膜下滴灌棉田冻融期土壤剖面水盐热分布动态

Dynamic distribution of water,salt and temperature in soil profile during freezing and thawing in cotton field under mulch drip irrigation

为了深入揭示干旱区膜下滴灌棉田冻融期土壤水、盐和温度的动态变化规律,利用Hydra水盐热系统实现对冻融期宽行、窄行和膜间位置15,25和40 cm深度土壤液态水分、温度和电导率实时等间隔加密监测,分析了冻融期土壤水盐热动态变化过程.结果表明:同一位置不同深度液态水分、电导率和温度动态变化规律一致;冻融期内盐分垂向运移规律为深层土壤内的盐分向表层运移,冻融作用使盐分发生了重分布,加重了土壤40 cm深度的盐分含量,电导率增值范围为20~80μS/cm,并且冻融前后不同位置电导率以位置排序由大到小为宽行,窄行,膜间;在冻融过程中不同位置土壤温度、液态水分和电导率两两之间存在着正相关关系(P<0.01),其相关系数大于0.74,而电导率与温度和液态水分两者也存在极强的多元一次函数关系(P<0.01),其相关系数大于0.90;冻结和融化并不是重合的过程,而是在期间会出现分叉点,分叉点出现在-1℃附近.研究结果对制定合理的非生育期灌溉制度具有重要参考意义.

In order to reveal the dynamic changes of soil water,salt and temperature in cotton field under mulch drip irrigation during freeze-thaw period in arid area,the Hydra water,salt and hydrothermal system was used to monitor the liquid moisture,temperature and conductivity at the depth of 15 cm,25 cm and 40 cm between wide rows,narrow rows and inter-membrane during freeze-thaw period.The dynamic change process of soil water,salt and heat during freeze-thaw period was analyzed.The results show that the dynamic changes of liquid moisture,conductivity and temperature in the same position at different depths were consistent.During the freeze-thaw period,the law of salt vertical migration is that the salt in deep soil moves to the surface layer.The freeze-thaw effect redistributes the salt and aggravates the salt content in the soil at the depth of 40 cm,and increase range of conductivity is 20-80μS/cm.The relationship between the conductivity values in different positions before and after freeze-thaw is:wide row>narrow row>between films.In the process of freezing and thawing,there is a strong positive correlation between soil temperature,liquid moisture and electrical conductivity at different positions(P<0.01),and the correlation coefficient is above 0.74.However,there is also a strong multivariate linear function relationship between electrical conductivity and temperature and li-quid moisture(P<0.01),and the number of phase relationships is greater than 0.90.Freezing and thawing are not coincident processes,but the bifurcation points will appear in the process,which will appear near-1℃.The research results have important reference significance for formulating reasonable water and salt management system in non-growth period.