Effects Of Straw Biochar On The Phosphorus Fractions And Improvement Of Soda Saline-Alkali Soil

The Songnen Plain in Northeast China is one of the world's three major soda-saline-alkali land areas.It is of great significance improving the saline-alkali land to the sustainable development of agriculture.However,due to the soil forming characteristics of saline-alkali land,the soil phosphorus fixation ability is weak,resulting in low soil available phosphorus content,which has one of the main limiting factors of crop yield.As a kind of soil amendment with high carbon content and more stable,biochar can affect the chemical properties of soil and phosphorus composition.Therefore,this study adopted the corn stalk biochar to conduct a location test established in the soda saline-alkali soil of the Songnen Plain.It was used to study different corn stalk biochar 0(CK),5(T5),10(T10),15(T15),20(T20),25(T25),30(T30)t/hm² treatment on the change law of saline-alkali soil salinity,soil nutrient characteristics,microbial biomass carbon and phosphorus,phosphatase activity and phosphorus form components,providing scientific basis for the scientific and rational use of biochar and guiding the application of biochar,which also provides scientific reference for the protection of saline-alkali land.The main findings are as follows:(1)After the application of biochar,the pH value of saline-alkaline soil was reduced by 9.04%;the salt content has been reduced by 28.75%;the Na⁺concentration reduced by 6.78%;and the alkalinity reduced by 22.88%.Soil cation exchange capacity,soil total nitrogen,total phosphorus,available potassium,available phosphorus and organic matter content increased by 22.06%,16.00%,21.74%,25.33%,17.63%and 17.84%,respectively.These soda saline-alkaline soil indicators had the better effect on T20 and T25 treatments.Soil nutrient content is negatively correlated with pH,Na⁺concentration,alkalinity and salinity,instead,positively correlated with CEC.(2)The phosphorus components of soda saline-alkaline soil are mainly HCl-P and Residual-P,accounting for 58.09%and 18.96%of the total phosphorus content,respectively.Biochar promotes the conversion of organic phosphorus to inorganic phosphorus.From the two-year data,the percentage of inorganic phosphorus in each treatment is 5.92%-19.94%higher than that of CK.Biochar treatments increased the content of Resin-Pi,Na HCO₃-Pi,Na OH-Pi and D.HCl-Pi,and reduced the content of C.HCl-Pi,Na HCO₃-Po,Na OH-Po,C.HCl-Po and Residual-P,among which the T20 and T25 treatments have the most obvious effect.(3)After the application of biochar,the activity of acid phosphatase is increased,and the activity of alkaline phosphatase is reduced,but it has no effect on the activity of neutral phosphatase.With T20 treatment the acid phosphatase activity increased by 43.72%,and the alkaline phosphatase activity decreased by 18.42%.Only T30 treatment increased the content of microbial biomass carbon and phosphorus,increasing by 11.55%and 17.81%,respectively.Soil pH,salinity,Na⁺concentration and alkalinity were negatively correlated with microbial biomass carbon when microbial biomass phosphorus and acid phosphatase activity,and positively correlated with alkaline phosphatase activity.(4)Biochar increased corn grain weight per spike weight,100-kernel weight and yield,among which the yield of corn treated with T25 was the highest in 2 years,at the level of 6.07 t/ha and 6.11t/ha,respectively.The yield of maize treated with T20,T25 and T30 was significantly higher than that of the control group in two years.In 2019,it increased by 12.76%,13.88%,and 10.51%,and in2020,it increased by 11.28%,12.94%,and 9.61%,respectively.The grain weight per spike weight and 100-kernel weight of corn treated with T25 were also the highest in 2 years.The grain weight per spike weight increased by 14.09%and 14.19%,and the 100-kernel weight increased by 8.76%and 8.00%.