Evaluation of lablab and velvet bean fallows in a maize production system for improved livestock feed supply in semiarid tropical Kenya

The mixed crop-livestock farming systems of semiarid tropical Kenya are characterised by low livestock feed supply. The contribution of lablab and velvet bean to fodder production in a maize production system was investigated in the eastern region of Kenya. The experiment was run in three cycles, where each cycle consisted of a short legume fallow phase of similar to 6 months, followed by a maize-cropping phase. At the end of the fallow phase, the legume herbage was incorporated in soil at three levels; 0, 50 and 100% of total DM yield and maize planted. Maize yield from the legume fallow plots was compared with maize grown after natural fallow and maize top-dressed with 40 kg nitrogen/ha and nil nitrogen fertiliser. Overall, herbage DM yield was highest in velvet bean (3.9 t/ha) followed by lablab (3.4 t/ha) and lowest in natural fallow (2.2 t/ha). Mean crude protein from velvet bean was 13.5% of DM, which was significantly (P < 0.05) higher than that of lablab (8.4% of DM) and natural weedy fallow (3.5% of DM). Maize grain yield following lablab fallow was 38% (3569 kg/ha) and 27% (1810 kg/ha) in short rains (SR) 2002 and SR 2004, respectively, higher than maize succeeding natural fallow. However, maize planted after velvet bean fallow was 43% (3728 kg/ha) and 29.4% (1828 kg/ha) in SR 2002 and SR 2004, respectively, higher than in maize grown after natural fallow. Generally, the highest maize yield among the fallows was recorded in plots where legumes were incorporated in soil at 50% of total DM implying that the other 50% was available for livestock feed. Maize stovers DM yields were highest at the higher (100%) and middle (50%) level of legume incorporation, and yields were more than those from natural weedy fallow. Maize production under the legume fallow system was more profitable than from natural weedy fallows. It was concluded that if lablab and velvet bean are integrated in cropping systems as fallows, they can provide highly nutritious livestock feeds and improve maize yield and are recommended in the maize production systems within semiarid tropical Kenya.