Are nutrient input and output in organic farming balanced?

Organically managed plots exhibit higher deficits in nutrients than conventional plots. Stocks of the most important plant nutrients should be analysed regularly.

Organic farming systems largely avoid the external input of mineral fertilizers. On the other hand nutrients are withdrawn from the soil by the crop. Accordingly, the nutrient-balance in the organic systems becomes negative for the main elements nitrogen, phosphorus and potassium.

The nitrogen balance was negative for all systems. This means N-fertilization was less than the withdrawal by the crop. Nitrogen mineralisation, N-fixation by legume crops and nitrogen precipitated with rain, however, were not considered in this calculation.

Phosphorus in the conventional systems showed a surplus, whereas in the organic systems the P-balance was negative.

Only the minerally-fertilized plots showed a surplus in potassium.

The bio-organic system showed the greatest deficiency. Calcium was sufficiently fertilized in all the systems with the highest surplus in the bio-dynamic system.

Balance of nutrients (1978–1998)