Groundnut production in Zimbabwe
Lecturer: T. Madhanzi
Agro 405- Food Crop Production
History
Widely believed to have originated in S. America. The Spaniards and Portuguese
brought groundnuts to Africa. Slaves from Africa introduced groundnuts in N.
America. Mutsege (dry roasted ground nuts) is popular in Zimbabwe.
Climatic and rotational limitations
In areas up to 1500 masl, the varieties Makulu Red, Egret and Flamingo will produce
maximum yields under irrigation. Good yields could be achieved in the lowveld with
Nyanda (new), Plover and Natal common. Although their yield potential is not as high
as the long season varieties, their short season length makes them suitable for
rotations. Similarly Valencia R2, Swallow, and Bobwhite could be considered in the
highveld.
Groundnuts should be grown in a very wide rotation to prevent the build up of
diseases, such as Cercospora leaf spot. Under dry conditions they must not be
cropped more often than once in four years. Under irrigation, where land producing
two crops per year; it is thought groundnuts can be grown as the fourth crop on the
same land. Spraying the field with fungicides and removal of voluntary plants and
crop residues can control the disease.
In the middleveld and highveld where harvesting of wheat interferes with planting of
late maturing varieties, groundnuts can be planted after a winter fallow. Use of
medium maturing varieties like swallow can help.
Varieties
Variety description
Groundnut varieties are divided into three groups according to the time taken to reach
maturity.
Maturity Variety
Group
Short
season
Medium
Season
Long
season
Growth
Habit
Days to Middleveld Highveld Seed
maturity
Colour
Lowveld
No.
Kernels
per Kg
Valencia R2
Bob white
Natal
common
Plover
Nyanda
Falcon
Swallow
Bunch
Bunch
Bunch
85-95
110
110
95-105
120
120
105-115
130
130
3 450
3 300
3 300
Bunch
Bunch
Bunch
Spreading
bunch
110
110
110
120
120
120
115
130
130
130
120
140
Makulu Red
Spreading
bunch
150
160
150
150
160
160
Egret
Flamingo
”
”
Tan
Red
Pale Pink
Yellowish
brown
Pink
Dark Red
4 000
3 300
3 300
2 800
170
Dark Red
2 .000
170
170
Pink
Light red
2 000
1 000
”
Seed dressing and inoculant
Plant populations may be drastically reduced if a seed dressing is not used. Use a
fungicide such as Thiram, Thiulin, or Brassicol at the following rates:
Chemical
Thiram 50 WP
Thiram 80 WP
Thiulin Seed Dressing
Brassicol 75 WP
g/100 kg Seed
180
110
180
250
Research has shown that it is not essential to inoculate seed; good nodulation will be
ensured by inoculation.
Soils and Land preparation
Soil suitability
Best results achieved in deep well drained soils e.g. sands, loamy-sands and sandy
loams as heavier soils cause problems at harvesting. Build out beds (tramline system)
on heavier soils and irrigate prior to lifting the pods. Do not attempt planting on soils
of poor soil fertility or soil well known to be worked out.
Land preparation
Well-ploughed lands with good tilth result in good germination. The rows should
allow good tractor access for cultivation, spraying and lifting e.g. 4 rows at 350 mm
between plants and the next set of rows 750 mm apart. Making ridges helps in lifting
pods when the soil is dry and hard at harvesting.
Planting
Planting date
Early planting maximises yields and depends on variety and temperature, delaying
results in decreased yield. Optimum planting date is given below:
Varieties an planting dates
Type of production
Variety type
Dry land
Short season
Irrigated
Long season
Short season
Long season
Altitude (metres)
Below 900
900-1500
Above 1500
All altitudes
Below 900
900-1200
1200-1500
Above 1500
Below 900
900-1200
1200-1500
Above 1500
Planting date
14-30 Nov
10-20 Nov
1-14 Nov
As early as possible
14-30 Nov
10-20 Nov
1-14 Nov
15-30 Oct
8-23 Oct
1-15 Oct
23 Sept-7 Oct
15-30 Sept
Early planting for maximum yield is dependent upon good management at reaping.
Both early and late maturing varieties must be lifted when they reach maturity to
prevent sprouting.
Plant spacing and depth of planting
An average row of 450 mm has been shown to give the highest yields. This spacing
allows access of machinery. The spacing between plants is 100-150 mm depending on
soil type. Shallow planting where the soil dries out results in patchy germination
while deep planting delays germination.
Plant population and seed rate
Plant population for early maturing varieties should be 250 000 to 300 000 per
hectare. For late maturing cultivars, use half the population (125 000 – 150 000 plants
per hectare).
Approximately 100 kg/ha should be sufficient for both types.
Planting methods
Groundnuts can be planted either by machine or by hand. Grade the seeds to reduce
breakages when using planters fitted with plates inclined at an angle. Cover all seeds
with sufficient soil when using a planter with a hoe. Pre-irrigation will help planting
furrows keep their shape.
