
N90
1.50
1.93
1.28
2.45
2.50
1.50
0.70
0.90
0.70
1.50
1.70
LSD Variety
NS
NS
0.44*
NS
NS
0.32*
0.23*
0.22*
0.25*
0.26*
0.19*
LSD Nitrogen
NS
NS
0.51*
0.61*
0.47*
0.36*
0.27*
0.25*
0.29*
0.30*
0.22*
NS
NS
0.88*
LSD Var. x N.
* = significant at 5% probability level
NS= not significant at 5% probability level
1.05*
0.81*
0.63*
0.47*
0.44*
0.50*
0.52*
0.39*
Mamaba
62
4.4.3 The Different Levels of Nitrogen on Larvae of Eldana spin Three
Varieties of Quality Protein Maize.
Analyses of the 2009 minor season data presented in Table 4.8 showed that the
varieties of maize recorded no significant (P>0.05) differences at various growth stages after
seedling emergence on the population of Eldana sp at 6WAE, 7WAE, and 12WAE. On the
other hand, 8WAE up to 11WAE showed significant (P<0.05) effect on the number of
Eldanasp sampled during the study period. The highest number of Eldanasp recorded was
observed in Mamaba maize variety from the 8WAE, up to 12WAE. This was followed by
Golden jubilee and Obatanpa maize varieties in that order. With regard to the levels of
nitrogen, the number of Eldana sp sampled were statistically similar (P <0.05) at the 6WAE,
10WAE, 11WAE and 12WAE. However, it was observed that 7WAE up to 9WAE showed
significant (P<0.05) effect on the number of Eldanasp recorded. The plots fertilized with
90kgN/ha, 60kgN/ha and 45kgN/ha produced the highest number ofEldanasp. than plots with
nitrogen dose of 0kgN/ha. The interaction between nitrogen and maize varieties was found to
be significantly (P<0.05) higher at 6WAE up to12WAE.
During 2010 major season, no significant (P>0.05) differences on the number of
Eldana sp were observed between the maize varieties at 8WAE, 9WAE and 10WAE.
However, from 11WAE to13WAE observation showed significant (P<0.05) differences on the
number ofEldanasp sampled. The various nitrogen levels also showed significant (P<0.05)
differences at 8WAE up to 13WAE on the number of Eldanasp sampled (Table 4.8).
Generally, Mamaba variety significantly (P<0.05) showed the highest number of Eldana sp
from 11WAE to 13WAE and was followed by Golden Jubilee and Obatanpain that order.
Similarly, the interaction between nitrogen and maize varieties observations indicated
significant (P <0.05) differences in the level of infestation from 8WAE up to the 13WAE.
63
Significantly lower (P<0.05) number of Eldanaspwere sampled from plots which received
0kgN/ha than plots treated with 90kgN/ha.
The highest number of Eldanasp was observed in Mamaba maize variety followed by
Golden jubilee and Obatanpa maize varieties which were significantly (P<0.05) similar.
Similarly, significant (P<0.05) differences were observed on the number of Eldanaspfrom
8WAE to 13WAE when the interaction between maize varieties and levels of nitrogen applied
was observed.
