Planting and Site Considerations

Plant Groundnuts on Suitable Soils

Groundnuts grow best in soils that contain enough organic matter and soil structure but are relatively well drained and do not constrain root growth and pegging or break off pods during digging and lifting. Soils with adequate water-holding capacity can retain soil moisture into dry periods of the season, increasing yield potential and reducing potential growth of aflatoxin-producing molds. Groundnuts are sensitive to high salinity and acidic soils (<5.5 pH) which could contribute to problems with aluminum toxicity. Proper soil pH is 6.0 or higher.

Prepare Land Adequately

Land should be prepared as early as possible, and residues from the previous crop incorporated into the soil.

Most groundnut fields are prepared with either a tractor and disc harrow or by hand. Some farmers use less invasive tilling, preparing the field by controlling vegetation with a non-selective herbicide (glyphosate or paraquat), then planting seed into the soil with minimum disturbance. Both practices can be effective as long as fields are free of weeds when groundnuts begin to emerge. Still other farmers avoid disturbing the soil at all, which often requires the farmer to apply herbicide to control weeds. If weeds are not controlled completely, they can compete with groundnut seedlings and reduce groundnut yield, even if the farmer removes the weeds later in the season.

Groundnuts may be planted on ridges or flat ground. Ridges promote drainage that can reduce water logging of soils. However, this requires additional labor for land preparation. Planting on flat ground requires less labor for land preparation but can allow water to pool and can reduce groundnut stands in low areas during the rainy season. If groundnuts are planted on ridges, it is important to prepare the ridges shortly before planting and make the ridges flat on top. Beds are often spaced about 75 cm from the centers of each bed. Establishing groundnuts on ridges or beds can also make digging or lifting plants from soil easier.

Soil pH will be discussed in more detail in Section 4. How and when land is prepared can affect the efficiency of lime that is applied and distributed into the root zone. Lime requires several months to reduce acidity and increase pH. The soil should be prepared a minimum of one month before seeding so that soil pH is higher when groundnuts begin growing.

Rotate Groundnuts with other Crops

As a legume crop, groundnuts fit well into crop rotation programs in most farming systems that include cassava, maize and tobacco. Growing groundnuts in the same field each year can lead to higher concentrations of pathogens and plant parasitic nematodes, which can reduce yield or require greater inputs to suppress in order to maintain yield. Also, growing groundnut continuously in the same field can mine soil nutrients and cause an imbalance among nutrients. Rotations may also reduce aflatoxin contamination, however, groundnut production following maize often suffers from higher aflatoxin contamination. It is important to plant crops that are not hosts for pathogens and nematodes that also affect groundnuts.

Groundnuts do contribute to fertility of other crops in the rotation through biological nitrogen fixation (BNF). A well-balanced and diverse cropping system leads all crops in the rotation to realize higher yields and often decreases production costs and increase financial return for the farm. Groundnuts can also produce good yields in new fields and in fields where appropriate grass or broadleaf crops were grown.

Establish the Most Effective Sequence of Crop

The order or sequence of crops in the rotation is important. Planting groundnuts after legumes such as soybean may contribute to pest problems; it is better to alternate non-legume crops, such as tobacco, with groundnut. A good rotation sequence in Malawi would be tobacco-groundnuts-maize. If tobacco is not available, planting one or two crops of maize between groundnut plantings would be a good choice.

However, while maize is a good agronomic choice because it can reduce pest problems and take advantage of the nitrogen groundnuts contribute to the soil, maize may increase aflatoxin contamination levels in the subsequent groundnut crop. There is a bit of a trade-off in the maize to groundnut rotation, which reduces the threat from pests and diseases, but may increase aflatoxin in the groundnut crop. When groundnut follows maize in a rotation, it is critical to harvest on time to minimize aflatoxin contamination. If soybean is an option, planting a rotation of soybean-maize-groundnut-maize can be effective for pest suppression. When a farmer wants to plant groundnut more frequently, it is best to plant groundnuts before soybean rather than following soybean. Plant groundnut in a field that grew a non-legume crop the season before.

The economic value of each crop in the rotation determines what will be planted each year, but regardless of economic drivers, a poor rotation will eventually result in lower groundnut yields or will require greater inputs to suppress pests that have become entrenched. The value of specific rotations will be further examined in the risk management tool at the end of this guide.