Tillage Effects on Soil Properties, Growth and Yield of Cocoyam
(Xanthosoma sagittifolium Schott) on an Alfisol of Southwest, Nigeria
Adekiya, A. O. 1, Ojeniyi, S. O.1 and Agbede, T. M.2
1
Department of Soil, Crop and Pest Management, Federal University of Technology, P.M.B.
704, Akure, Ondo State, Nigeria; E-mail address: adekiya2009@yahoo.com
2
Department of Agricultural Technology, Rufus Giwa Polytechnic, P.M.B. 1019, Owo, Ondo
State, Nigeria; E-mail address: agbedetm@yahoo.com
Abstract
Hitherto information on tillage requirement of cocoyam (Xanthosoma sagittifolium Schott) is
scarce on Alfisols of humid tropics. Five tillage methods were compared as to their effects on
soil physical and chemical properties, growth and yield of cocoyam on an Alfisol at Owo in
the forest-savanna transition zone of southwest Nigeria. The experiment which consisted of
five tillage methods [manual clearing (MC), manual ridging (MR), manual mounding (MM),
ploughing + harrowing (P+H) and ploughing plus harrowing twice (P+2H)] was carried out
over 3 years at two sites in a randomized complete block design with three replications. In
the first two years (2007 and 2008), P+H had the least soil bulk density and highest growth
and yield, whereas in the third year (2009), MC produced the lowest soil bulk density and
best performance of cocoyam. Manual clearing (MC) had the highest values of soil chemical
properties in both years (2008 and 2009). Averaged over the 3 years, P+H, MR and MM had
lower soil bulk density hence better growth and yield compared with P+2H and MC.
Compared with P+2H, MC, MM, MR and P+H increased cocoyam cormel yield by 10, 21,
23 and 32%, respectively. The corresponding increases in corm yield were 7, 15, 13 and
21%, respectively. Bulk density rather than soil chemical properties dictated the performance
of cocoyam in the Alfisol of the experimental area. Ploughing plus harrowing twice (P+2H)
degraded soil quality. For small farms, either MR or MM is recommended while P+H is
recommended for large scale farming of cocoyam.
1.
Introduction
The estimate of world population with an annual growth rate of 1.8% as reported by Litvin
(1998) would put the current world population at about 6.3 billion. This figure will exceed 8
billion by the year 2020. To be able to feed the growing population adequately, food
production should approximately double its present output. The fallout of the effort to
achieve food security in Nigeria is the stimulation of greater interest in research, production
and consumption of cocoyam (Mbanaso et al. 2005). Onwueme (1991) observed that the
global average yield for cocoyam cormels is only about 6 t ha-1. This implies that more
research is desirable to raise production level to meet the current demand for food.
One of the major constraints to crop production in the tropics is the low fertility status of
most of the soils. The majority of Alfisols available for crop production in the tropics is
strongly weathered and inherently of low organic matter and nutrient status (Lal 1987). In
addition, Alfisols have a weak structure, and are highly susceptible to crusting, compaction
and accelerated erosion (Lal 1987) leading to low crop yields. Cocoyam like any other root
385
and tuber crops is a heavy feeder exploiting greater volume of soil for nutrients and water
(Osundare 2004). Tillage is an important cultural practice that can be used to increase the
yield of cocoyam. In humid tropics where most farmers are poor and fertilizer is expensive,
soil working and tillage methods can temporarily serve as an alternative to fertilizer
application (Adekiya and Ojeniyi 2002).
Traditionally, cocoyam is grown on heaps, ridges and occasionally on flat, manually cleared
soils. Before now, a wide range of mechanised tillage methods e.g. ploughing, harrowing,
ridging and disking are use for crop production in southwest Nigeria, without the benefit of
experimental data on soil properties and crop response. Hence, there is need to examine the
potential of growing cocoyam using traditional tillage method and mechanized ploughing
plus harrowing and their effects on nutrient uptake and cocoyam performance. There is lack
of information on tillage requirements of cocoyam on the tropical Alfisol. This research is
necessitated by the fact that previous tillage studies in the tropics on cocoyam are
concentrated on acidic Ultisols of southeast Nigeria (Anikwe et al. 2007; Ndaeyo et al. 2003;
Hulugalle et al. 1985). Tillage methods for crops are known to depend on soil type and depth,
micro-climate and topography. Tillage studies mainly compared the effect of conventional
tillage practices on cocoyam yields. The few studies undertaken largely neglected minimum
or traditional and conventional tillage practices and their effects on soil properties and
cocoyam yield. The few studies carried out in Nigeria and other tropical countries produced
inconclusive and controversial result under different tillage practices (Hulugalle et al. 1985).
