Effect of grass planting on soil nitrogen transformation and dissolved nitrogen concentration of urban greening lands

Nitrogen (N) transformation is an important ecological process for the maintenance of soil N availability. To determine the effect of grass planting on soil nitrogen transformation, potential N mineralization was measured for the surface 0–30 cm soil layer from different greening lands in the campus of Anhui Agricultural University and Hefei Huancheng Park, using a laboratory incubation method. A comparative analysis of dissolved N (DN) concentrations between different greening land types was performed. The results showed that soil bulk density was significantly decreased by grass planting. Grass planting had a significant effect on soil inorganic N, but had no significant effect on soil moisture, total N, or DN. The mean net N mineralization potential was 85.99 μg·(kg·d)^–1 in greening lands with grass planting, which was 15.6% higher than in greening lands without grass planting. Grass planting significantly increased net ammonification potential, whereas it had no effect on net nitrification potential. Our findings indicated that the characteristics of soil N transformation in urban soils were changed by grass planting, with significantly enhanced N ammonification. This may help improve N availability and decrease N loss in urban soils.