NEED FOR PHOSPHORUS INPUT IN AUSTRIAN ORGANIC FARMING?

Summary

On organic farms, phosphorus (P) balances are often negative because no or little P is imported into the farms. Negative P balances may deteriorate P availability over time. We calculated P balances of the main farm production types in organic farming for the main Austrian production areas. Using data from various data bases and expert knowledge, we applied the sustainability assessment tool REPRO for calculations. The P balances were balanced to slightly deficient for organic forage dairy farms, cash crop farms and permanent crop farms, and slightly to highly surplus on organic refinement, pig producing farms. Deficient P balances, mainly on organic cash crop farms, call for P input especially on farms where available P fractions in the soil are very low and / or P stocks in the soils are low, i.e. on sandy soils and on some calcareous soils. Possibilities for enhancing P mobilisation are discussed. There is an urgent need to close nutrient cycles on the farm and regional scale and to substitute P from rock phosphate reserves by alternative P fertilisers also in organic farming.