Groundnut Production in Zimbabwe

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
Group / Variety / Growth
Habit / Days to maturity
Lowveld / Middleveld / Highveld / Seed
Colour / No. Kernels per Kg
Short season / Valencia R2
Bob white
Natal common
Plover
Nyanda
Falcon / Bunch
Bunch
Bunch
Bunch
Bunch
Bunch / 85-95
110
110
110
110
110 / 95-105
120
120
120
120
115 / 105-115
130
130
130
130
120 / Tan
Red
Pale Pink
Yellowish brown
”
Pink / 3 450
3 300
3 300
4 000
3 300
3 300
Medium Season / Swallow / Spreading bunch / 120 / 130 / 140 / Dark Red / 2 800
Long season / Makulu Red
Egret
Flamingo / Spreading bunch
”
” / 150
150
150 / 160
160
160 / 170
170
170 / Dark Red
Pink
Light red / 2 .000
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:

Chemicalg/100 kg Seed

Thiram 50 WP180

Thiram 80 WP110

Thiulin Seed Dressing180

Brassicol 75 WP250

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 / Altitude (metres) / Planting date
Dry land / Short season / Below 900
900-1500
Above 1500 / 14-30 Nov
10-20 Nov
1-14 Nov
Long season / All altitudes / As early as possible
Irrigated / Short season / Below 900
900-1200
1200-1500
Above 1500 / 14-30 Nov
10-20 Nov
1-14 Nov
15-30 Oct
Long season / Below 900
900-1200
1200-1500
Above 1500 / 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
P2O5
K2O / Nil
Nil
Nil / Nil
20-40
20-40 / 20-30
40-60
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