耕作方式和土层厚度深度对紫色土胶体迁移的影响

【目的】研究不同的田间管理措施对不同粒径土壤胶体迁移的影响。【方法】通过微区试验,设置不同耕作措施(平作、垄作、平作+完整秸秆覆盖、垄作+完整秸秆覆盖、平作+粉碎秸秆覆盖、垄作+粉碎秸秆覆盖),并在平作条件下设置不同紫色土土层厚度(20、40、60、80、100、120 cm)处理,研究不同措施对地表径流和壤中流中产流量、不同粒径范围(0.45~2、0.22~0.45μm、<0.22μm)胶体出流浓度和流出量的影响。【结果】①秸秆还田覆盖处理能够显著减少地表径流的产流量,但是会增加壤中流的产流量,特别是完整秸秆还田覆盖;平作条件下,壤中流产流量会随着土壤深度的增加而减少。②垄作或垄作+秸秆覆盖处理与平作处理相比能够显著降低地表径流和壤中流中大粒径范围胶体的出流质量浓度和流出量,而且对壤中流中<0.22μm粒径的胶体出流质量浓度和流出量降低程度也比较显著。③小粒径的胶体容易随地表径流迁移,而壤中流中粒径较大的胶体更加容易迁移,小粒径胶体颗粒随着紫色土土层厚度的增加出流质量浓度和流出量都会减少。【结论】对于不同耕作措施而言,垄作+粉碎秸秆覆盖处理对于减少地表径流和壤中流产流量,以及减少地表径流和壤中流中胶体的流出质量浓度和流出量都比较显著。对于不同紫色土土层厚度处理而言,土层深度越深胶体流出量越少,而且小粒径胶体比大粒径胶体更难从壤中流中流出。

The Movement of Colloids in Purple Soil is Affected by Tillage

【Background】Colloids facilitate migration of contaminants,such as heavy metals,phosphorous,pesticides,in soil,in which colloid sizes play an important role.However,there is a paucity of study on this under field condition.【Objective】The objective of this study is to experimentally study the impact of colloids of different sizes on their movement through both surface runoff and subsurface flow in soils under different tillage.【Method】The experiment was conducted from July to September in 2019 at a field in Sichuan province.The tillage we compared included conventional tillage,ridge tillage,conventional tillage with full straw mulching,ridge tillage with full straw mulching,conventional tillage with pulverized straw mulching,and ridge tillage with pulverized straw mulching.In all treatments,we measured the subsurface flow and colloids concentration at depths of 20 cm,40 cm,60 cm,80 cm,100 cm and 120 cm in the soil.【Result】Straw mulching significantly reduced surface runoff and increased subsurface flow,especially in conventional tillage with full straw mulching.In all treatments,subsurface flow rate decreased with soil depth.The ridge tillage and ridge tillage with straw mulching reduced migration of the colloids larger than 0.22μm in both surface runoff and subsurface flow,compared to the conventional tillage.Fine colloids migrated more easily with surface runoff than large colloids,whereas large colloids moved more easily with subsurface flow and their concentration decreased with soil depth.【Conclusions】Among all tillage we studied,ridge tillage and ridge tillage with pulverized straw mulching can reduce colloids migration with both surface runoff and subsurface flow.Colloids migration flux in soil decreased with soil depth and the fine colloids migrated faster than the coarse colloids with both surface runoff and subsurface flow.