64
Table 4.8 Different Levels of Nitrogen on the Number of Larvae of Eldana sp Sampled in Three
MaizeVarieties during 2009 Minor and 2010 Major Seasons
Weeks after Seedlings Emergence (WAE)
2009 Minor Seasons
TREATMENT
6
7
8
9
2010 Major Seasons
10
11
12
8
9
10
11
12
13
Variety X Nitrogen
Obatanpa
N0
1.35
1.85
1.58
1.78
1.90
1.88
1.95
0.70
0.70
0.90
0.90
1.20
0.70
N45
1.03
2.15
0.95
1.68
2.33
1.83
2.68
1.00
1.35
0.90
1.30
0.90
0.90
N60
1.25
1.38
1.48
1.58
2.55
2.35
2.58
2.00
1.63
1.10
1.10
1.20
0.70
N90
1.43
1.43
1.45
2.30
2.73
1.75
2.45
2.45
1.90
1.83
1.65
1.88
1.88
N0
1.43
1.30
1.90
2.05
2.83
2.25
2.68
0.70
0.90
0.90
0.70
0.70
0.90
N45
1.25
1.85
1.68
2.48
3.20
2.30
2.40
1.58
1.00
1.15
0.90
1.10
0.70
N60
1.45
0.83
2.30
2.28
2.70
2.40
2.50
0.70
2.70
1.45
2.20
1.95
2.13
N90
0.70
2.15
2.25
2.53
2.90
2.60
2.93
2.60
2.33
2.00
2.55
2.48
3.10
N0
N45
0.70
0.83
1.43
1.65
1.13
1.25
1.68
1.75
1.63
1.83
1.13
1.50
1.93
1.58
0.70
0.70
0.90
1.08
0.90
0.90
0.70
0.90
0.70
1.35
0.70
0.70
N60
N90
1.20
1.43
1.45
1.63
1.45
2.10
1.85
2.25
2.15
2.13
1.95
1.40
2.83
2.25
2.35
2.45
1.88
1.95
1.88
1.58
1.80
2.43
0.90
1.75
1.40
2.10
NS
NS
NS
0.60*
0.42*
0.49*
0.31*
0.36*
0.53*
NS
0.48*
NS
NS
NS
NS
0.35*
NS
0.63*
NS
0.52*
0.29*
0.33*
0.35*
0.40*
0.20*
0.24*
N. 0.61* 1.09* 0.89* 0.57* 0.69*
* = significant at 5% probability level
NS= not significant at 5% probability level
0.41*
0.65*
1.04*
0.85*
0.61*
1.06*
0.95*
0.95*
Mamaba
Golden Jubilee
LSD Variety
LSD Nitrogen
LSD Var.x
65
4.4.4 Percent Stem Borer Damage in 2009 Minor and 2010 Major Seasons as
Affected by Different Rates of Nitrogen.
During the 2009 minor and 2010 major cropping seasons, statistical analyses of the
various maize varieties indicated that differences in percent borer infestation were significant
(P<0.05). Similarly,the different nitrogen rates as well as the interaction between the nitrogen
levels and the maize varieties observed significant (P<0.05) differences in percentage stem
borer infested plants (Table 4.9).
During the 2009 minor season, significantly (P<0.05) high percent stem borer damage
was observed inMamaba maize variety followed by Obatanpa and Golden Jubilee in that
order. In the 2010 major season, similar results were obtained. With regard to the rates of
nitrogen applied to the plants, it was observed that increase in the levels of nitrogen
significantly (P<0.05) increased the percentage of the stem borer damage to maize plants.
Generally, the level of infestation was higher in the 2009 minor season than the 2010 major
season. Again, plots treated with 90kgN/ha nitrogen rates produced the highest percentage
damage maize plants. This was followed by plots treated with 60kgN/ha, 45kgN/ha and
0kgN/ha in that order (Table 4.9).
66
Table 4.9 Different Levels of Nitrogen on the Percent Stem Borer Damage during
2009 Minor and 2010 Major Seasons.
TREATMENT
2009 Minor Season
Percentage Stem Borer
Damage
Variety X Nitrogen
Obatanpa
N0
26.83
N45
28.95
N60
28.18
N90
37.40
Mamaba
N0
37.05
N45
41.73
N60
44.20
N90
50.78
Golden Jubilee
N0
19.38
N45
22.85
N60
27.00
N90
27.43
LSD Variety
6.89*
LSD Nitrogen
7.96*
LSD Variety x Nitrogen
13.78*
* = significant at 5% probability level
NS= not significant at 5% probability level
2010 Major Season
Percentage Stem Borer
Damage
6.05
8.98
10.50
17.18
6.40
7.80
16.93
25.55
6.43
10.75
11.10
16.53
2.37*
2.73*
4.73*
67
4.4.5 Different Levels of Nitrogen on the Number of Pupae Sampled in Three
Varieties of Maize
Field observations for the 2009 minor season revealed that the number of pupae
recorded at harvest was significantly (P<0.05) affected by the maize varieties, the different
nitrogen levels applied and the interaction between the nitrogen and the variety (Table 4.10).
