Nitrogen returns to soil by selected cropping systems on a Vertisol in the semi-arid tropics of IndiaM DAbdurahmanauthorBSeelingauthorT JRegoauthorB BReddyauthorLimited nitrogen (N) availability is a common constraint for crop production on Vertisols. Erratic rainfall in the semi-arid tropics and relatively high cost of N fertilizers make its application a risky investment, therefore, most farmers do not apply N fertilizer in dryland crops. Cropping systems which improve soil fertility can minimize the need for synthetic fertilizers. In a two-year experiment, four cropping systems and mirror images of two systems were examined for their returns of N to soil in roots and fallen leaves. Sorghum/pigeonpea intercrop for two years (S/PP S/PP) and cowpea/pigeonpea intercrop rotated with sorghum followed by safflower (COW/PP S+SAF) contributed around 54 kg N ha-1 in roots and fallen leaves when no nitrogen fetilizer was applied. The largest proportion of this N was returned to soil through fallen leaves of pigeonpea. In terms of root mass a rotation of sorghum followed by safflower in the post-rainy season (S+SAF S+SAF) deposited almost the same amount of N in roots if adequately fertilized. Under S/PP S/PP the soil mineral N content was measurable higher compared to other systems.Soil ScienceAgriculture-Farming, Production, Technology, Economics1999The Gaurav Society of Agricultural Research Information Centre (GSARIC)Article