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Soil ecological engineering and management of soil biology. <BR>A contribution to achieving zero hunger? (Communication session)

EUROSOIL2020CONT-2061

COVER CROP-MICROBIAL INTERACTIONS INCREASE THE AVAILABILITY OF ORGANIC P POOLS: AN OPTION TO TIGHTEN P CYCLING IN AGRICULTURAL SOILS?

Moritz Hallama^{* 1, 2}, Paula Mayer-Gruner¹, Carola Pekrun³, Ellen Kandeler¹

¹Soil Biology, Universität Hohenheim, Stuttgart, Germany, ²Microbiology, University of Girona, Girona, Spain, ³Agronomy, HfWU Nürtingen-Geislingen, Nürtingen, Germany

Content:  

Cover crops are currently experiencing increasing attention for the sustainable intensification of agroecosystems. The beneficial effects include the enhancement of microbial nutrient cycling, potentially improving availability of P while decreasing environmental hazards. In this presentation, the mechanisms of cover crop-derived P benefit are outlined, and the results of microbiological variables and enzymatic availability of organic P pools (glycerol-P, DNA-P and inositol-P) of two own field experiments in SW Germany are used to evaluate these mechanisms in detail.

From a meta-analysis, we postulate that cover crops benefit the P nutrition of main crops by distinct, simultaneous mechanisms. Of these, the most important process is the microbial enhancement pathway, where the cover crops enhance the soil microbial community, leaving a legacy of increased microbial biomass P, phosphatase activity and increases in arbuscular mycorrhizal abundance that translate into an improved capacity for the main crop to access organic P in the soil. Another process is the biomass pathway, where soil P is stored temporarily in the cover crop biomass and the main crop profits from the P released by the litter mineralisation.

In both of our field experiments, the microbial enhancement pathway was clearly identified by increases in microbial abundance and activity, accompanying shifts of the soil organic P pools towards a higher availability. In comparison, the biomass pathway, being most relevant for cover crops with a large biomass, was less relevant. Management, such as tillage reduction, had a limited influence on the cover crop effects.

Cover crops enhance the capacity of the soil microbial community for P cycling and shift the pools of organic P towards a higher availability. However, the effects on P availability do not necessarily translate into enhanced yields and are difficult to detect by standard soil P tests. In summary, cover cropping requires practical experience, but has the potential to tighten nutrient cycling and P efficiency in agricultural systems.

Disclosure of Interest: None Declared

Keywords: agricultural management practices, cover crops, mycorrhizal fungi, organic phosphorus, phosphorus availability, Rhizosphere P dynamics