湖北省三峡库区不同种植模式下农田地表径流氮磷流失特征

为了识别湖北省三峡库区氮磷流失的高风险种植模式和高风险区，以种植模式为单元研究区域农田地表径流氮磷流失特征，采用流失系数法，分析了湖北省三峡库区4个县（区）18种主要种植模式农田地表径流途径土壤本底、肥料氮磷流失情况。结果表明：库区农田氮磷流失量分别为2 035.0 t和213.2 t，其中夷陵区最高，分别占库区总量的53.8%和50.5%，该区氮磷流失强度也最高。当季施肥造成的氮磷流失量分别占农田流失总量29.6%和26.3%。18种模式中，平地-露地蔬菜和平地-园地是氮流失量最大的两种种植模式，占库区农田总流失量53.2%；平地-露地蔬菜是磷流失量最大的种植模式，占库区农田总流失量的43.3%。平地、缓坡地、陡坡地三类坡度农田中，平地农业集约程度高，氮磷流失量最高，分别占库区氮磷流失量56.1%和57.1%，缓坡地次之，陡坡地的种植强度低，氮磷流失量最低。几种土地利用方式中，平原旱地利用方式氮磷流失量分别占库区氮磷流失量的38.5%和48.5%，流失强度为17.1、2.3 kg·hm^-2，远高于园地、坡耕地、水田。研究表明，夷陵区是氮磷流失高风险区，平地-露地蔬菜和平地-园地是氮磷流失的高风险种植模式。

Characteristics of nitrogen and phosphorus losses from farmlands through surface runoff under different cropping patterns in the Three Gorges Reservoir area of Hubei Province

Designating cropping patterns as a unit in which to study the characteristics of surface runoff nitrogen and phosphorus losses in the regional field have important guiding significance to manage farmland nutrients and reduce the agricultural non-point source pollution. By using the loss coefficient method, this paper analyzed the loss of nitrogen and phosphorus in soil background and fertilizer loss in 18 main cropping patterns of 4 counties(districts) in Three Gorges Reservoir area(TGRA) of Hubei Province. The results showed the loss of nitrogen and phosphorus in TGRA were 2 035.0 and 213.2 t, where the Yiling District was the highest, which accounted for 53.8% and 50.5% of the total area, not only had the largest farmland area, but also nitrogen and phosphorus loss intensity was the highest. Flat-open vegetables and flat-garden were the two cropping patterns with the largest nitrogen loss, which accounted for 53.2% of total reservoir loss. Plain-open vegetables were the largest pattern of phosphorus loss, accounting for 43.3% of the TGRA. The fertilizer loss in-season of nitrogen and phosphorus accounted for 29.6% and 26.3% of the total loss respectively. The loss of nitrogen and phosphorus in the flat was the highest among the three kinds of slope farmland(flat, gentle slope land and steep slope divided by cropping patterns) because of high agricultural intensification, which accounted for 56.1% and 57.1% of the total loss, followed by the gentle slope, the steep slope was lowest due to low planting intensity. In all land use, plain dry land accounted for 38.5% and 48.5% of nitrogen and phosphorus loss in TGRA, and the nitrogen and phosphorus loss intensity were 17.1, 2.3 kg·hm^-2, much higher than that in the garden, sloping fields, and paddy fields.