Research On The Improvement Effect Of Humic Acid On The Coastal Clayey Saline Soil

Coastal clayey saline soil has the characteristics of low hydraulic conductivity,high salt content,low organic matter content,and low crop yield.In response to these problems,this study selected humic acid(humic acid powder and potassium humate)as the improved material.The indoor soil column experiment reveals the influence of humic acid on the saturated hydraulic conductivity and salt leaching of clayey saline soil.Field experiments were conducted to explore the effect of applying humic acid powder on the physical and chemical properties of clayey saline soil and the yield of winter wheat.The purpose of the research is to clarify the optimal application rate of humic acid and provide theoretical basis and guidance for the improvement of clayey saline soil.The main results of this research are as follows:(1)The original humic acid powder can effectively improve the bulk density and saturated hydraulic conductivity of clay saline soil.With the increase of the original humic acid powder dosage,the soil bulk density showed a trend of first decreasing and then increasing.The soil bulk density of the 0-20cm soil layer decreased by 1.45%-4.35%,and the T2 treatment(0.4g/kg)was significantly different from the control treatment.(P<0.05).With the increase of the amount of humic acid powder,the saturated hydraulic conductivity of the soil first increased and then decreased.(2)Humic acid can effectively improve the water status of clay saline soil.Applying the same amount of humic acid raw silt column has a stronger water adsorption capacity than potassium humate treatment.With the increase in the amount of humic acid powder in the field,the soil water content showed a trend of first increasing and then decreasing.The soil water content of the 0-20cm soil layer increased by 17.04%-27.12%,and the T2 treatment(0.4g/kg)was significantly different from the control treatment(P<0.05).(3)Humic acid can effectively improve the salt content of clay saline soil.Laboratory experiments show that during fresh water leaching,the salt content of the soil column decreases with the increase of the amount of humic acid raw powder;with the increase of the amount of potassium humate,the salt content of the soil column first decreases and then increases.With the increase in the amount of humic acid powder,the salt content of the field soil first decreased and then increased.The soil salt content of the 0-20cm soil layer was reduced by 29.88%-34.75%,and the T2 treatment(0.4g/kg)was significantly different from the control treatment(P<0.05).(4)Humic acid can effectively improve the ion composition of clay soil.Indoor experiments show that during fresh water leaching,with the increase in the amount of humic acid powder,the content of sodium and chloride ions in the soil column decreases.With the increase of potassium humate dosage,the content of sodium ion and chloride ion in the soil column first decreased and then increased.With the increase in the amount of humic acid powder in the field,the sodium ions,magnesium ions,chloride ions,and sulfate ions in the0-20cm soil layer respectively decreased by 4.82%-34.69%,5.05%-21.41%,19.15%-29.76%,21.10%-49.70%;potassium ion and calcium ion content respectively increased by17.55-40.19%and 40.87%-74.46%.(5)The original humic acid powder can effectively improve the organic carbon content of clayey saline soil and increase the yield of wheat.With the increase in the amount of humic acid powder,the soil organic carbon content increased first and then decreased,increasing by0.9%-40.81%respectively;with the increase in the amount of humic acid powder,the wheat yield showed an increase first and then decrease The trends increased by 4.89%-22.84%,respectively.The T2 treatment(0.4g/kg)was significantly different from the control treatment(P<0.05).In summary,the combined application of humic acid can effectively improve the physical and chemical properties of clayey saline soil.It can not only improve the saturated hydraulic conductivity of soil,increase the adsorption capacity of soil to water,improve the soil water content,but also reduce the soil salt content,improve the ion adsorption performance of clayey saline soil,and adjust the salt ion composition of soil.Through the analysis of the comprehensive improvement effect of clay saline soil improvement and wheat yield,the optimal application rate of humic acid powder is 0.4g/kg,and the field application rate is 600kg/hm~2.