Pisha Sandstone Application Methods Determined the Processes of Nitrogen Leaching in Sandy Soil

Nitrogen (N) leaching loss in sandy soil reduces the effectiveness of N fertilizer and increases the risk of polluting groundwater. Pisha sandstone could be used to maintain the water and nutrients in sandy soil due to the presence of montmorillonite, but the impacts of application methods (patterns and levels) on N leaching loss remain unclear. Leaching experiments were conducted to investigate the impacts of Pisha sandstone application patterns and levels on N leaching loss. Soil columns were constructed, including four application patterns (U, upper layer in soil column; M, middle layer; L, lower layer; Mix, mixing with sandy soil) and three application levels (10%, 30%, 50%, mass ratio). Results indicated that not all treatments showed a decrease in N leaching from sandy soil, and the application patterns had a higher effect than application levels. Compared with the sandy soil, the Mix application pattern presented the best impact in reducing N leaching (18.8%—28.3%) and could reduce more leaching N by increasing application levels. The L pattern effectively reduced N leaching loss (3.5%—20.2%) and water drainage loss (12%—33.8%). A cautious attitude should be adopted in selecting U and M patterns due to the risk of increasing N leaching loss. The reasonable use of Pisha sandstone was helpful in reducing N leaching loss from sandy soil. More fieldwork is needed to extend our findings in the future.