Soil Chemical Properties as Affected by Incorporated Legumes and Nitrogen in Soil with Maize (Zea mays L.) in a Semi-Arid Environment

Soil infertility is a critical constraint in crop production in savanna soils. Hence, there is a need to develop a cropping system which will enhance soil nutrient availability and usage. In a bid to address this, field experiments were conducted 2005, 2006 and 2007 wet seasons at the Research Farm of the Institute for Agricultural Research, Ahmadu Bello University, Zaria, Nigeria, to evaluate the effect of incorporated short duration legume fallow and nitrogen levels on soil chemical properties. The treatments consisted of two maize varieties (SAMMAZ 12 and SAMMAZ 27) and five rates of nitrogen (0, 30, 60, 90 and 120kg N ha-1) in the main plots while three green manure crops (Lablab (Lablab purpureus), Mucuna (Mucuna pruriens) and Soybean (Glycine max (L.) Merrill) and a weedy fallow were accommodated in the sub-plots. The plots with SAMMAZ 27 had more soil organic carbon, soil total N and soil C:N than plots with SAMMAZ 12 whereas plots with SAMMAZ 12 had more soil exchangeable Ca than plots with SAMMAZ 27. Application of 30 and 90 kg N ha-1 significantly increased soil organic carbon while application of 90 and 120 kg N ha-1 improved soil available P. Nitrogen application had no consistent effect on soil exchangeable Mg but significantly reduced soil pH and soil exchangeable K. Nitrogen addition had no significant effect on soil total N, soil C:N and soil exchangeable Ca. Incorporation of mucuna, lablab and soybean showed beneficial effects on soil chemical properties . Incorporation of green manure crops increased significantly soil organic carbon, soil total N and soil available P but reduced significantly the soil pH, soil C:N and soil exchangeable cations compared with weedy fallow.