Effect of some Herbicides on Weed Suppression in Forage Sorghum (Sorghum bicolor L. Moench)

This study was performed to evaluate the efficacy of combination of two pre-emergence herbicides with broad and narrow leaf weed spectrum and four post-emergence herbicides with broad leaf spectrum for use in forage sorghum in three locations)Iran):Mashhad, Ahwaz and Varamin during 2010. The experiment was conducted in a RCBD design with four replications. Treatments consisted of acetochlor (Acenit EC 50%, at 3.5 L ha-1) and pendimethalin (Stomp EC 33%, 4 L ha-1) as pre-emergence in combination with post application of 2,4-D+MCPA (U46 Combi Fluid SL 67.5%), Bromoxinil+MCPA (Bromicide MA EC 40%), 2,4-D+Dicamba (Dialen Super SL 46.4%), and Bentazon (Basagran SL 48%) at 1.5, 1, 1.5 and 1.2 L ha-1 respectively and the weed free and weed infested controls. As expected, all treatments were successful in broad leaf weed suppression and therefore increased forage yield comparing to weed infested check. These results showed that all herbicides used in this research can be used alternatively in sorghum. Acetochlor in combination with 2,4-D+MCPA was the best treatment in weed suppression and yield increase while treatments containing bentazone were weak. Neither acetochlor nor pendimethalin succeeded in Johnsongrass (Sorghum halepense (L.)Pers.) suppression while Jungle rice (Echinochloa colonum (L.) Link) was controlled by these two herbicides. Acetochlor in combination with bentazone were effective in Nutsedge (Cyperus sp.) suppression but they show some injury on sorghum. This injury did not affect the yield in Mashhad but in Ahwas decreased yield. Since only broad leaf spectrum herbicides were used as post-emergence in this research, more study on post narrow leaf spectrum herbicides for sorghum are recommended.