Effects Of Humic Acid On Water Properties Of Clay Saline Soils

Based on a series of problems such as low soil organic matter content,high soil salinity and low land quality in the Yellow River Delta,this study carried out experiments and theo-retical analysis on the addition of humic acid modified clay soil.The experiment used a com-bination of laboratory test and field test to design a soil moisture characteristic curve test with different humic acid additions to determine the different humic acid additions to the clay soil moisture type,soil water availability and motility.And soil moisture retention capacity and other soil moisture characteristics.Explore the mechanism and measures of humic acid on the improvement of coastal clay soil.The main findings are as follows:(1)Using the measured data to compare and fit the four main water characteristic curve equations,and clearly define the expression form of the soil water characteristic curve equa-tion suitable for the coastal clay soil.It is found that the empirical equation II has high fitting precision and the equation correlation coefficient R~2.The minimum value is 0.9872 and the highest value is 1.0000,which is suitable for the study of humic acid modified clay soil.(2)Humic acid can increase the saturated water content of the soil,the water holding ca-pacity of the capillary tube,the moisture content of the capillary tube,and the capillary water.The saturated water content and capillary water holding capacity of T2 treatment were the highest,which were 13.68%and 13.85%higher than CK,respectively.The difference was significant.(3)Humic acid can effectively improve the water retention capacity of the soil.The field water holding capacity of T1,T2,T3 and T4 increased by 6.87%,13.97%,15.31%and19.59%,respectively.The difference was significant.The effective water content of each treatment increased by 9.69%,17.12%and 14.87%,20.60%,the difference is significant.(4)Humic acid can increase the effective water content of the soil and the effective water content,and improve the soil water availability.The effective water content of each treatment was higher than that of CK treatment,and the difference was significant compared with CK.The soils with T1,T2 and T5 treatments were more effective than CK,which increased by8.98%,11.96%and 2.18%,respectively.The T2 treatment was the most effective water con-tent.(5)The gravity water content of the soil increased first and then decreased with the in-crease of humic acid content.The soil gravity water treated by T1 and T2 increased by 10.73%and 10.24%,respectively,and the difference was compared with CK treatment.Significantly(P<0.05),T3,T4,T5,T6,T7,T8 were 14.59%,20.50%,14.14%,43.48%,36.66%,and46.17%lower than CK treatment,respectively,and six treated gravity waters.The difference in the reduction in content was extremely significant(P<0.01).(6)Humic acid reduces soil salinity while effectively increasing soil water content.In the surface layer of 0-20cm soil,the salt content of T1,T2 and T4 treatment in 2017 was signifi-cantly lower than that of CK,which was reduced by 20.3%,23.5%and 17.0%,respectively,and the difference was significant(P<0.05).The water content of each treatment increased significantly,which was 7.3%,0.4%,1.4%,and 4.4%higher than CK,respectively.