水蚀条件下土壤初始含水量对黄土坡地溶质迁移的影响

Effect of Soil Antecedent Water Content on Soil Solutes Release and Transport on Loess Slope under Water Erosion Condition

水蚀条件下坡地水分溶质迁移规律对农业生产和水土资源保护具有重要作用。通过室内模拟降雨试验,研究了1.3%,5.7%,9.7%,14.2%和18.9%共5个含水量坡地土壤PO43-、K+和Br-的迁移特征。结果表明溶质流失量和流失率均随土壤初始含水量的增加而增加,径流中溶质平均浓度与前期含水量呈抛物线关系,1.3%含水量坡地平均浓度均高于5.7%和9.7%坡地,18.9%含水量坡地最高。溶质在土壤剖面的垂向迁移量由大至小依次为:Br->K+>PO43-。前期含水量越低,非吸附性的Br-向较深土层的入渗量越大。K+和PO34-的质量传递系数Km均随土壤初始含水量增加而增加,Br-和K+的Km较大,PO34-的Km最小。基于对流-弥散理论的质量传递系数Km可以反映非吸附性Br-随地表径流迁移的特征,但不能够反映土壤侵蚀对吸附性K+和PO34-地表流失的影响。避免在雨季里喷施大量速效肥料,可以有效地减少养分,尤其是吸附性养分的地表流失。

Transport mechanisms of soil water and solute on slope land are important to promote the water and nutrient efficient and protect the water and soil resources in erosive region.According to the results of indoor simulation rainfall experiments,the transport traits of soil PO3-4,K+ and Br-on loess slope lands with different soil antecedent water content,1.3%,5.7%,9.7%,14.2% and 18.9%,respectively,are investigated.It shows that loss amount and loss percent of solutes climbs with the increase of soil antecedent water content.The mean concentration of solute in surface presents a parabola relation with soil antecedent water content.The mean concentration of 18.9% slope land is the highest,and it of 1.3% slope land is more than that of the 5.7% and 9.7%.The infiltration amount of soil Br-is the most of the three solutes,then K+,and PO3-4 least.Increase of soil antecedent water content will improve the infiltration amount of soil Br-.Km of soil K+ and PO3-4 is gaining with the increase of water content,and it of soil Brand K+ is more than that of PO3-4.Quality transport coefficient Km,based on the solute convection-dispersion theory and well reflecting the transport traits of non-adsorbed Br-with surface runoff,is unfit for the impacts of soil erosion on adsorbed soil K+ and PO3-4 transport.Avoiding spraying fertilizer in rainy season is favorable to lessen the surface loss of soil solute,especially the adsorbed solute.