Abiotic nitrate incorporation in soil: is it real?

In acid forest soils nitrate (NO3-) from anthropogenic nitrogen deposition is retained at levels beyond what can be explained by known biological mechanisms. A number of researchers have hypothesized that abiotic NO3- incorporation into soil organic matter might be responsible for this phenomenon, however studies have been limited to a few temperate forest sites. The goal of this study was to determine if abiotic NO3- incorporation is important across a wide range of soil types. We collected 44 soils from a number of different ecosystem types in North and South America and measured the extent of abiotic NO3- incorporation. Significant abiotic nitrate incorporation did not occur in any of the soils examined. We show that the apparent abiotic incorporation observed in previous studies is likely the result of iron interference with NO3- measurements. Our results suggest that abiotic NO3- incorporation is not a likely explanation for the high rates of NO3- retention observed in some ecosystems.