Comparative Study On Several Improvement Measures Of Saline Soil In Houtao Plain Of Inner Mongolia

The Houtao Irrigation District is located in an arid and semi-arid climate zone with an average annual rainfall of 200 mm and an average annual evaporation of 1984.3 mm.It is a typical no-irrigation or no-agricultural area.With the long-term flood irrigation of the Yellow River,the groundwater level rises and the secondary salinization of the soil is serious,which restricts the agricultural development in the region.In this study,the sulphate-type moderate saline soil in the Houtao Irrigation District was studied.Under the drip irrigation under the membrane and the flood irrigation of the Yellow River,biochar,straw burial,straw returning,gypsum,gypsum+organic fertilizer were improved.The effects of irrigation methods and improvement measures on the soil properties of saline and alkali and ammonia volatilization,in order to provide technical support for the improvement of saline-alkali soil in Houtao Irrigation District.The results of this study indicated that:(1)With the progress of the experiment,the degree of soil salinization in this area was alleviated to varying degrees.The soil alkalization,soil salinity,soil salinity,SO42-,Cl-,and K+contents were significantly reduced under the treatment of straw burying,straw returning,biochar,gypsum treatment,and the alkalization degree was reduced by 39.72%?31.25%?26.99%?24.99%,respectively.Each treatment had different degrees of reduction on soil pH.The soils of the lower layer of biochar,gypsum+organic fertilizer and gypsum were reduced by 0.59,0.57 and 0.49,respectively.The content of Na+in biochar and gypsum treatment was 23.6%-65.6%,7%-50.7%lower than that of the control,and it had significant inhibition.The Ca2+and Mg2+ions were significantly increased under the treatment of gypsum,gypsum and organic fertilizer.The soil CO32-and HCO3-content in this area was small,and there was no significant difference between the treatments.(2)The soil nutrient content increased under different treatments,and the soil chemical properties were improved.Compared with other treatments,the effects of biochar,gypsum+organic fertilizer and straw returning on soil organic matter,alkali nitrogen and available potassium were more obvious.The average soil organic matter in the surface soil increased by 7.01,2.7,1.6 g/kg,The organic matter content of 5-15cm and 15-30cm soil was relatively stable,and there was no significant change in each treatment.The effect of straw returning and straw burying on the improvement of soil available phosphorus content was more obvious,with an average increase of 22.7 and 13.5 mg/kg compared with the control.(3)The dynamic trend of ammonia volatilization is basically the same,showing a trend of increasing first and then decreasing,reaching a peak at 2-3 days after fertilization,and then gradually decreasing.Each treatment has different degrees of inhibition on soil ammonia volatilization.In 2017,the order of ammonia volatilization loss is gypsum+organic fertilizer>control>gypsum>straw burying>straw returning>biochar,2018 is control>Gypsum>stalk returning to field>Biochar,ammonia volatilization was significantly reduced under biochar treatment,and the loss rate under drip irrigation and yellow irrigation decreased by 54.9%and 40.39%,respectively.(4)Sunflower production increased significantly with the extension of planting years.The order of treatment was biochar>gypsum>gypsum+organic fertilizer>stalk returning field>control>stalk burying deeply,and the yield increase of sunflower under biochar and gypsum treatment was as high as 48.07%and 37.23%.(5)The degree of soil salinization of all improved treatments under different irigation methods was alleviated,and the effect was basically that the drip irigation under the membrane was larger than that of the Yellow River.The content of available P and available potassium in the soil under drip irrigation was higher than that in the Yellow River flood irrigation,and there was no significant change in the content of organic matter and alkali nitrogen.The loss of ammonia volatilization under drip irigation was significantly lower than that of Yellow River flood irrigation,and the yield of sunflower was higher than that of Yellow River flood irrigation.In summary,each treatment has different degrees of improvement on soil salinization in the post-irrigation area.Among them,sub-drip irrigation+biochar treatment has the best effect,and it is suitable for promotion and application in saline-alkali areas in the post-irrigation area.