Effect of weather on organic cropping systems in Kenya

Summary

Rainfall is the single most important factor affecting yield and biomass accumulation by crops as well as residue decomposition in the tropics. The ability to capture this resource in organic systems calls for appropriate techniques. Kenya experiences bimodal type of rainfall with two rainfall peaks; the long (730 mm) and the short (376 mm) rains. Rainfall fluctuations in both seasons are becoming more common in the recent years with a likelihood of crop failure in one out of five years. The question addressed was how to utilize the short rains for food and biomass production. Lablab (Dolichos lablab), a N-fixing legume was sown in the short rains and the seeds harvested. The effect of lablab biomass incorporation on organic maize and potatoes planted in the long rains was evaluated in comparison with farmyard manure application. The 3-year trial showed that dry matter biomass (1.95 t/ha) and grain yield (0.5 t/ha) of lablab was a factor of the amount of rainfall. The amount of lablab biomass applied was proportional to maize grain and potato tuber yields. Similarly, amount of yield and biomass in the long rains was species specific and were a factor of both rainfall amounts and distribution.