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Effects of slurry acidification on soil N2O fluxes and denitrification (2021)

Malique F., Wangari E., Andrade‐Linares D., Schloter M., Wolf B., Dannenmann M., Schulz S., Butterbach‐Bahl K.

Journal of Plant Nutrition and Soil Science, 184 (6), 696-708

doi:10.1002/jpln.202100095

Abstract

Background

Reductions of ammonia volatilization resulting from slurry applications to intensively managed grassland may be achieved via slurry acidification. However, it remains uncertain if this may result in pollution swapping, that is, due to reduced ammonia volatilization and increased soil N availability, emission of nitrous oxide from soils may increase.

Aims

In this study, we compared control (no fertilizer) and slurry fertilized grassland treatments [not acidified (S) and acidified (AS)] to assess whether slurry acidification results in changes of soil N availability, denitrification potential and activity as well as soil fluxes of nitrous oxide.

Methods

The study was carried out in a montane grassland system in southern Germany, and parameters were followed over a 43-days period with continuous measurements of soil GHG fluxes and biweekly measurements of microbial and soil parameters preceding and following two fertilizing events.

Results

Over the entire observation period cumulative N2O emissions were significantly elevated for treatments receiving slurry applications, with differences between acidified and non-acidified slurry treatments being overall insignificant. Transcripts of the nirK type nitrite reductase showed significantly higher numbers in soils of the AS treatment. While soil potential denitrification rates (PDR) did not differ between treatments, there was a strong tendency of increased PDRs for the AS treatment.

Conclusions

Against expectation, we did not find that application of AS affects PDR or soil N2O emissions significantly, though in tendency higher rates of soil N2O emissions as well as higher potential denitrification rates were found in treatments receiving acidified slurry as compared to the slurry only treatment. Our results indicate that longer observation periods and given the significant spatial variability, higher numbers of replicates are needed, to finally assess if slurry application indeed results in increased soil denitrification activity, soil N2O production and soil-atmosphere N2O emissions.

 

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