Howeler et al. (1993) suggested that research efforts should be directed towards the
characterization of the physico-chemical and biological factors which determine the tillage
requirement of a given soil for a given root crop.
This study compared five tillage methods (manual clearing, manual mounding, manual
ridging, ploughing plus harrowing and ploughing plus harrowing twice) as to their effects on
soil physical and chemical properties, growth and yield of cocoyam on an Alfisol of
southwest Nigeria.
2.
Materials and Methods
2.1
Site description and tillage treatments
Field experiments were carried out on Alfisols at two sites (Site A and Site B), in Owo in the
forest-savanna transition zone of southwest Nigeria during 2007, 2008 and 2009 cropping
seasons. The average annual rainfall varies from 1000-1240 mm. The sites were under two
years fallow after arable cropping.
Five tillage treatments were replicated three times in a randomized complete block design.
The treatments were (a) manual clearing (MC), (b) manual ridging (MR), (c) manual
mounding (MM), (d) ploughing plus harrowing (P+H) and (e) ploughing plus harrowing
twice (P+2H). Each plot was 12 m by 10 m. Tillage treatments were carried out in April each
year. The same location was used in each site for the 3 years of the experiment.
2.2
Planting of Cocoyam
Cocoyam was planted in April each year of the experiment after tillage. Cocoyam
(Xanthosoma sagittifolium cv. Owo local) cormels weighing about 150 g were planted. One
cormel was planted per hill at a spacing of 1 m x 1 m to give a plant population of 10,000
plants ha-1. Weeding was done manually at 45 and 110 days after planting.
386
2.3
Soil sampling and analysis
Prior to the commencement of the experiment in 2007, soil samples were taken from each site
for the determination of soil physical and chemical properties. After one month of imposition
of treatments, soil samples were also collected five times each year from each site for the
determination of bulk density and gravimetric moisture content. Total porosity was calculated
from bulk density using a particle density of 2.65 Mg m-3. Soil temperature was determined at
15:00 h with a soil thermometer inserted to 10 cm depth. Five readings were made per plot at
each sampling time and the mean computed.
Soil samples were also collected at harvest of cocoyam from 0-15 cm depth in 2008 and 2009
on per plot basis and similarly analysed for routine chemical analysis. The soil samples
collected were bulked, air-dried and sieved using a 2-mm sieve and analysed for soil organic
matter, N, P, K, Ca, Mg and pH. Samples were analysed as described by Carter (1993). The
organic matter was determined by the procedure of Walkley and Black using the dichromate
wet oxidation method. Total N was determined by micro-Kjeldahl digestion method, P was
determined by Bray-1 extraction followed by molybdenum blue colorimetry. K, Ca and Mg
were extracted using ammonium acetate. Thereafter, K was determined on a flame
photometer and Ca and Mg by the EDTA titration method. Soil pH was determined by using
a soil-water medium at a ratio of 1: 2 using the digital electronic pH meter.
2.4
Determination of growth and yield parameters
Ten plants were selected per plot for determination of plant height and leaf area at 168 days
after planting when the cocoyam plant reached its peak growth. Plant height was measured by
metre rule and leaf area by graphical method. The cormel and corm yields were determined
by weighing on a balance to determine their fresh weights.
2.5
Statistical analysis
Data collected from each experiment were subjected to Analysis of Variance (ANOVA) test
and treatment means were compared using the Duncan’s Multiple Range Test (DMRT) at
p=0.05 probability level (Steel et al. 1997).
3.
Results and Discussion
3.1
Results
3.1.1 Initial soil fertility status
The pre-treatment soil analysis results for 0-15 cm soil depth for Site A and Site B
respectively, gave soil properties as sand (682 g kg-1, 660 g kg-1), silt (160 g kg-1, 140 g kg-1),
clay (158 g kg-1, 200 g kg-1), bulk density (1.55 Mg m-3, 1.55 Mg m-3), pH ( 5.58, 5.72), soil
organic matter ( 2.97%, 2.90%), Total N ( 0.18%, 0.19%), P ( 4.5 mg kg-1, 5.0 mg kg-1 ),
K ( 0.15 cmol kg-1, 0.13 cmol kg-1), Ca ( 1.78 cmol kg-1, 2.39 cmol kg-1) and Mg ( 0.81 cmol
kg-1, 1.03 cmol kg-1). The soils at both sites were sandy loam, acidic and had high bulk
density. The soils at both sites were generally low in essential nutrients except Mg for site A
and Ca and Mg for site B which were adequate.
