Constraining the conditions conducive to dissimilatory nitrate reductionto ammonium in temperate arable soils

Here we offer the first assessment of conditions conducive to dissimilatory nitrate reduction to ammonium (DNRA) in temperate arable soils, through an examination of the potential for this process to occur in a range of soils of contrasting characteristics. NH415NO3 (6.2 g N m−2, 25 atom % excess 15N) was applied, and recovery of 15N in the View the MathML source pool taken as indicative of occurrence of DNRA. Up to 5% of applied 15N was recovered in the View the MathML source pool 2 d after addition of N, glucose (44.6 g C m−2) and l-cysteine (7.7 g m−2, 0.9 g N m−2, 2.3 g C m−2). View the MathML source concentrations were positively correlated with soil pH, View the MathML source ratio, bulk density, sand content and View the MathML source concentration, but negatively correlated with soil C and organic N content. Our results demonstrate the potential for DNRA to contribute to N cycling in temperate arable soils, but its detection and significance is likely to depend on the provision of a low molecular weight C source.Highlights► We demonstrate the potential for DNRA to contribute to N cycling in temperate arable soils. ► DNRA was positively correlated with soil pH, bulk density, sand %, View the MathML source concentration and C:View the MathML source. ► Significance of DNRA is likely to depend on the provision of a low molecular weight C sourc.