“Umkreis”

This project is the first research topic that has been developed together with the farmers involved in the Hesse practical research network in the arable farming project group. It examines the influence of different intercropping methods on the fate of the nitrogen (N) that the catch crops have absorbed into their shoot mass before winter.

Farmers want to gear their measures in such a way that the nitrogen does not escape in liquid or gaseous form, but is absorbed into the soil in an organically bound form. As various studies have shown, this is only partially achieved with the classic method of plowing in before winter. Two possible alternatives are shallow incorporation, e.g. with a tiller in the spring, or snapping off the stalks with subsequent windrowing and soil accumulation in the fall and incorporation of the catch crop biomass in the spring. These methods promise a rapid microbial decomposition of the harvest and root residues of the catch crops in spring and can thus possibly reduce liquid and gaseous losses.

In the joint project, the influence of all three plowing methods on the N cycle in soil, plant and atmosphere will be tested in field trials on the Frankenhausen domain and on the participating practical farms. The trial results, supplemented by farm data, will be used to model the site-specific effects of the plowing variants on the humus balance. In the trial on the Frankenhausen domain, the nitrogen in the microbial biomass, the nitrogen leached downwards and the gaseous nitrogen escaping into the atmosphere with an effect on the climate are also recorded. In one variant, the fate of the nitrogen absorbed by the catch crops in the pools described is measured using isotope labeling.

Both the trial in Frankenhausen and the network trials are carried out every two years, and the effects of the trial variants on Nmin contents in the soil, yields and N uptake of two subsequent crops are monitored on all plots.