化肥减量配施生物炭和秸秆增加了坡耕地壤中流磷流失风险

紫色土坡耕地是中国西南地区的重要农耕用地，也是三峡库区农业非点源污染的主要来源地之一，采取合理的措施控制其土壤养分流失对该区域非点源污染治理具有重要意义.以紫色土坡耕地为研究对象，通过3 a(2018～2020年)大田试验，设置不施肥(CK)、常规施肥(CF)、优化施肥(OF)、生物炭+优化施肥减量15%(BF)和秸秆+优化施肥减量15%(SF)这5个处理，对自然降雨条件下坡耕地地表径流(0～20 cm)和壤中流(20～60 cm)磷流失规律进行监测与评估.结果表明，施肥减少了紫色土坡耕地产沙量和地表径流流失通量，但增加了壤中流流失通量.地表径流正磷酸盐(PO^3-₄-P)、全磷(TP)和颗粒态磷(PP)总流失通量以BF处理最高，SF处理最低.各施肥处理壤中流磷流失通量均高于CK处理，且PO^3-₄-P和TP流失通量以BF处理最高(213.88 g·hm^-2和694.54 g·hm^-2),其次为OF和SF处理.冗余分析(RDA)结果表明，地表径流流失通量和生物...

Biochar or Straw Substituting Chemical Fertilizer Increase the Risk of Phosphorus Loss in Subsurface Runoff in Sloping Farmland

The purple soil slope farmland is an important agricultural land in southwest China but is also one of the main sources of agricultural non-point source pollution in the Three Gorges Reservoir area. Taking reasonable measures to control the loss of soil nutrients is of great significance to the treatment of non-point source pollution in the region. Here, a three-year (2018-2020) field runoff experiment was conducted to monitor and evaluate the phosphorus (P) loss in sloping farmland via surface runoff (i.e., surface flow, 0-20 cm) and subsurface runoff (i.e., subsurface flow, 20-60 cm), with five treatments including no fertilization (CK), conventional fertilization (CF), optimal fertilization (OF), biochar combined with 85% of OF (BF), and straw combined with 85% of OF (SF). The results showed that fertilization application reduced the sediment yields and surface runoff flux but increased the subsurface runoff flux. The total loss flux of phosphate (PO^3-₄-P), total phosphorus (TP), and particulate phosphorus (PP) in surface flow were the highest in the BF treatment and the lowest in the SF treatment. All fertilization applications increased the P loss fluxes in subsurface flow relative to that in CK. The highest PO^3-₄-P and TP loss flux in subsurface flow was found in the BF (213.88 g·hm^-2 and 694.54 g·hm^-2, respectively) treatment, followed by that in the OF and SF treatments. Redundancy analysis (RDA) results showed that surface runoff flux and biochar application were the main factors contributing to increased P loss in surface flow, and subsurface runoff flux was the main factor contributing to increased P loss in subsurface flow. In summary, the SF treatment reduced the amount of sediment yield and surface runoff flux in sloping farmland of purple soil and was the most effective for controlling P loss, whereas the risk of subsurface runoff flux requires further attention.