Weed management based on phonological stages in corn in north Khuzestan province, Iran

Abstract

The critical period for weed control (CPWC) is the period in the crop growth cycle during which weeds must be controlled to prevent unacceptable yield losses. Field study was conducted in 2008 in the University of Shushtar at the north Khuzestan province in Iran to determine CPWC of corn using a randomized complete block design with 12 treatments and 3 replications. The treatments consisted of two different periods of weed interference, a critical weed-free period and a critical time of weed removal, were imposed at 3leaf stage, 6leaf stage, 9leaf stage, 12 leaf stage, and R1 (based on phonological stages of corn development) with a weedy check and a weed-free check. The CPWC was determined with the use of 5% and 10% acceptable yield loss levels by non-linear Regression method and fitting Logistic and Gompertz nonlinear equations to relative yield data. The CPWC of corn was from 5- to 9-leaf stage (17-36 DAP) to prevent yield losses of 5%. This period to prevent yield losses of 10% was 6- to 8-leaf stage (21-29 DAP).