秸秆覆盖秋浇后盐渍土壤冻融过程及水盐运移特征

为了探讨在寒旱盐灌区覆盖秋浇后冻融土壤的冻融特性及水热盐协同调控机制,在盐渍土壤进行覆盖后秋浇田间冻融试验,设5个处理,秸秆覆盖量1.2kg/m~2(F1.2)、秸秆覆盖量0.9kg/m~2(F0.9)、秸秆覆盖量0.6kg/m~2(F0.6)、秸秆覆盖量0.3kg/m~2(F0.3)、未覆盖(CK)。结果表明:秸秆覆盖影响了土壤冻结融化推进过程,改变了土壤温度对气温变化的响应关系,影响了水分、盐分在土壤剖面(特别是土壤表层和耕作层)的重新分配,提高了翌年春季水分可利用量,抑制了表层及耕作层春季返盐,提高了秋浇的灌水效果。秸秆覆盖处理的最大冻结深度小于CK处理4~26cm,初冻时间滞后0~12d,融化时间滞后0~21d;秸秆覆盖的各处理由于覆盖层的存在,消融水蒸发受到抑制,表层积盐现象较弱;消融期结束后,在土壤表层0—10cm,F0.9的土壤含水率最高,处理F1.2较秋浇前脱盐率为81.18%,脱盐效果最好;在耕作层0—40cm,F0.9的土壤含水率最高,处理F0.6较秋浇前脱盐率为75.65%,脱盐效果最好;为保证在翌年春播时的适宜含盐量及含水率,以覆盖量0.6~0.9kg/m~2为宜。研究结果可为河套灌区秋浇制度的优化提供参考。

Salinized Soil Freeze-thaw Process and Water-salt Movement After the Autumn Irrigation with Straw Mulch

Soil water and salt transfer are important processes under freezing-thawing conditions in nature.The effects of soil salt concentration on soil water and heat transfer have not been investigated thoroughly under freezing/thawing conditions.The freeze-thaw characteristics of salinized soil and thecorresponding control mechanism of water-heat-salt after the mulched autumn irrigation in cold-drought-salt irrigation district were explored in the study.The field freez-thaw-experiment was conducted on the salinized soil after the mulched autumn irrigation with 5 treatments in terms of straw mulching quantity of 1.2 kg/m2 (F1.2),0.9 kg/m2 (F0.9),0.6 kg/m2 (F0.6),0.3 kg/m2 (F0.3) and no mulching (CK).Results showed that:straw mulch promoted process of soil freeze-thaw,and changed the relationship between soil temperature and air temperature,resulting in the redistribution of water and salt in soil profiles,especially in the surface soil and tillage layer,which enhanced the available amount of spring water in the next year and restrained the spring salinification in surface soil and tillage layer,thus,the quality of autumn irrigation was improved.The maximum freezing depth of mulching was 4～26 cm smaller than CK,the initial freezing time and thawing time are lagged by 0～12 d and 0～21 d.The vaporization of melting water was restrained due to the straw mulch,which resulted weak surface salt accumulation.After the thawing period,the soil moisture content in F0.9 was the largest one in soil depth of 0～10 cm,and the F1.2 related ratio of desalinization was 81.18％,which was the best one among all the treatments.As for the tillage layer of 0～40 cm,the soil moisture content of F0.9 was the highest one and the best one desalinization occurred in F0.6,which was 75.65％.In order to ensure the appropriate salt content and water content in the coming year,the coverage amount of 0.6～0.9 kg/m2is the optimal one.The findings can be used to provide references for the optimization of autumn irrigation system in Hetao Irrigation District.