Groundnut farming is an important crop cultivated by smallholder farmers in Kenya. In many countries groundnuts are consumed as peanut butter or crushed and used for the groundnut oil or simply consumed as a confectionary snack roasted, salted or in sweets. In other parts of the world they are boiled, either in the shell or unshelled.

groundnut farming in kenya

Despite its name, groundnut, also called peanut, is not a nut. It is a member of the legume family, which also includes common bean, cowpea and soybean amongst others.

Groundnut grows well in the arid and semi-arid tropics, does not require large amounts of inputs and fits well into rainfed crop rotations and intercrop systems. In some countries, it covers up to 60% of the area under crop production.

Groundnut varieties

Throughout Africa many different varieties of groundnut are grown. These vary quite widely in important characteristics such as growth habit (either bunch types which grow upright, or runner types which grow close to the ground), number of seeds per pod, colour of seed coat, seed size, time to maturity of crop, dormancy of seed after harvest, oil content and taste.

Varieties found in Kenya include Red Oriata, Manipinta, Makulu Red, Bukene, Homabay, Texas Peanut, Red Valencia and Atika.

Varieties of groundnut take varying times to reach maturity: from early varieties, which are ready to harvest in 85-95 days after planting, to medium varieties, which are ready to harvest in 95-120 days, and late maturing varieties, which are ready from 121 days onward after planting. Although early maturing varieties are more drought resistant or escape onset of drought, the later maturing varieties tend to have higher yields and larger sized seed.

The varieties grown include traditional local ones that have been grown by smallholder farmers for many generations as well as new, improved varieties. The improved varieties have been developed by breeders and researchers in the national research programmes and or regional/international research institutes (e.g. ICRISAT) to have certain desirable traits, such as high grain yield, high oil content, early maturing to cope with increased risk of drought, or resistance and tolerance to drought and important pests and diseases.

The many different varieties of groundnut fall into four main groups:

  • Virginia types can be either spreading or upright in growth habit and are mostly late maturing. They have large kernels and are used in confectionary, roasted and salted, or roasted in the shell.
  • Runner types are spreading and mostly late maturing. They have medium sized kernels and  are used for making confectionary and butter, and also for salting.
  • Spanish types are mostly upright and are easier to pull from hard soil because the pods cluster around the tap root and they also have strong pegs. They have small to medium sized kernels with high oil contents and so are good for crushing for oil. They are also used in confectionary, as salted nuts and made into butter.
  • Valencia types are upright with small to medium sized kernels. They are usually roasted and sold in the shell.

Smallholder farmers need to check which varieties are available locally. If they are aiming to sell their produce to a specific buyer then they need to ensure the variety they select meets the buyer’s requirements in terms of size, colour, taste and other characteristics.

Groundnut production per acre

Production per acre on groundnut farming in Kenya mostly depends on the variety used and environmental factors.

A groundnut variety like Red Valencia produces 2.2 tonnes per hectare while the Manipita produces up to 2.4 tonnes (2,400kgs) per hectare every season.

Cost of groundnuts in Kenya

In Kenya you cannot walk in a shop and miss groundnuts packed in small sachets going for Sh20 to Sh300 depending on the size and flavor that has been added to it.

It is estimated that groundnuts retail at Sh12,000 per 100kilograms, where one is likely to earn a whopping Sh192,000 in just 90 days on the lower side.

The crop requires less maintenance and adds valuable nitrogen to soils if compared to maize.

Soil requirements on groundnut farming

Groundnut grows best on deep, loose, well-drained sandy soils without compaction layers. Such soils are easily penetrated by pegs and roots and permeated by water. The crop can also more easily be pulled up at harvest without leaving pods behind in the soil. Such soils are not prone to water-logging; groundnut cannot tolerate water-logging. Sandy, sandy loams or loamy sand soils are all suitable.

If a handful of soil rolled between the palms of the hand can be formed into a stable ball or flattened into a ribbon then the soil has a high clay content. This is not suitable for groundnut cultivation.

The soil should also be light coloured. This indicates that it is relatively low in organic matter, which helps prevent fungal diseases. It also means that the soil will not stain the pods, which can reduce the market value of the crop if it is sold in the pod.

The pH should be 5.5 to 7.0 (slightly acidic to neutral). Groundnut cannot tolerate saline soils.

