Influence of different leguminous crop on the ultisol that had been continuously cropped to cassava /maize for over six years

Leguminous crops play an important role in developing sustainable and low input crop production system and have shown good potential for inclusion in alley cropping systems. Hence, a study was carried out at the Teaching and Research Farm of the Faculty of Agriculture, Chukwuemeka Odumegwu Ojukwu University to evaluate the productivity of an impaired ultisol under cassava/maize for over six years planted with different legumes. The experiment was laid out in a randomized complete block design. The treatments studied were, cowpea, groundnut, bambara groundnut, pigeon pea and control which is maize. Data collected was subjected to an analysis of variance test based on randomized complete block design (RCBD) and treatment means were separated using least significant difference (LSD<0.05). The findings from the study showed that there were significant (P<0.05) differences among the treatments in growth, yield and soil chemical parameters assessed as well as the texture of the studied soil. The legume crops planted on the impaired soil had good nodulation which helped to replenish soil nutrient lost and good yield of pigeon pea (0.34 tha-1), Bambara groundnut (0.17 tha-1) cowpea (0.12 tha-1), Groundnut (0.10 tha-1), respectively. The result of the soil chemical parameters assessed from post harvest soil analysis indicated that the nutrient content of the studied soil increased except for exchangeable acidity (EA), K and effective cation exchange capacity which generally reduced in all the plots planted with leguminous crop. The plots planted with Bambara groundnut and groundnut showed a slight reduction in exchangeable Mg2+ relative to pre planting soil analysis which was 50% reduction relative to the control, while exchangeable Na+ content reduced in plots planted with Bambara groundnut. Evidence from this study, then showed that leguminous crop can be used to reclaim an impaired soil and improve the fertility status of the soil. Key words: Chemical properties, growth, legume crops, ultisol, yield.