Coupling Effect Of Desulphurized Gypsum And Biochar In Improving New Cultivated Land Reclaimed From Coastal Mudflat

With the rapid development of coastal economy,construction land oc-cupies a large amount of land,and agricultural land is increasingly insuffi-cient,so it is increasingly urgent to reclaim new cultivated land re-sources.Fujian province has a lot of mountains and little land,while coastal beach resources are rich.Reclamation of coastal beach resources can effectively relieve the tension between man and land,which is of great significance to the healthy and sustainable development of economy and the protection of cultivated land resources in Fujian Province.But coastal tidal flats are influenced by ocean,often contains a lot of salt,is not con-ducive to crop growth commonly,through natural leaching will need a lot of time to complete,therefore,this study new coastal tidal flats reclamation of cultivated land as the research object,and utilization of desulfurization gypsum and biochar amendment of different ratio of coastal tidal flats new modified reclamation of cultivated land.The study was divided into indoor pot experiment and field experiment.In the indoor pot experiment,8 treat-ments were set up,which were CK:no modifier was applied;A:100g/kg desulfurization gypsum was applied;B:Desulfurization gypsum 75g/kg plus biochar 30g/kg;C:desulfurization gypsum 75g/kg plus biochar20g/kg;D:50g/kg desulfurization gypsum plus 20g/kg biochar;E:apply-ing desulfurized gypsum 50g/kg plus biochar 30g/kg;F:50g/kg biochar was applied;G:Improve the farmland soil for many years without applying any amendments.Through indoor pot experiment,the effects of soil phys-ical and chemical properties,nutrient properties and crop growth were studied,and the evaluation index system of new cultivated land was estab-lished to comprehensively evaluate the improvement effect.Four good proportions were screened out through pot experiment,which were A:100g/kg desulfurized gypsum;B:Desulfurization gypsum 75g/kg plus bi-ochar 30g/kg;C:desulfurization gypsum 75g/kg plus biochar 20g/kg;E:Apply desulfurization gypsum 50g/kg plus biochar 30g/kg.The experimental plots were set up in the field,and the selected better ratios were verified by field experiments.The following conclusions are obtained:（1）Desulphurized gypsum and biochar significantly improved soil physical and chemical properties,desulphurized gypsum and desul-phurized gypsum combined with biochar significantly increased soil Ca²⁺,SO₄^2-,Mg²⁺contents,and significantly decreased soil p H value,SAR and soil bulk density;biochar and desulphurized gypsum combined with bio-char significantly reduced soil bulk density,and significantly increased the contents of water-soluble K⁺,field water holding rate,soil available K,available P and organic matter.The combined treatment of biochar and desulfurized gypsum can absorb the advantages of both amendments and achieve better improvement results.Treatment C（75g/kg plus 20g/kg desulfurized gypsum）was the best in both indoor pot experiment and field experiment.（2）In the indoor pot experiment,desulfurized gypsum and biochar improved the living environment of peanut,significantly increased the fresh weight,dry weight,plant height and leaf area of peanut,and promoted the growth of peanut.Among them,treatment A（desulfurized gypsum100g/kg）had the most significant effect on increasing fresh weight and dry weight of flowers by 152.5%and 130%,respectively.However,treatment C（desulfurization gypsum 75g/kg plus biochar 20g/kg）had the most sig-nificant improvement effect on plant height and leaf area of peanut,which increased by 58.7%and 291.6%,respectively.In the field experiment,there was no significant change in each treatment compared with CK 50days before planting,and the fresh weight,dry weight,plant height and leaf area of each treatment increased after 50 days compared with CK,among which treatment C（desulfurization gypsum 75g/kg plus biochar20g/kg）had the best effect.By 10.73%,42.6%,17.33%and 43.3%,respec-tively.（3）The combined treatment of desulfurized gypsum and biochar has a good coupling effect.In such aspects as the physical and chemical prop-erties and nutrients provide can make up for the inadequacy of the other party,the desulfurization gypsum lower p H value for biochar provide ef-fective phosphorus absorption,and biochar reduce soil bulk density,improve soil water-holding capacity in the field for the acceleration of desulfurization gypsum substitution reaction and salt leaching,and can provide the desulfurization gypsum lack of available k,available p and or-ganic matter and other nutrients,It can also reduce the risk of heavy metal pollution caused by desulfurized gypsum.Combined application of the two can better promote the absorption of nutrients such as alkali-hydrolyzed nitrogen and organic matter and provide better living space for plants.（4）According to the comprehensive evaluation of TOPSIS-entropy weight model,the improvement effect of each treatment in indoor pot ex-periment was ranked as C>E>A>B>D>F>G>CK.In field treatment,treat-ment C（75g/kg desulfurized gypsum plus 20g/kg biochar）had the highest fitting degree,which was the best treatment,followed by treatment E（50g/kg desulfurized gypsum plus 30g/kg biochar）,A（100g/kg desulfu-rized gypsum）,and B（75g/kg desulfurized gypsum plus 30g/kg bio-char）.According to the results of indoor pot experiment and field experi-ment,treatment C（desulfurization gypsum 75g/kg plus biochar 20g/kg）was the best proportion scheme.