Sustainability of Soybean-based Cropping Systems on a Vertic Inceptisol: 1. Effects of Management on Runoff, Soil Erosion, Soil Fertility and Crop Yields

Effects of improved versus traditional management of a Vertic Inceptisol on the productivity and resource use of two soybean-based cropping systems was studied from 1995 to 2003. Improved management comprised of sowing on broadbed-and-furrow landform and additions of nutrients through composted crop residues and prunings of Gliricidia (Gliricidia sepium (L.)); while traditional management consisted of sowing on flat landform and no addition of organic sources of nutrients. These management treatments were applied on both the shallow and medium-deep phases of an operational scale watershed. Cropping systems evaluated were soybean-chickpea sequential (SB-CP) and soybean/ pigeonpea intercrop (SB/PP) systems.

Improved management decreased surface runoff by 24 to 27% and soil loss by 44 to 47% on the two soils when compared with traditional management. Organic carbon (OC), total nitrogen and extractable phosphorus in the soil declined across all management treatments over the study period. Extractable micronutrients (Zn, S and B) in the soil were also deficient at the end of the study period. In spite of decrease in productivity of the cropping systems over the years, total grain yield productivity of the SB-CP system in the last three seasons was 21% higher on the medium-deep and 9% higher on the shallow soil with improved management compared to traditional management. Grain yield productivity of the SB/PP inter-crop system was marginally higher with improved management. It is concluded that, in addition to improved land and water management practices, significant improvements in soil fertility status of Vertic Inceptisols would be needed for balanced nutrition of crops for sustaining production on these soils.