CHEMICAL CURING OF RANGE GRASSES WITH PARAQUAT

When applied at anthesis to native and introduced grasses, paraguat effectively altered redistribution of N, P, K, and Ca in the herbage. The decline of these elements following treatment in dry summers was minimal until fall rains; then, losses of P, K, and Ca were greater than N. In wet summers, decline of N, P, K, and Ca in treated herbage occurred throughout the summer and was greater than in a dry summer; however, summer rains also caused new growth on treated plots. Following either wet or dry summers, herbage in the fall on treated plots was higher in estimated feed value then herbage on plots cured naturally. Either evening or morning applications of 0.2 lb/A of paraquat cation in 5 to 30 gal of water plus a cationic surfactant provided an acceptable level of curing in these grasses. Herbage yield from plots treated in a wet summer was reduced 45% but in dry summers no yield reduction on treated plots was measured. Herbage yield following 1 or 2 consecutive treatment years was not reduced. Two ppm or less of paraquat residue was measured in crested wheatgrass 30 days after treatment with 0.2 lb/A. In a more dense meadow vegetation treated with 0.5 lb/A paraquat, residue concentrations of 10 ppm were measured 90 days after treatment.