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Maize intercropping systems in Africa

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Intercropping in the past and present

Traditional agriculture, as practiced through the centuries, has always included different forms of intercropping. Farmers grew a variety of crops, often intermingled in the same field, to sustain themselves and their families. Modern agriculture has shifted the emphasis to a more market-related economy and this has tended to favor intensive mono-cropping. Large-scale farmers, in particular, have found it easier to plant and harvest one crop on the same field using machinery and inorganic fertilizers. However, small-scale farmers who do not have ready access to markets and who can normally only grow enough food to sustain themselves, recognize that inter-cropping is one way of ensuring their livelihood. Growing an increased number of crops helps to safeguard production from shocks such as drought and intercropping can also help to maintain the productivity of relatively fertile land.

Intercropping strategies

Intercropping can be carried out in two main ways:

• Mixed intercropping
• Row intercropping

In mixed intercropping, the seeds of two or more crops are sown in a field without any particular arrangement. For example, pumpkin seed may be scattered amongst maize plants. This takes very little effort but may lead to problems when farmers try to weed their fields or harvest their crops. The plants of the different crops can also compete with each other for sun, water, and nutrients.

In row intercropping the main crop and intercrop are grown in separate rows. This makes weeding and harvesting a little easier. However, competition may still be a problem. And, allocating too much

land to small plants, such as legumes, may reduce the overall production since the smaller plants will produce lower yields than the maize.

Potential advantages of intercropping

● Risks of crop failure may be reduced.
A single crop may fail because of adverse conditions, such as drought, disease, or attack by pests. The farmer reduces his risk by growing more than one crop in his field.

● Farmers may be better able to cope with price variability.
Sometimes, the market price may be more favorable for one crop than for others. Farmers may be able to benefit from good prices and may suffer less due to poor prices for particular crops if they grow several types of crops.

● Land use may be maximized.
Properly chosen intercrops, such as pigeon pea, may be grown in the same field as maize without reducing maize yields. However, since pigeon peas can also be harvested from the same parcel of land, farmers produce a valuable “bonus” yield to increase their overall productivity from limited field space.

● Diets may become healthier.
A more diverse diet that includes intercrops such as beans and vegetables should improve the nutrition of farmers and their families.

Intercropping may help to reduce weeds.
Intercrops may smother weeds. In the case of Striga, a parasitic maize weed, the intercrop reduces the potential of Striga to flower and therefore reduces the spread of its seeds.

● Soil fertility may increase.
Leguminous intercrops fix nitrogen in the soil. In addition, the green parts and roots of intercrops can decompose and release nitrogen into the soil where it may be made available to other crops.

● Soil structure may improve if plants with various root structures are grown.
Deep roots penetrate far into the soil breaking up hardpans and use moisture and nutrients from deeper down in the soil. Shallow roots bind the soil at the surface and thereby help to reduce erosion. Shallow roots also help to aerate the soil.

Potential uncertainties of intercropping

● Intercropping may not significantly improve the soil nitrogen levels.
Farmers might still have to use fertilizer or manure to increase the yield of their maize crop

● A poorly chosen intercrop may compete with the maize.
Vigorous climbers, such as lablab, may grow up along a maize plant, smother it, and reduce its yield. In addition, maize is very susceptible to competition especially during the first four weeks of growth. Ideally, therefore, the intercrop should be planted four weeks later than the maize.

● In some cases the intercrop may contaminate the yield of the main crop.
The intercrop could potentially cause impurities in the harvested seed of the main crop, resulting in lower prices.

● Herbicide use may be constrained.
Farmers who traditionally use herbicides to protect their maize plants from competition may face problems if their intercrops are susceptible to the herbicides. Therefore farmers may have fewer options for herbicide-based weed control, or may have to completely abandon this strategy.

● Harvesting produce may be more difficult.
Harvesting two crops from within one field may be more challenging than harvesting the different crops from separate fields. This difficulty may be greater in mixed intercropping systems.

● Farmers may need to organize their own seed systems for intercrop legumes.
The seeds of suitable intercrops, such as sunn hemp and lablab, are often difficult to obtain.

● Intercropping may not help farmers with very low soil fertility problems
Generally, intercropping does not rehabilitate poor land successfully.

Examples of successful maize intercrops in Africa

Cowpea, pigeon pea, beans, sunn hemp, and groundnuts have all been used by farmers in Africa with various success. Each one offers different benefits and faces specific limitations that farmers need to consider before they choose an intercrop for their fields.

Prospects for the future

Intercropping can be successfully integrated into small-scale farming. Though this practice may have some drawbacks, some may be overcome by proper intercrop selection and management. And, intercropping offers many important benefits. Legumes have a great potential for improving the sustainability of maize production. However, this potential remains largely untapped because of the slow uptake of this farming system. Better understanding of intercropping and improved farming systems should lead to the increased adoption of intercropping in the smallholder agricultural sector.

Examples of maize intercropping systems

Intercropping systems, where maize and another crop are planted in the same field simultaneously, may offer several advantages to small-scale maize farmers in Africa. By intercropping with appropriate crops, these farmers may benefit from improved soil fertility, healthier diets, increased productivity, and reduced risk of total crop failure.

 

 

Maize-Cowpea

Maize-Pigeon pea

Where has it been successfully introduced?

Many smallholder farms in Zimbabwe

Widely practiced in Malawi, eastern Zambia, and northern Mozambique

Type of soil needed

Well-drained soils of moderate to high fertility

Benefits

·    Will boost the soil nitrogen content in the medium to long term. 

·    Amount of nitrogen accumulation will depend on type of cowpea, the yield of the cowpea, the amount of residue left on the ground, and soil type.

·    Requires less labor than other grain legumes and is cheaper to grow.

·    Are very drought resistant.

·    Often the legume with the biggest effects on soil fertility and maize yield improvement, especially with long duration types. However, the full impact on soil fertility will only become apparent after several years.

·    Good source of protein for the family.

·    Dry stems make good fuelwood.

 

Uncertainties

·    In fields with a low phosphorus status, or with acidic soils, the impact of growing legumes is reduced, because the rate of nitrogen fixation is reduced.

·    Needs to be protected from grazing animals, as soil benefit will be reduced if little residue left on the soil.

·    Susceptible to pod borers, termites and some nematodes.

Planting Guidelines

Should be sown in the maize row with one or two seeds per station In fertile soils, these stations should be one meter apart, whereas in less fertile soils, one station every half a meter should be planted.

The best planting density for pigeon pea is about 2  plants/m2. This density gives the best nitrogen inputs into the maize without causing competition for water.

 

Other maize intercrops

Maize and beans are another popular intercrop. Farmers can benefit from the high protein of the beans as well as the improved soil fertility. Sunn hemp has been successfully introduced into Zimbabwean maize cropping systems for green manuring and can be intercropped with maize. Groundnuts can also be intercropped with maize although this grain legume is often better grown as part of a rotation.

Developed with input from A.L.MacRobert, P.Kosina, J. Jones • 2007