The Relative Performance of Forage Legumes as Rotational Crops in the Gezira

Abstract

SUMMARYA study was made of the nitrogen fixing systems of various forage legumes and their rotational effect on yield of subsequent cotton crops, as well as of yields of the different legumes. Phillipe-sara, clitoria and lubia out-yielded all the others. Nitrogen yields of the various forage legumes showed that they are active fixers of atmospheric nitrogen, but yields of cotton following the various legumes showed wide seasonal variability and were neither significantly nor consistently different in different seasons. On the other hand, the increase in cotton yield due to fertilizer nitrogen was highly significant, indicating a comparatively small end-of-season contribution of cut legumes to soil nitrogen. It was therefore difficult to differentiate between the legumes on the basis of any consistent ability to influence yields of following cotton, suggesting that the choice of a legume in the rotation should depend primarily on economic considerations.