Residual effect of leguminous crops and inorganic fertilizer on soil properties and maize grain yield

Abstract

Soil management practices that utilize organic matter have great potential to increase productivity in sub-Saharan Africa. Field studies were carried out between September 1995 and August 1998 to determine the effects of three leguminous crop species: velvet bean ( Mucuna pruriens var. utilis ), groundnut ( Arachis hypogaea L.) and cowpea ( Vigna unguiculata (L.) Walp), and inorganic fertilizer on the soil properties and succeeding maize grain yield when grown in rotation on a sandy soil classified as Haplic Lixisol in the forest-savannah transition zone of Ghana. The legumes were established in the minor seasons and maize in all the plots in the major cropping seasons. A 2 × 3 factorial design laid out in a randomized complete block was used. The main plots consisted of three leguminous crop residues and the sub-plots of two fertilizer levels (0 and 45 kg N ha −1 , 19 kg P ha −1 , 19 kg K ha −1 ). The control consisted of maize following maize with the recommended fertilizer rate (90 kg N ha −1 , 37 kg P ha −1 , 37 kg K ha −1 ). On average the Mucuna plots added 4.0 t ha −1 of crop residue to the soil in a season and cowpea 1.0 t ha −1 . The preceding crops had little effect on the soil properties. Leaf area index, total dry matter and maize grain yields were significantly affected by fertilizer. The best maize grain yield (6787 kg ha −1 ) was recorded in the first year on Mucuna plots with half the recommended rate of fertilizer. The cropping sequence with Mucuna residue was the most efficient. The gap in maize grain yield between the fertilized and unfertilized treatments widened each successive year. The interaction between organic matter and fertilizer may have been limited due to the surface application of the organic residue.