Pesticide runoff from conventional tillage, minimum tillage, and no-tillage cropping systems: Meta-analysis of published North American data.

Abstract

Pesticide applications may soon be regulated by laws predicated on the presupposition that reducing tillage, and thereby increasing soil surface crop residue cover, decreases sorbed and soluble agrochemical losses in surface runoff and erosion. This analysis was conducted to determine whether pesticide transport via surface runoff and erosion could be manipulated by tillage practices. Estimates of the amounts of crop residue cover within each tillage practice were averaged from data reported in the original articles. Response ratios of the paired means of runoff, erosion, and pesticide losses and concentrations from the effects of tillage practices were meta-analyzed as paired Student's t-tests using inverse-variance weighted least squares means from data reported from research experiments conducted in the United States and Canada and published between 1984 and 2006. Transitioning from conventional tillage to minimum tillage increased crop residue cover 5.4-fold while concurrently reducing runoff, sediment, and soluble and sorbed pesticide losses 26%, 64%, and 15%, respectively, despite an 11% increase in pesticide concentrations in runoff. Conversely, converting from conventional tillage to no-tillage increased crop residue cover 15.3-fold, reduced runoff 43%, and decreased sediment loss 87%, yet had no effect on pesticide losses because eliminating tillage increased pesticide concentrations in runoff 77%. Soil, environmental, time, and physiochemical factors were not included in the analysis due to lack of data. Consequently, minimizing rather than eliminating tillage may be effective at decreasing agrochemical losses in surface runoff and erosion, but more research is needed to examine the potential effects of cofactors to make recommendations to reduce pesticide runoff.