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Changes in soil profile carbon and nitrogen dynamics <BR>by agricultural management practices (Communication session)

EUROSOIL2020CONT-1681

EFFECTS OF SHALLOW INCORPORATION OF COVER CROP MIXTURES ON SHORT-TERM SOIL ORGANIC MATTER CYCLING IN AGRICULTURAL SOILS – AN ON-FARM FIELD TRIAL

Simon Oberholzer^{* 1}

¹Institute of Geography, University Bern, Bern, Switzerland

Content: Short term soil organic matter (SOM) cycling is an important part of soil fertility, soil health and crop performance. In agricultural systems the habitat for soil microbiology is constantly altered by farmer’s management. Within a single crop rotation there are periods of SOM formation and periods of SOM mineralization. Compared to the total amount of SOM, the quantities of these short-term changes are rather small. Therefore, it is challenging to measure these short-term SOM dynamics and accordingly current knowledge is quite limited. However, according to the state of research, cover crops are considered to play a major role in short-term SOM formation. The standard treatment to terminate green cover crops is either ploughing or herbicide application. A new and propagating method in agricultural praxis is to incorporate green cover crops into the first 0-5 cm of topsoil. Thereby, plant biomass is brought into the biologically most active soil layer and can serve as high quality energy source for soil microbiology which leads to a rapid decomposition. By this method farmers expect i) stimulation of soil microbiology ii) efficient formation of soil organic matter, iii) improvement of soil structure and iv) constant nutrient supply for the following crop. In this on-farm trial the direct influence of shallow incorporation of green plant biomass is assessed by taking soil samples in high density. The trial comprises the period of nine months between cereal harvest and sowing of spring crop. In this period two cover crops are sown and shallowly incorporated. The summer cover crop mixture consists of 12 species and the winter cover crop mixture of four species. Soil samples are taken right before cover crop incorporation and about one month after which leads to for sampling time points. At each time point samples are taken at 39 GPS referenced points and three soil depth (0-5, 5-10, 10-20 cm) resulting in 117 samples per time point. The trial is conducted on three fields in Eastern Switzerland. All samples are analyzed for total C, total N and permanganate oxidizable carbon (POXC, also referred to as active C). Additionally, soil microbial biomass is measured per field in a mixed sample with four replications. To analyze the 1400 GPS-referenced samples near infrared spectroscopy is used. The calibration of the spectral models is done for each field separately to achieve a high prediction accuracy.

The presentation in the session will discuss the first results of the trial and the suitability of spectral measurements for high density sampling to detect small changes in SOM.

Disclosure of Interest: None Declared

Keywords: agriculture, cover crops, field trial, soil organic carbon, soil organic matter, spectroscopy