During the 2010 major season however, significant (P<0.05) differences were observed only
inthe nitrogen levels. The number of pupae sampled during the 2009 minor season was
generally higher than the number in the 2010 major cropping season. Significantly (P<0.05)
high number of pupae was recorded in Mamaba maize variety. This was followed by
Obatanpa with the Golden jubileebeing the lowest. Table 4.10 shows that maize plants on
plots fertilized with 90kgN/ha were significantly (P<0.05) infested in both seasons. This was
followed by 60kgN/ha, 45kgN/ha and 0kgN/ha in both cropping seasons in that significant
order.
68
Table 4.10 Different Levels of Nitrogen on the Number of Pupae Sampled
During 2009 Minor and 2010 Major Seasons.
TREATMENT
2009 Minor Season
Number of pupae at harvest
Variety X Nitrogen
Obatanpa
N0
N45
N60
N90
Mamaba
N0
N45
N60
N90
Golden Jubilee
N0
N45
N60
N90
LSD Variety
LSD Nitrogen
LSD Variety x Nitrogen
* = significant at 5% probability level
NS= not significant at 5% probability level
2010 Major Season
Number of pupae at harvest
0.83
0.83
1.33
1.15
0.90
0.90
1.58
2.35
1.25
1.20
1.15
1.03
0.90
1.10
1.93
2.28
0.70
1.03
1.15
1.03
0.22*
0.25*
0.43*
0.70
1.30
1.78
2.90
NS
0.33*
NS
69
4.4.6 Different Levels of Nitrogen on Percent Plant Lodging in Three Varieties of
Maize
The percent plant lodging recorded during both cropping seasons is shown in Table
4.11 The analyses showed significant (P<0.05) differences occurring in the maize varieties,
and the interaction between the maize varieties and the different rates of nitrogen applied on
the percent plant lodging during 2009 minor season. No significant (P>0.05) differences were,
however, observed between the different rates of application of nitrogen on the percent plant
lodging. Percent plant lodging was significantly (P<0.05) higher in Mamaba variety than in
Obatanpa and Golden Jubilee. During the 2010 major cropping season, the differences
between the maize varieties, differences between the rates of nitrogen applied and the
differences between their interaction were all significant (P<0.05). As observed during the
2009 minor season, Mamaba variety significantly (P<0.05) suffered heavier lodging of plants
than the Golden Jubilee and Obatanpa varieties. However, the differences observed between
these varieties were not significant (P>0.05). Plant lodging on plots which received 0kgN/ha
was significantly (P<0.05) the lowest in comparison with the other rates of nitrogen
application in the 2010 major season. Plant lodging on plots fertilized with 90kgN/ha was
significantly (P<0.05) heaviest.
70
Table 4.11Levels of Nitrogen on the Percent Plant Lodging in the Three Varieties
of Maize during 2009 Minor and 2010 Major Seasons.
2009 Minor Season
TREATMENT
Lodge (%)
Variety X Nitrogen
Obatanpa
N0
N45
N60
N90
Mamaba
N0
N45
N60
N90
Golden Jubilee
N0
N45
N60
N90
LSD Variety
LSD Nitrogen
LSD Variety x Nitrogen
2010 Major Season
Lodge (%)
21.87
22.15
19.48
17.15
10.05
7.80
17.35
23.98
25.83
24.83
26.08
34.48
12.55
23.10
37.73
53.53
13.30
13.50
15.80
18.48
5.07*
NS
10.15*
7.08
9.15
17.60
30.63
2.81*
3.25*
5.63*
* = significant at 5% probability level
NS= not significant at 5% probability level
71
CHAPTER FIVE
DISCUSSION
5.1
The Rates of Nitrogen Applied and Crop Growth.
The results obtained from this study showed thatthe tallest plant height was produced with the
application rate of 90kgN/ha and the shortest being the application rate of 0kgN/ha. This
observation can be attributed to the fact that higher levels of nitrogen fertilizer promote
vegetative growth in maize.Generally, there was an increased in leaf area as well as the plant
height with increasing rate of nitrogen fertilizer. This results agreed with the previous findings
of Roth and Fox, (1990) that, higher rate of nitrogen promotes growth and leaf area during
vegetative development and also helps maintain functional leaf area during the growth period.
