石盘丘小流域不同土地利用方式下土壤氮磷流失形态及通量

为了解三峡库区小流域不同土地利用方式下土壤氮、磷流失特征，为农业非点源污染防控提供科学依据；采用田间试验的方法，研究了三峡库区石盘丘小流域水田、旱坡地、林地、柑橘园和菜地这5种土地利用方式下地表径流不同形态氮、磷流失浓度与通量的特征.结果表明：全氮流失通量的顺序为水田17.73 kg·（hm²·a）^-1] > 柑橘园4.86 kg·（hm²·a）^-1] > 旱坡地4.33 kg·（hm²·a）^-1] > 菜地4.00 kg·（hm²·a）^-1] > 林地2.41 kg·（hm²·a）^-1]；全磷流失通量的顺序为菜地4.97 kg·（hm²·a）^-1] > 柑橘园1.87 kg·（hm²·a）^-1] > 水田0.93 kg·（hm²·a）^-1] > 林地0.27 kg·（hm²·a）^-1] > 旱坡地0.19 kg·（hm²·a）^-1]；5种土地利用方式下氮、磷流失主要集中在降雨频繁的4~5月，占全年氮、磷流失总负荷的53.80%~96.52%和56.03%~87.78%；氮流失主要以硝态氮（16.16%~52.70%）的形态流失，全氮流失通量与径流量呈现出显著正相关关系（R²=0.9826）；在菜地中颗粒磷是磷流失的主要形态（83.30%），但在其他土地利用方式中表现不显著.不同土地利用方式下不同形态氮、磷流失存在显著差异，其中菜地应针对强降雨情况下颗粒磷流失的问题采取措施，水田应避免在降雨集中时期施肥；科学施肥和合理地土地利用方式配置是治理小流域农业非点源污染的重要途径.

Characteristics of Soil Nitrogen and Phosphorus Losses Under Different Land-use Schemes in the Shipanqiu Watershed

In order to understand the characteristics of soil nitrogen and phosphorus loss under different land use patterns in the small watershed of the Three Gorges Reservoir area and provide a scientific basis for the prevention and control of agricultural non-point source pollution, a field test method was used to study the paddy fields and drought in the small Shipanqiu Watershed in the Three Gorges Reservoir area. The characteristics of different runoff concentrations and the fluxes of nitrogen and phosphorus in surface runoff under the five land use schemes of paddy filed, slope land, woodlands, citrus orchards, and vegetable land. The results show that the annual total nitrogen loss followed the order of paddy field17.73 kg·(hm²·a)^-1] > citrus orchards4.86 kg·(hm²·a)^-1] > dry slope land4.33 kg·(hm²·a)^-1] > vegetable field4.00 kg·(hm²·a)^-1] > woodland2.41 kg·(hm²·a)^-1]. The annual total phosphorous loss followed the order of vegetable fields4.97 kg·(hm²·a)^-1] > Citrus orchards1.87 kg·(hm²·a)^-1] > paddy fields0.93 kg·(hm²·a)^-1] > woodlands0.27 kg·(hm²·a)^-1] > dry slope land0.19 kg·(hm²·a)^-1]. The nitrogen and phosphorus losses under the five land use methods were mainly concentrated from April to May with frequent rainfall events, accounting for 53.80%-96.52% and 56.03%-87.78% of the total annual nitrogen and phosphorus losses. Nitrogen loss was mainly in the form of nitrate nitrogen (16.16%-52.70%), and the total nitrogen loss flux and runoff showed a significant positive correlation (R²=0.9826). Particulate phosphorus was the main form of phosphorus loss in vegetable fields (83.30%), but in other land use schemes it is not significant. There were significant differences in the loss of different forms of nitrogen and phosphorus under the different land use schemes. Among them, measures should be taken in vegetable fields to deal with the problem of particulate phosphorus loss under conditions of heavy rainfall. Fertilization should be avoided in paddy fields during periods of concentrated rainfall. Scientific fertilization and reasonable land use configurations are important ways to control agricultural non-point source pollution in small watersheds.