The groundnut plant produces runners (horizontal stems) which in turn produce flowers at each node. These flowers self-pollinate and produce an anchor or peg which penetrates the ground. The groundnut pod is produced underground at the tip of the pegs. The topsoil must thus have a low clay content (less than 20%) with a loose structure so that the peg may penetrate the soil freely.

Water

Depending on the type of groundnut being grown, the crop requires between 250 and 1,000 mm of rain during the growing period: extremely early maturing varieties need 250-400 mm; early varieties 300-500 mm; late maturing varieties 500-1,000 mm.

If the rainfall is above 1,000 mm then groundnut should be grown on ridges unless the soil is very well drained.

Temperature requirements

Optimum temperatures for growing groundnut are 25-30° C. Temperatures above 35° C are detrimental to groundnut production. Under lower temperatures, the germination is delayed; the delay in germination exposes the seeds to soil pathogen attack for a longer period.
Below 17° C, crop growth almost ceases. Cooler temperature, especially at night, will also delay harvesting.

The lower limit for germination of groundnuts is around 18°C. Temperatures between 20-30°C result in 95% germination. However at 33°C this declines to 84%. Optimum germination temperatures are thus between 20-30°C with a minimum of 18°C.

The temperature of the water absorbed by the seed is also critical as far as germination is concerned. If the water temperature is initially low and gradually increases we find reduced germination. Planting in cold wet soil is therefore unsuitable. Planting in warm soils results in fast germination and healthy seedlings. Do not plant in dry soil and irrigate with cold water.

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The warmer the environment, the faster the plant reaches the reproductive phase. Flower formation is closely related to mean temperature on condition that the variation between day/night temperature does not exceed 20°C. The most flowers are formed at a day temperature of 27°C, while a warm day (29°C) and a cool night (23°C) gives the highest pod formation.

Land preparation for groundnut farming

Groundnut requires a deep seedbed without compaction layers or a hardpan. This means that groundnut is more suited to conventional tillage than to conservation agriculture.

As soon as the previous crop has been harvested, the stalks and other crop residues should be cut into small pieces and incorporated into the top 10 cm of soil, either using a hand hoe or a tractor or oxen pulled disc plough. This allows the crop residues time to decay and helps prevent root rot disease in the groundnut crop.

Deep ploughing breaks the hardpan, buries weed seeds deeper making them less likely to be a problem later, and leaves the soil easier for roots and pegs to penetrate and for the pods to be pulled from the ground at harvest.

Groundnut can be grown either on flat beds or ridges. Ridges are recommended if water-logging is a problem. Also, groundnut grown on ridges tends to have higher yields. This is probably because the soil is looser which enables better rooting and pod formation.

If box ridges are spaced at 75 cm apart, double rows of groundnut can be planted along them at a row spacing of 30 cm. This results in the soil being rapidly covered, which shades out weeds.

If water scarcity is likely to be an issue, tied ridges can be used for moisture conservation by reducing runoff and enhancing percolation.

If the soil is acidic, lime should be applied.

Ideally, a phosphorus (P) fertilizer such as SSP or TSP should be applied before planting.

Crop rotations

Groundnut should not be grown on the same piece of land for successive years. Rather it should be grown in a rotation system, with groundnut being grown every 2 to 5 seasons. There are several reasons for this, including:

  • to prevent build-up of pests and diseases, such as nematodes, white mould, leaf spots and insect population
  • to avoid depletion of soil nutrients and improve organic matter
  • to improve physical structure of soil and avoid loss of humus due to the soil loosening that occurs at harvest.

Groundnut is considered a soil depleting crop if the whole plant is removed but a soil improving crop if the vines and leaves are returned to the soil.

Good crops to include in a rotation system with groundnut include maize, sorghum and millet. Other suitable crops include cassava, sweet potato and sunflower.

Crops to avoid in rotations with groundnut include soybean and other legumes, tobacco, cotton and tomatoes. This is mainly due to the risk of nematodes and other soil-borne diseases.

Groundnut also does well on virgin land and after a grass fallow.

Groundnut and heavily fertilized cereals are an especially good rotation: maize following groundnut had been reported to show a 20% increase in yield. This is due to the groundnut’s ability to fix nitrogen (N) from the atmosphere. Groundnut following on from heavily fertilized cereals benefit from the residual nutrients in the soil.

A good example of a groundnut-cereal rotation is groundnut grown in season 1, maize grown in season 2, 3 and 4 with heavy application of fertilizer, and then groundnut grown in season 5. Alternatively, a cereal could be grown one season and then groundnut the next, reverting to a cereal in season 3.

