|Rotz, Clarence - Al|
Submitted to: Grasslands Federation European Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 4/20/2002
Publication Date: 5/20/2002
Citation: ROTZ, C.A., WACHENDORF, M., HERRMANN, A., KORNHER, A., TAUBE, F. A MODELLING APPROACH TO MANAGEMENT IMPACTS ON NITROGEN FLUXES IN SPECIALISED DAIRY FARMS. GRASSLANDS FEDERATION EUROPEAN PROCEEDINGS. 2002. Interpretive Summary: In Europe there is considerable interest in developing efficient agricultural systems that reduce nitrogen losses to the environment. For specialised dairy farms in Northern Germany, nutrient balances often show relatively high nitrogen surpluses because much more nitrogen is brought onto the farm in purchased feed and fertilizer than that which leaves in the milk and meat produced. High surpluses can lead to serious environmental problems, mainly due to increased losses of nitrogen as nitrate to groundwater or as nitrous oxides to the atmosphere. Cropping and feeding strategies are needed to more efficiently use the available nitrogen and thus reduce these losses. A farm simulation model was used to evaluate the effects of crop and pasture management on nitrogen losses from dairy farms on the extremely light soils typical of this region in Northern Germany. Analysis of these farms showed that using more corn and/or grazing less pasture reduced nitrogen losses. These results can help direct producers and policy makers toward more sustainable production strategies for this region.
Technical Abstract: Whole farm simulation was used to evaluate the long-term effects of cropping and feeding strategies on nitrogen losses from a typical dairy farm on the sandy soils of Northern Germany. Animal numbers supported by the farm-produced forage decreased with greater use of grazing and increased with the use of higher yielding corn silage. The import of purchased feed was directly related to animal numbers, and the surplus nitrogen per unit of milk produced decreased with increased use of corn silage. Nitrogen was utilized most efficiently on the dairy farm when 50 to 80% of the forage produced and fed came from corn silage. Greater use of grazing decreased nitrogen volatilization loss but increased leaching loss because urinary nitrogen deposits on pasture were more quickly absorbed into the soil. Use of corn on the farm reduced nitrogen volatilization considerably because manure could be injected into the soil before spring planting. Higher levels of manure nitrogen in the soil caused small increases in denitrification. Total nitrogen losses per unit of milk produced increased with the use of grazing and decreased with greater use of corn.