The highest plant height was observed in Obatanpa maize variety at 10WAP and 8WAP
during the 2009 minor and 2010 major seasons respectively. This was followed by Golden
Jubilee and Mamaba varieties.
The results of the data showed in Figure 4.2 indicated that significant differences in
plant girth were observed at 6, 7 and 8WAP during the 2010 major season in maize varieties.
The biggest plant girth was recorded in Golden Jubilee which was statistically similar to
Obatanpa at 8WAP. The smallest stem girth was recorded in Mamaba. Application of
90kgN/ha was found to have significantly enhanced maize plant girth followed by nitrogen
levels of 60kgN/ha and 45kgN/ha than 0kgN/ha. The smallest plant girth observed at 0kgN/ha
might be explained by the fact that nitrogen promotes growth and development of maize plant.
This observation confirms the work done by Tweneboah (2000) who reported that nitrogen
72
deficiency retarded growth of maize and caused stunted growth and poor root development.
The trend observed in stem girth growth is similar to that of plant height.
The study showed that the largest leaf area was recorded in Obatanpa variety in both
cropping seasons. This was followed by Golden Jubilee and Mamaba. Plots fertilized with
90kgN/ha, 60kgN/ha and 45kgN/haproduced the largest leaf area in that order. It is known that
nitrogen plays important roles in plant growth and development. This observation in this study
totally agrees with the findings of Raven etal. (1999)that nitrogen is a component of a number
of compounds (proteins, nucleic acids, chlorophyll) and has an important role in many plant
physiological processes.
With regard to the number of days to 50% tasselling and 50% silking, the least number
of days to 50% tasselling occurred in Mamaba in the 2009 minor cropping season (Table 4.3).
In the 2010 major season, however, the least number of days to 50% tasselling occurred in
Obatanpa. On the number of days to 50% silking, the maize varieties did not show any
significant differences in the 2009 minor season. However, in the 2010 major season, Mamaba
showed the least significant number of days to 50% silking than Golden Jubilee and Obatanpa.
In both seasons, the varieties of maize which received 0kgN/ha significantly resulted in the
highest number of days to 50% silking. The differences observed could be attributed to the
rates of nitrogen applied and the varietal differences in them. Obatanpa is an open pollinated
maize variety while Mamaba and Golden Jubilee are hybrid maize varieties. The genetic
attributes possibly influenced these varieties as to their tasseling and silking.
73
5.2.
The Different Rates of Nitrogen on Yield and Yield Components
The Golden Jubilee produced the largest number of cobs per plant as compared to
Obatanpa and Mamaba. The differences observed were however, not significant in 2009 minor
seasons but significant in 2010 major season. This might possibly be due to the fact that
Golden Jubileeis a hybrid maize variety and its genetic make up as well as the rates of
nitrogen applied could influence the production of cobs. It was also noted during the study
that number of cobs per plant did not increase with the increase in nitrogen in 2009 minor
season but significant in 2010 major season. This finding confirms the earlier findings of
Bangarwa et al.(1988) and Khan et al.(1999) that the number of cobs per plant did not
increase with the increase in nitrogen rates.
The analyses of the data in Table 4.5 revealed significant differences on the cob length
and cob width in both cropping seasons between the maize varieties. Obatanpa showed a
marginal increase over Golden Jubilee and Mamabain the 2010 major season.
The high value of harvest index (%) observed in Mamaba was statistically similar with
that Obatanpa maize variety in the 2009 minor season. On the contrary, Obatanpa in the 2010
major season showed the highest harvest index followed by Mamaba and GoldenJubilee. The
results possibly suggest that the supply of 90kgN/ha and 60kgN/ha are essential for favourable
partitioning of dry matter between grain and other parts of maize plant. The higher the
efficiency of converting dry matter into economic yield, the higher the value of harvest index
74
(%). Other workers such as Bangarwa et al.(1988) and Sabir et al. (2000) have
reported of similar results. Application of nitrogen at 0kgN/ha producedthe lowest harvest
index per plot.
