DISTRIBUTION AND TRANSPORT OF ATRAZINE AS INFLUENCED BY SURFACE CULTIVATION, EARTHWORM POPULATION RAINFALL PATTERN

Several laboratory studies were conducted to evaluate the effects of s oil surface cultivation, earthworm (Allolophora caliginosa L) populati on, and rainfall pattern on C-14-atrazine 2-chloro-4-ethylamino-6-isop ropylamino-s-triazine) leaching through intact soil cores. Soil cores (16 cm dia x 20 cm deep) were collected from a seven year no-till (NT) corn field. Earthworms (0, 4, or 8 core(-1)) were introduced into the cores. Half of the cores were cultivated (2.5 cm depth) and the rest of the cores were left uncultivated prior to C-14-atrazine treatment ( 2.74 mg core(-1)). Cores were subjected to a rainfall pattern in which a low intensity rain (16 mm of rain in 2.5 h) was followed 48 h later by a high intensity rain (27 mm of rain in 1.5 h). The saturated hydr aulic conductivities (Ksat) of cores with 0, 4, and 8 worms core(-1) w ere 0.8, 3.4, and 5.3 cm h(-1), respectively. Increasing the number of earthworms in each core from 0 to 8 worms, increases the amount of at razine (% of applied) leached through untilled cores from 8.5 to 13.5% and for tilled cores from 1.0 to 5.0%. Much more atrazine was leached through untilled soil cores than tilled cores at both low and high ra infall intensities. The results of this study suggest that herbicide t ransport is dependent on a combination of rainfall parameters, soil ma croporosity, and disruptive surface cultivation.