Effects of Soil Nutrient efficiencies and Fertilizer Practice on the Decline of Rainfed Rice yield in the Humid forest zone of West Africa.

Abstract

Nutrient depletion in soils depending to nutrient removal and fertilizer practice is adversely affecting soil quality and stabilization of crop yield as a threat to global food security. To identify soil deficient nutrients and the related amount of nutrient uptakes by rice, an omission trial was conducted from 2003 to 2005. There was increasing soil nutrient deficiency along the study involving soil P (2003), P and K (2004) while yield reduction occurred for N, P, K and Mg in 2005. The highest yield of 3-4 tha-1 recorded in 2003 was decreased three times in 2005 mainly, as consequence of low Mg-uptake in K and Mg exclusion treatments. Furthermore, yield declining occurred in Zn exclusion treatment as consequence of unbalanced ratio of K:Mg that could disturbed P-nutrition. Applying these nutrients was recommended as basal fertilizer and 20kgha–1 and 150kgha–1 was suggested for the rates of P and K respectively.