Study on the characteristics of ammonium nitrogen and nitrate nitrogen in soil and groundwater under different nitrogen application rates

Abstract In this study, we investigated the characteristics of ammonium nitrogen and nitrate nitrogen in soil and groundwater under different nitrogen application rates through a field experiment in a maize-growing area in Northwest China. The experiment set four nitrogen application rates: CK (0 kg · hm − 2 ), F1 (100 kg · hm − 2 ), F2 (200 kg · hm − 2 ), and F3 (300 kg · hm − 2 ). The results showed that nitrogen application significantly increased the nitrogen concentration in soil and groundwater, and the high nitrogen application treatment (F3) showed a stronger effect at most growth stages. The results showed that nitrogen application significantly increased the nitrogen concentration in soil and groundwater, and the high nitrogen application treatment (F3) showed a stronger effect at most fertility periods. 0–40 cm shallow soil nitrogen was strongly affected by nitrogen application and fertility period, while 60–80 cm deep soil content was lower and stable. Correlation analysis revealed the synergistic effects of environmental factors on nitrogen transformation. Soil water content was positively correlated with ammonium nitrogen and negatively correlated with nitrate nitrogen. The ammonium nitrogen of groundwater was negatively correlated with nitrate nitrogen, and nitrate nitrogen was positively correlated with dissolved oxygen (DO) and oxidation reduction potential (ORP). Ammonium nitrogen of soil and groundwater showed positive correlation, nitrate nitrogen of soil and groundwater showed positive correlation, and soil water content and ORP of groundwater showed negative correlation. This study reveals the dynamic influence mechanism of nitrogen application on soil and groundwater nitrogen, which provides a theoretical basis for optimizing nitrogen fertilizer management and preventing and controlling groundwater nitrogen pollution. It has important scientific significance for the study of agricultural nitrogen fertilizer management and groundwater environmental protection in arid areas.