Abstract

Between 1999 and 2010 the RIVM monitored the water quality on sixteen Dutch dairy farms participating in the Cows & Opportunities (Koeien & Kansen) project. One of the main objectives of the project Cows & opportunities is to implement future stricter manure policy on sixteen pioneer farms and to examine the impact of the policy on water quality. The manure policy aims to limit the use of fertilizer and manure in order to improve the quality of groundwater and surface water.

This report serves as a reference with analysis data of the quality of groundwater, drainage water and ditch water on farms. To determine the effect of future manure policy it is necessary to consider both water quality and agricultural practice (including the application of manure). This analysis is performed by LEI Wageningen UR in collaboration with Plant Research International and the RIVM.

The sampling of the farms is covered by the National Monitoring Network Minerals Policy (LMM: Landelijk Meetnet effecten Mestbeleid). Due to the high density of measurement points and the prolonged, continuous measurement series the group Cows & Opportunities farms is unique within the LMM. For all the participating farms, trend graphs are made for the nitrate or total nitrogen concentration in all sampled water types (depending on the soil this is groundwater, drainage water, ditch water and soil moisture). For each outlier, the individual sample points are examined to asses a possible cause. In addition, for all farms the soil type, the groundwater regime and the groundwater table is reported. The groundwater regime is a measure of the dryness of a parcel, which, like the groundwater table and the soil type, affects the nitrate concentration.