Monday, 6 October 2008
George R. Brown Convention Center, Exhibit Hall E
Jouke Oenema1, Saskia Burgers2, Hein Ten Berge1, Koos Verloop1, Arno Hooijboer3 and Cor de Jong3, (1)Plant Research International, Agrosystems Research, Wageningen UR, Wageningen, Netherlands
(2)Plant Research International, Biometrics, Wageningen UR, Wageningen, Netherlands
(3)National Institute of Public Health and the Environment (RIVM), Bilthoven, Netherlands
Intensive dairy farming in Western Europe is associated with high nitrate leaching to aquatic
systems. In the project �Cows & Opportunities', farm management strategies
are developed to reduce nitrate leaching on 16 commercial pilot dairy farms on
different soil types in the Netherlands. To evaluate these management
strategies, N flows and nitrate concentrations were regularly monitored. For a
sound evaluation, insight is required in the interactive effects of farm
management and environmental factors on nitrate leaching. The objective of this
paper is to analyze the effects of� farm management, soil properties,
hydrology and weather on nitrate concentrations in the upper groundwater on
sandy soils. Data from 9 dairy farms were analyzed at three scales: whole farm,
crop and sampling point. For crop and sampling point we distinguished two
crops: grassland and silage maize. Regression models were used to identify the
factors affecting nitrate concentration in groundwater. At farm level, nitrate
concentration was best described by (unit and parameter estimate in brackets):
N surplus of the farm balance (kg ha-1; 0.18), water soluble organic
matter in groundwater (mg l-1; -0.51), fraction grassland within the
farm (unitless; -45) and grazing intensity (hours ha-1;
0.09). Nitrate concentration under grassland, was best described by a similar
model. Nitrate concentration under maize was best described by total N input to
the soil (kg ha-1; 0.12), mean highest groundwater level (cm below
soil surface; 0.27), depth of presence of soil organic matter (cm below soil
surface; 0.20), C:N ratio in the top soil (unitless; -5.4) and cumulative precipitation between
November 1 and February 28 (mm; -0.2). Based on this analysis, we can quantify
the effects of restricting grazing, crop rotation, management of catch crops,
plowing up grassland, and fertilizer management (amount and timing) on nitrate
concentrations in the upper groundwater.