Inner farm nutrient flows between arable land and permanent grassland via the stable in organic cropping systems |
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| Authors: | Kurt Mller |
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| Institution: | aInstitute for Plant Nutrition, Universität Hohenheim, D-70593 Stuttgart, Germany |
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| Abstract: | Organic farming systems are characterized by the strong regulation of the import of nutrients into the farming system. Recently, nutrient budgets in organic farming especially with regard to potassium (K) and phosphorus (P) have gained interest. In the present study inner farm mineral nutrient flows of P, K and magnesium (Mg) among the farmland sub-compartments arable land and permanent grassland via the dairy stable were analysed. The objectives of the current study were (1) to quantify the inner farm nutrient flows among different farmland sub-compartments, and (2) to assess the effect of purchased biomass on inner farm nutrient cycles. Results indicated that the ratio of the nutrients N, P and K in the stable inputs (feed, bedding) greatly differed depending on the kind of biomass introduced into the stable (roughage in comparison to concentrates or straw for bedding), i.e. via grassland biomass much more K (7.9 kg) per kg P were introduced than with feeds harvested on arable land like silage maize (4.9 kg K per kg P), concentrates like cereals (1.3–1.6 kg K per kg P) or grain pulses like peas (2.4 kg K per kg P). The different inputs are mixed in the manures leading to intermediate concentration in the stable manures, with the consequence that nutrient composition of the manures does not match the composition of the single stable inputs. Therefore, balances of nutrient flows in such mixed systems indicate a relative transfer of K from grassland to arable land via the stable manure (approximately 10–30% of the manure derived from grassland K, depending among others on the amounts of straw high in K needed for animal bedding), if P was used as reference nutrient for stable manure allocation to permanent grassland and arable land. Yields of non-legumes in arable cropping in organic farming systems is very often limited by nitrogen (N) supply, whereas it is well known that manure additions are rather ineffective on permanent grassland high in legumes. The higher N demand of arable crops as well as P and K offtakes from arable land via sold animal and plant products give some scope for a preferable use of stable manures for manuring arable land to replace mineral nutrient outputs and to improve the soil N and the soil humus status, increasing the demand for supplement of mineral nutrients on the permanent grassland area to avoid long-term impoverishment of soil fertility. |
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| Keywords: | Nutrient cycle Phosphorus Potassium |
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