Stoichiometric determination of nitrate fate in agricultural ecosystems during rainfall events

Abstract

Ecologists have found a close relationship between the concentrations of nitrate (NO 3 -) and dissolved organic carbon (DOC) in ecosystems. However, it is difficult to determine the NO 3 - fate exactly because of the low coefficient in the constructed relationship. In the present paper, a negative power-function equation (r 2 = 0.87) was developed by using 411 NO3 - data points and DOC:NO 3 - ratios from several agricultural ecosystems during different rainfall events. Our analysis of the stoichiometric method reveals several observations. First, the NO 3 - concentration demonstrated the largest changes when the DOC:NO 3 - ratio increased from 1 to 10. Second, the biodegradability of DOC was an important factor in controlling the NO 3 - concentration of agricultural ecosystems. Third, sediment was important not only as a denitrification site, but also as a major source of DOC for the overlying water. Fourth, a high DOC concentration was able to maintain a low NO 3 - concentration in the groundwater. In conclusion, this new stoichiometric method can be used for the accurate estimation and analysis of NO 3 - concentrations in ecosystems.