Nolan, B.T., Dubus, I.G., Surdyk, N., Fowler, H.J., Burton, A., Hollis, J.M., Reichenberger, S. and Jarvis, N.J. 2008. Identification of key climatic factors regulating the transport of pesticides in leaching and to tile drains. Pest Management Science, 64, 933-944, doi: 10.1002/ps.1587.

Abstract

BACKGROUND: We identified key climatic factors influencing the transport of pesticides to drains and to depth.  Climatic characteristics such as the timing of rainfall in relation to pesticide application may be more critical than average annual temperature and rainfall.  We simulated the fate of three pesticides in nine contrasting soil types for two seasons, five application dates, and six synthetic weather data series using the MACRO model and analyzed predicted cumulative pesticide loads with statistical methods.

RESULTS: Classification trees and Pearson correlations indicated that 75^th percentile simulated losses (>0.046 mg/m² for leaching, 0.042 mg/m² for drainage) generally occurred with large rainfall events following autumn application on clay soils, for both leaching and drainage scenarios.  The amount and timing of winter rainfall were important factors whatever the application period and these interacted strongly with soil texture and pesticide mobility and persistence.  Winter rainfall primarily influenced losses of  less mobile and more persistent compounds, while short-term rainfall and temperature controlled leaching of the more mobile pesticides.

CONCLUSIONS: Numerous climatic characteristics influenced pesticide loss, including the amount of precipitation as well as the timing of rainfall and extreme events in relation to application date.  Information regarding the relative influence of the climatic characteristics evaluated here can support the development of a climatic zonation for European-scale risk assessment for pesticide fate.