Selectivity of pre-emergent herbicides in bird’s-foot trefoil crops

Abstract

Competition with weeds and lack of selective herbicides registered for bird’s-foot trefoil crops affect their development and limit productivity. Therefore, this study aimed at evaluating selectivity of pre-emergent herbicides in bird’s-foot trefoil crops. Experiments were carried out in a greenhouse and on a field where the following herbicides were evaluated and compared with the control: imazethapyr, diclosulam, flumetsulam, metribuzin, s-metolachlor, sulfentrazone, clomazone and isoxaflutole. Regarding variables under evaluation, phytotoxicity (PHYTO), plant stature, dry mass of the aerial part (DMAP) and dry mass of roots (DMR) were evaluated in the greenhouse, while plant population, PHYTO and DMAP were assessed on the field. The criterion to determine selectivity were: PHYTO below 15% and not reducing the plant population nor morphological variables, by comparison with the control. The variables were negatively affected by the herbicides clomazone, metribuzin, isoxaflutole, diclosulam, s-metolachlor, in which the crop population was reduced in 98, 92, 83, 63, 48 and 22%, respectively. Following the criteria, only the herbicide sulfentrazone as a pre-emergente is selective to bird’s-foot trefoil crop (cultivar ‘Sao Gabriel’).