Ql. Ma et al., Persistence and leaching of the herbicides acetochlor and terbuthylazine in an allophanic soil: comparisons of field results with PRZM-3 predictions, PEST MAN SC, 56(2), 2000, pp. 159-167
Rates of degradation and adsorption of acetochlor[2-chloro-N-ethoxymethyl-6
'-ethylaceto-o- toluidide] and terbuthylazine [N-2-tert-butyl-6-chloro-N-4-
ethyl-1,3,5-triazine-2,4-diamine] in a Horotiu sandy loam soil (Typic Orthi
c Allophanic) were determined under controlled temperature and soil moistur
e regimes. These were then combined with site-specific soil properties and
climatic conditions in the Pesticide Root Zone Model (PRZM-3) to predict di
ssipation and leaching of the herbicides in the field. PRZM-3 significantly
under-estimated dissipation of both herbicides in the field using paramete
rs derived from the laboratory incubation studies. When these parameters we
re derived from the field trials, PRZM-3 adequately predicted dissipation o
f both herbicides using a two-rate dissipation sub-model but under-predicte
d the dissipation when a simpler single-rate sub-model was used. Earlier-th
an-expected appearance of both herbicides in sub-soil layers were postulate
d to result from the non-equilibrium adsorption/transport of the herbicides
and preferential flow, which cannot be simulated by PRZM-3. (C) 2000 Socie
ty of Chemical Industry.