Study region
Artificially drained agricultural land in northwest Europe.

Study focus
The use of application timing as a mitigation tool for pesticide leaching to drains was investigated by simulating pesticide fate after application every day in a pesticide-specific application window, using the agro-hydrological model DAISY. The simulations were carried out for six combinations of pesticide-crop-seasons using three synthetically generated climate series and 800 soil profiles. The simulated drain concentrations were transformed to normalized pesticide concentrations in a hypothetical adjacent stream. Each application day was then characterized by the maximum normalized hourly pesticide concentration in the stream, expressed as the maximum hourly toxic unit (mTU), occurring within 300 days after application.

New hydrological insights for the region
The result showed that if the pesticide was applied consistently every year at the best application day, pesticide leaching, in terms of the 90th percentile of mTU, could be reduced by up to 62% compared to a random application. If the pesticide application day was restricted to vary in a five-day period, the 90th percentile of mTU could be reduced by up to 21%. Thus, our study shows that there is a significant mitigation potential for reducing pesticide leaching to drains by tailoring the timing of pesticide application to weather conditions.