HERBICIDE DISSIPATION AND DYNAMICS MODELING IN 3 DIFFERENT TILLAGE SYSTEMS

The half-lives (t(50)) of the herbicides metolachlor, terbuthylazine a nd isoproturon and the occurrence of desethyl-terbuthylazine and monom ethyl-isoproturon were measured in soils managed with three different tillage systems (conventional tillage, ridge tillage and no tillage). The first-order dissipation model was well adapted to the field data. Under the trial conditions, characterised by silty soil, scarce permea bility, and reduced rainfall, the tillage system did not substantially influence the dynamics of the herbicides; the t(50) was reduced in no tillage only with metolachlor, the more volatile herbicide. The measu red concentrations were then compared with those calculated with SoilF ug, a fugacity-based mathematical model; the calculated values approxi mate the kinetics of both herbicides and metabolites with good precisi on. Copyright (C) 1996 Elsevier Science Ltd