Multiscale Effects of Management Environ

Nitrate leaching in intensive grassland- and silage maize-based dairy farming systems on sandy soil is a significant environmental concern. This study presents statistical relationships between nitrate concentration in shallow groundwater at different scales in the Netherlands based on a participatory approach over a 7-year period. Data were collected from one experimental and eight commercial pilot dairy farms, revealing that farm milk production varied from 10 to 24 Mg ha-1. Soil and hydrological characteristics were derived from surveys, and meteorological data supplemented the analyses. Multiple regression models revealed that mean nitrate concentrations at the farm scale decreased from 79 mg L-1 in 1999 to 63 mg L-1 in 2006. Notably, groundwater nitrate concentrations decreased under grassland but increased under maize land during the study period. Management practices affected nitrate concentrations differently across spatial scales, with nitrogen surplus, grazing intensity, and land type being significant contributors. The study concludes that intensive dairy farms must adopt measures to comply with the European Union's water quality standard of 50 mg nitrate L-1, with promising strategies including the omission of fertilization of catch crops and adjustments in maize fertilization levels.