Thousand(1000)-grain weight, maize grain yield (t/ha), and shelling percentage
(%),increased significantly (P<0.05) with increasing nitrogen levels. Maximum yield and yield
components were achieved with application rate of 90kgN/ha. Fertilizer rate of 60kgN/ha and
45kgN/ha also supported maizegrain yield compared to the 0kgN/ha. Thousand (1000)-grain
weight of Obatanpa was a slightly higher than that of Golden Jubilee and Mamaba in 2009
minor season. In the 2010 major season however, Golden Jubilee recorded the highest 1000grain weight. This observation could be attributed to the fact that Golden Jubilee is the yellow
version of Obatanpa and that they share some traits. The results obtained in this study are not
in conformity with the results obtained at the Crop Research Institute, Kumasi by Asiedu et al.
(2003) that the 1000-grain weight in Mamaba was heavier than that in Obatanpa. The 1000grain weight values of Obatanpa and Golden Jubilee observed over Mamaba were influenced
by the nature of their seeds which makes it compact and heavier than other maize varieties.
Besides, it could also be due to differences in grain filling period (partition factor).
Table 4.6 showed no significant differences in number ofgrains per cob observed
between the maize varieties in the 2009 minor season. Similarly, no significant differences
were observed in both the nitrogen applied and the interaction between the nitrogen and the
maize varieties during the 2009 minor season. However, significantly higher number of grains
per cob and grain yield per hectare was observed in the maize varieties during the 2010 major
season than the 2009 minor season. This observation could be attributed to the fact that the
75
2009 minor season showed significantly heaviest stem borer infestation than the 2010 major
season.
The highest number of grains per cob and grain yield per hectare was observed in
Obatanpa maize variety during 2009 minor season. This was followed by Golden Jubilee and
Mamaba in that order. This could partially be due to the good climatic conditions recorded
throughout the period (Appendix I).
During the 2010 major season, however, Obatanpa maize showed the lowest number of
grains per cob with Mamaba showing the highest which was slightly followed by Golden
Jubilee maize varieties. The differences observed, however, did not show any significant
differences. Again, the highest number of grains per cob and grain yield was observed in plots
fertilized with 90kgN/ha, 60kgN/ha and 45kgN/ha than plots fertilized with 0kgN/ha in the
maize varieties. With regard to the level of N needed for maize production the result obtained
in the study confirmed previous result of Lucas (1986) that yield response of maize to N
fertilizers could be obtained up to 150 kg N/ha. This study therefore shows that yield response
of various maize varieties to different rates of nitrogen follow the same trend. Increase in
maize grain yield with an increased in the rates of nitrogen was also observed by Luschinger et
al. (1999), Sabir et al.(2000) and Younas et al.(2002), in their investigations on nitrogen levels
and maize grain yield.
5.3
The Different Rates of Nitrogen and Stem Borers Infestation
Lepidopterous stem bores are among the most damaging pests of cereal crops
worldwide (Seshu Reddy and Sum, 1991). Their occurrence on cereal crops have also been
reported by several workers in Ghana (Kumar and Sampson, 1982; Sampson and Kumar 1983,
76
1985; Gounou, et al. 1992). A reviewed of stem borers and their control in Ghana had been
undertaken by Abu (1986).
The common species found in the study area include: The pink stalk borer
Sessamiacalamistis, S. botanephaga(Lepidoptera: Noctuidae)andthe African sugarcane
borerEldana saccharina (Lepidoptera: Pyralidae). Sesamia spp were the dominant maize
borers from the 3WAE up to 8 WAEand E. saccharina was most dominant from 9WAE up to
harvesting. Botchey (1984) also reported of a similar encounter with Eldanasp, making its first
appearance in the maize field9 weeks after crop emergence.
The number of stem borers collected from the experimental field fluctuated
significantly at weekly interval during the minor and the major cropping seasons.
