Field establishment

Participants’ knowledge of groundnut production

To find out about the farmers’ perception of groundnut production, ask them the following questions:

Have you experienced any decline in groundnut yields over the years?
What do you think are the main causes of declining yields?
What do you think needs to be done to improve groundnut yields?

Write down the answers. If possible, the answers can be reviewed later.

Key growing requirements

a. Rainfall/Water: Groundnut is commonly cultivated as a rain-fed crop in Malawi with less than 1 percent under irrigation. Generally, groundnut requires evenly distributed rainfall between 450 mm and 1250 mm annually for effective growth, development and high yields. Although the crop is tolerant to droughts, insufficient water at the time of sowing, flowering and fruiting will significantly reduce yield. It is therefore important to strictly time the onset of the rainfall season for sowing of the crop, and where possible to use supplementary irrigation during prolonged drought periods (especially at flowering and fruiting stages). Early maturing small seeded varieties require 300 to 500 mm rainfall whilst the late maturing large-seeded varieties need 1000 to 1200 mm rainfall. With supplementary irrigation, the plant population per hectare can be increased, yields are guaranteed, and off-season production is possible. Groundnut is not suited to growing at high altitudes above 1500 m, as its optimum temperatures are 27–30 °C.

b. Soil fertility: A deep and well-drained sandy loam soil facilitates better pegging of the groundnut pods into the soil, and hence better yields. Groundnut will not grow well or fix nitrogen in acidic soils with pH below 5 or infertile soils. Therefore, on such soils application of good amounts of farm yard manure (10 t per ha depending on availability) at the time of sowing will not only help moderate the soil pH conditions, but will also support good establishment. In acidic soils, addition of lime (0.5 t per ha in the absence of a soil test) improves cell wall thickness and pod filling, and decreases fungal infection.

How to test for key soil properties for groundnut production

A soil test done at a reputable soil analysis laboratory is an ideal tool to determine whether the soil is acidic or alkaline, and meets the recommended soil fertility requirements for groundnut production, and to learn what corrective measures are required.

Instead of a soil test, a ‘simple feel method’ can be used to determine the soil texture – a key soil property for groundnut production.

Variety selection

The most common varieties of groundnut currently used in Malawi belong to two botanical or market types, namely: Virginia types that are commonly grown in mid altitude locations and Spanish types with either a bunch (erect) or spreading (runner) growth habit, and are grown in the lowlands.

The most popular varieties are CG7 (red in colour) and Chalimbana (tan in colour). New varieties are continuously being introduced and promoted by the Ministry of Agriculture and other agents, recently Nsinjiro, Baka, Kakoma, and Chalimbana 2005. Table 1 shows the common groundnut varieties in Malawi and their specific attributes. Farmers are encouraged to inquire from the local Extension Officer about the most suitable groundnut varieties for their locations.

To achieve higher yields, it is advisable to use high-quality seed, preferably seed that is resistant to diseases (especially rosette and aflatoxin) and pests and is tolerant to drought. Drought tolerant varieties have been found to have reduced vulnerability to aflatoxin contamination.

The variety CG7, although well known for high yields, high oil content and marketability, is susceptible to the Groundnut Rosette Disease (GRD). The disease thrives in drought conditions and can lead to more than 50 % yield reduction. ICRISAT, together with the Department of Agricultural Research Services (DARS) in Malawi, released new groundnut varieties in more than four countries, including Malawi that have a high yield potential, are tolerant to abiotic stress, and well adapted to a wide range of environments. They also have better seed quality and weight, and therefore provide greater market opportunities. These varieties include:

1. Medium duration Virginia varieties maturing between 120–130 days and well adapted to mid-altitude growing conditions: CG 8 (ICGV-SM 08501),
CG 9 (ICGV-SM 08503), CG 10 (ICGV-SM 01724), and CG 11 (ICGV-SM 01731).

2. Short duration Spanish varieties, which mature within 90–110 days and are well adapted to low-altitude conditions: CG 12 (ICGV-SM 01514), CG 13 (ICGV-SM 99551), and CG 14 (ICGV-SM 99556).

