Investigation on low doses of atrazine, metribuzin and pendimethalin on weeds and yield of wheat

The results obtained showed that there was severe competition between wheat and the predominant weed species Phalaris minor, Avena ludoviciana and Melilotus indica. Competition by other weed species was normal. The maximum reduction in grain and straw yields due to weed competition was 34.8% and 43.7%, respectively. Weed control treatments lowered the weed population and weed biomass accumulation and boosted up the crop yield. A significant reduction in the weed population and weed dry weight was observed with increasing doses of both atrazine and metribuzin. Metribuzin at 200 g ha-1 killed all the plants of M. indica and gave excellent control of both P. minor (98%) and A. ludoviciana (89%). Atrazine at higher doses had an almost similar effect on P. minor, A. ludoviciana and M. indica with 83-87% control. Pendimethalin gave good control of P. minor and M. indica (75-83%) but poor control of A. ludoviciana (55%). The highest yield was recorded in hand weeding which was significantly superior to all other treatments. Metribuzin at 100 g ha-1 was the next best treatment, and this rate was superior to the higher doses. Pendimethalin and atrazine also brought about a marked increase in the crop yield. Higher doses of atrazine and metribuzin had a phytotoxic effect on the crop, reducing the number of productive tillers and finally lowering the crop yield, despite their excellent control of dominant weed species.