Performance of mixed cropping in the yala swamp, Kenya

Development options of the 17500 ha Yala Swamp, when reclaimed by drainage, fall into two broad categories, namely: large estate develQpment or smallholder mixed farming. Mixed cropping is a common farming system in smallholder farming which is expected to happen at Yala Swamp in a semi-humid, warm climate. An experiment involving inter-cropping maize with legumes and tuber/root crops (food beans, cowpeas, cassava, sweet pota¬toes) was conducted at a reclaimed part of the Yala Swamp to assess the feasibility of small holder mixed cropping systems. The water balance of a cropped field on the dominant soil in the swamp, the Swamp clay, was computed using long term meteo¬rological data and soil data determined for the experimental site. This shows moisture deficit of 435 mm/year with deficits occur¬ring in all months except in April, May and November. Although the rainfall is bimodal only the long rains, in March to May, are reliable for growing a crop. There is a prolonged drought from December to March and then from June to October. Under average rainfall, maize yields were reduced by 34-37% when the maize was inter-cropped with either food beans, cassa¬va and cassava/ cowpeas. These other crops were also reduced in the intercrops. Yield of sweet potatoes was low. During the year with below average rainfall the yield pattern was similar; the yields were even reduced further. Cassava and sweet potatoes failed to form tubers/roots. Cassava with a maturity period of over 8 months could not survive the drought peri¬ods between July and October and December to March identified in the water balance computation. Sweet potatoes, a perennial crop, survived during the long rains of average rainfall but failed during the long rains of below average rainfalL The sweet potatoes, it appears, requires more water than maize and legumes. The prolonged drought periods are a limitation to sweet potatoes production. Despite the reduced yields under intercrop¬ping systems, monentary value of the pro¬duce was highest for the intercrops maize/beans/cowpeas for the below aver¬age rainfall season, and maize/ cowpeas/ cassava intercrop in aver¬age rainfall year. From the limited two sea¬son trials and long term water balance study it is evident that intercropping of drought escaping/ resistant crops (cereals and legumes) in the area is feasible. In addition to higher monetary returns for the intercrops, it is argued that mixed cropping makes sense in meeting the subsistence needs of the farmers, maintenance of soil fertility and protecting soil from surface erosion.