Author : Yunus Musa

Summary : A field experiment was conducted at the Central Experiment Station, University of the Philippines at Los Banos (UPLB), from November 1988 to May 1989. The objective was to determine performance of monocropped maize and soybean planted after seven types of cropping, i.e. intercrop of rice + legume (cowpea or mungbean) and monocrop of rice, maize, or legume (cowpea or mungbean), and control (followed for four planting seasons). Residues of previous crops were incorporated into the succeeding crop of disking, while inorganic fertilizer was applied on control plots. The experiment was designed to verify if the type of previous cropping and incorporating of the residue into the soil does have an immediate effect on the succeeding crop, and how this practice compare with a system where no previous crop was grown for some time and where inorganic fertilizer was used. Soil analysis for organic matter (OM), cation exchange capacity (CEC), pH and some macronutrients (P, K, Ca and Mg) did not reveal significant differences among plots including control at any stage of production. However, significant differences among treatments were found for some crop characters indicating that previous croppings did have an immediate effect on the next season's crop of maize and soybean. Maize and soybean in control plots had higher dry matter production (DMP), crop growth rate (CGR), net assimilation rate (NAR), leaf area index (LAI) and specific leaf weight (SLW). Control plants also took shorter time to flower, tassel, and silk, but were four days delayed in maturity, compared to plants grown in plots previously cropped and with residues. Grain yield of maize and soybean planted in the control plots were also approxiamtely 80 and 20 percent higher, respectively, than those in plots previously cropped. Among previously cropped treatments, maize planted after legume monocrop had highest DMP, CGR, NAR, LAI, and grain yield. In contrast, soybean planted after legume monocrop or intercrop had lower DMP, CGR, LAI and grain yield.