Critical period of weed control in chickpea under non-irrigated conditions

The present study was conducted during the growing seasons of 2005, 2006, and 2007 to determine the critical period of weed control (CPWC) in chickpea (cv. Aziziye 94). In order to evaluate the beginning of CPWC, weeds were allowed to compete at weekly intervals for 1 to 8 weeks after emergence (WAE) and, at the end of CPWC, plots were kept weed-free at weekly intervals for 1 to 8 WAE by periodic hand hoeing. The beginning and the end of CPWC were based on 5% acceptable yield loss (AYL) levels, which were determined by fitting logistic and Gompertz equations to relative yield data, representing increasing duration of weed-interference and weed-free period, estimated as growing degree days (GDDs). The major weed species were Centaurea depressa Bieb. and Bromus tectorum L. for the 1st year, Salsola ruthenica Iljin., Amaranthus sp. and Heliotropium europaeum L. for the 2nd year and Amaranthus spp., Salsola ruthenica Iljin., Sisymbrium septulatum DC. and Heliotropium europaeum L. for the 3rd year. Overall weed density was 190 plants m(-2) in 2005, 215 plants m(-2) in 2006, and 191 plants m(-2) in 2007. Yield losses were 26.4% in 2005, 31.5% in 2006, and 25.0% in 2007 when the crop was not weeded. It was found that at the 5% AYL level CPWC was 2.32 WAE to harvest in the 1st year, from emergence to harvest in the 2nd year, and from 0.34 WAE to harvest in the 3rd year. The present findings suggest that the determination of CPWC is crucial in chickpea production.