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

EUROSOIL2020CONT-2474

NO EVIDENCE OF A COVER CROP SPECIES DIVERSITY EFFECT ON PLANT CARBON INPUT, SOIL MICROBIAL PROPERTIES AND SHORT TERM NUTRIENT CYCLING IN AN INTENSIVE ARABLE CROPPING SYSTEM

Florian Wichern^{* 1}, Charlotte Schlösser², Christian Fritz³, Nicole Wrage-Mönnig⁴, Michael Hemkemeyer²

¹Professor of Soil Science and Plant Nutrition, ²Soil Science and Plant Nutrition, Rhine-Waal University of Applied Sciences, Kleve, Germany, ³Aquatic Ecology & Environmental Biology, Radboud University, Nijmegen, Netherlands, ⁴Grassland and Fodder Sciences, University of Rostock, Rostock, Germany

Content: Cover crops (CC) fulfil a range of purposes like preventing soil erosion, restoration of compaction, impairing nematode and weed growth, catching and releasing nutrients. Some CC species are better suited to provide certain services than others. Thus it is appealing to compose complex plant mixtures for combining as many benefits of individual species as possible. Several studies found synergistic effects of CC mixtures due to higher species diversity, which were observed especially in low-input or low-intensity systems. However, it is less clear, if these effects are valid for intensive arable systems with higher inputs. Such systems are typical for the Lower Rhine region, where many soils have been formed on loess and received high organic fertiliser inputs over decades. In a field experiment set up in 2016 a fallow, seven species in monoculture (Phacelia tanacetifolia*, Brassica rapa*, Raphanus sativus*, Sinapis alba*, Avena strigosa, Sorghum x drummondii, Fagopyrum tataricum) and four mixtures with numbers of species ranging up to six were analysed. In 2017 the number of species was reduced to four (*) and likewise only a two- and a four-species mixture was included. Ten weeks after sowing, aboveground biomass was determined and roots were extracted. Elemental analysis revealed the amount of plant biomass-carbon (C) and -nitrogen (N) on the fields. Four months later another part of the plots was mulched. During plant development, after harvest, and after mulching soil samples were taken for several analyses including inorganic N and soil microbiological properties. Following CC, Hordeum vulgare was cultivated on the specific soils to analyse the N release from CC residues. First results revealed no differences between CC monocultures and mixtures for plant biomass C and N in 2016, with the exception of treatments containing high yielding species. Also in 2017 no differences in plant biomass C and N were found. Further, no difference in soil microbial biomass C and N, development and biomass of subsequent Hordeum, and soil pH could be detected between fallow, CC monoculture and mixtures. In conclusion, the high intensity of the cropping system with high soil nutritional background was probably a stronger driver for soil fertility properties as compared to CC species diversity in the short term. Consequently, studies evaluating CC diversity effects have to be much stronger contextualised, with a particular focus on cropping intensity and nutrient status.

Disclosure of Interest: None Declared

Keywords: catch crops, cover crops, Diversity, Nitrogen, Nutrient cycling