Use of crop residue and manure to conserve water and enhance nutrient availability and pearl millet yields in an arid tropical region

Crop residues and manures are often used in temperate regions to control soil erosion and maintain soil organic matter. Because crop residues and manures oxidize more rapidly in warmer climates, benefits from use of these materials may not be as evident for tropical as for temperate region agriculture, especially in drier regions where residues are limited. In 1991 and 1992, a field experiment was conducted to study the effect of crop residue incorporation in a loamy sand (Typic Camborthid) in Rajasthan, India. Residues of clusterbean [Cyamopsis tetragonoloba (L) Taub], mung bean [Vigna radiata (L) R. Wilczek], and pearl millet [Pennisetum glaucum (L) R. Br.], and farmyard manure (FYM) were incorporated by disking in October. A pearl miller crop was grown the following Kharif (summer) season with and without fertilizer N. Crop residues increased soil water content at seeding in the order pearl miller > mung bean = farmyard manure > clusterbean. Addition of crop residues and FYM generally enhanced soil fertility status (N and P availability, organic matter, enzyme activity) 10 to 20%, Clusterbean residues and FYM increased pearl miller grain yield 0.1 to 0.2 mg ha(-1), compared with no residue. These treatments also increased straw yields 0.4 to 0.6 mg ha(-1), but mung bean and pearl miller residues increased pearl miller straw only marginally when compared with no residues. Crop residues plus 20 kg fertilizer N ha(-1) provided pearl miller grain yield equivalent to that for 40 kg fertilizer N ha(-1) with no residues, thus effecting a 50% savings of fertilizer N. The use of clusterbean residues or FYM with fertilizer N improved N-use efficiency 20 to 30%. Results indicate that like temperate regions, incorporation of crop residues and FYM in arid tropical soils benefits soil water storage, soil nutrient availability, and crop yield.