Effect of coffee residue and intercropping on soil physicochemical properties and yield of component crops in southern Ethiopia.

Nutrient depletion is attributed to leaching, volatilization and mainly use of multiple cropping with low fertilizer input. Coffee residue produced from coffee processing plants is dumped into rivers or burnt as a cheap method of disposal. Both methods bring about environmental pollution. Coffee residue, however, can provide plant nutrients and serve to improve soil fertility. Information on the effect of coffee residue and intercropping on soil physicochemical properties and crop yields is not available in southern Ethiopia. A study was conducted to determine crop and soil nutrient response to intercropping treated with different rates of coffee residue (0, 3, 6, 9 t ha-1) and N fertilizer (0.30, 60 and 90 kg N ha-1) in a factorial arrangement using randomized complete block design. Intercropping increased the uptake of N (11%), P (9%) and K (3%) in intercropped maize and haricot bean. Despite the significant reduction in intercropped-maize grain yield, total production efficiency of intercropping increased by 13%. Intercropping significantly reduced total soil N (17%) indicating mining of N but increased soil pH (1.3%), available K (27%) and P (8%), Ca (19%), and Mg (33%) compared to sole cropping. The increase in pH was due to addition of exchangeable cations (Ca, Mg, and K) from the residue. Depletion of soil N in the control was much higher (varied between 48 and 18 kg N ha-1). More N depletion, ranging from 4 to 53 kg N ha-1 , was observed at the lower rate of coffee residue (3 t ha-1) combined with 30 and 60 kg N ha-1. On the other hand, removal of N declined at higher treatment combinations (30 to 90 kg N ha-1 combined with 6 and 9 t ha-1 residue). More than 89% of the total variation in soil N balance at each level of N fertilizer is attributed to the addition of coffee residue. The finding shows that nutrient requirement of intercropped crops treated with higher fertilizer rate combinations was met. The positive effect of coffee residue on soil physicochemical properties and crop yield points is use as soil ameliorant can increase soil fertility and reduce environmental pollution.