Assessing non-point source pollution in an apple-dominant basin and associated best fertilizer management based on SWAT modeling
Yiwen Han, Zhong Liu, Yafei Chen, Yafei Chen, Yingxuan Li, Haipeng Liu, Lianghong Song, Yong Chen, Yong Chen
Abstract
Investigating the impact of apple-dominated areas on nitrogen (N) and phosphorus (P) losses at a basin scale was essential for the sustainable development of apple industry in China. This study conducted a survey on fertilizer application and built a Soil and Water Assessment Tool (SWAT) model to quantitatively analyze the N and P losses in the Qixia apple-dominated area. Additionally, the decreases in N and P losses through adjusting the fertilizer application modes were evaluated. Results showed that average N and P losses in the Wulong River Basin (WRB) were 44.4 and 0.365 kg ha−1 in 2011–2017, respectively, and apple orchards accounted for 73.3% and 51.4% of the total N and P losses in the basin. Under nine fertilizer scheduling scenarios, three fertilizer schedule scenarios, automatic fertilizer application (S-AUTO), “one shot” mode (S1), and regulated fertilizer application (S-BSD), had the lowest N and P losses in apple orchards. The decreases in N loss ranged from 20.6% to 26.1% at the subbasin scale and 14.8%–30.7% at the basin outlet when applying the S-AUTO, S1, and S-BSD fertilizer application modes in Qixia apple orchards and all apple orchards in the WRB. The reductions in P loss varied from 22.0% to 46.1% at the subbasin scale and 14.6%–25.6% at the basin outlet. In orchard-dominated basin, N and P losses can be effectively reduced by optimizing the orchard fertilizer scheduling strategies.