Removal of N, P from seepage and runoff by different vegetated and slope buffer strips

The migration of nitrogen (N) and phosphorous (P) from farmland to river not only results in fertilizer inefficiency, but also aggravates water pollution and eutrophication. It is of great significance to construct a reasonable vegetation buffer zone between the river and farmland to protect water quality. By using constructed buffer strips and runoff hydrometric devices, quantitative research was conducted on removal loads of N and P in a field experiment of different vegetated and slope strips. Results showed that removal rates of TN, NH₄ ⁺-N, and TP by different vegetated strips were 2-3 times higher than the control group. The removal ratios of seepage accounted for 73.6%, 66.9%, 73.9% of total seepage and runoff in three vegetated strips, respectively. On the 2% gradient strips with Cynodon dactylon, the removal ratios of TN, NH₄ ⁺-N, and TP were 36%, 34%, 37%, which were higher than that with 5% gradient, respectively. And removal ratios from the seepage of 2%, 3%, 4%, and 5% gradient strips were 71.66%, 68.14%, 64.39%, and 61.93% of the total, respectively. The conclusion can provide the basis of vegetation and slope optimization for the design and construction of a riparian buffer zone, so as to control non-point source pollution effectively.