A number of smallholder farmers in Trans Nzoia District are experiencing low maize yields as a result of continuous cultivation without addition of adequate external nutrients. Integrating the use of green manure legumes into the smallholder farming systems may form an important strategy for soil improvement and hence yield. An on-farm trial was designed in 1997 to introduce legume intercrops and green manures in a maize-based cropping system. A randomised complete block design was used and each farmer served as a replicate. Maize hybrid H614 was intercropped with either common bean (Phaseolus spp.), soybean (Glycine max) groundnuts (Arachis hypogea), and cowpea (Vigna unguiculata). After harvesting the food legumes these four plots were relayed with green manure legumes, Sunhemp (Crotolaria brevidens), Velvet bean (Mucuna spp.) or Dolichos (Lablab purpureus). The green manure legumes remained in the field after maize was harvested and were incorporated 2-3 weeks before planting the following season. Maize yields harvested from the plots were compared with yields from control plots. The soils under experimentation were strongly to moderately acidic (pH 5.0 -pH 6.9) with marginal amounts of exchangeable bases. Green manure dry matter (DM) varied for both years. In 1997 Dolichos spp. gave the highest yield of 2.5 t ha-1 while Mucuna spp. gave the lowest yields (0.38 t ha-I). Crotolaria spp gave the highest DM yield (2.80 t ha-l) in 1998, followed by Velvet bean (1.20 t ha-l) and Dolichos (0.40 t ha-l) in that order. There were no significant maize yield differences (p<0.05) after one or two years of green manure incorporations and fertilized maize. After one year maize following Mucuna spp. gave yield of 9.3 t ha-1 while after two years it was Dolichos spp that gave the highest yield of 8.5 t ha-l, followed by Crotolaria spp and Mucuna spp. which yielded 6.3 t ha-1 each. After three years of incorporations maize yields following Dolichos spp continued to give the highest yield of 8.1t ha-l. Throughout the four years growing period no fertilized maize gave the lowest significant yields (P<0.05). The utilization workshops for soybean and groundnuts were well attended. Initially farmers insisted on growing legumes as intercrops due to land pressure, but after three years exposure, they requested seeds for planting pure stands. Farmers may accept rotating legumes with maize in future to increase and diversify their food supply and at the same time improve their soils.

English

0410|AGRIS 0401|AL-Maize Program

Juan Carlos Mendieta

CIMMYT Publications Collection