Editorial Note, Indonesia, volume 51, (April 1991)

<p>a, all data; b, non-rainfall days (≥7 days after rainfall); c, final day of rainfall; d, 1 day after rainfall; e, 3 days after rainfall; f, 5 days after rainfall.</p

Stoichiometric Determination of Nitrate Fate in Agricultural Ecosystems during Rainfall Events

<div><p>Ecologists have found a close relationship between the concentrations of nitrate (NO₃^-) and dissolved organic carbon (DOC) in ecosystems. However, it is difficult to determine the NO₃^- fate exactly because of the low coefficient in the constructed relationship. In the present paper, a negative power-function equation (<i>r</i>² = 0.87) was developed by using 411 NO₃^- data points and DOC:NO₃^- ratios from several agricultural ecosystems during different rainfall events. Our analysis of the stoichiometric method reveals several observations. First, the NO₃^- concentration demonstrated the largest changes when the DOC:NO₃^- ratio increased from 1 to 10. Second, the biodegradability of DOC was an important factor in controlling the NO₃^- 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 NO₃^- concentration in the groundwater. In conclusion, this new stoichiometric method can be used for the accurate estimation and analysis of NO₃^- concentrations in ecosystems.</p></div

NO₃- concentration as a function of changes in the molar DOC:NO₃- ratio among major ecosystems of the rainfall transport route.

<p>a, all data; b, experimental systems; c, rainfall; d, runoff; e, drainage ditch; f, porewater; g, groundwater; h, river.</p