Weed interference on soybean performance by using integrated weed management and empirical model

ABSTRACT: A field experiment was carried out to investigate the efficacy of various weed control methods and johnsongrass (Sorghum halepense L.) water extract (SHWE) spray on soybean (Glycine max L. Merrill) yield, some morphological and phenological traits and weed infestation in 2008. Two factors included SHWE spray at four levels as No- spray, spraying at 15 days after emergence (DAE), spraying at 15 and 30 DAE and spraying at 15, 30 and 40 DAE and current weed control methods at four levels as two hand- weeding, Trifluralin, Trifluralin plus two hand weeding and weedy check. The experiment was carried out as factorial based on randomized complete block design with three replications. All current weed control methods and SHWE spray treatments increased weed dry weight loss, and decreased days to flowering and maturity and so improved grain yield of soybean, significantly. Maximum number of leaves and branches per soybean plant observed in two hand weeding+Trifluralin plots. The SHWE spray at one, two and three times increased soybean grain yield by 21.2, 32.0 and 42.6% in comparison with control, respectively. Based on Cousens model the response of protein yield loss with weed density was hyperbolic, and increasing of weed density decreased protein yield in comparison with the grain and oil yield. Two foliar sprays of SHWE could substitute chemical herbicides and it can be integrated with physical method to produce efficient weed control in integrated weed management of soybean.