Discussion about groundnut varieties

To assess the suitability of groundnut varieties commonly used in the different areas of Malawi, ask the participants the following questions:

Which groundnut varieties are suitable in the dry and wet or high and low areas of the central region of Malawi, etc. ?
What are the advantages and disadvantages of these varieties?
Which criteria are considered in variety selection?

Seed selection and preparation

Selection and handling of seeds

Most small-scale groundnut farmers in Malawi use seeds saved from the previous harvest, while a few buy seeds from vendors, or receive them from the government or NGOs.

Groundnut’s indeterminate growth habit results in seeds of varying sizes and maturity at harvest. Groundnut seed can be infested by seed-borne fungi (mainly Aspergillus) and viruses, bacteria and nematodes. As a result, seed quality and germination rate can vary strongly. Seeds that are taken from own crops also become weaker and progressively lose their good characteristics from one season to another, as they cross-pollinate with other varieties cultivated nearby.

If seeds are bought from an agro-dealer or seed agent, the seed should be checked, whether it is quality-certified or not. Quality-certified seed has a packet label with the following information: name of the seed producer, date of packaging, name of the variety, germination rate (percentage), seed purity (indicates how much free the seed is from debris), and net weight of the seed.

If in doubt, or as a matter of fact, the farmer should also inspect the seed visually to ensure that there are no seed quality problems. Careful seed selection is important to ensure good emergence of the crop. Immature, damaged, skinned, mouldy, small or shrivelled seeds should be sorted out. The selected seeds must also be free from contamination mainly of seed-borne fungi, irrespective of the sources of supply. It is recommended to purchase new seed stock every 2 to 3 seasons. Groundnut seed is very susceptible to physical damage and should be handled with care at all times. Generally, seed intended for sowing is hand-shelled 1 to 2 weeks before sowing by choosing only good quality ones.

Seed quality testing

The germination capacity of the seeds should be tested prior to planting. As a single test of seed germination of a single seed lot is not a reliable estimate of the quality, germination tests of different seed lots should be made.

If a farmer has a very limited amount of seed, he or she can use 20 seeds only for the germination test instead of 50 or 100. For a good representation of the seed batch, the seeds should be taken randomly. Selecting the best or worst seeds only should be avoided. The soil / medium for the seed germination test must be kept moist, but not damp, otherwise the seeds will rot before they sprout.

Seedling emergence in the field generally is about 20 % lower than in the germination test. A germination capacity of more than 85 % is recommended. If the germination in the test is lower than 90 %, then the number of seeds sown must be increased accordingly. A good field emergence is above 70 %.

Demonstration of the germination test

Show the participants, how to proceed for the germination test. Prepare a germination test in advance to show a possible result.

Seed treatment

Conventionally, seeds are treated with a fungicide to control seedling blights caused by seed-borne bacteria and fungal diseases. Sometimes, the fungicide is mixed with an insecticide to protect the seeds from insect damage during germination. However, in organic production, seed treatment with synthetic chemicals is restricted.

The organic approach is to carefully select seeds from healthy and mature plants to minimise the transfer of infections from one field to another. This practice is complimented with proper hygiene during crop production avoiding the use of tools and materials from other farms.

Seed inoculation with Rhizobia

The natural symbiosis of groundnut with nitrogen-fixing Rhizobia bacteria is essential for optimum plant growth, especially under low nitrogen input conditions. The root nodule building rhizobium Bradyrhizobium is in general present in soils that have been cultivated with groundnut before. However, fields where groundnut is planted for the first time may not contain this specific rhizobium. In this case, the rhizobium should be added to the soil at planting. Commercially sold rhizobia for groundnut inoculation consist of selected rhizobium strains with a higher nitrogen fixation rate than native strains. As native rhizobia compete with inoculated strains for root infection, some recommendations suggest to inoculate groundnut fields every season to maximise yields.

Research has shown that inoculation of Bradyrhizobium together with other rhizobia such as Serratia marcescens and / or the fungus Trichoderma harzianum can have a positive effect on root nodulation, and thus increase nitrogen fixation of the groundnut plants. Inoculation of soils with other beneficial soil-borne bacteria or fungi can result in better root growth, increased phosphorus uptake, or reduced pathogen incidences on the roots.

NOTE: To access the appropriate rhizobia, farmers should contact their agricultural extensionist, national organic agricultural movement (NOAM) or nearby agricultural research institute.

