| Salt accumulation in the surface soil in Hetao Plain of Inner Mongolia is serious,which is harmful to crop growth.Buring straw layer or sand layer in the soil is an effective measure to improve saline-alkali soil.However,most studies foucsed on the thickness and location of straw or sand,there are few studies on the difference of water and salt regulation effect of straw interlayer and sand interlayer especially the particle size of sand interlayer.And the improvement effect of the combination interlayer of straw and sand is also not clear.Hence,this research adopted a combination of soil column column simulation test and a 3-year field experiment to:(1)explore the effect sand particle sizes(SC1: 1?2mm;SC2: 3?4mm;SC3:5?6mm)on water and salt transport,and compare the water and salt regulation effects of no interlayer(CK),sand layer with different particle sizes and straw layer,as well as the single material interlayer(JG: straw interlayer;SC: sand interlayer)and the combination interlayer of straw and sand(JS),by infiltration and evaporation simulation test with soil column;(2)study the effect of no interlayer(CK),straw interlayer(JG),sand interlayer(SC)and the combination interlayer of straw and sand(JS)on soil water and slat transport,soil pores,soil nutrients,diversity and structure of bacterial in rhizosphere soil,and the yield of sunflower by a 3-year field experiments.The purpose of this paper is to reveal the mechanism and effect of different interlayer on soil water and salt regulation,fertilization and yield,and to provide the basis for the construction of long-term effective water and salt regulation interlayer in saline-alkali soil in Hetao Plain.The main results are as follows:1?The regulation of water and salt of interlayer was explored,and the effect of particle sizes of sand and the single material interlayer and the combination interlayer were revealed.Burying interlayer slowed down the front wetting.After infiltration test,soil water content in 0-40 cm soil layer under treatment with interlayer was significantly higher than that under CK by 17.36%?26.02%,and soil salt content was significantly lower than that under CK by 9.72%?20.52%(P<0.05).With the increase of sand particle size,the infilitration reduction and salt leaching was enchanced.For 0-40 cm soil layer,soil water content was the highest and soil salt contend was the lowest the under SC3,followed by the JG.The soil water content in 0-40 cm soil layer under JG and JS was higher than that under SC,and the soil salt content under JG and JS was lower than that under SC.The interlayer also had the function of inhibiting groundwater evaporation and preventing the rising of capillary water and salt.After evaporation test,soil water content and salt content in 0-40 cm soil layer under CK were significantly higher than that under the treatment with interlayer by16.95%?38.13% and 51.49%?78.71% respectively(P<0.05).The soil water content and salt in 45-60 cm soil layer under the treatment with interlayer was significantly higher than that under CK.The inhibition effect strengthened with the increase of sand particle size.The inhibition effect under JG was weaker than that under SC3,but was stronger than that under SC1 and SC2.The inhibition effect under JG and JS was better than that under SC.2?The effect of interlayer on water and salt regulation by field experiment,and the relationship between soil water and salt with porosity were studied.After spring irrigation the soil water content in 0-40 cm soil layer under treatment with interlayer significantly increased than that under CK by 4.85%?16.78%,soil salt content under treatment with interlayer significantly decreased by 7.00%?17.01%(P<0.05),and the soil salt content under JG and JS was significantly lower than that under SC.The soil salt content in 0-40 cm soil layer under JS was the lowest in 2019 and 2020.The interlayer can inhibit the evaporation of groundwater and prevent the salt uptrend in the middle and late growth stages of sunflower.The stratification ratio of salt remained below 1 during the whole growth period of sunflower.At harvest,evaporation flux under JG?SC and JS significantly decreased by23.17%?58.37%,24.61?40.63% and 27.99%?56.33%(P<0.05).Further study on the change of pore structure of interlayer and its influence on water and salt regulation showed that the treatment of interlayer increased soil total porosity and decreased soil pore connectivity.The total porosity under JS was significantly higher than that under CK?JG and SC by254.90% ? 31.32% and 99.21%,respectively.The increased of total porosity and the decreased of pore connectivity in soil inhibited the upward of soil salt.The pore equivalent dimeter less than 5mm promoted the leaching of salt after irrigation and inhibit the upward of salt at harvest.3?The the effect of interlayer on soil fertilization and the influence of interlayer on microbial community structure were explored.Soil organic carbon(SOC)?total nitrogen(TN)and available nutrients in 20-60 cm soil layer under JG and JS siginificantly increased,especially in 40?60 cm soil layer.And the largest increase occurred in2019 compared with 2018(P<0.05).SOC?TN?available N?available K and available P in 40-60 cm under JG and JS increased by 20.72% and15.20%,23.81% and 16.33%,23.64% and 16.36%,16.42%?14.60%,31.91% and 23.40%.SC significantly reduced the diversity of rhizosphere bacterical community(P<0.05).JG and JS increased the relative abundance of bacterial which participated in soil carbon and nitrogen cycle,such as Chloroflexi and Acidobacteria.SC increased the relative abundance of Actinobacteria.Soil water content was an important factor in 2018,and p H and soil water content were the important factors in 2019 affecting bacterial community distribution.4?The effects of water and salt regulation,fertilization and bacterial community diversity in rhizosphere soil on yield were revealed.The emergence rate under treatment with interlayer significantly increased.The emergence rate under SC was the highest,but yield increased slightly and the seed yield even reduced by 9.61% in 2019.In 2018,seed yield under JG was the highest and significantly increased by 18.67%.Seed yield under JS was the highest in 2020 and siginificantly increased by 24.14%(P<0.05).The seed yield of sunflower was affected by soil salinity,rhizosphere microorganism and soil fertility.Generally,the decresed of soil salinity in 0-40 cm soil layer and increased of diversity of community and the soil fertility in 20-60 cm soil layer promtoted the seed yield of sunflower.In conclusion,interlayer had obvious effect on water and salt regulation.In 2018 straw interlayer siginifcantly regulated the soil water and salt.The effect of the combination interlayer of straw and sand on soil water and salt in 2019 and 2020 was better than that under straw interlayer.Both straw interlayer and the combination interlayer of straw and sand can improve the fertility,microbial community structure and increase the yield of sunflower. |
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