| The groundwater level of coastal saline-alkali land in Dongying City stays high,the surface evaporation is large,and the primary salinization becomes serious.New saline-alkali land will be formed every year due to regression and impact of the Yellow River.At present,various ways are being adopted for Dongying City to improve saline-alkali land,such as salt drainage through hidden pipes,“upper farming and lower fishing”,fish cultured in paddy field,planting of salt-tolerant trees and pastures.However,these improvement methods are timeconsuming,laborious and fresh water consuming,so it is very important to find a quick,simple and fundamental way to improve Dongying saline-alkali land.The chemical improvement of saline-alkali land is a method of improving saline-alkali land by adding calcium or acidic modifiers to it.It has the advantages of small investment,quick effect and simple operation.In this paper,laboratory-made liquid biological humic acid and powdered biological humic acid,as well as two kinds of wastes,red gypsum and fly ash,which are widely sourced and inexpensive,are used as modifiers.The capillary action formed by the fine aggregate structure of the soil is the most critical factor in the formation of salinealkali soil,the physical and chemical properties of saline-alkali soil are studied by optimizing the formula of the modifier,in order to improve the aggregate structure of saline-alkali soil,weaken the capillary phenomenon and realize the sustainable improvement of saline-alkali land from the source.In this paper,liquid biological humic acid,powdered biological humic acid,red gypsum and fly ash were added to saline-alkali soil in a certain proportion respectively,and we compared the improvement effects of liquid biological humic acid and powdered biological humic acid made in the laboratory with the traditional improver fly ash and gypsum improver red gypsum on saline-alkali soil.It was found that the four amendments could improve the soil structure,increase the proportion of water-stable large aggregates with a particle size greater than 0.25 mm in the soil from 11.27% to 20.24%～63.98%,14.16%～34.92%,11.74%～16.68%and 15.24%～28.04% respectively,and fundamentally reduce the capillary phenomenon of the soil.However,the organic content in saline-alkali soil would be reduced to 1.13%～1.31% after the application of red gypsum,and the p H of saline-alkali soil would be significantly increased to 8.63～9.53 after the application of fly ash.Moreover,the effect of agglomerating and the decrease of capillary phenomenon of the saline-alkali soil with single application of red gypsum and fly ash were not as good as that of liquid biological humic acid and powdered biological humic acid.It was necessary to combine red gypsum and two kinds of biological humic acid,fly ash and two kinds of biological humic acid to improve saline-alkali soil.The results reflected that the p H of improved saline-alkali soil after the compounding of the amendment was severally 0.12%～3.13% and 0.23%～8.33% lower than that of red gypsum and fly ash alone,the organic matter content increased by 7.09%～49.42% and 22.01%～57.23%,and the effect of agglomeration increased by 7.12%～81.41% and 5.19%～59.86% compared with the single application of red gypsum and fly ash,the capillary phenomenon was significantly reduced.Comprehensive analysis of the improvement results of saline-alkali land suggested that single application of liquid biological humic acid and the combination of 5% fly ash with different proportion of liquid biological humic acid had a better effect on improving saline-alkali soil.Therefore,the original saline-alkali soil and the saline-alkali soil treated by these eight groups of amendments were used for pot experiment.Through the analysis of wheat survival rate,seedling height,seedling diameter,rooting,dry weight and so on,it was found that 3% liquid biological humic acid had the best improvement effect on saline-alkali soil. |
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