Tied-ridging and integrated nutrient management options for sustainable crop production in semi-arid eastern Kenya

A field experiment was conducted for two seasons at Emali, Makueni District in Eastern Kenya to compare the effect of tied ridging and integrated nutrient management practices on the yield of rainfed maize (Zeamays L.) and cowpeas (Vigna unguiculata L.). The main treatments were flat bed (FB, traditional farmers' practice) and tied ridging (TR) as main plots. The manure and fertilizers were farmyard manure (FYM, goat manure at 0 and 5 t ha(-1)) in a factorial combination with nitrogen (N fertilizer at 0, 40, 80 and 120 kg N ha(-1)) and P fertilizer at 0 and 40 g P ha(-1) as the subplots in a split-plot treatment arrangement of a randomized complete block design (RCBD). Results from maize yield data in the continuous maize cropping systems indicate that maize stover was significantly (P <= 0.05) increased by the application of 5 t ha(-1) of manure in both seasons. Tied ridges, manure and fertilizer did not affect grain yields in the first season. However, mean grain yields obtained in plots with tied-ridges and manure were higher by 11% and 14% compared to plots without tied ridges and manure respectively. There was a significant interaction between manure and nitrogen which gave higher stover yields in the 2003 long rains season. Under the cowpeas-maize intercropping system, tied ridges and manure application did not have a significant effect on maize yields in both seasons. Application of nitrogen significantly (P <= 0.05) increased maize stover by 29% and TDM yields by 50% in first and second season respectively when compared with treatments without nitrogen. Nitrogen application also increased cowpea stem and TDM yields by 57% and 45% respectively in the second season. Cowpea yields were not affected by tied-ridges in both seasons. There was significant effects of manure, nitrogen, manure * nitrogen and tied ridging * nitrogen interactions on cowpea stem and TDM in 2003 short rains season. In general, the combination of tie-ridges with manure or nitrogen gave higher maize and cowpea yields than when these factors are applied alone. These preliminary results indicate that tied ridging in combination with integrated nutrient management has the potential to improve crop production in semi-arid eastern Kenya.