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Book of Abstracts

11th IFOAM
Scientific Conference
11-15 August 1996
Copenhagen, Denmark

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Total Nutrient Fluxes in Organically Managed Farms S1

Stein-Bachinger, K.

Centre for Agricultural Landscape and Land Use Research e.V. (ZALF), Müncheberg Institut for Land Use Systems and Landscape Ecology, Eberswalder Str. 84, D-15374 Müncheberg

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The major difficulties with practising organic agriculture in the new federal states of Germany are the specific site conditions (light sandy soils, low precipitation), the structural situation (large farms, few Livestock Units (LU) per ha) and the lack of models from other European countries. The research project aims at acquiring a data-base of organically managed farms in typical regions of north-east Germany for the determination and evaluation of the overall nutrient fluxes. Different methods of calculating carbon and nitrogen balances will help to identify individual weak points and to work out criteria to optimize the internal farm nutrient fluxes. The results are also intended to provide a basis for assessing potential nutrient losses and to develop strategies for sustainable agricultural systems with regard to specific locations and farm structures. Models will be derived to work out methods transferable to other farming systems.

Five organically managed farms ranging in size from 200 ha up to 1200 ha and stocking rates of between 0.3 to 0.6 LU per hectare (dairy and suckler cows, pigs) are being investigated. The annual average precipitation amounts to about 500 mm, yearly average temperature is about 8$C. The soils are mainly diluvial sandy soils with a Ct-content between 0.6-1.4%. The average loss with regard to the purchase and sale of nutrients at the 'farm gate' was negative for nitrogen (8.4 - 17.3 kg N/ha), phosphorus (1.7 - 3.7 kg P/ha), potassium (2.1 - 4.3 kg K/ha) and magnesium (0.3 - 1.3 kg Mg/ha). These figures are based on analysis of the nutrient content of the plant products as well as on data derived from organic trials. By using data derived from conventional agricultural systems the deficit of nitrogen increased by up to 30% and that of potassium by up to 40%. In order to balance the nutrient fluxes within the farm it is important to establish a system to calculate the contribution from symbiotic dinitrogen fixation according to the specific locations more accurately than has been done in the past. This demonstrates the necessity of testing the common balance methods as well as the data that are used to run these methods in organic agricultural systems. Further details about the total nutrient fluxes will be presented.