Crop-weed competition and weed management studies in direct seeded rice (Oryza sativa)

Sorghum [Sorghum bicolor (L.) Moench] is a staple cereal grown on marginal and least fertile soils where only few other crops can survive. The steep decline in sorghum cultivated area during last 40 years and changing climate scenario have necessitated to reorient the agronomic research to increase its productivity, input-use efficiency and profitability. The systematic agronomic research in sorghum started in 1960’s with the development of sorghum hybrids and improved varieties. Initially the research was concentrated on evaluating response of improved sorghum cultivars to NPK under different agro-ecological conditions, nutrient-use efficiency, sorghumbased intercropping systems, water requirement and evaluating herbicides for weed control efficacy in kharif grain sorghum. Later on the agronomic research was strengthened and more emphasis was given on integrated nutrient and weed management in sorghum-based cropping systems. New genotypes of sorghum and component crops were evaluated for better resource-use efficiency and productivity of sorghum-based intercropping systems. In post-rainy sorghum, major emphasis was given on development of in-situ moisture conservation technologies, identifying critical stage of irrigation under limited water availability, optimizing plant population and nutrient management based on soil types. Recently sorghum cultivation in rice-fallows of coastal Andhra Pradesh, a new niche area, has been identified and new agronomic practices for this area are being developed.