Rapid decay of dolichos [Lablab purpureus (L.) Sweet] residue leads to loss of nitrogen benefit to succeeding maize (Zea mays L.)

The legume dolichos [Lablab purpureus (L.) Sweet] has become a popular fallow cover crop in sub-Saharan Africa, intended to supply nitrogen to succeeding cereal crops. The objective of this study is to determine the rate of decay of incorporated dolichos residue in order to enhance the nitrogen benefit to the following grain crops. The results show that 50% of residues decay within two to four weeks of incorporation. Thus, if residues are incorporated well in advance of cereal planting, much of the nitrogen benefit is lost. The authors suggest that waiting to incorporate residues until closer to the time of maize planting.