‘Umkreis’

This project represents the first research topic that has been developed together with the farmers involved in the arable farming project group of the Hesse Farmers-led Research Network. The influence of different tillage methods for catch crops on the retention of the nitrogen (N) that the catch crops have absorbed into their shoot mass before winter is being investigated.

Farmers want to adjust their practices in such a way that the nitrogen does not dissipate in liquid or gaseous form, but contributes to the soil nitrogen reserves in organically bound form. As various studies have shown, this is only partially achieved using the traditional method of pre-winter ploughing. Two possible alternatives are shallow incorporation of catch crops into the soil, e.g. with a tiller, only in spring, or bending down the stalks with subsequent windrowing and earthing up in autumn and then incorporating the catch crop biomass into the soil in spring. These methods promise rapid microbial decomposition of the crop and root residues of catch crops only in spring and may therefore be able to minimise liquid and gaseous N losses.

In the collaborative project, the influence of all three incorporation methods on the N cycle in the soil, plants and atmosphere will be assessed in field trials on the Frankenhausen domain and on the participating farms. The trial results, supplemented by farm data, are used to model the site-specific effects of the different incorporation methods on the humus balance. In the trial on the Frankenhausen domain, the nitrogen in the microbial biomass, the nitrogen leaching and the gaseous nitrogen escaping into the atmosphere with an effect on the climate are also recorded. In one variant, the distribution of the nitrogen taken up by the catch crops to the pools described is measured using isotopic labelling.

Both the trial in Frankenhausen and the network trials will be carried out over a period of two years, and the effects of the trial variants on Nmin content in the soil, yields and N uptake of two subsequent crops will be monitored on all the trial fields.