دوره بحراني كنترل علف هاي هرز در سورگوم علوفه اي

The critical period of weed control in sorghum (Sorghum bicolor L.)

The study was conducted in Mashhad (NE of Iran) during 1996 to determine the critical weed control period in Sorghum. Treatments included weed free and weed infested period to 3,5,7,9 leaf stages and total growth season (weed free and weed infested check). Treatments were replicated four times in complete randomized block design. Results showed that a critical weed control period in Sorghum between 20-31 days after sorghum emergence (about 3 to 5 leaf stage) with 5% allowance reduction for yield. By increasing allowance reduction for yield to 8%, the critical period was changed to a critical weed control time (24 days after emergence or about 5th leaf stage). Weed free period up to 5th leaf stage decreased weed dry matter and population to 90% and 70% respectively. Nightshade (Solanum nigrum), Redroot pigweed (Amaranthus retroflexus), Common lambsquarter (Chenopodium album) and Field bindweed (Convolvulus arvensis) were the dominant weed of this experiment.