Experimental Study Of Biochar And Organic Fertilizer On The Comprehensive Regulation Of Water,Fertilizer,and Salt In The Salt-Alkali Land Of Lubei Plain

Soil salinization and nutrient deficiencies are important factors limiting soil quality and primary productivity.As waste-derived soil amendments from agriculture and breeding industry,biochar and organic fertilizers have gained considerable attention for their advantages in improving soil physicochemical properties and soil quality and promoting crop growth.Therefore,this study conducted field experiments based on the winter wheat-summer maize rotation system in the Lubei Plain,the experiment used the principle of equal phosphorus and nitrogen to establish six treatments:CK(N:200 kg·（hm²·a）^-1,P₂O₅:120 kg·（hm²·a）^-1);biochar:B1(5 t·（hm²·a）^-1),B2(10 t·（hm²·a）^-1),B3(20 t·（hm²·a）^-1);organic fertilizer:OF1(7.5t·（hm²·a）^-1),OF2(10 t·（hm²·a）^-1).Based on three crop rotation cycles,we analyzed the effects of biochar and organic fertilizer on soil water content,salt content,cation content,p H,soil fertility indexes,soil microbial biomass,soil microbial entropy,and wheat yield of moderately saline-alkali soils,explored the influence mechanism of the above-mentioned indexes,revealed the interactions among soil water-salt,soil nutrient elements,and soil microorganisms,conducted a comprehensive evaluation of saline-alkali land improvement through principal component analysis and combined with the changes of wheat yield,screened out the best amendment and its dosage,aiming to provide data support for comprehensive regulation of water-fertilizer-salt,increase of crop yield and long-term application of amendments for saline-alkali soils in the Lubei Plain.The main findings are as follows:（1）The water content of soils treated with biochar is better than that of soils treated with organic fertilizer.The application of organic fertilizer increased the soil salt and Na⁺content,and its application rate was the key to control the soil salt and Na⁺content;while the opposite was true for biochar-treated soils,and initially decreased to a minimum value in B2 as the increased application rate and then increased;the soil salt and Na⁺content in B2 were5.10-17.63%and 2.82-18.23%lower than those in organic fertilizer,respectively.The effect of organic fertilizer on increasing soil Ca²⁺and Mg²⁺and decreasing soil sodium adsorption ratio（SAR）,exchangeable sodium percentage（ESP）,and p H was more pronounced compared to biochar treatment.The results showed that biochar was more beneficial to water retention and salt reduction in saline-alkali soils than organic fertilizer,B2 provided a better soil water-salt environment for crop growth.（2）The application of biochar and organic fertilizer had a positive effect on soil fertility under salt stress;soil organic matter,organic carbon,total nitrogen,total phosphorus,NO₃^--N,NH₄⁺-N,available phosphorus and phosphorus activation coefficient all increased with the biochar and organic fertilizer application.In comparison to biochar treatment,organic fertilizer was more beneficial to the increase of soil nutrients,and all were significantly different from CK（P<0.05）,with OF2 having the best effect.Moreover,correlation analysis showed that soil Ca²⁺,Mg²⁺,and alkalinity are the key factors affecting soil fertility.（3）Three years of data showed that biochar and organic fertilizer both significantly increased soil microbial biomass carbon（MBC）,soil microbial biomass nitrogen（MBN）,soil microbial entropy carbon（q MBC）,and soil microbial entropy nitrogen（q MBN）with increasing application rate,where organic fertilizer was more effective in increasing them than biochar.Correlation analysis showed that soil nutrients,salinity,and alkalinity are key factors affecting soil microbial biomass and soil microbial entropy.（4）Compared to CK,biochar application increased wheat yield by 8.35-14.71%and initially reached a maximum in B2 treatment（14.71%）and then decreased as the amount of biochar increased,while organic fertilizer treatment increased by 0.36%-7.30%and decreased as the amount of fertilizer increased.The experimental results showed that biochar was more advantageous in increasing wheat yield,with the highest yield in B2.（5）Principal component analysis indicated that biochar was superior to organic fertilizer in improving soil water content,soil salinity,and sodium damage and increasing wheat yield,while organic fertilizer was mainly focused on increasing soil fertility and microbial biomass.In conclusion,biochar not only provided a good water-salt environment for crops and significantly increased wheat yield,with the B2 treatment having the better effect,but also increased soil fertility,soil microbial biomass,and soil microbial entropy.Therefore,it is more appropriate to apply 10 t·（hm²·a）^-1 of biochar to the moderately saline-alkali land in the Lubei Plain for improvement.