Nitrate accumulation in an intensive small agricultural catchment: challenges and solutions
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Nitrogen (N) fertilization in the intensive horticultural systems is usually high, especially in China during past decades. We have studied nitrate accumulation in soil profiles and nitrate in groundwater of a small catchment dominated by kiwifruit orchard at northern sloping region of Qinling Mountains in Shaanxi. We found that long-term N fertilization resulted in high nitrate accumulation in 4 m profile. The averaged NO3 – -N concentrations and δ 15N-NO3 – values of groundwater increased from natural forest to arable land and to the orchards; on the contrary, the δ18O-NO3 – decreased. The nitrate sources in the groundwater at different regions were identified.
The long term application of nitrogen (N) fertilizer has changed the global N biogeochemical cycle (Erisman et al, 2008). Understanding the fate of N fertilizer in soil and plant system (crop uptake, residual in soil, and loss) is important to increase N use efficiency and decrease its loss. Nitrification is very fast in upland soil. Therefore, the accumulation of nitrate in soil profile is one of important fate of N fertilizer after application. China has consumed about one thirds of the global N fertiliser now. Fruits and vegetables together in China have consumed at least 30% of N fertilizers. However, there are limited researches to study nitrate accumulation in soil profiles both at field and catchment scales, to evaluate their potential risk to the groundwater quality.