The foundation of a biodynamic farm lies in its ability to generate its own fertility.
Imported fertility needs to be monitored carefully, and the need for it must be clearly documented i.e. via soil analysis, tissue analysis, visual deficiency in crop, etc. Nitrogen and phosphorous are permitted to be imported to a maximum of .5 mu/ hectare. This translates to 16.2 kg N/ acre and 13.95 kg P205/ acre. In perennial planting situations (such as in orchards and vineyards) a maximum equivalent of 1.2-mu/ hectare is permitted to be imported. This translates to 36 kg N/ acre and 31 kg P205/ acre.
For cropping systems with high nutrient exports in the form of harvested crops, (such as vegetable market gardens) a maximum of 65 kg N/ acre and 55kg P/ acre can be imported. The applicant needs to adequately demonstrate need via a calculated nutrient budget that demonstrates a minimum of 100 lbs N/ acre is exported via harvested crops. This can only be considered if the requirements previously listed are adequately met.
Note: This is an excerpt of "Biodynamic Farm Standard (2010). Demeter Association Inc."