Monitoring And Evaluation Of Different Improvement Measures On Salinized Soil In South Bank Irrigation Area Of Ordos

Dalat Banner is an important agricultural crop producing county in Ordos City.Soil salinization is the key factor affecting the demonstration project of high-standard farmland construction in the demonstration area.The comprehensive treatment technology of saline-alkali land is the primary purpose of saline-alkali land improvement.In 2020,Dalat Banner started to implement the science and technology demonstration and promotion project of"Water and Salt Monitoring and Evaluation of Dalat Banner Salinized Farmland Improvement Demonstration Area"of 20,000 mu.In this paper,the soil improvement situation under the condition of no improvement measures was studied in the test area,and the improvement measures most suitable for soil texture were selected for different research areas.The main results are as follows:(1)Soil moisture content increased with the increase of soil depth in both two years.Soil salt in the test area was of surface aggregation type,and spatial variability in vertical depth of soil salt decreased gradually.The variation coefficients of soil water and salt in two years were in the range of 10%～100%,belonging to medium variation.During the two-year improvement period of the heavily salinized farmland in Wang Aizhao Town,the gold lump coefficient of the 0-20cm soil moisture layer was greater than 25%,while that of the 20-100cm soil moisture layer was less than 25%,indicating that the 0-20cm soil moisture content was affected by spatial structural factors and random factors(rainfall,irrigation and evaporation).The soil water and salt content in 20-100cm soil is greatly affected by spatial structure factors,and the gold lump coefficient of water content layer in the moderately salinized farmland layer in Shulinzhao and Zhaojun Town is lower than 25%,indicating that the soil water content in 0-100cm soil layer is mainly affected by spatial structure factors,and is less affected by random factors.(2)During the improvement period from 2020 to 2021,the surface clustering characteristics of soil salt profile weakened significantly,and soil salt mainly migrated from surface to deep.The decrease of Na~++K~+salt ions in 0-20cm soil of wang aizhao town,shulinzhao town and zhaojun town was 0.138g/kg,0.115g/kg and 0.058g/kg respectively,that is,5.3%>3.9%>1.2%.It is concluded that desulfurization gypsum improver has a more obvious effect on reducing the content of Na~++K~+in soil,while no desulfurization gypsum improver has a worse effect on reducing the content of Na~++K~+in soil,that is,desulfurization gypsum has a more significant effect on reducing the content of Na~++K~+in soil as a whole.(3)The variation of groundwater salinity in the study area is lower in the north and higher in the south.The dominant ions of total salt content in groundwater are SO42-,Cl-,HCO3-and Na++K+.In view of the heavy saline-alkali land mainly sandy loam in Wang Aizhao town,the improved measures of adding decayed farm manure and desulfurized gypsum into sandy loam have a significant effect on groundwater depth.The desulfurizing gypsum measures have a significant effect on groundwater depth in the silty loam area of shulinzhao town.Aiming at the moderate saline-alkali land with loam sandy soil in Zhaojun Town,the groundwater depth in the southern area with soil conditioner+subsoiling improvement measures is significantly greater than that in the northern area with soil conditioner+subsoiling measures,indicating that soil conditioner and subsoiling measures have a certain effect on the groundwater depth.(4)In order to reduce soil salinity and increase maize yield,it is suggested that engineering measures should be taken to remove salt from hidden pipe,and the improvement measures should be taken to reduce soil p H by using humic acid.In order to reduce soil salinity and increase maize yield,it is suggested to adopt the measures of decomposing farm fertilizer,desulphurizing gypsum,and using humic acid to redu ce soil p H in Shulinzhao town.In order to reduce soil salinity and increase maize yield,it is suggested to adopt the measures of soil conditioner and subsoiling to reduce soil p H in moderately saline-alkali soil of Zhaojun town.(5)Under saline-alkali land improvement measures,the maize yield in wang Aizhao town,Shulinzhao Town and Zhaojun town was 8.19～16.66t/hm~2,10.05～17.37t/hm~2 and11.46～14.02t/hm~2 respectively.In Shulinzhao town and Zhaojun Town,the yield of moderately saline-alkali land is 10%and 2.5%higher than that of the moderately saline-alkali land.For the saline-alkali land area,especially for the severely saline-alkali land,the preferred soil improvement measures are decaying farm manure and desulfurized gypsum,which can effectively control and improve the degree of soil salinization and is conducive to the growth and development of crops.