Legumes and livelihoods

In the semi-arid northern communal areas of Namibia, pearl millet is the staple cereal. However, phosphorus and nitrogen are known to be limited in cultivated soils in the region and, with declining soil fertility as a result of continuous cropping and unreliable rains, millet yields are often poor. Mono cropping of legumes, such as cowpea or Bambara, is common but usually restricted to small plots, and varietal choice and seed supply is generally inadequate. 'Improved' intercropping systems of pearl millet and cowpea appear to offer the greatest potential for contributing legume nitrogen to the system. But, whilst researchers may believe that this is a possible option for improving soil fertility, farmers have to be convinced that there are added benefits of growing a greater proportion of leguminous crop.

The North Central Region (NCR) is only 6.3% of the total land area of Namibia but it is home to almost 50% of the country's population, partially due to the good year-round provision for domestic water. The region has a long history of agriculture and some relatively good soils, but rainfall is a serious constraint with only 300-500 mm per annum. In the Kavango region, to the east of NCR, rainfall is somewhat higher (~ 600 mm per annum), and the area is more sparsely populated and extensively utilized. However, few places have a domestic water supply year-round and soils are, in general, extremely sandy and poor. With the traditional shifting cultivation systems giving way more recently to more continuous cropping systems, soil fertility in this area is undoubtedly an issue.

A simple solution?

Foremost in farmers' minds is to improve pearl millet production. However, in an environment where rainfall is unreliable and pests and diseases can have a serious impact on production, it is difficult to prove to farmers that poor cereal yields are related to declining or poor soil fertility. Recent research, conducted by the DFID Plant Science Programme in collaboration with Namibian partners, has shown that the solution to soil fertility is not simple. Despite expectations that legumes have considerable potential to contribute to soil fertility and sustainable yield increases in semi-arid African farming systems, on-station and on-farm research conducted in the northern regions has shown that grain legumes alone cannot substantially improve soil fertility. In addition, the livelihoods of people in northern Namibia have increasingly diversified away from solely agriculture over the last decade, and it is likely that this would only change if agricultural options, notably cash-cropping opportunities, were improved. New farm activities therefore need to be particularly attractive if farmers are to be persuaded to increase the investments they make on farm.

This is not to say that soil fertility cannot be improved in the region. It is possible that a number of legumes could be identified to attract farmers' interest and fill niches within the millet farming system. Short duration varieties are particularly appealing as they provide food security in the event that the millet crop fails due to lack or shortage of sufficient rain for the millet to mature. During the most recent trials, traditional legumes, such as cowpea, groundnut and bambara, have been tested along with legumes new to the region. The latter include moth bean, horse gram, lablab, mungbean, and cluster (guar) bean, all of which have demonstrated potential to be grown successfully in Nambia. Some, such as mungbean, can be grown as short duration varieties whilst others have multipurpose properties and can be grown for fodder as well as providing leaves for use in salads and pods, to be eaten as a green vegetable. All varieties can also be used as green manure but incorporation of residues in this way often competes with farmers' requirement for animal fodder and, overall, the use of legumes as green manure has been found to be unattractive to farmers.

Farmers involved with testing new varieties of legume have been enthusiastic in their approach but it is generally felt that a strong incentive to increase legume production would only result from a higher market demand. How an improved market situation might develop in the remoteness of northern Namibia is difficult to see, particularly with neighbours, notably South Africa, which have environments and an infrastructure more conducive to commercial crop production. But, despite these reservations, the approaches used through the recent research led by the DFID Plant Science Programme are continuing to be used on-farm by the in-country partners, and many farmers appear keen to carry on experimenting with new legume varieties. And, although there have been concerns as to how much fixed nitrogen is contributed to the soil through growing legumes, there is no doubt that growing some legumes is better than growing none at all.

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