If it is unavoidable to plant groundnut in successive seasons, soil fertility may be maintained with regular application of manure and fertilizer, and the risk of diseases can be reduced by deep ploughing to bury all crop residues as well as applying other crop protection measures.

Intercroping groundnut

Results obtained for groundnut intercrops by researchers have often been inconsistent and some experts are therefore reluctant to recommend this practice. In this section, some information is presented on intercropping. Based on the information given and their own preferences and conditions, farmers might like to try intercropping for themselves.

Groundnut is tolerant of shading – yields will only be reduced if subjected to very shady conditions. Groundnut has therefore been successfully grown as intercrops with crops, such as cereals and cotton, and can also be planted under tall crops such as bananas, pigeon peas, castor beans, sugar cane, or even permanent crops such as coconut palms, oil palms.

When groundnut is intercropped with maize, sorghum or millet, the total yield of the intercrop and the total profit can be higher than for either grown as a sole crop.

The choice of planting pattern will depend on whether farmers prioritise the cereal or groundnut. As an example, if sorghum and groundnut are being grown in an intercropping system and the farmers prioritizes sorghum, then an intercrop pattern with 2 rows of sorghum alternated with 1 row of groundnut should be used. Alternatively, if the farmer prioritises groundnut, then 2 rows of groundnut alternated with 1 row of sorghum should be used.

If the farmer just wants to achieve the highest combined yield and profit then 2 rows of groundnut alternated with 1 row of cereal will usually be the best option.

Fertilizer schedule on groundnut farming

Groundnut responds well to fertilizers that contain useful nutrients such as P, N, K, Ca, Mg and others. Although affordability may be a problem for smallholder farmers, applying fertilizers is important to harvest optimum groundnut yields in a sustainable manner for market oriented groundnut production system.

In rotations in which groundnut follows heavily fertilized crops, such as maize, the groundnut can benefit from the residual nutrients remaining in the soil from the previous cropping season.

Usually the most important nutrient needed during the early stages of growth is phosphorus (P); most of the groundnut production regions in Africa are known to be deficient in P. One option is to apply 20 kg P per hectare during land preparation just before planting (e.g. during making ridges), for example:

Either 250 kg per hectare single superphosphate (SSP): 25 g SSP should be broadcasted for every one square metre during land preparation for planting. This is equivalent to about 7 beer or soda bottle-tops level full of SSP fertilizer.

Or 100 kg per hectare triple superphosphate (TSP): 8-9 g TSP should be broadcasted for every one square metre during land preparation. This is equivalent to just about 1 beer or soda bottle-top heaped full of TSP fertilizer.

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Or 100 kg per hectare diammonium phosphate (DAP): 10 g DAP should be broadcasted for every one square metre during land preparation. This is equivalent to 2 beer or soda bottle-tops level full of DAP fertilizer. Once the fertilizer is broadcasted, it has to be covered with soil, and then the groundnut seed can be planted.

In addition, if farmers have previously experienced a large number of empty shells – sometimes called ‘pops’ – gypsum should be applied to provide a readily available source of calcium (Ca): 400-1000 kg per hectare gypsum should be applied on top of the plants at peak flowering stage. This is equivalent to 40-100 g of gypsum applied to every square metre. The gypsum will fall to the soil at the base of the plants where it will make Ca available in the top 5 cm of soil, where the pods will be developing.

Under most conditions, groundnut fixes enough N from the air through symbiotic relations with rhizobium to avoid deficiency throughout its life cycle. However, N deficiency can occur due to poor and eroded soils, lack of or inefficient rhizobium in the soil, drought and high temperatures. Hence, N applied to the crop at the rate of 10 to 30 kg per hectare can be useful. The crop could obtain the required N if DAP is used as P source as DAP also supplies N: 100 kg DAP per hectare will supply 20 kg N per hectare.

Application of manure

In place of or in addition to mineral fertilizers, farmers can also apply manure. In addition to supplying nutrients, manure also improves soil health, helps reduce aflatoxin contamination and also helps balance soil acidity. If available, 2 handfuls of manure can be applied per planting hole / hill.

Planting groundnuts

Sources of seed: The sources of seed for planting could be from the informal (e.g. own saved seed) or the formal (e.g. certified seed) seed systems, or both depending on the amount
required and accessibility.

