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close this bookCERES No. 158 March - April 1996 (FAO Ceres, 1996, 50 p.)
close this folderCerescope
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View the documentField findings: Farmers embrace a creeper
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Field findings: Farmers embrace a creeper

Farmers in southern Benin have found the best way to deal with their biggest problem, a grass weed, is to smother it with another plant, a ground creeper. And in doing so, they have taught researchers once again the valuable lesson that working with farmers rather than for them is the key to increasing production.

The problem arose in the mid-1980s. The traditional farming system with a long fallow period had collapsed because of pressure to produce more food. The ultimate result was a drop in production because soil fertility took a nosedive. As soils degraded, fields became infested with the grass weed Imperata cylindrica, known as spear grass, and were then abandoned.

Researchers at the Institut national des recherches agricoles du Bn joined forces with the International Institute of Tropical Agriculture in looking for a leguminous cover crop to improve soil fertility. They selected Mucuna pruriens, the velvet bean, brought in from Latin America.

Mucuna, an annual leguminous, ground-creeping plant, produces a lot of growth, and when it dies down during the dry season, it leaves behind large amounts of organic matter. Initial trials in 1988 and 1989, showed that if maize is planted into this thick mulch at the beginning of the next rainy season, grain yields more than double. The maize crop benefits because the mucuna debris provides nitrogen and helps the soil retain more rainfall.

Demonstration plots with farmers produced some sensational increases in yields - as much as tenfold. But that didn't convince most farmers to plant mucuna. They weren't interested in a crop that yielded no food.

Some farmers did persist with mucuna, however, because they saw its potential in another more important direction. They found it could eliminate imperata grass from badly infested fields. If they cut down the grass just before the rains and then planted mucuna, the creeper had the chance to outgrow the imperata and smother it. In its search for light through the thick carpet of mucuna, the imperata uses up its root reserves, and by the end of the season there is very little left in the field. Next season maize can be planted into the mucuna mulch.

That finding, spread from farmer to farmer by word of mouth, was enough to get more people to plant mucuna.

Because imperata does creep back within three to four years, farmers will have to re-introduce mucuna periodically to suppress the imperata once again, and this also ensures soil fertility is maintained. So in a roundabout way, the researchers have achieved their objective.

Experience has shown when maize follows mucuna, yields are increased. Some farmers have got yields of 2 000 kilograms per hectare, others have seen yields treble. But mucuna only supplies organic matter and nitrogen, so it may be necessary to apply phosphorous and potassium if these nutrients are deficient.