Soil nitrogen transport and transformation of reclaimed water irrigated summer-maize under different groundwater levels

The effect of reclaimed water irrigation on soil nitrogen content, nitrate concentration in groundwater at different groundwater depths (2 m, 3 m and 4 m) was investigated. Experimental results indicate that soil nitrate nitrogen content obviously increases after irrigation. Ammonia nitrogen is not significantly affected by groundwater table and reclaimed water irrigation. Nitrate nitrogen concentration in groundwater at different depths (2 m, 3 m and 4 m) increases by 34.67%, 24.94% and 20.88% at 900 m³·hm^-2 irrigation, and it increases by 58.42%, 38.98% and 27.21% at 1 200 m³·hm^-2 irrigation respectively. The deeper the groundwater the lower is nitrate nitrogen concentration in groundwater. Pollution risk of nitrate nitrogen from leaching and nitrification increases with increasing groundwater level.