Soil Organic Carbon Stock, Moisture Availability and Crop Yield as Influenced by Residue Management and Tillage Practices in Maize-Mustard Cropping System Under Hill Agro-Ecosystem

Residue management can notably influence crop production under any agro-climatic situation. A field experiment was conducted for three consecutive years (2005-2007) to evaluate various residue management and tillage practices on soil organic carbon (SOC), moisture conservation and crop productivity (maize: Zea mays L. and mustard: Brassica campestris L.) in a clay loam soil under hilly eco-system of northeast India. Six residue management combinations [M-0-control, M-1-Maize stalk cover (MSC), M-2-MSC + Ambrosia sp. at 5 t ha(-1), M-3-MSC + Ambrosia sp. at 10 t ha(-1), M-4-MSC + poultry manure at 5 t ha(-1) + Ambrosia sp. at 5 t ha(-1) and M-5-MSC + FYM at 10 t ha(-1)] were tested under conservation and conventional tillage. Results showed that all residue management practices significantly increased SOC density and SOC stock (with increases ranging from 40 to 165 %) relative to the control through incorporation of crop biomass and vegetation over the time period. Highest values were obtained with the M-4 treatment (1385 g m(-2) and 13.78 Mg ha(-1), 1292 g m(-2) and 12.94 Mg ha(-1), respectively under conservation and conventional tillage practice). Conservation tillage had higher SOC (7.3 %) than conventional tillage practice. The soil moisture content measured at various soil depths revealed that it was consistently higher in residue management treatments, which is also reflected in relative leaf water content and water saturation deficit values. Higher moisture content prevailed under residue management practices at 15-30 cm soil depth, highest being in M-4 treatment (33.14 %). All the residue management practices recorded higher crop yield, with increases ranging from 41 to 165 and 235 to 450 % for mustard in relation with control without residue. Among all the treatments, M-4 recorded highest crop yield (mean value 2,503 kg ha(-1) for maize and 2,418 kg ha(-1) for mustard) than control (1,006 and 465 kg ha(-1), respectively for maize and mustard). The study indicated that the integrated supply of MSC, poultry manure and Ambrosia sp. at 5 t ha(-1) each under conservation tillage contributed most suitable soil physical environment for crop growth. However, a simple maize stock cover also resulted in significant effects on SOC, soil moisture and improved crop yield. Therefore, residue management should be adopted for support of double cropping in hill eco-system of north-east India.