Interactions between cover crops and soil microorganisms increase phosphorus availability in conservation agriculture

Aims An essential task of agricultural systems is to im- prove internal phosphorus (P) recycling. Cover crops and tillage reduction can increase sustainability, but it is not known whether stimulation of the soil microbial commu- nity can increase the availability of soil organic P pools. Methods In a field experiment in southwest Germany, the effects of a winter cover crop mixture (vs. bare fallow) and no-till (vs. non-inversion tillage) on microbial P- cycling were assessed with soybean as the main crop. Microbial biomass, phospholipid fatty acids (PLFAs), P cycling enzymes, and carbon-substrate use capacity were linked for the first time with the lability of organic P pools measured by enzyme addition assays (using phosphodi- esterase, non-phytase-phosphomonoesterase and fungal phytase). Results Microbial phosphorus, phosphatase, and fatty acids increased under cover crops, indicating an en- hanced potential for organic P cycling. Enzyme-stable organic P shifted towards enzyme-labile organic P pools. Effects of no-till were weaker, and a synergy with cover crops was not evident. Conclusions In this experiment, cover crops were able to increase the microbially mediated internal P cycling in a non-P-limited, temperate agroecosystems