Barnyardgrass [Echinochloa crus-galli (L.) P. Beauv.] is one of the most problematic weeds in Kerala rice (Oryza sativa L.) ecosystems because of its morphological similarity to rice and its potential to cause substantial yield losses. This study evaluated integrated cultural weed management strategies by examining the effects of seed burial depth, flooding depth, and rice straw mulch on weed emergence and seedling vigor. Surface-sown seeds recorded the highest emergence, whereas burial at 1 cm reduced emergence by 84%, with negligible emergence (<1%) at burial depths of 6 to 8 cm. Flooding significantly suppressed weed establishment, with a water depth of 5 cm reducing emergence by 75% and seedling biomass by 83%, while depths of ≥6 cm completely inhibited emergence. Rice straw mulch also effectively reduced weed emergence by 50% or more at application rates of 6,000 to 8,000 kg ha−1 and completely prevented emergence at 10,000 kg ha⁻1. Correlation analysis revealed significant negative relationships between seed burial depth, flooding depth, mulch rate, and weed emergence and seedling vigor. Regression analysis showed significant negative linear relationships between seedling biomass and both seed burial depth and mulch rate, and between seedling length and these factors, whereas the response to flooding depth was best described by a significant quadratic model. Integrating deep tillage or the stale seedbed technique with appropriate water management in wet direct-seeded rice or rice straw mulching (6,000 to 10,000 kg ha⁻1) in aerobic and rainfed upland rice, can suppress E. crus-galli emergence and growth by 80% to 100%, providing a sustainable alternative to herbicide-based weed management.

A bioassay, based on seedling shoot inhibition with difenzoquat at 10 mg/L, provides a rapid means of predicting hard red spring wheat (HRSW) cultivar response to foliar-applied difenzoquat. The tolerance of several cultivars to difenzoquat was determined by shoot length inhibition in the laboratory, and by visible crop injury and shoot dry weight in the greenhouse. Of the 19 cultivars tested, one cultivar that was susceptible in the laboratory assay was intermediate in tolerance to difenzoquat in the greenhouse assay; two cultivars that were tolerant in the laboratory bioassay were of intermediate tolerance in the greenhouse assay. Results from laboratory and greenhouse studies both identified cultivars distinctly susceptible to difenzoquat. Shoot inhibition indicated that HRSW cultivar susceptibility to difenzoquat involves continuous variation from tolerant to susceptible. This may explain why some cultivars show differential responses to difenzoquat under different environmental conditions.