TRIAZINE HERBICIDE FATE IN A NO-TILLAGE CORN (ZEA-MAYS L) CROWNVETCH (CORONILLA-VARIA L) LIVING MULCH SYSTEM

Chloro-s-triazine herbicide dissipation and leaching potential were examined in two untilled soils planted to corn (Zea mays L.) in a crownetch (Coronilla varia L.) "living mulch" sod. Herbicides studied were simazine (6-chloro-N,N′ -diethyl-1,3,5-triazine-2,4-diamine), atrazine (6-chloro-N-ethyl-N′-(1-methylethyl)-1,3,5,-triazine-2,4-diamine, cyanazine (2-[[4-chloro-6-(ethylamino)-1,3,5,-triazin-2-yl]amino]-methylpropanenitrile) and procyazine (2-[[4-chloro-6-(cycloproylamino)-1,3,5,-triazin-2-yl]amino]-2-methylpropanenitrile). Each was applied at 2.2 and 4.5 kg (active ingredient) ha-1. Soil profiles were sampled twice yearly in 15-cm increments to 91 or 122 cm deep. These soil fractions were analyzed for parent herbicide residues. Herbicide dissipation and translocation were rapid and extensive under no-tillage management, and herbicide distribution in the different soil profiles was not predictable solely on the basis of water solubility of the chemicals or soil texture. The probability of detecting subsoil levels of these herbicides was as great in the Murrill silty clay loam as in the Morrison sandy loam. Simazine and atrazine were more persistent and detected more frequently at lower profile depths than cyanazine and procyazine, which are considerably more water soluble. Redistribution of simazine and atrazine by leaching from early to mid-season was also more evident in each soil. © 1990.