| Based on a series of problems such as poor physical properties,low organic matter content,shortage of fresh water resources and low wheat yield in the Yellow River Delta region,this study adopted the method of combining laboratory experiment with field experiment.To study the effects of different yellow sediment and humic acid dosage on soil water characteristic curve,main soil water constant,soil available water and readily available water content,soil macropore water content and wheat yield of coastal saline soil,and explore the influence mechanism of yellow sediment and humic acid on the improvement of coastal saline soil.The main research conclusions are as follows:(1)Through the fitting comparison of the three empirical equations of Van-Genuchten,Rational and Gardner,it is concluded that Van-Genuchten equation is suitable for the fitting amount of low yellow sediment and the fitting curve of soil water characteristics in the low soil water suction section,and the difference between the fitting value of the equation and the measured value is small.The Rational equation can be used to fit the soil water characteristic curve of low sediment distribution amount and high soil water suction section,and the difference between equation fitting value and measured value is large.The Gardner equation is not suitable for soil water characteristic curve fitting because of the large errors between the fitting values and the measured values in different treatments.Compared with the other two equations,the Van-Genuchten equation is more suitable for fitting soil water characteristic curve under the condition of combined application of yellow sediment and humic acid.(2)Combined application of yellow silt and humic acid can increase the wilting coefficient,capillary fracture water content,field water capacity and saturated water content of coastal salt soil.The soil wilt coefficient,capillary fracture water content and field water capacity increased significantly with the increase of humic acid dosage when the yellow diversion sediment dosage was above 5.04%,and the field water capacity of soil under S4T4 treatment was the highest,which increased by 46.70%compared with the control treatment.When the combined application of yellow silt was between 1.68%and 5.04%,the soil saturated water content increased with the increase of the combined application of humic acid,and S3T4 treatment had the highest saturated water content,which increased by 15.41%compared with the control treatment.(3)Combined application of yellow silt and humic acid can improve the available water content,easy available water content and macropore water content of coastal salt soil.The soil available water content and available water content increased with the increase of humic acid application amount when the combined application amount of yellow sediment reached 5.04%.The soil available water content and available water content increased rapidly with the increase of humic acid application rate when the combined application rate of yellow sediment reached 6.72%,and the increase rate was significantly higher than that of other treatments.Soil macropore water content was stable with the increase of humic acid application when the yellow sediment application rate was 1.68%to 5.04%.However,soil macropore water content decreased significantly with the increase of humic acid application rate when the yellow sediment application rate was 6.72%.(4)The combined application of yellow silt and humic acid could increase the soil moisture content in 0-40cm soil layer,and the effects of yellow silt and humic acid on soil moisture content gradually decreased with the increase of soil depth.When the humic acid dosage was constant,the soil moisture content decreased slightly with the increase of the yellow sediment dosage.The soil moisture content increased with the increase of humic acid application when the amount of sediment was constant.(5)Through the wheat field experiment,the wheat yield of each treatment was higher than that of the control treatment,and the wheat yield of S3T3,S3T4,S4T3,S4T4 and treatment increased the highest,which increased by 30.32%,30.40%,29.27%and 30.96%compared with the control respectively.In the grey correlation analysis of wheat yield composition and yield,the number of wheat ears is the key factor affecting wheat yield.According to the above studies,the combined application of yellow sediment and humic acid has significant effects on the main water constant,different water types and wheat yield of coastal saline soil.Considering the high economic cost of humic acid,the recommended combined application of yellow sediment and humic acid is 150-200t/hm2 and 0.9-1.35t/hm2,which can provide reference for the improvement of coastal saline soil in the Yellow River Delta region. |
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