Impact of fertilization with pig slurry on the isotopic composition of nitrate retained in soil and leached to groundwater in agricultural areas

The isotopic composition of N and O nitrate (NO3?) is usually employed to trace its sources pollution in groundwater. In agricultural areas, the amount NO3? that reaches aquifers after fertilization controlled by different transformation processes can affect nitrogen species composition. Aiming address reliability using isotope tools groundwater NO3?, goal this study was check effect on compounds retained leached from soils. concentration (?15N ?18O) ammonium (NH4+), nitrite (NO2?) characterized application pig slurry lysimeters containing either soil under fallow (LF) or same continuously cropped fertilized (LC) during previous six years. Results showed signature did not directly reflect applied slurry. Just fertilization, nitrification led lower ?15NNO3 values extracts leachates (e.g. +5.9 ± 0.9‰ +3.8 3.1‰ LF lysimeters). These increased complete (+11.5 1.3‰) towards ?15Nbulk (+19.6 0.5‰). Later on, due organic matter plant debris mineralization subsequent nitrification, decreased initial but remained above them (+8.6 1.0‰). Both LC experiments a similar trend latter ones allowed reinforce long-term with increase ?15NNO3. Concerning ?18O leachates, it mainly depended irrigation water oxygen, NH4+ Therefore, studies aiming rural areas an approach should consider history each setting. Also, analyzing recommended, since could mask through fertilization.