Flat fan and air induction nozzles affect soybean herbicide efficacy

Fifteen field experiments were conducted from 2002 to 2005 to determine the influence of the nozzle type, spray volume, spray pressure, and herbicide rate on herbicidal efficacy in soybean. There was no effect of the nozzle type on herbicidal efficacy with fomesafen, bentazon, glyphosate, and cloransulam-methyl when applied at the manufacturer's recommended rate. The control of Echinochloa crus-galli (barnyardgrass) with quizalofop-p-ethyl was improved when applied with flat fan (FF) nozzles compared with air induction (AI) nozzles. There was an increase in weed control with the FF nozzles compared with the AI nozzles in four of the 13 comparisons when the herbicides were applied at half the recommended rate, while in two situations, application with the AI nozzles resulted in improved weed control. With the FF nozzles, there was no effect of the water carrier volume on weed control with bentazon, glyphosate, and cloransulam-methyl. The control of Abutilon theophrasti (velvetleaf) and Chenopodium album (common lambsquarters) with fomesafen and E. crus-galli with quizalofop-p-ethyl was improved at the higher water carrier volume. With the AI nozzles, the control of A. theophrasti and Ambrosia artemisiifolia (common ragweed) with fomesafen and E. crus-galli with quizalofop-p-ethyl was improved at the higher water carrier volume, while the control of A. theophrasti and Polygonum persicaria (ladysthumb) was improved with glyphosate at the lower water carrier volume. With the AI nozzles, the control of C. album with bentazon and E. crus-galli with quizalofop-p-ethyl was improved at the higher spray pressure. There was no effect of the nozzle type on the soybean yield with glyphosate, cloransulam-methyl, and quizalofop-p-ethyl. The use of the FF nozzles compared with the AI nozzles to apply fomesafen and bentazon increased the soybean yield by 6 and 7%, respectively. Based on this study, the optimum nozzle type, water carrier volume, and spray pressure is herbicide- and weed species-specific.