Groundnuts are the second most-widely grown legume in Uganda, after beans.
There has been a substantial increase in the growing of groundnut as both a food and cash crop because of increased awareness of its value as a source of protein (23-25% content) and oil (45-52% content).
It also has the advantage of generating residual nitrogen in the soil, which benefits subsequent crops, especially when groundnut residues are incorporated into the soil during ploughing.
Despite the high local demand for groundnuts, farmers’ yields continue to be low, averaging 700 per acre of dry seed. Well managed plots, using the right varieties, can yield 1-1.4 tonnes kg/per acre or more. There is no doubt about the market for groundnuts. At the moment, a kilogramme goes for sh3,500- sh5,000. Groundnut paste goes for sh6,000. To commercially produce an acre of good quality groundnuts, the average investment is about sh1.5m.
Most varieties mature in three months.
Groundnut is not suited to growing in very dry areas or at altitudes above 1,500m (around 5,000ft). Optimum temperatures are 27-30°C for vegetative growth and 24-27°C for reproductive growth. Between 450mm and 1250mm of evenly distributed rainfall is required annually for good growth and yield.
All soils, other than heavy, are suitable for growing groundnut, but the best are deep, well drained sandy loam or loamy sand soils.
Groundnut requires adequate levels of phosphorus, potassium, magnesium and particularly calcium, which are required for maximising yield and good quality seed. You can know the actual requirements after a soil test.
For farmers who use tractors, deep turn the soil to bury residue and weeds, using a disc plough, three to four weeks before planting. In wet, low-lying areas it may be worth considering using ridges in which to plant groundnuts. The use of ridges can prevent waterlogging and improve weed control and harvesting. Ridges should be made at, or just before, sowing and they should be flat-topped.
According to plant scientists, it is important for the farmers to grow high quality seed of varieties adapted to their farm situations. Seeds can be considered basing on their regional performances.
It is good practice to purchase certified seeds from reputable suppliers. An acre takes around 50kg of seeds. It is important to be aware that some varieties of groundnut seed require a period of dormancy between harvesting and sowing and the leaflet on varieties should be consulted before sowing the same seed soon after harvesting.
Farmers should plant as soon as there is adequate moisture in the ground to ensure good germination. In general, groundnuts are planted between 15 February and 15 April during the first season and in early August for the second season. Planting early in the season helps to improve yields and seed quality and reduce the incidence of rosette disease. Long duration varieties should only be planted with the first rains in the first season.
Groundnuts respond better to residual fertility than to direct fertilisation. Direct fertilisation may not increase the yield or quality of the groundnuts. Farmers are cautioned, if possible, a soil test needs to be carried out to establish whether fertiliser or lime is required. Lime is only necessary when the soil pH is below 5.8. If soil a test is not done, fertiliser recommendation is 25kg of NPK per hectare. A sack of NPK costs between sh130,000 and sh150,000.
Alternatively, a farmer can use organic farmyard manure to fertilise the farm.
Groundnuts cannot compete with weeds, particularly 3–6 weeks after sowing, therefore, early removal of weeds is important. Generally, two to three weedings are recommended, the first before flowering and at least one other during pegging.
The first one is at least two weeks after germination, five weeks after germination and eight weeks. If early weeding is done well and crop spacing recommendations followed, then the weeds that come up later are smothered with the vigorous growth of the crop.
Using chemicals against weeds Pre and post emergence herbicides may be used to eradicate weeds, but have been found to be costly for most small scale farmers. Herbicides such as alachlor (lasso) can be used before crop and weed emergence, and bentazone (Basagran) and fluazifop-p-butyl (Fusilade Super) following emergence.
Groundnut rosette disease is caused by a complex of viruses that are transmitted by aphids. It can occur at very high levels and can often produce 100% loss in yield.
There are two forms of symptoms seen in the crops: ‘chlorotic’ (yellow and stunted) and ‘green’ (green and stunted). Late planted crops and wide spacing can increase the incidence of rosette disease so these should be avoided. Rosette resistant varieties of groundnut are available (e.g. Serenut 5r, Serenut 2, Igola 1) and these eliminate the need for spraying insecticides to control the aphids. If a high yielding non-rosette resistant variety is grown (e.g. Serenut 1) then insecticides will be needed.
Systemic insecticides can be sprayed 14 days after crop emergence and then at 10-day intervals for a total of four sprays. There are two main forms of the leaf spot fungal disease — early and late.
Early leaf spot may occur as early as two weeks after crop emergence. Lesions produced by this fungus are roughly circular, dark brown on the upper surface with chlorotic (yellow).