Farmers can use own saved seed for 1 – 3 years, but it is advisable to purchase certified seed every 2-3 years to avoid build-up of disease problems and to maintain the genetic integrity of the variety.

Seed treatment

If using own-saved seed, this should be stored in the pod until 1-2 weeks before planting when they should be carefully shelled. Prior to planting the seed should be sorted; small, shrivelled, immature, skinned, split or otherwise damaged and mouldy seed should be rejected.

Before planting, it is advisable to treat seed to prevent blight and other fungal diseases, and also some pests, such as termites and millipedes. In some countries, combined products are available that include both one or more fungicide plus an insecticide.

Smallholder farmers should seek advice from their extension officer or local agro-dealer.

The best way to treat seeds before planting is to half fill a manually operated mixing drum with seed and then to add the correct amount of pesticide, carefully following the instructions as indicated on the product label. The drum is then slowly rotated to ensure thorough coverage of the seed. Suitable drums can be made relatively inexpensively by local roadside manufacturers using largely scrap materials.

In some areas, it may be possible to buy pre-treated seed. This eliminates the need for the smallholder to treat seed themselves although safety precautions should be taken when handling and storing the seed – hands should be washed after handling the seed and the seed must be stored out of reach of children and animals.

Before using any agrochemicals, the manufacturer’s instructions must be carefully read and/or advice sought from the local agro-dealer or extension worker.

Seed sowing

Early planting is recommended, soon after the rainy season begins – delaying planting can reduce both yields and quality of grain/seed. Planting should therefore occur within 2 weeks of the onset of the rains. A warm most soil is ideal. However, planting immediately after heavy rain should be avoided as the seeds can absorb too much water, which leads to rotting.

Seed should be planted about 6 cm deep in either holes or a shallow furrow. The holes or furrows should then be filled in and the soil compressed to ensure good contact between the seed and soil. Too shallow planting will result in patchy germination as the surface soil can dry out if there is no further rainfall after planting. Planting too deep will delay germination.

Some experts recommend planting two seeds per hole, which increases the quantity of seed required for planting. If this is done thinning is not needed: the seed is expensive and thinning can disturb the small plants. Preferably just one seed can be planted per hole provided the germination rate is high (more than 85%). It is important to determine germination percentage in the seed lot 3-4 days before planting so the seed rate can be adjusted accordingly and also to detect the  presence of post-harvest seed dormancy.

Gap filling can be done within the first 10 days of planting if uniform emergence is not achieved for good stand establishment.

Germination test

To determine the germination rate of groundnut seed, 50 seeds should be placed on 4 layers of newspaper which have been thoroughly wetted. The seeds should be spaced with 2 cm between seeds in a row and 4 cm between rows. The newspaper is then rolled and tied with thread or secured with an elastic band. The newspaper needs to be kept wet by adding water as needed each day. Five days later, the number of seeds which have germinated is counted.

For example, if 50 seeds have been used and 44 germinate, the germination rate is: (44/50) x 100 = 88%, which is a good rate of germination, i.e. more than 85%.

Groundnut Spacing

Recommended spacing varies with the growth habit of the variety grown and nature of crop cultivation (irrigated or rainfed, fertility level). Bunching varieties (e.g. Spanish types) are planted with smaller spaces between rows and plants than semi-spreading and runner varieties (e.g. Virginia types). The aim should be to obtain full ground cover as quickly as possible.

In general, bunching types should be planted with 30-45 cm between rows and 7.5-10 cm between plants in a row; runner types should be planted with 60 cm between rows and 10-15 cm between plants in a row.

The optimum spacing will, however, vary from variety to variety with the recommended spacing between rows reaching as high as 90 cm; ideally advice should be sought locally as to the optimum spacing for the chosen variety under the local conditions. A wider row spacing leaving uncovered ground allows proliferation of thrips/aphids, which can carry viruses (rosette, peanut bud necrosis, peanut stem necrosis, peanut mottle and peanut stripe diseases), and promotes weed growth.

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In general, a lower plant population is used in rainfed cultivation to avoid inter-plant competition  or soil moisture in case of prolonged dry spells. Smaller spacing could be used for irrigated  groundnut production, as there will not be competition for moisture.

Inoculation

Being a legume, groundnut is able to fix atmospheric nitrogen and convert this important nutrient into a form that the plant can use to help it develop and grow. Like other legumes, the groundnut does this through partnership with certain types of bacteria, called rhizobia, which exist in nodules in the plant’s root system.

