PERFORMANCE AND SOIL PERSISTENCE OF CHLORSULFURON WHEN USED FOR WHEAT PRODUCTION IN SPAIN

Chlorsulfuron was preemergence applied in field trials at La Coruna, Spain, at rates from 5 to 30 g ai ha-1 (1987-88) and from 5 to 100 g ai ha-1 (1988-89) for weed control in winter and spring wheat. Excellent control of broadleaf weeds was obtained in both; however, narrowleaf control at the last evaluation (heading) was poor. Chlorsulfuron at 30 g ha-1 did not cause a residual problem in 1987-88, with only 0.24 mu-g kg-1 of dry soil recovered after both a winter and spring wheat cropping season. However, chlorsulfuron persistence at the same rate was very high in the dry year 1988-89, with 0.43 mu-g kg-1 and 0.53 mu-g kg-1 recovered in winter and spring wheat, respectively. 'Cardeno' spring wheat showed no phytotoxic symptom at any rate of chlorsulfuron from 5 to 100 g ha-1. Its yield and yield components (spikes m-2, grain number spike-1, grain weight) were greater with all chlorsulfuron rates, but not in 'Fiel' winter wheat for rates of 30 g ha-1 or higher.