三峡库区紫色土柑桔园氮流失控制研究
A Trial for Nitrogen Loss Control in Purple Soil of Citrus Orchards in the Three Gorges Reservoir Area

为了研究三峡库区紫色土柑桔园在不同配方施肥，不同施肥深度和不同耕作方式处理下氮素流失规律及其控制力变化.以重庆紫色土柑桔园为研究对象，采用同一氮磷钾配方施肥水平，2个施肥深度与3种耕作方式组合，以地面撒施肥与中耕2次为对照，单次计量分析各处理地表径流量、0~40 cm土层和40 cm以下至母岩层侧渗流渗出水量及养分流失量，并用SPSS软件统计分析.结果表明，试验园同一耕作方式下，降雨量越大，地表径流及侧渗流总量越大；单次降雨中，覆盖处理流失水量最大，其流失量由大到小的顺序是：覆盖深施肥、覆盖浅施肥、中耕2次地面撒施肥、生草深施肥、清耕深施肥、生草浅施肥、清耕浅施肥；本试验一年中约1.39%~1.71%的化肥氮被雨水淋洗出土体并排放到环境中(对照为1.64%)，各处理0~40 cm土层侧渗流氮最大，其次是40 cm以下至母岩层，地表径流中氮最小，侧渗流是桔园土壤氮流失的主要途径；生草深施肥有增加氮流失趋势，氮肥浅施比深施氮素养分流失量小10%以上.结果表明，三峡库区紫色土柑桔园地耕作制对柑桔果园氮养分流失有很大影响，地面撒施肥和生草深施肥有增大氮流失趋势；氮肥浅施、调节土壤容重等措施可有效控制氮流失.
In order to explore the characteristics of nitrogen loss in the purple soil of citrus orchards and design control measures for it, an experiment was conducted in a purple-soil citrus orchard in the Three Gorges Reservoir Area of Chongqing, in which 6 treatments were made with the same NPK level and two fertilizer application depths and three tillage patterns. Surface broadcasting of fertilizers combined with twice tillage was used as the control. The runoff of each treatment, the interflow seeping water and the nutrient loss at 0-40 cm horizon and below were measured, and the data were analyzed with the software SPSS (Statistical Product and Service Solutions). The results showed that both the surface runoff and soil horizon interflow increased with the accumulation of rainfall at the same tillage. In terms of the same rainfall conditions, mulching farming was the major factor for rainfall loss. The descending order of rainfall loss at different fertilization was: mulching + deep fertilization > mulching + superficial fertilization > twice tillage + surface broadcasting fertilization > grassing + deep fertilization > clean tillage + deep fertilization > grassing + superficial fertilization > clean tillage + superficial fertilization. In this experiment, 1.39%-1.71% of fertilizer nitrogen leached from the soil per year. (In the control group the percentage was 1.64%). The descending order of loss of soil nitrogen at different horizon was: 0-40 cm soil horizon > below 40 cm horizon > surface horizon. Generally, interflow was the major factor for soil nitrogen loss and grassing combined with deep fertilization was liable to increasing nitrogen loss. Compared with deep fertilization, shallow fertilization reduced soil nitrogen loss by 10% or more. In conclusion, in the Three Gorges Reservoir Area, the cultivation system is the decisive factor for soil nitrogen loss in purple-soil citrus orchards, surface broadcasting of fertilizers and grassing + deep fertilization can aggravate soil nitrogen loss whereas shallow fertilization