Field studies were conducted at Shiraz, Iran, during 2000 and 2001 to investigate the effect of separate and combined herbicide treatments on weed control and corn yield. Separate and combined herbicide treatments included 14 combinations applied at two rates. Herbicides reduced weed biomass compared with the weedy check. In both years, maximum reduction in weed biomass was observed with atrazine plus alachlor at 1 2.44 and 1.5 1.92 kg ai/ha and minimum reduction in weed biomass was observed with rimsulfuron at 0.02 and 0.04 kg/ha. In 2000 and 2001, 2,4-D plus MCPA at 0.36 0.31 and 0.54 0.46 kg/ha, and alachlor plus 2,4-D plus MCPA at 1.92 0.54 0.46 kg/ha, and 2.44 0.36 0.31 kg/ha, controlled 80 to 100% of field bindweed and rimsulfuron at 0.02 and 0.04 kg/ha controlled 17 to 70% of field bindweed. All herbicide treatments controlled redroot pigweed 60 to 100%. In 2000, at 6 and 17 WAP, minimum biomass reduction of Chinese-lantern-plant was observed with 2,4-D plus MCPA at 0.36 0.31 and 0.54 0.46 kg/ha, and primisulfuron plus prosulfuron at 0.02 0.02 and 0.03 0.03 kg/ha. Rimsulfuron plus primisulfuron plus prosulfuron at 0.02 0.03 0.03 and 0.04 0.02 0.02 kg/ha reduced johnsongrass biomass 96 to 100% and the efficacy of rimsulfuron increased when tank mixed with primisulfuron plus prosulfuron. Results of both years showed that all herbicide treatments increased corn grain yield as compared with the weedy check. Maximum corn grain yield was obtained with combinations of atrazine plus alachlor at 1 2.44 and 1.5 1.92 kg/ha.
Nomenclature: Atrazine; alachlor; bentazon; bromoxynil; 2,4-D; MCPA; primisulfuron; prosulfuron; rimsulfuron; chinese-lantern-plant, Physalis alkekengii L. #3 PHYAL; field bindweed, Convolvulus arvensis L. # CONAR; johnsongrass, Sorghum halepense L. # SORHA; redroot pigweed, Amaranthus retroflexus L. # AMARE; corn, Zea mays L.
Additional index words: Corn grain yield, weed biomass, herbicides.
Abbreviation: WAP, weeks after planting.
