Long term farming systems affect soils potential for N2O production and reduction processes under denitrifying conditions
N2O is a potent greenhouse gas with an atmospheric lifetime of 114 years which also contributes to ozone layer destruction. Mitigating N2O emissions is especially challenging to the agricultural sector that is responsible for the majority of anthropogenic N2O release. In order to develop effective mitigation strategies, a detailed understanding of drivers for N2O production and reduction in agriculturally managed soils is needed. Denitrification is recognized as one of the most important source processes for N2O emissions from soils. However, the last step in denitrification, the reduction of N2O to N2 is the only known sink for N2O in soil. Although the impact of single parameters on denitrification is quite well documented, there is still a knowledge gap when it comes to the impact of complex farming systems on N2O production and reduction. In this experiment, we incubated soil samples from the DOK long term field trial in Therwil/Switzerland comparing organic (BIOORG) and conventional (CONMIN) farming systems with an a non-fertilized control (NOFERT). Soil samples were incubated under 90% WFPS after fertilization with NH415NO3 equivalent to a moderate fertilization event in the field with 40 kg N ha-1. In order to assess soil's potential for N2O production and reduction, we combined direct measurements of denitrification end products N2O and N2 with molecular analysis of functional denitrifying communities involved in NO2- and N2O reduction on DNA and mRNA levels...
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