Impact of urease inhibitors on microbiology and groundwater quality

Preparation of extracts from soil samples

According to the version of the Fertilization Ordinance of May 26, 2017, urea as a fertilizer "from February 1, 2020, may only be applied for fertilization if a urease inhibitor has been added to it or if it is applied immediately, but no later than within four hours after application". The interaction of urease inhibitors with microbiology and groundwater is rarely described to date. This study aims to deepen the state of knowledge and identify possible effects.

The effectiveness of nitrification and urease inhibitors as well as the effects with regard to the formation of climate gases have already been discussed in many studies with partly different results. Information on the interaction with microbiology as well as on the degradation or displacement behavior of the individual urease inhibitors has hardly been described so far, or information on possible inputs into groundwater is not yet available.

In order to close this knowledge gap, field and laboratory scale experiments will be carried out. In the field, selected soil samples will be taken from agricultural land in two water protection areas. In one of the project areas, two arable fields will be divided into two further sub-areas and fertilized with urea, with and without urease inhibitor. These samples will be analyzed with regard to microbiological parameters (e.g. cultivation methods) and urease inhibitors. In parallel, different urease inhibitors will be used in lysimeter experiments in the laboratory under the same conditions. The resulting leachate will also be analyzed for the urease inhibitors used and for microbiological parameters.

The aim is to characterize the interactions between urease inhibitors and microbiology. Furthermore, the admixture will be examined and recommendations for the selection of a suitable urease inhibitor with the lowest possible groundwater hazard will be given. The most meaningful parameters for site assessment will be identified and a transferable monitoring strategy will be derived.