PESTICIDE FORMULATION AND APPLICATION TECHNIQUE EFFECTS ON SURFACE PESTICIDE LOSSES

Abstract

The impacts of pesticide formulation, application technique, and tillage direction on surface losses of alachlorand terbufos were studied on field plots subjected to simulated rainfall. Two alachlor treatments (emulsifiable concentrateand microencapsulated formulations) and four terbufos treatments (granular and controlled-release formulations incombination with banded and in-furrow application) were applied to plots tilled either up-and-down the slope or on thecontour. Total alachlor losses averaged 6.2% of applied from up-and-down plots and 2.4% from contour plots. Similarly,terbufos losses averaged 0.5 and 0.4% from up-and-down and contour plots, respectively. Impacts of tillage directionwere more pronounced with alachlor because sediment-borne losses constituted a larger fraction of total losses comparedto terbufos. Application of terbufos in bands over the furrow resulted in greater surface losses than did application infurrow,averaging 25.4 and 5.8 mg from banded and in-furrow, respectively. Finally, the microencapsulated formulation ofalachlor and the controlled-release formulation of terbufos yielded higher surface losses than did the emulsifiableconcentrate or granular formulations. Greater losses of the microencapsulated and controlled-release formulations wereattributed to transport of discreet particles of pesticide with eroded sediment. Overall, losses of microencapsulatedalachlor were 631.8 mg compared to 284.5 mg for the emulsifiable concentrate. Losses of terbufos were 14.6 mg for thegranular formula and 16.5 mg for controlled-release.