387
3.1.2 Effect of tillage methods on soil physical properties
Tables 1, 2 and 3 show data on the effect of tillage methods on soil physical properties in
2007, 2008 and 2009 cropping seasons, respectively. In the first two seasons, ploughing +
harrowing (P+H) had relatively low bulk density and higher total porosity compared to other
tillage methods. Ploughing + harrowing twice (P+2H) and manual clearing (MC) treatments
had the highest bulk density and expectedly least porosity. There were no significant
differences (p=0.05) between the bulk densities of mound and ridge. MC had higher moisture
content compared with other treatments. This was significantly followed by P+2H. There
were no significant differences in the moisture content of MR, MM and P+H. Lower
temperatures were recorded in the first two seasons at both sites from manually cultivated
plots. The highest temperature was recorded by MR and MM and was not significantly
different from that recorded by P+H and P+2H.
In the last cropping season (2009), the highest bulk density and least porosity were recorded
in the P+2H plots, although these values were not significantly different from that produced
by P+H at both sites (Table 3). The least soil bulk density were recorded in MC plots. MC
significantly produced (p=0.05) the highest moisture content and lowest temperature
compared to other tillage methods.
The mean values of bulk density (Mg m-3) for the 3 years of the experiment for MC, MR,
MM, P+H and P+2H were 1.56ab, 1.46b, 1.46b, 1.45b and 1.64a, respectively. The values for
total porosity (%) were 41.1ab, 44.9a, 44.9a, 45.3a and 38.1b, respectively. The equivalent
values for moisture content (%) were 17.95a, 13.98bc, 13.62c, 13.15c and 15.15b,
respectively. Soil temperatures (0C) were 29.3c, 32.9a, 33.4a, 32.2ab and 32.6a, respectively.
Mean followed by similar letters are not significantly different according to Duncan’s
multiple range test (DMRT). P+2H significantly (p=0.05) produced the highest bulk density.
P+H had the least bulk density and highest porosity. MC had the least soil temperature and
highest moisture content. Moisture content was on the decreasing order of MC>P+2H>MR,
MM and P+H. The values of soil temperature for all tilled treatments were similar. After 3
years of cultivation, the bulk density of P+2H exceeded that of MC, MR, MM and P+H by 5,
12, 12 and 13%, respectively.
3.1.3 Effect of tillage methods on soil chemical properties
Table 4 contains data on the mean values of soil chemical properties for 2008 and 2009. MC
significantly (p=0.05) produced the highest values of soil organic matter (SOM.), N, P, K, Ca
and Mg compared with other tillage methods. In all cases, there were no significant
differences between soil chemical properties of MR and MM. P+2H produced least values of
soil chemical properties.
3.1.4 Effect of tillage methods on growth parameters and yield
Tables 5, 6 and 7 show data on the effect of tillage methods on the growth and yield of
cocoyam. In the first 2 seasons of cropping cocoyam, at both sites, P+H plots produced the
plant having the highest plant height, leaf area, cormel and corm yields while MC and P+2H
plots produced the least values. There were no significant differences in these parameters in
MC and P+2H plots and between MR and MM plots. However, in 2009 (third) season, MC
produced the highest values of growth and yield parameters while P+2H had the least values
of growth and yield.
388
The mean values of plant height (cm) for the 3 years of the experiment for MC, MR, MM,
P+H and P+2H were 53.5bc, 57.8ab, 57.9ab, 63.2a and 49.0c, respectively. The
corresponding values of leaf area (cm2) were 119.5c, 139.5b, 137.8b, 158.5a and 112.5cd,
respectively. Cormel yields (t ha-1) were 9.5c, 10.6ab, 10.4ab, 11.4a and 8.6c, respectively.