The bacterial inoculum can be added by mixing it to the seeds before planting. Instead of direct seed inoculation, the rhizobium can be poured into the planting furrows in a suspension or applied in a granular form with the seed at planting to avoid damage to the seed. Alternatively, granular inoculum can be dispensed.

Procedure for inoculation of groundnut seeds:

Soak the groundnut seeds tied in a gunny bag in water for 4 to 6 hours, or spread groundnut seeds on a gunny bag and cover them with another wet gunny bag for 12 to 14 hours.
Prepare the inoculum as described in the product instructions.
Then treat the seeds with rhizobium at a rate of 5 gms per kg of seeds (i.e. 600 gms for a full sack of 110 to 120 kg of seeds). Mix the seeds carefully with the rhizobial inoculum. Make sure not to bruise the seed coats.
Let the seeds dry under shade for 30 minutes.
Sow the seeds within 1 or 2 days.

Sharing ¬experiences on crop rotation

Encourage participants to share experiences about crop rotation in groundnut production. Let them share and discuss possible advantages and inconveniences of the different options that are presented.

Land preparation

Groundnuts grow well in soils that have been worked to a depth of 20 – 30 cm. This enables the roots to grow deep into the soil for good anchorage and better access to moisture, especially during dry spells. Good land preparation by hoe, oxen or tractors to loosen the soil provides suitable soil conditions for rapid and uniform germination, good root penetration and growth, and eventually steady pod formation, filling and seed development.

Land should be prepared early, before the rains start, so that planting can take place early in the rains. On slopy land, ploughing should be done along the contour lines to reduce the risk of soil erosion through runoff, when it rains.

At land preparation all previous crop residues and weeds should be completely removed or buried, and seedbeds should be smooth to provide good soil-to-seed contact after planting. Removed weeds can be used for composting or as mulch to control in-field soil erosion.

Commonly, farmers use ridges to plant groundnut, because the loose soil in ridges encourages pod development, improves weed control and harvesting, leading to higher yields. Ridges are especially required in wet, low-lying areas to prevent waterlogging.

Ridges are normally 75 to 90 cm wide and flat-topped to allow double rows to be planted on the ridge. Planting double rows results in groundnut plants covering the soil quickly, which shades out weeds. An evenly prepared seedbed on the ridges helps to assure a uniform planting depth and facilitates better seed germination and emergence.

Crop rotation and intercropping

The continued cultivation of groundnut on the same plot of land leads to a build-up of high populations of aflatoxins in the soil, which will increase the probability of infection and aflatoxin contamination.

For best results, groundnut should not be grown in the same field for two consecutive seasons. It should be grown in rotation with cereals (maize, sorghum or millet), root tuber crops (cassava or sweet potato) or sunflower. However, to minimise diseases and pests, groundnut should not be sown after any legume crop, cotton or tobacco, as they cause build-up of nematodes and soil-borne diseases.

In Malawi, groundnut does well when it is grown in succession with a well-managed and fertilised maize crop. This is because groundnuts are good at utilising residual nutrients. Slide 12 shows, how groundnut can be grown in rotation with other crops.

Groundnut is mostly grown under monocropping. This is because it requires a lot of sunshine and the shading effect from intercrops reduces yields. However, under smallholder farming, groundnuts are commonly grown in mixtures with other crops on the same plot or land. Sometimes the crops are directly intercropped within the groundnuts with irregular spacing or as different patches without any distinct row patterns. In other cases, the crops are grown in alternating rows or strips.

The numbers of crops intercropped with a groundnut main crop by smallholders may vary. Some of the crops which are often found growing together with groundnuts on smallholder farms, include maize, sorghum, pigeon-pea, cotton, and cassava. There is not so much information on intercropping groundnuts in organic production compared to conventional systems. Research on conventional groundnut intercropping reflect some conflicting results on the performance of intercropped groundnuts compared to the sole or monocropping systems. For example, while some of the research in India showed up to 50 % groundnut yield increase in a sorghum-groundnut intercropped system, other research showed similar reduction levels compared to sole groundnut cropping. One of the reasons leading to the yield reduction include poor light interception and nodulation by groundnuts in the intercrop systems. When the yields of both crops are considered, the overall benefits of intercropping are sometimes greater than monocropping. Cotton-groundnut intercrops on alternate ridges (75 cm apart) gave higher cotton and groundnut yields in high rainfall areas with more than 1000 mm per year areas in Zambia, but no yield advantages were observed in lower rainfall areas with less than 800 mm per year.

