Environmental consequences of fertilization with acidified cattle slurry

Acidification of cattle slurry is a significant change to the composition and biology of the cattle slurry and can therefore change its response in the soil environment as well as cause leaching of phosphate and sulphate. It is well known that cattle slurry acidification leads to an unknown, but increased mobility of phosphorus in the cattle slurry, and thus an increased risk of phosphorus loss. Leaching of excess sulfur can also affect the mobility of phosphorus, if sulfate is reduced and binds iron as iron sulfide, thereby mobilizing phosphate that was associated with iron. These processes are well studied in wetlands, where the water is transported through a matrix with a relatively long residence time and an often high content of organic matter, which promotes sulfate reduction. There is therefore a clear need for more knowledge about the quantitative significance of these processes in min-eral agricultural soils as well as their dependence on physical and chemical soil properties. Changes in the soil ecology must also be expected, which is be assessed based on objectives for a healthy soil corresponding to a soil ecological risk assessment. Soil health is assessed on the basis of soil biodiversity and selected microbial processes by comparison with acidified cattle slurry and cattle slurry without acid addition. The methodology involve both conventional soil biodiversity assessment as well as eDNA for metabarcoing on Illumina platforms. Chemical fertilizer is used as an additional reference.