Evaluation of Agricultural Soils Amended with Crop Straw and Straw Biochar on Reduction of Nitrogen and Phosphorus Runoff and Leaching Losses

Nitrogen (N) and phosphorus (P) losses throughout agricultural soils runoff and leaching can contribute to agricultural non-point source pollution. Here, we conducted an evaluation of long-term effects of mineral fertilizer (NPK), crop straw combined with mineral fertilizer (CSNPK), crop straw biochar combined with mineral fertilizer (BSNPK), and the control with no fertilizer (CK) on runoff and leaching losses of N and P forms in the intensive agricultural cropland. Following that, nitrogen and phosphorus runoff and leaching losses were measured using the free-drain field lysimeter method overs a two years experiment. The results indicated that, the nitrogen forms runoff losses of nitrate N, dissolved organic N and particulate N, accounted by 12.0-64.0%, of the total N runoff losses, while the phosphorus forms runoff losses of particulate P accounted about 98.0% of the total P runoff losses. Similarly, nitrate N, dissolved organic N and particulate N leaching losses, accounted for 25-61% of total N leaching losses, whereas, particulate leaching loss accounted 87% of the total P leaching losses. The total N and P losses fluxes strongly correlated with runoff and leaching discharges, while the relationships between total P losses fluxes and leaching discharges was described by a significant exponential function. The study shows that the combination of crop straw of either straw of biochar with mineral fertilizer could significantly reduce N and P runoff and leaching losses.