Optimization of N fertilization in organic vegetable cultivation by means of a better estimation of the N release from base fertilization and from soil organic matter

The aim is to determine the influence of the soil condition on the organic matter management and thus on the N-availability, based on the effect of the basic fertilization and the mineralization of soil organic matter (SOM). The project focuses on organic vegetable cultivation, because the need for efficiency gains in the use of nitrogen is the largest in this sub-sector. External inputs of organic matter and nitrogen are severely limited by the stringent legal restrictions for phosphorus application (within the MAP: Manure Action Plan), especially in the case of crop rotations mainly involving vegetables.

The research will be carried out on about 30 farmers’ plots, which guarantees a sufficiently wide range of soil conditions and makes the research results immediately translatable to the grower's practice. The grower who provides a plot of land also chooses the basic fertilizer of which the N release will be monitored. The N-dynamics will be followed up in two objects, one with the application of the basic fertilizer and one without any basic fertilizer. We aim to develop rapid tests to quantify this N mineralization, and will relate it to the soil management history and current soil condition.

The results of the research will provide the organic vegetable grower with tools for a better fertilization practice in the context of sustainable soil management. This will also reduce the use of concentrated commercial organic fertilizers in crops with high N demand, reducing nitrate leaching risks to soil and surface water.