AbstractHerbicides Metribuzin [4-amino-6-tert-butyl-3-(methylthio )-as-triazin-5-(4H)one] at 0.8 and 1.6 kg/ha active ingredient, Prometryn [2,4-bis (isopropylamino)- 6-(methylthio)-s-triazine] at 3.3 and 6.6 kg, and Chloramben [3- amino-2,5-dichlorobenzoic acid] at 3.3 and 6.6 kg/ ha were evaluated for preemergence weed control on pigeon peas during 1976 at Lajas, Puerto Rico, in a Vertisol soil. The yield with Metribuzin at 0.8 kg/ha a.i. was similar (P=0.01) to that of the hand-weeded treatment. No statistical differences in yields were observed among the hand-weeded plots, Metribuzin 1.6 kg/ha a.i., and the two Prometryn rates. The least effective herbicide was Chloramben at 3.3 kg/ha, which at the rate of 6.6 kg was toxic to the crop. Good preemergence weed control was obtained from the other herbicide treatments with no toxicity to the legume. The higher herbicide rate of each compound controlled the weeds better than the lower rate. Metribuzin and Prometryn are in the process of evaluation for registration according to the Environmental Protection Agency regulations.
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