The rhizobium species that can nodulate with groundnut is often naturally present in the soil. If groundnut has not been grown before in an area it may, however, be absent. In this case, it can be beneficial to artificially inoculate the seeds before planting with a commercially prepared inoculant that contains the right type of rhizobium.

Inoculants suitable for use with groundnut are available in some Africa countries, including Kenya  and Zimbabwe.

Compared with other legume crops, the use of inoculants on groundnut can be difficult. One reason is that groundnut seeds are fragile; if they are split during handling they will not germinate, so it can be hard to apply the products to the seed. Secondly, it is usually recommended that groundnut seed is treated with a fungicide and insecticide to prevent problems with pests and diseases during the early stages of growth.

These products may be toxic to the inoculants, which contain live bacteria, so it may not be possible to apply living inoculants as well as chemical pesticides.

Before using an inoculant together with chemical pesticides as seed treatments expert local agronomist advice should be obtained.

Weeding

Groundnut does not compete well with weeds and yields will be severely reduced if the crop is not adequately weeded.

Weed control is especially important when the plants are small, during the first 6 weeks, and as the pod is setting. Usually 2-3 weedings will be needed. Later, if the correct plant spacing has been observed, the crop will cover the ground effectively preventing weed growth.

Crop rotation helps control weeds. Also, good preparation of the field, with deep turning of the soil, will help ensure the seed bed is weed-free.

Some farmers use pre- and post-emergence herbicides although many smallholder farmers may find these to be too expensive.

Weeding groundnut needs to be done with care:

  • Avoid covering the developing plants with soil as this increases the risk of disease and reduced yield.
  • Take care when walking through the field when the crop is flowering to prevent disturbing the flowers.
  • At pegging, avoid disturbing the soil near the plants: at this stage pull weeds by hand and avoid use of hoes.

Irrigation

Although groundnut is considered to be a relatively drought tolerant crop and performs well in the semi-arid tropics, some varieties are more tolerant than others. Smallholder farmers should check which varieties are available locally and which of these are most drought tolerant if this is a major concern.

To ensure high yields, groundnut requires adequate moisture at two critical stages in its growth cycle: during the first 2 weeks, from planting to emergence of the seedlings, and around the time of peak flowering, pegging and pod development – this period lasts around 8-9 weeks.

If available and needed, light but frequent irrigation should be used during these periods. The sprinkler method of irrigation is found more efficient and beneficial to groundnut. Flood irrigation is not a good method as it wastes water, results in overwatering and trampling of plants in the field by persons engaged in irrigation.

Harvesting

Timing: Groundnut produces flowers daily over several weeks. This means that, even on the same plant, while some pods will be mature, others will be developing. This makes it difficult to know when to harvest the groundnut crop.

Correct timing of harvest is, however, important – harvesting too early or too late will lead to serious yield losses and decreased quality, and increased risk of contamination with aflatoxins, which can cause serious, life-threatening diseases.

If the crop is harvested too early, the seeds will shrink when drying which will lower the yield, oil content and quality.

If the crop is harvested too late, especially in hard or dry soils, the pegs will break off when the plant is pulled up and pods will be left in the ground. Also, if left too long in moist soil, the seed might germinate.

Leaf fall is not a good indicator of harvesting. To determine whether the time is right for harvesting, around 5 plants should be pulled up, the pods removed and shelled. If more than 70% of the pods are dark brown inside and the seeds are plump and are the correct colour for the variety being grown, then the crop is mature and ready for harvest.

Also, if the crop has lost its leaves due to disease, or if the soil is desiccated and the plant withers and the seeds in the pods begin to shrivel and take on a ripe appearance due to terminal drought, or if the seeds are sprouting in the field, the crop should be harvested immediately.

The challenge of groundnut farming

Yields of groundnut in Kenya are generally low – on average about one-quarter or less of that achieved in the Americas and less than half that in Asia. The main reasons for this include:

  • Unreliable rainfall and lack of irrigation
  • Lack of mechanisation
  • Presence of pests and diseases, especially groundnut rosette, aflatoxin and leaf spot diseases
  • Use of marginal land and poor fertility soils
  • Use of low yielding, unimproved varieties
  • Lack of access to seed of improved groundnut varieties
  • Generally, use of poor agronomic practices and little access to extension services.

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