The present study also revealed that infestation of the maize plants by stem borer
larvae was more in the minor season than the major season. This observation was reported by
Atkinson (1980) who indicated that heavy rains in the major season could reduce the incidence
of stem borers by preventing contact of males and females for mating. Similarly, Sampson and
Kumar (1983) reported that heavy rains increased predations and normally washed off eggs
and newly hatched larvae. Other reasons are thatduring the long period of fallow after the
minor season in December, most of the stem borers would die and the remaining moved to
alternate host plants which are less nutritive.Eldana saccharina lays its eggs in the soil and
during heavy rains the eggs get drowned and are destroyed. The rains may also destroy the
moth as well as larvae. Dispersing first and second instar larvae could have been easily
washed away by rains and that could explain the observation of Bowden (1976) that adults of
Sesamia spp which emerged at the beginning of the cropping season are smaller in terms of
numbers and less fecund than those emerging later in the year and that the combined effect of
77
smaller numbers and less fecund adults result in the lower incidence of Sesamia spp. in the
major season maize crop, This study also agrees with that of Girling, (1980) who reported
that maize stem borers are far more abundant in the minor season than in the major season and
that the minor season crop sometimes suffers a complete loss.
In this study, Sesamiaspp were found infesting the maize in both cropping seasons and
particularly high in the minor season which also agrees with work done by Endrody-Younga
(1968), who reported that Sesamia infestation in the Ashanti Region of Ghana was negligible
in the major season but very high in the minor season and thus causing serious damage to the
maize crop.
In this study, E. saccahrina infested the crops near maturity. This is also in agreement with
reports by Sampson and Kumar (1985) whose findings revealed that females of Eldana sp lay
their eggs in batches on dry leaves, thus partially explaining why the insect normally
infests matured crops.
Yield losses due to maize stem borer complex, were not investigated during the study
period. However, reported yield losses due to lepidopterous borers in Africa vary greatly (0100%) between ecological zones, regions and seasons (i.e. first and second seasons in West
Africa). The severity and nature of stem borer damage depends upon the borer species, the
plant growth stage, the number of larvae feeding on the plant and the plant’s reaction to borer
feeding. Observation during the study revealed that, feeding by borer larvae on maize plants
usually results in crop losses as a consequence of death of the growing point (dead heart),
early leaf senescence, reduced translocation, lodging and direct damage to the cobs (BosquePerez and Schulthess, 1994).
78
Leaf damage by stem borers was observed both in the major season and the minor
season which means that even though the infestation levels in the major season were not
as much as in the minor season, still damage was inflicted on the crops.
The role of ants in regulating borer population was not investigated in this study.
However, they have been reported to contribute to the reduction of borer population (Kumar
and Sampson, 1982). Some of these ants were either found on or inside the maize stem.
Observation showed that bored maize stems had no stem borer larvae in them when the ants
were present on the maize plant. The ants are predators and they attack and kill the dispersing
larvae.
The succession of the stem borer species was as follows; the noctuid, Sesamiaspp
entered the maize fields earlier in both major and minor seasons than the pyralidEldanasp.In
the major season,Eldanasp was found on the maize farm 10 weeks after plant emergence and
its population kept on rising, reaching relatively maximum population at harvest. Botchey
(1984) also reported of a similar observation with Eldanasp, making its first appearance in the
maize field 9 weeks after crop emergence. This observation is further supported by an earlier
experiment conducted by Bosque-Perez and Mareck (1990) in six locations in Southern
Nigeria from August to November, 1985 and 1986. These authors reported that Sesamiaspp
were the dominant maize borer up to 8 weeks after planting whileEldana sp was most
dominant from 9 weeks after planting. Again, Kaufmann (1983) observed that the larvae of
Eldana sp first appeared in the stem shortly before flowering of the host plant and reached its
peak at maturity. Possible reasons for this observation include the following:
79
a) The adult could not fly out to find mates. This agreed with the findings of Atkinson
(1981) who observed that the moth`s (Eldana sp) activity including egg-laying was
decreased or stopped altogether by high wind or rains
b) Eldana sp lays its eggs in the soil and during heavy rains the eggs are drowned and are
destroyed.
c) The rains may also destroy the moth as well as larvae. Dispersing first and second
instar larvae could have been easily washed away by rains.
In the 2009 minor and the 2010 major seasons, the highest percent number of stem
borer infestation as well as plant damage during the study period was significantly higher in
Mamaba maize variety. This was followed by Obatanpa and Golden Jubilee maize varieties.