The respective values of corm yields (t ha-1) were 6.5bc, 7.0ab, 6.9ab, 7.4a and 6.1c,
respectively. Mean followed by similar letters are not significantly different according to
Duncan’s multiple range test (DMRT). P+H significantly produced higher values of growth
and yield, although these values were not statistically different from the one produced by MR
and MM. P+2H produced the least values. Averaged over the 3 years of the experiment,
compared with P+2H; MC, MM, MR and P+H increased cocoyam cormel yield by 10, 21, 23
and 32%, respectively. The corresponding increases in corm yield were 7, 15, 13 and 21%,
respectively.
3.2
Discussion
In the first 2 years of the experiment and the mean over the 3 years, MC and P+2H plots had
higher bulk densities compared with other tillage methods. The higher bulk density of MC
was adduced to non-tillage and compaction. Ojeniyi and Adekayode (1999) had earlier
reported higher bulk density for MC compared with tilled soils in southwest Nigeria. The
higher soil bulk density produced by P+2H compared with MR, MM and P+H was attributed
to wheel-traffic of tractor and implement passes (Agbede 2005). There were no significant
differences between the bulk density of ridge and mound,. This agrees with the report of
Ojeniyi (1991). The low bulk densities of P+H, MR and MM compared with MC could be
due to loosening effects of tillage (Agbede 2008). P+H with less bulk density had higher
values of total porosity. Also in the first two years and the mean of the 3 years, MC soil had
higher moisture content and lower temperature compared with tilled soils. This could be
related to organic matter in soil surface which acted as mulch to reduce temperature and loss
of water by evaporation.
In 2009 (third season), the highest bulk density produced by tractorized treatments (P+2H and
P+H) compared with MC was due to break down of soil structure due to slaking and raindrop
impacts. Ojeniyi and Agboola (1995) had earlier reported that repetitive tillage degraded soil
qualities and caused rapid collapse of soil structure. Therefore in the sub-humid and humid
regions of the tropics, the high intensity rainstorms tend to nullify the loosening effects of
tillage. Intensive soil cultivation which may increase soil bulk density is intimately connected
with reduced porosity and the alteration of pore size distribution (Ojeniyi 1990). This
explains the low porosity of tilled soils compared with manually cleared soils.
Manual clearing (MC) had the highest values of SOM, N, P, K, Ca and Mg in both years
compared with other treatments. This can be related to the presence of organic matter. The
decline in the nutrient reserve of tilled soils especially P+2H could be adduced to high
destruction of soil structure during land preparation which encourages soil erosion (soil wash)
that preferentially removes colloidal fraction with high “enrichment ratio” (Agbede 2008;
Agbede and Ojeniyi 2009), resulting in a progressive depletion of its nutrient reserves. MR
and MM produced higher values of soil nutrients compared with P+H and P+2H. This was
due to minimal disturbance of soil by MR and MM compared with mechanized tilled soils.
The degradation of soil brought about by repeated passes of tractor and implements which
encourage heavy erosion and leaching explains the lower values of nutrients on P+2H
compared with P+H. There were no significant differences in soil nutrient contents between
MR and MM. This is similar to the report of Agbede and Adekiya (2009) who also did not
find significant differences in soil chemical properties in manually ridged and mounded soils.
389
In the first 2 seasons of study at both sites, P+H produced the highest values of plant height,
leaf area, cormel and corm yields compared with other tillage methods. This finding can be
related to lower bulk density and higher porosity produced by P+H. Pardales and Villamayor
(1983) also found that in the Philippines ploughing and harrowing once was sufficient for
cocoyam (taro) production. In the last season (third year), the highest performance of
cocoyam under MC was due to better soil conditions resulting from this treatment that helped
in better establishment, growth and yield of cocoyam. These are associated with reduced soil
bulk density and higher porosity of manually cleared soil in the third season, compared with
other tillage systems. The higher yield produced by MC is also consistent with the higher
SOM, N, P, K, Ca and Mg values of the treatment. The least growth and yield of P+2H could
be due to deterioration of soil quality resulting from repeated passage of implements and low
SOM and plant nutrient. The mean values of growth and yield for the 3 years of the study
showed that P+H, MR and MM resulted in the highest values of growth and yield. This is
also consistent with the low mean soil bulk density and high porosity recorded for these
treatments. P+2H with highest bulk density had inferior growth and yield. The differences in
bulk density dictated differences in cocoyam growth and yield in the 3 years of the
experiment. The influence of bulk density seems to be more pronounced on performance of
cocoyam than on soil chemical properties. This is so because reducing bulk density was
consistent with increase in cormel and corm yields, although MC had the highest SOM, N, P,
K, Ca and Mg status, cocoyam yield was lower compared with P+H, MR and MM
treatments. These results suggest that a small decrease in soil bulk density can considerably
increase cocoyam yield. From this study, the degree of tillage appears to be indispensable for
sustainable cocoyam production on tropical Alfisols. However, because of the degradation of
the soil quality due to P+2H, it should be discouraged for cocoyam production. P+H, MR and
MM were found to be better for soil conservation.
