INVESTIGATIONS ON THE NUTRIENT CYCLE AND ITS COMPONENTS OF A BIODYNAMICALLY-MANAGED FARM

Experimental analyses of the nutrient cycle and its components in orga nically managed farms have not yet been performed. This paper summariz es results of a three-year (1985 to 1987) research project aimed at ba lancing the overall nutrient cycle on a biodynamically managed farm (' Boschheidehof'), located in the lower Rhine valley of Germany. The 'Bo schheidehof farm, with 29 ha of worked land and a stocking rate of 1.0 4 Livestock Units (LU) per ha, has been under biodynamic management si nce 1979. Fields are cropped with a seven-year rotational scheme, begi nning with a two-year grass/clover ley. Fertilization is based on farm yard manure and green manures. There is no closed nutrient cycle on th is farm. The phosphorus and magnesium balance amounted to a deficit of 2.9 kg phosphorus and 8.4 kg magnesium per ha per year, whereas the p otassium balance had a deficit of 65 kg potassium per ha per year. The nitrogen balance could not be calculated exactly. A range from +16 to -38 kg nitrogen per ha per year was found, when subtracting the maxim um farm output from the minimum farm input and vice versa, i.e. the ma ximum range for all variables used. Losses were caused by different fa ctors for each nutrient and, therefore, different measures are require d subsequently to balance the nutrient cycle as far as possible. 73% o f the estimated annual phosphorus loss was due to sale of products, 23 % was caused by deficits in the internal nutrient cycle and 4% by phos phorus leaching in the field. A calculated 14% of the overall potassiu m loss was caused by exporting products for sale and 78% was lost duri ng the inner-farm nutrient cycling, whereas only 8% was due to leachin g in the field. The farm lost 26% of its nitrogen through the sale of products, 38% through losses in the inner-farm cycle and 36% at the fi eld level.