Critical period for weed control in corn in the South-West of Iran

Abstract

The Critical Period for Weed Control (CPWC) identifies the phase of the crop growth cycle when weed interference results in unacceptable yield losses. Field study was conducted in 2008 in the University of Shushtar at the South-West of Iran to determine CPWC of corn using a randomized complete block design with 12 treatments and 3 replications. The experiments consisted of 2 sets of treatments. In the first set, the crop was kept weed-free until the growth stages of V3, V6, V9, VI3 and VT (based on phonological stages of corn development). In the second set, weeds were permitted to grow within the crop until the above-mentioned growth stages. 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. Increasing the duration of weed interference decreased corn yield significantly. The CPWC for weed control 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). Results from this experiment suggest that weed control should be carried out between fifth to ninth leaf stages to provide maximum grain yield. © 2010 Knowledgia Review, Malaysia.