When intercropped, groundnuts will perform differently depending on a number of factors such as:

Rainfall amount or availability of supplementary irrigation.
Spacing: wider spacing is recommended, but spacing also depends on the type of intercrop. In Egypt, for example, some research showed that planting maize at 50 % of its monocropping density in the intercrop on a sandy soil led to the highest weight of seed per plant and pod yields while an intercrop with 100 % of the recommended sole maize planting density reduced groundnut seed weight and pod yields.
Type of groundnut planted: some researchers report higher yields from groundnut varieties which have a longer growing season.
Type of intercrop: species with less shading effect are more preferable, e.g:
- A crop like cotton, which has a late-developing leaf canopy and can tolerate a wide range of population densities, may be better suited to intercropping with groundnuts.
- Forage sorghums, for example, produce larger foliage and are likely to impart more shading to the groundnuts.
Timing of planting of the intercrop is important. For example, delaying maize planting by about 4 weeks after sowing the groundnuts (relay cropping) provides a competitive advantage for the groundnuts compared to simultaneous sowing.
Given the generally small landholdings in the Malawian smallholder context, some farmers may find it more appropriate to intercrop groundnuts with cereals and other crops rather than practicing crop rotations.

Given that many factors influence the performance of groundnuts in an intercrop, farmers should consult with local extension staff and try out various combinations of crops and management practices within their prevailing production conditions and make an informed choice. It is important, though, to keep in mind some of the key advantages and disadvantages of groundnut intercropping.

Discussion on intercropping

Discuss with the farmers about their experiences with rotations as well as intercropping (mixed, strip and relay intercropping).

Highlight the pros and cons of intercropping (as mixed, relay or strips) and the additional management requirements for intercropped systems.

Planting

Groundnut is grown in all areas where tobacco and maize are grown, maize being the staple food and tobacco the main cash crop among smallholders in Malawi. Groundnut is frequently given the last priority in timing for planting. Farmers in Malawi plant groundnut before the full rains, normally after the first ‘effective rains’ that are sufficient for planting. Groundnut should be sown into moist soil; not immediately after heavy rains, because they will absorb too much water and rot. Planting after heavy rains can also result in excessive soil compaction, which may block germination and/or emergence. The normal time of planting of groundnut is supposed to be mid-October to mid-November, but rains are increasingly becoming more erratic. Late planting may lead to crop failure and aflatoxin incidence due to drought effect, lower yields of up to 50 %, pests (especially aphids) and disease (rosette and leaf spot) incidences, and reduced quality of the nuts.

Plant spacing and planting depth

The recommended distance between rows in bunch types is 30 to 40 cm, and 15 cm between plants in the rows, resulting in a recommended seed quantity of 80 to 100 kg per hectare. For spreading groundnut varieties, 45 to 60 cm between rows and 30 cm between plants are recommended, resulting in 60 to 80 kg of seeds needed per hectare. Lower-limit row spacing allows earlier ground cover and helps prevent serious weed problems.

Groundnut should be planted at 5 to 7 cm depth. Deeper sowing will result in slow germination, whereas shallow planting should only be considered when enough moisture is available.

Other planting techniques used by farmers include:

Hand hoe: When farmers plant with the hoe, they simultaneously open a shallow planting hole using a small hand hoe held in one hand, and place the required number of seeds held in the other hand into the planting hole. Then, the sown seeds are covered with soil. This technique is mostly used when the sowing is done in a random manner.
Mechanised sowing involves sowing using a seeder mounted on a tractor or other equipment depending on availability and access to such machinery. The ridges can be pre-made, or they can be prepared in one operation by the machine when a more sophisticated machine is used. In the latter case, the machine performs ridging and sowing.

Discussion on establishment of groundnut fields

Inquire about the local process for establishing groundnut fields and discuss possibilities of improvement. Begin by asking the following questions:

What time of the year do you start groundnut planting? Why?
Do you know, how far to space groundnut plants to obtain appropriate plant density?
What is special about seed handling, land preparation and planting of groundnut?