前期含水量对机械压实土壤结构特征的影响

Effect of Antecedent Moisture Content on Soil Structure Compacted by Machinery

使用美国MT865履带式拖拉机对东北典型黑土区耕地土壤进行1,3,8,13次的积累压实试验,通过对土壤硬度、广义土壤结构指数的测定及计算,并结合土壤三相的二维三系图对比分析了不同前期含水量条件下土壤机械压实特征。结果表明：由于表层0-10 cm含水量的不同,相对高含水量的土壤剖面受机械压实的影响范围较低含水量时深10 cm,且各个层次的土壤硬度增量的变化趋势也相对低含水量时滞后10 cm,从初次碾压开始就体现了积累压实作用,在其压实影响范围内硬度与对照相比提高了22.58%-753.85%;而低含水量的土壤则具有相对较强的抗机械压实的能力。同时发现,在土壤承受能力范围内,适当的压实可以有效调节土壤三相,改善土壤结构;秸秆还田不仅具有传统的蓄水保墒、培肥改土的效用,还可以缓解作业机械对土壤的压实。

Compaction induced on cultivated fields during to overuse of machinery is strongly influenced by the prevailing soil water content, so understanding the relationship between water status, number passes and the level of compaction for a given load is imperative. The work was performed with a heavier crawler tractor （MT865, made in USA, 17 599 kg） on typical black soil of Northeast of China, at two levels of water content using four different passes： one, three, eight and thirteen, and then soil strength, soil three phases and soil three phases integrated index （GSSI） were measured and calculated to identify changes in soil structure. The topsoil （0-- 10 cm） with high water content was influenced deeply by 10 cm, and the change of soil strength was lagging about 10 cm than that of lower water content. The accumulated compaction was obvious from the first pass, and improved by 22.58% -753. 85% during the affected region. Comparatively lower water content had stronger compaction resistance. Interestingly a slight degree of topsoil compaction may prove beneficial for soil three phases structure, furthermore, straw residues returning could not only holding water and ameliorate fertile condition but also alleviate soil compaction induced by cultivation traffic.