The Effect of Nutrient Management and Crop Rotation on Weed Dynamics in Rice under Dry Zone (DL1B) of Sri Lanka

Abstract

The Integrated weed management (IWM) is widely used to manage we eds in diverse cropping systems. Crop rotation and diverse n utrient management strategies are essential components in IWM. However, the effect of crop rotation and nutrient management systems on weed dynamics in Sri Lankan rice-based cropping systems is scarce. Therefore, an experiment was conducted to identify weed density, biomass, and abundance of two different nutrient management systems (Synthetic; SNM and Integrated; INM) and under rice monoculture and rice-maize rotation during four seasons within the farm premises of the Faculty of Agriculture, Rajarata University of Sri Lanka. Rice variety Bg300 and maize hybrid Pacific-998 were cultivated. Growing maize in the Yala season increased weed density and weed biomass compared to growing rice in both crop rotation cycles. During the first cycle, weed den sity was high under INM in the Rice crop phase. However, in the second cycle, both crop phases (rice and maize) had low weed density under INM compared to SNM. A higher density of sedges was reported with the crop rotation in the Yala season s, and grasses were dominant in the mono-cropping in both seasons. Grass biomass did not change with the nutrient manageme nt systems, while the biomass of sedges increased with synthetic fertilizer only. High weed density and biomass in maize during the first cycle were substantially reduced in the second cyc le for both nutrient management systems. Overall, reducing chemical fertilizer by 50% and incorporating organic matter, INM, substantially supported weed management in both rice and maize crops.