Abstract

The movement and persistence of picloram (4-amino-3,5,6-trichloropicolinic acid) and 2,4,5-T (2,4,5-trichlorophenoxyacetic acid) were studied on a western North Carolina watershed on which extensive agronomic, hydrologic, and climatic data had been accumulated over a period of 18 years. Picloram was more persistent than 2,4,5-T; approximately 60% of the picloram and 90% of the 2,4,5-T disappeared in 15 days. There was some penetration into the soil, but a very high percentage of the total amount present at the different sampling periods was in the 0- to 7.5-cm layer. Doubling the application rate (4.48 vs. 2.24 kg/ha) resulted in a twofold increase in the amount of herbicide recovered at each sampling period. Very little downslope movement of either herbicide occurred even though the average slope on the plots was approximately 27%. Practically no herbicide was found more than 0.3 m, and none beyond 1.2 m, downslope. More picloram than 2,4,5-T moved.

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