BENTAZON FOR ANNUAL WEED-CONTROL IN NEWLY SEEDED ALFALFA (MEDICAGO-SATIVA L)

Preplant-incorporated (PPI) herbicides were applied to suppress annual weeds in new seedings of alfalfa, then additional annual weed control and crop tolerance from selected bentazon treatments were evaluated. Bentazon applied at 0.8 kg ai ha-1 without an adjuvant caused an average of 8% visual injury to newly seeded alfalfa but did not reduce first-harvest alfalfa yields. Bentazon improved common lambsquarters control in newly seeded alfalfa and reduced weed biomass in first-harvest forage. No significant difference in crop injury, weed control, alfalfa yield, or weed yield was observed when bentazon was applied at 0.6, 0.8, or 1.1 kg ha-1. Greater alfalfa injury occurred when bentazon was applied with 1.25% v/v oil-emulsifier mixture, than when applied alone or with 5% v/v 28% liquid nitrogen fertilizer (28%N). Ten alfalfa cultivars did not differ in sensitivity to bentazon applied early postemergence (POST) or POST.