Effect Of Humic Acid Based Organic Materials On Soil Improvement In Cultivated Sodic-saline Soil

The West Liao River Plain is a typical ecotone between agriculture and animal husbandry in China.The existing cultivated land is 1.34×10⁶ hm²,and more than half of the cultivated land is saline-alkali land,which is dominated by soda saline-alkali land.Soil salinization has become an important factor restricting the development of local agriculture.Therefore,it is of great significance to explore suitable soil improvement measures for cultivated sodic-saline soil for cultivated sodic-saline soil management and agricultural sustainable development.Humic acid based organic material is the general term of humic acid and its derivatives.Because of its outstanding improvement effect on saline soil and no pollution to soil,it is widely used in saline soil improvement.In order to comprehensively explore the effect of humic acid-based organic materials on soil improvement of cultivated sodic-saline soil in West Liao River Plain,this paper explores the effect of humic acid-based organic materials on soil physical and chemical properties,nutrients and crops of cultivated sodic-saline soil from three aspects:the effect of humic acid-based organic materials on soil improvement of cultivated sodic-saline soil with different saline-alkali degrees,the effect of different humic acid-based organic materials on soil improvement of cultivated sodic-saline soil and the effect of comprehensive measures of tillage and humic acid-based organic materials on soil improvement of cultivated sodic-saline soil,in order to provide theoretical basis and technical support for soil improvement of cultivated sodic-saline soil.The results of this paper are as follows:（1）By analyzing the effects of humic acid-based organic materials on the growth of soil（moderate and severe）and maize with different saline-alkali degrees,the effects of single and combined application of humic acid-based organic materials（compound conditioner and humic acid）on the improvement of cultivated sodic-saline soil were studied.The results showed that single and combined application of humic acid-based organic materials could improve soil with different saline-alkali degrees.Among them, the improvement effect of compound conditioner 22500 kg·hm^-2 in the soil of moderate cultivated sodic-saline soil was better than that of other improvement treatments,the soil bulk density and hardness of plough layer（0～40 cm）decreased in varying degrees,and the soil structure was significantly improved.s Soil p H decreased by 0.61 units on average,and soil alkalinity and sodium adsorption ratio decreased by 31.4%and 19.8%on average,significant increase in soil organic matter and maize yield.The application of compound conditioner 22500 kg·hm^-2 and humic acid 6000 kg·hm^-2 in the soil of severe cultivated sodic-saline soil had the best improvement effect.The specific performance was as follows:significant indigenous increased the total soil porosity in the 0～10 cm soil layer,reduced the soil hardness and solid ratio in the 0～30 cm soil layer,and improved the soil structure by increasing the soil-liquid ratio.The soil p H of plough layer decreased by 0.29 units on average,and the soil alkalinity,total alkalinity and sodium adsorption ratio decreased by 19.1%,30.8%and 20.7%on average,the soil organic matter in plough layer increased by 22.5%,maize yield increased by 22.4%.（2）The effects of different humic acid-based organic materials（composite conditioner,humic acid and fulvic acid）and their application rates on soil physical and chemical properties,nutrient content and maize growth of cultivated sodic-saline soil were analyzed,and the optimal application rate of humic acid-based organic materials was screened by regression analysis.The results showed that different humic acid-based organic materials and their application rates had different effects on soil improvement of soda cultivated sodic-saline soil.The promoting effect of fulvic acid treatment on crop growth was better than that of compound conditioner and humic acid.When the application amount of fulvic acid was 6 kg·hm^-2,the improvement effect was the best.The plant height,disc diameter and yield of sunflower increased by 32.6%,24.3%and28.1%respectively compared with the control.The reducing effect of composite conditioner on soil salinization was better than that of humic acid and fulvic acid.When the application amount of composite conditioner was 22500 kg·hm^-2,the improvement effect was the best.Under this treatment,the average p H of topsoil decreased by 1.13units,and the average total alkalinity and SAR decreased by 57.9%and 38.6%,respectively.The contents of soil organic matter and available potassium increased significantly,and the plant height,chlorophyll and yield of sunflower increased by16.3%,11.4%and 36.9%,respectively.（3）Field experiments were conducted to study the effects of tillage and humic acid-based organic materials on soil physical and chemical properties,nutrients and crop growth of cultivated sodic-saline soil.The results showed that the comprehensive improvement measures of tillage and humic acid organic material addition could effectively improve soil physical and chemical properties,improve soil nutrients and maize yield.Among them,the treatment of 40 cm ridge and 22500 kg·hm^-2 composite conditioner and 6000 kg·hm^-2 humic acid had the best effect.This improved treatment reduced soil bulk density,improved soil total porosity,and soil structure was close to the ideal state.Soil p H and SAR in plough layer decreased by 12.1%and 74.9%,soil organic matter and available phosphorus content increased by 39.5%and 124.6%,respectively,and maize yield increased by 37.6%.（4）The correlation between soil physical and chemical properties,nutrient content and maize yield of cultivated sodic-saline soil was comprehensively analyzed.The results showed that soil salinization index was negatively correlated with maize yield,and soil p H and total alkalinity had significant indigenous effects on maize yield.Soil nutrient content was positively correlated with maize yield,and increasing soil organic matter content had an important effect on maize yield.