The possible season could be that Mamaba maize genetically possesses a weaker stem which
could easily be bored into by insect pests. Significantly high percent number of stem borer
larvae and the high percentage plant damage were observed during the 2009 minor season than
the 2010 major season. This could be due to the fact thatduring the long period of fallow after
the minor season in December, most of the stem borers died and the remaining moved to
alternate host plants which are less nutritive. This study also agrees with that of Girling(1980)
who reported that maize stem borers are far more abundant in the minor season than in the
major season and that the minor season crop sometimes suffers a complete loss. Similarly, it
was observed during the 2009 minor and 2010 major cropping seasons that increased in
nitrogen rate resulted in an increased in stem borer infestation and crop damage.
It was also observed that the internodes 6-10 are the most preferred by the stemborers
due to their frequency of tunneling. Most of the ears were found on the internodes 7-9 which
is an indication that the stemborers feeding habit is related to the fact that of the plants’
80
nutrients are being channeled into the ears for development of the maize kernels. These
nutrients, probably required by these larvae for development and growth are concentrated in
this zone. This study also revealed that most of the tunneling occurred between internodes 6
and 10. The earstalk which connects the ear to the stem probably had most of the nutrients
hence the highest frequency of occurrence of larvae in the earstalk. It was also evident that the
node bearing earstalk and the earstalk were completely tunneled.
Tunneling across the
transverse section of stem is more harmful. The vascular bundles of monocotyledonous plant
like maize are scattered through the cross-section of the stem, therefore tunneling across cuts
through many vascular bundles and thus disrupts translocation of water, minerals and
photosynthase to other parts of the plant. This affects the physiology of the plant and in the
long run reduces yield since nutrient flow to the various parts of the plant is hampered.
Tunneling at both nodes and internodes destroys the strengthening tissues of the stem thus
weakening the stem and causing lodging of the maize plants.
It was also observed during the 2009 minor and the 2010 major cropping seasons that
the stem borers were marginally more prevalent in the crops fertilized with higher nitrogen
rate than in the crops fertilized with lower nitrogen rate. This observation agrees with the
report by Kfir et al. (2002) who stated that fertilized crops can enhance infestation and
survival of borers through an increase in the nitrogen content of the plant.
During the 2009 minor and 2010 major cropping periods, significant differences were
observed between the maize varieties on the number of lodged plants (Table 12). The percent
lodged plants were significantly high in the Mamaba variety. This could be due to high wind
speed, stem borer infestation, high fertilizer application and weak stem. This reflects the high
level of infestation and damaged observed in the Mamaba variety (Table 12). In the 2009
81
minor season, though the differences between the rates of nitrogen were not significant on the
percent lodged maize plants, high percentage lodging was observed with 90kgN/ha. In the
2010 major season, significantly higher percentage was observed on plots fertilized with
90kgN/ha. The percentage lodging of maize plants increased with increase in the level of
nitrogen applied due to high level of stem borer infestation and damage.
Stalk lodging of maize has been described as a major problem of maize production
(Hicks, 2004; Ransom, 2005). It was described as the breakage of the stalk below the maize
ear (Nielsen, 2006). According to Ransom (2005), stalk lodging is a term used to describe the
crop when its stem has partially or completely fallen over from their normal near-vertical
orientation. Ransom (2005) divided corn lodging into two major types. The first is root
lodging which occurs at the base of the plant or at soil level when the roots fail to anchor the
crop properly. The second is the stem lodging which occurs at any location on the stem above
the prop root level. Both types of lodging are accomplished by the plant bending markedly
from its usual upright position. On the effect of lodging on the plants, Hicks (2004) reported
that lodged plants are likely to yield lower and make harvesting more difficult. This agrees
with Ransom (2005) who reported that yield losses as high as 40% could result from lodging.
In the 2009 minor season revealed that percent number of pupae recorded at harvest
had significantly (P<0.05) affected the three maize varieties. The 2009 minor cropping season
recorded a higher percent number of pupae at harvest over the 2010 major cropping season.
The reason for this observation could be attributed to differences in climatic conditions in the
two cropping seasons (Appendix I). Climatic conditions are said to be more favourable for the
growth and development of the stem borer species complex in minor season than major
82
season. This totally agreed with findings of Sampson and Kumar (1983) that population of
pests also respond to changes in environmental conditions such as rainfall, temperature,
relative humidity and wind movement which vary with the seasons of the year.