4.
Conclusion
A degree of soil manipulation appears to be indispensable for cocoyam production. The
differences in bulk density dictated the differences in the growth and yield of cocoyam
between manual clearing, manual tillage and mechanized tillage systems. P+H, MR and MM
increased growth and yield of cocoyam relative to MC and P+2H. These tillage systems
(P+H, MR and MM) showed promising potential in conserving soil fertility on an Alfisol
compared with P+2H tillage methods. P+2H was found to be most disadvantageous to soil
and cocoyam productivity and therefore not recommended for cocoyam cultivation. On a
small scale, either manual ridging or manual mounding is recommended. For large scale
cocoyam production, ploughing + harrowing is recommended.
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391
Table 1. Effect of tillage methods on soil physical properties in 2007
Bulk density (Mg m-3) Total porosity (%, v/v) Moisture content (%)
Tillage method
SITE A SITE B
SITE A SITE B
Manual clearing (MC)
1.55a
1.54a
41.4c
Manual ridging (MR)
1.39b
Manual mounding (MM)
Ploughing + harrowing (P+H)
Temperature (0C)
SITE A SITE B
SITE A
SITE B
41.9c
20.50a
22.3a
28.1b
30.0c
1.38bc
47.5b 47.9ab
15.10c
16.60c
32.0a
34.1a
1.38b
1.38bc
47.9b 47.9ab
14.72c 16.01c
32.5a
34.5a
1.26c
1.32c
52.5a 50.2a
14.95c 16.50c
31.5a
32.9ab
Ploughing + 2 harrowing (P+2H) 1.54a
1.56a
41.9c 41.1c
17.50b 20.40b
31.8a
33.4a
Values followed by similar letters under the same column are not significantly different at p=0.05 according to
Duncan’s multiple range test (DMRT)
Table 2. Effect of tillage methods on soil physical properties in 2008
Tillage method
Bulk density (Mg m-3) Total porosity (%, v/v) Moisture content (%)
SITE A SITE B SITE A SITE B
SITE A SITE B
Temperature (0C)
SITE A SITE B
Manual clearing (MC)
1.56a
1.55a
41.1c
41.5b
17.90a
18.40a
29.7b
31.1b
Manual ridging (MR)
1.40b
1.38b
47.2b
47.9a
14.30c
13.60c
33.1a
34.2a
Manual mounding (MM)
1.39b
1.39b
47.5b
47.5a
14.10c
13.30c
33.9a
34.6a
Ploughing + harrowing (P+H)
1.27c
1.32bc
52.1a
49.8a
14.35c
13.50c
32.8a
33.3a
Ploughing + 2 harrowing (P+2H)
1.55a
1.57a
41.5c
40.8b
16.10b
16.50b
32.9a
33.9a
Values followed by similar letters under the same column are not significantly different at p=0.05 according to
Duncan’s multiple range test (DMRT)
392
Table 3. Effect of tillage methods on soil physical properties in 2009
Bulk density (Mg m-3)
Total porosity (%, v/v)
Moisture content (%)
Temperature (0C)
Tillage method
SITE A SITE B
SITE A SITE B
SITE A
SITE B
SITE A SITE B
Manual clearing (MC)
1.56c
41.1a
41.5a
13.30a
15.30a
27.5b
29.1b
Manual ridging (MR)
1.59bc 1.60cd
40.0a
39.6a
11.60b
12.70b
31.1a
33.1a
Manual mounding (MM)
1.59bc
1.60cd
40.0a
39.6a
11.10b
12.50b
31.5a
33.4a
Ploughing + harrowing (P+H)
1.75a
1.76ab
33.9bc 33.6bc
9.10cd
10.50cd
30.3a
32.4a
1.82a
31.2c
8.60d
9.80d
30.9a
32.8a
Ploughing + 2 harrowing (P+2H) 1.79a
1.55d
