不同施肥条件下紫色土旱坡地可溶性有机碳流失特征

Characteristics of Dissolved Organic Carbon Loss in Purple Soil Sloping Fields with Different Fertilization Treatments

明确紫色土旱坡地可溶性有机碳在不同施肥条件下的流失特征,得出最佳的养分管理方式,对提升三峡库区的耕地质量、维持土壤碳平衡和减轻土壤碳流失造成的环境污染具有重要意义.在中国科学院三峡库区水土保持与环境研究试验站内设置标准化径流小区,研究紫色土旱坡地在不同施肥处理[不施肥(CK)、常规施肥(常规)、优化施肥(优化)、85%优化施肥配施生物炭(生物炭)和85%优化施肥配施秸秆(秸秆)]条件下的产流产沙情况和土壤有机碳的流失特征.结果表明:(1)壤中流径流量占径流总量(径流包括地表径流和壤中流)的52.84%~92.23%,壤中流可溶性有机碳(DOC)流失通量占DOC总流失通量的43.64%~87.35%,壤中流是雨季径流的主要方式和土壤DOC流失的主要途径.(2)秸秆处理的地表径流量、产沙量、地表径流DOC流失通量和泥沙有机碳流失通量较优化处理分别降低了30.39%、39.41%、28.71%和23.97%,壤中流径流量和壤中流DOC流失通量较优化处理略有升高.生物炭处理的产流产沙量、地表径流DOC流失通量、壤中流DOC流失通量和泥沙有机碳流失通量均显著高于优化处理.(3)DOC流失通量占土壤有机碳总流失通量的99.31%~99.94%,DOC是紫色土旱坡地土壤有机碳流失的主要形式,各处理的DOC流失通量呈现:生物炭>优化>秸秆>常规>CK.(4)生物炭和秸秆处理的SOC含量较优化处理分别提高了95.79%和32.16%.85%优化施肥配施秸秆能显著减少紫色土旱坡地的地表径流量、泥沙流失量和土壤有机碳流失通量,同时提高土壤有机碳含量,是紫色土旱坡地的最佳养分管理方式.

The characteristics of dissolved organic carbon loss with different fertilization treatments were examined to derive the best nutrient management method for sloping farmland in the Three Gorges Reservoir area where maintaining the soil carbon balance and reducing environmental pollution caused by carbon loss is crucial.Experimental runoff plots were set up at the Experimental Station for Soil and Water Conservation and Environmental Research in the Three Gorges Reservoir Region,Chinese Academy of Sciences,involving the following five treatments:No fertilization(CK),conventional fertilization(conventional),optimum fertilization(optimum),biochar combined with 85%optimum fertilizer(biochar),and straw combined with 85%optimum fertilizer(straw).The effects of the five treatments on runoff flux,sediment yield,and soil organic carbon flux were monitored and evaluated.Results show that:(1)Subsurface flow accounted for 52.84%-92.23%of the runoff(both surface and subsurface flow)and the loss flux of dissolved organic carbon(DOC)in the subsurface accounted for 43.64%-87.35%of the total loss flux.Thus,in this sloping farmland,subsurface flow was the main pathway of runoff and dominated dissolved organic carbon transport.(2)Compared with the optimum treatment,straw treatment reduced the surface runoff flux,sediment yield,surface loss flux of DOC,and loss flux of organic carbon in the sediment by 30.39%,39.41%,28.71%,and 23.97%,respectively,but increased the subsurface runoff flux and loss flux of DOC.Compared with the optimum treatment,the biochar treatment significantly increased the surface and subsurface runoff flux,sediment yield,loss flux of DOC in the surface and subsurface,and the loss flux of organic carbon in the sediment.(3)The loss flux of DOC accounted for 99.31%-99.94%of the loss flux of soil organic carbon,and DOC was the major species of organic carbon in the organic carbon loss in this type of sloping farmland.The loss flux of DOC under the different fertilization treatments was ranked biochar>optimum>straw>conventional>CK.(4)Compared to the optimum treatment,the straw treatment and biochar treatment increased the soil organic carbon(SOC)content by 95.79%and 32.16%,respectively.Based on these results,straw combined with 85%of optimum fertilizer is the best nutrient management method for this sloping farmland as it can reduce surface runoff flux,sediment yield,and the loss flux of soil organic carbon while increasing the soil organic carbon content.