Fertilisation
Although groundnuts do well in loose well-drained soil, heavier textured soils give
the highest yield. The crop should be grown in rotation with heavily fertilised crops as
they respond better to fertiliser applied the previous season. However a proper soil
analysis will give a good picture on the required nutrients.
The cropping history and previous fertiliser applications determine how much
fertiliser to apply. The table below give an average recommendation:
Fertiliser nutrient
Nutrient status of the soil
Good
Medium
Poor
Fertiliser requirement in kg/ha
N
Nil
Nil
20-30
P2O5
Nil
20-40
40-60
K2O
Nil
20-40
40-60
N.B the rates can be increased by 50 % where high yields can be attainable e.g. in
early planted, irrigated crops.
Calcium status of the soil
Groundnuts have a high calcium requirement, particularly during pod development;
low availability will result in decreased shelling percentage and a high incidence of
pops or empty pods. Gypsum should be applied at the rate of 200-400 kg/ha to ensure
an adequate available calcium status.
Method and time of application
All fertilisers are applied before planting. These should be broadcast and ploughed in
deeply before ploughing. Gypsum is applied on the top of rows at early flowering
under dry conditions.
Lime requirement
The pH of the soil should be above 5.3 (CaCl2) for maximum yields, and must be
modified where possible by adequate application of lime. The lime applied should
contain large amounts of magnesium. An application of 200-300 kg ground dolomite
is adequate.
Weeds
Weed control is very necessary if high yields are to be maintained. Groundnuts are
planted closely spaced and hence herbicide control is very essential. The herbicides
should breakdown within three months and should not affect the following winter
crop.
A certain amount of hand and mechanical weeding is essential as herbicides will not
have complete control.
Problem weeds
Shamva grass, Rapoko grass, pig weed, Apple of Peru, Mexican clover, blackjack,
Mexican marigold, Gallant soldier, wandering Jew and yellow nutsedge.
Groundnut diseases
Cercospora leaf spot
Initially appears as small chlorotic spots on the lower leaflets 7-9 weeks after planting
and on long season varieties 4-5 weeks after planting. Infected leves die prematurely.
All varieties on the market are susptible.
Other diseases are: Phoma wet blotch, Grey mould, Sclerotonia wilt, Root and crown
rot, Rosette virus.
Pests
The following insects are important and correct insect control is essential as excessive
chemical residue results in rejection of crop on the external market. The insecys are as
follows:
Termites, cutworms, Aphids, Hilda (Hilda patruelis) Semi-looper caterpillars, Looper
caterpillars, Heliothis bollworm, Leaf hoppers and Snout bettles.
Irrigation
High yields of late maturing groundnuts can be produced under irrigation.the
increased production is due to:
Early production- plants utilise excellent growing conditions.
Adequate supply of water
Early control of diseases
The points to borne in mind in irrigation of ground nuts are:
Pre-planting: Irrigate to field capacity. Soil moisture must be brought to field
capacity to a depth of 900-1200 mm. This will be 75 mm of water on sandy soils and
125 mm of water on heavy soils.
Post planting: A light irrigation will be necessary to assist germination. This
irrigation can be used to incorporate pre-emergent herbicides. It is critical not to
irrigate at the cracking stage as this was found to retard emergence.
Post emergence
Vegetative phase
Covers germination to early flowering. If the soil is irrigated to field capacity and the
groundnuts have germinated successfully, no irrigation will be required for 4-6 weeks.
This length will depend on soil type, and prevailing environmental conditions. An
irrigation will be required between 4-8 weeks if early rains are unduly late.
Reproductive stage
This period lasts from 8 weeks to 16 weeks after planting. Groundnuts are particularly
sensitive to drought at flowering, peg and rapid pod production. At this stage, a light
irrigation is necessary to prevent the 50-100 mm soil from drying. An irrigation of 30
mm should be applied every five days if moisture is limited.
Grain filling stage
An adequate moisture schedule is necessary during this period, which continues up to
harvesting. An irrigation of 60 mm should be applied every seven to ten days, if
required.
Irrigation to assist harvesting
An irrigation of 15 mm may be required to assist harvesting under certain conditions.
Harvesting
Is a broad term used to describe the operations necessary to remove groundnuts from
the soil and prepare them for the market.
Aflatoxin
Conditions prevailing just before harvesting until seed moisture content is reduced to
10 % encourage storage fungal growth. Of the many fungi that can attack groundnuts
at this stage, Aspergillus flavus is the most dangerous as it produces toxins known as
aflatoxins. This toxin leads to death of both animals and humans. Correct harvesting
and removal of moisture to correct levels reduces fungal attack and growth.
Determination of maturity
Development of a brown discolouration due to tannin inside the pod has been used as
an indication of the degree of maturity. A method based on the testa colour has been
proven to be more reliable. The testa of a mature kennel:
-Tends towards drying out
- is not easily rubbed off by hand;
- is thin and has a papery texture
- has developed a colour of the expected variety