USE OF CROP RESIDUE AND MANURE TO CONSERVE WATER AND ENHANCE NUTRIENTAVAILABILITY AND PEARL-MILLET YIELDS IN AN ARID TROPICAL REGION

Crop residues and manures are often used in temperate regions to contr ol soil erosion and maintain soil organic matter. Because crop residue s and manures oxidize more rapidly in warmer climates, benefits from u se of these materials may not be as evident for tropical as for temper ate 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 Cambor thid) in Rajasthan, India. Residues of clusterbean [Cyamopsis tetragon oloba (L) Taub], mung bean [Vigna radiata (L) R. Wilczek], and pearl m illet [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 r esidues increased soil water content at seeding in the order pearl mil ler > mung bean = farmyard manure > clusterbean. Addition of crop resi dues and FYM generally enhanced soil fertility status (N and P availab ility, organic matter, enzyme activity) 10 to 20%, Clusterbean residue s and FYM increased pearl miller grain yield 0.1 to 0.2 mg ha(-1), com pared 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. Cro p 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 residue s, thus effecting a 50% savings of fertilizer N. The use of clusterbea n 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.