In the 2009 minor season, the highest percentage of pupae infestation was recorded in
Mamaba maize variety. This was followed by Obatanpa with the Golden jubilee being the
lowest. The possible season could be that during the cropping seasons, the highest percent
borer infestation as well as plant damage was significantly observed in Mamaba maize variety
than Obatanpa and Golden Jubilee maize varieties. The differences observed was however, not
significant between the varieties of maize during the 2010 major season. The data presented in
(Table 11) revealed that plots fertilized with the highest nitrogen levels recorded the highest
pupae infestation in both 2009 minor and 2010 major cropping seasons.
83
CHAPTER SIX
SUMMARY, CONCLUSION AND RECOMMENDATION
6.1
Summary and Conclusion
The experiment was conducted at the maize farm of the University of Education,
Winneba, Mampong - Campus during August 2009 and January 2010, designated as 2009
minor cropping season for the first trial and April to July 2010, designated as the 2010 major
cropping season for the second trial in Ashanti Mampong. The trials were laid as 3x4 factorial
experiment fitted into Randomize Complete Block Design.
The study showed that the number of stem borers collected from the experiment field
fluctuated significantly at weekly interval during the minor and the major cropping seasons.
Internodes bearing the ears were the most preferred by the stemborers. Two (2) major
species of lepidopterous stemborer, namely,and Sesamia spp and Eldana spwere identified.
The noctuids, Sesamia spp entered the maize field earlier than the pyralids, ie. Eldana sp.The
level of infestation in the crop was significantly higher in the minor season than in the major
cropping seasons.
The application of 90kgN/ha did not only result in the highest stem borer infestation
but also produced thehighest maize grain yield in both cropping seasons in the studyarea.
However, application rates of 60kgN/ha and 45kgN/hawere also able to bring about increase
in the yield of maize. This will greatly benefit farmers in the area where supply of nitrogen
fertilizer is low or in cases where farmers are unable to afford the cost of high fertilizer input.
84
6.2. Recommendation

Farmers who want to plant Mamaba maize variety during the minor season in the study
area should do so at the right time, use nitrogen rates of 45kgN/ha and 0kgN/ha,
control weeds effectively to reduce heavy stem borer infestation. Since Mamaba is the
most vulnerable maize varieties to maize stem borers.

Higher nitrogen application results in higher stem borer infestation but the three maize
varieties did not show significant differences in maize grain yield and hence 60kgN/ha
and 45kgN/ha nitrogen rates could be used to avoid volatilization, heavy plant lodging
and cost of production.

Tentatively, farmers in this zone could plantObatanpa and Golden Jubilee maize
varieties during both cropping seasons and plant Mamaba during the major cropping
season.

Further studies should be conducted to validate the results obtained in this study.
85
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APPENDICES
Appendix I. Rainfall, Temperature and Humidity Patterns in 2009 and 2010 for
Mampong-Ashanti.
Month
January
February
March
April
May
June
July
August
September
October
November
December
Total
Rainfall
(mm)
Trace
131.4
110.6
138.8
164.6
376.7
273.5
17.6
99.3
138.6
45.2
33.4
127.5
Temp
Max
33.4
33.6
33.4
32.6
32.3
30.7
29.1
28.0
29.4
30.9
32.0
32.7
2009
(oC)
Min
21.8
23.2
23.2
22.9
22.9
22.1
21.5
21.9
22.1
22.1
22.2
23.1
Humidity (%)
High
76
92
93
95
96
98
97
97
97
98
98
97
Low
36
54
57
61
61
67
73
76
71
67
60
56
*Source: Ghana Meteorological Agency – Kumasi, 2009 & 2010.
97
Rainfall
(mm)
14.7
52.7
52.6
77.3
108.8
225.8
83.0
113.1
165.9
99.3
Temp
Max
33.6
35.2
34.3
33.8
32.4
30.9
29.6
29.4
30.1
-
2010
(oC)
Min
22.9
23.3
23.3
23.4
23.3
22.3
21.7
22.1
22.1
-
Humidity
(%)
High
95
94
94
94
96
97
97
97
98
-
Low
50
47
54
56
63
68
69
70
69
-