Effect of Antecedent Moisture Content on Soil Structure Compacted by Machinery

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.