31.3c
Values followed by similar letters under the same column are not significantly different at p=0.05 according to
Duncan’s multiple range test (DMRT)
Table 4. Mean values of soil chemical properties for 2008 and 2009 cropping seasons
P (mg kg-1)
K (cmol kg-1)
0.15a
4.3a
0.12a
1.90a
0.84a
2.56b
0.13b
3.8b
0.10b
1.58b
0.77ab
5.53ab
2.53b
0.13b
3.8b
0.10b
1.57b
0.75bc
P+H
5.14ab
2.19c
0.11c
3.0c
0.09c
1.43c
0.70c
P+2H
5.06b
2.06cd
0.09d
2.5d
0.07d
Tillage method
pH (water)
SOM (%)
MC
5.60a
2.85a
MR
5.51ab
MM
N (%)
Ca (cmol kg-1)
1.40d
Mg (cmol kg-1)
0.69c
Values followed by similar letters under the same column are not significantly different at p = 0.05 according to Duncan’s
Multiple range test (DMRT)
MC= Manual clearing; MR= Manual ridging; MM= Manual mounding; P+H= Ploughing + harrowing; P+2H= Ploughing + 2 harrowing
393
Table 5. Effect of tillage methods on the growth and yield of cocoyam in 2007
Plant height (cm)
Leaf area (cm2 )
Cormel yield (t ha-1)
Corm yield (t ha-1 )
Tillage method
SITE A SITE B
SITE A SITE B
SITE A
SITE B
SITE A
SITEB
Manual clearing (MC)
60c
66c
152c
161c
10.7c
11.3c
7.1c
7.5c
Manual ridging (MR)
72b
73b
186b
192b
12.5b
12.9b
7.9b
8.7b
Manual mounding (MM)
71b
73b
183b
189b
12.3b
12.6b
7.9b
8.6b
Ploughing + harrowing (P+H)
80a
83a
207a
216a
14.5a
14.6a
8.8a
9.7a
Ploughing + 2 harrowing (P+2H)
63c
68bc
156c
165c
11.1c
11.5c
7.2c
7.6c
Values followed by similar letters under the same column are not significantly different at p=0.05 according to Duncan’s
multiple range test (DMRT)
Table 6. Effect of tillage methods on the growth and yield of cocoyam in 2008
Plant height (cm)
Leaf area (cm2 )
Cormel yield (t ha-1)
Corm yield (t ha-1)
Tillage method
SITE A
SITE B
SITE A
SITE B
SITE A
SITE B
SITE A
SITE B
Manual clearing (MC)
55c
51c
110c
108c
9.7c
10.2c
6.8c
7.1c
Manual ridging (MR)
64b
62b
140b
157b
11.9b
12.2b
7.8b
8.1b
Manual mounding (MM)
63b
60b
142b
150b
11.6b
12.0b
7.7b
8.2b
Ploughing + harrowing (P+H)
74a
76a
188a
195a
13.8a
13.9a
8.6a
9.3a
Ploughing + 2 harrowing (P+2H)
56c
51c
113c
112c
10.1c
10.5c
7.0c
7.3c
Values followed by similar letters under the same column are not significantly different at p=0.05 according to Duncan’s multiple
range test (DMRT)
394
Table 7. Effect of tillage methods on the growth and yield of cocoyam in 2009
Plant height (cm)
Leaf area (cm2)
Cormel yield (t ha-1)
Tillage method
SITE A SITE B
SITE A
SITE B
SITE A
SITE B
Manual clearing (MC)
49a
40a
98a
88a
7.1a
Manual ridging (MR)
40b
36b
87b
75b
Manual mounding (MM)
41b
35b
87b
Ploughing + harrowing (P+H)
35c
31c
Ploughing + 2 harrowing (P+2H)
30d
26d
Corm yield (t ha-1)
SITE A
SITE B
7.8a
5.6a
5.1a
6.0b
6.1b
4.7b
4.5b
76b
5.9b
6.0b
4.6b
4.5b
76c
69c
4.9cd
5.3cd
4.1c
4.0c
69d
60d
4.7d
5.0d
3.6d
3.6d
Values followed by similar letters under the same column are not significantly different at p=0.05 according to Duncan’s multiple
range test (DMRT)
395