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Occurrence of 2,4,5-T and Picloram in Subsurface Water in the Blacklands of Texas¹

ABSTRACT

This investigation was conducted to determine the concentration of 2,4,5-T [(2,4,5-trichlorophenoxy)acetic acid] and picloram (4-amino-3,5,6-trichloropicolinic acid) in subsurface water after spray applications of the herbicides to the surface of a seepy area watershed and lysimeter in the Blacklands of Texas.

A 1:1 mixture of the triethylamine salts of 2,4,5-T + picloram was sprayed at 2.24 kg/ha every 6 months on the same area for a total of five applications. Herbicide content in the Houston Black clay during the study ranged from 0 to 162 ppb. Herbicide content on grass was high (28 to 113 ppm) immediately after spraying, but degraded rapidly after each treatment. Concentration of 2,4,5-T and picloram in seepage and well water from the treated area was extremely low (<1 ppb) during the 3-year study. No 2,4,5-T was detected from 122 drainage samples from a field lysimeter sampled for 1 year after treatment with 1.12 kg/ha of 2,4,5-T + picloram (1:1). Picloram was detected in small amounts (1 to 4 ppb) 2 to 9 months after treatment in lysimeter water.

Key Words: ground water • residue • herbicides • lysimeter • watershed

¹ Cooperative investigation of the Agricultural Research Service, USDA, and the Texas Agr. Exp. Sta.

² Agronomist, Soil Scientist, Agricultural Engineer, and Plant Physiologist, respectively, USDA-ARS, College Station 77843, and Temple, Texas.

³ Professor and Associate Professor, respectively, Dept. of Soil & Crop Sciences, Texas A&M Univ., College Station, and Blackland Conservation Research Center, Texas Agr. Exp. Sta., Temple.

Received for publication March 13, 1974.