Effect Of Irrigation Water Volume On Organic Carbon And Water And Salt Movement In Saline-alkali Land

As an important cultivated land resource in China,the Yellow River Delta restricts the ecological health of the Yellow River Delta and the sustainable development of agriculture.Therefore,the importance of developing and utilizing saline-alkali land is particularly prominent.Large-water irrigation is the most important measure to improve saline-alkali land.Irrigation ensures the normal production of agriculture and also affects soil organic carbon.In this paper,indoor soil column simulation combined with field micro-zone experiment was conducted to study the effects of different irrigation amount on soil salinity and organic carbon migration,and provide theoretical basis for the improvement and utilization of coastal saline-alkali land in the Yellow River Delta.The main research results are as follows:?1?Soil organic carbon content decreased after irrigation,and carbon leaching was most serious under S3 treatment with the largest irrigation amount.surface SOC leaching rate of surface was positively correlated with the irrigation water.The organic carbon content of soil layer in 40-60 cm under S1 began to accumulate,soil layer in 60-80 cm under S2 began to accumulate,soil layer in 0-80 cm under S3 treatment were all in leaching state,indicating that high irrigation water quantity caused a large amount of organic carbon loss in soil.Micro area test different before and after treatment leaching of soil organic carbon distribution similar to that of L1 and L2,60-80 cm soil organic carbon accumulation,L3 processing leaching in 0-100cm,shows low irrigation on soil organic carbon leaching is less,the irrigation water to the upper leaching of organic carbon in the lower intercept,high irrigation water on soil carbon leaching effect is bigger.?2?After leaching of soil column,soil moisture content increased to different degrees.The moisture change rules under different irrigation water treatments were basically the same.The moisture content of soil layer in 20-40 cm was less affected by irrigation amount,while the moisture content of other soil layers increased with the increase of irrigation amount.The water content of soil layer in 0-40 cm increased with the increase of irrigation water.The water content irrigation was higher in 60-100 cm before irrigation,and different irrigation amounts had little influence on the soil water content in this layer.?3?The total salt content of soil profile reduced significantly through irrigation,the amount of salt leaching is greatly affected by the amount of irrigation of soil layer in 0-40 cm,The greater the amount of irrigation,the greater the amount of desalination,show the S3>S2>S1.0-20 cm desalting rate is highest,between 68.11%with 84.58%,20-40 cm desalting rate is below the surface,between 39.46%with 52.21%,S1,S2 treatment at 40-60 cm of salt deposition,S1 product salt level higher than that of S2,three processing at 60-80 cm all salt deposition condition,the degree of salt deposition show that:S3>S2>S1.?4?After the three treatments of irrigation,the contents of K⁺,Na⁺,Ca²⁺,Mg²⁺,Cl^-,SO₄^2-and HCO₃^-decreased significantly,and the dissolution rate of each ion increased with the increase of irrigation water.The changes of each ion in 0-20 cm with the increase in the volume of irrigation showed different patterns of change.Ca²⁺first dissolved and then accumulated;HCO₃^-showed the opposite,first accumulated and then dissolved.The other ions all decreased with the increase in the volume of irrigation.?5?There was a significant difference in the change of soil pH under different irrigation water treatments.Before leaching,the soil pH showed a parabolic trend of increasing and then decreasing with the increase of soil layer.After leaching,the distribution of pH under S1,S2and S3 treatment was similar to that before leaching.The pH of soil layers in 0-40 cm increased first and then decreased with the increase of irrigation water,while the pH of soil layer in 40-80 cm showed no obvious rule.After leaching in fields with different leaching amount,the pH of each soil layer decreased,and the pH of soil layer in 0-20 cm decreased more than other soil layers,which increased with the increase of irrigation amount.The pH of L1 and L3 decreased with the increase of soil layer,while the pH of L2 did not change with the depth of soil layer.?6?There was a complex correlation between soil organic carbon and soil physical and chemical properties.The total nitrogen and available potassium were significantly positively correlated with organic carbon?p<0.01?,and the pH was significantly positive?p<0.05?.It was associated with significant negative?p<0.05?of organic carbon,total nitrogen and available potassium.The interaction of SOC and salt was affected by irrigation amount,soil layer and irrigation amount and soil layer.Further analysis showed that the amount of irrigation was 0-The SOC migrations of 20 cm,40-60 cm and 60-80 cm showed significant positive correlation?p<0.01?,and there was a significant positive correlation with the total salt leaching of 0-20 cm,20-40 cm and 60-80 cm?p<0.01?.?7?SOC flux was positively correlated with the migration flux of total salt,K?,Na?,Mg2?,Cl?,and irrigation water of 300 mm not only can improve the soil layerand greatly but also reduce the loss of organic carbon.