Simple regression models for the qualitative prediction of atrazine and terbuthylazine leaching

Leaching of atrazine [6-chloro-N-ethyf-N′-(methylethyl)-1,3,5-triazine-2,4-dlamine] and terbuthylazine [6-chloro- N-(1,1-dirnelhylethyt)-N′-ethyl-1,3,5-triazlne-2,4-diamine] was studied in 23 soils by means of the soil thick-layer leaching method. The equivalent of 4 kg ai ha−1 of both herbicides was leached with water equivalent to 129 mm rain Distances leached were measured qualitatively in bioassays with the test plant Tnfolium repens L. Leaching distances in different soils varied from 6–20 cm for atrazine, and from 2–16 cm for terbuthylazine. Atrazine leached at least 10 cm in 13 soils, while terbuthylazine did not move from the zone of application in 12 soils. Of the five soil properties assessed by means of simple regression, organic matter content (%C) and P-reversion were significantly correlated with the leaching distance of atrazine, and %C with the mobility of terbuthylazine. Relationships between herbicide leaching and either total clay content or soil pH were relatively weak. The combination...