A field trial was performed on a loamy soil, for two consecutive years, to study the effect of trifluralin, vernolate and alachlor and two rates of nitrogen, on nodulation and yield of inoculated soybeans. The herbicides did not affect the nodulation or yield during the crop cycle, in any of the experiments. The N application depressed the weight of dry nodules at 58 days and its number and weight at 98 days in the first year. The yield of the different treatmens showed no difference. In the second year the nitrogen application did not affect the nodulation of inoculated plants, but the weight of dry nodules of the treatments with spontaneous nodulation was significantly reduced in the three periods of sampling. This year the inoculated treatments showed higher yields when compared with those not inoculated, and the herbicide treated plots yielded more than the checks without herbicide.
Herbicides; nodulation; soybeans