Effects Of Biochar-based Organic Fertilizer On Sugar Beet Growth And Rhizosphere Soil Property Under Saline Alkali Stress

Sugar beet is one of the most important sugar crops in China.It is mainly planted in arid and semi-arid areas of Northwest,Northeast and North China.Sugar beet has become an important rotation crop in the north because of its strong salt and alkali tolerance.Organic fertilizer can not only provide the needed nutrients for crop growth,but also improve the physical and chemical properties of saline-alkali soil,increase the number of soil microorganisms and the soil enzyme activity related to the transformation of soil nutrients.Therefore,the effects of different levels of biochar-based organic fertilizer on the growth of sugar beet and the microorganism and enzyme activity in rhizosphere soil were studied in order to improve the saline-alkali soil and increase crop yield with organic fertilizer.In this study,the sugar beet cultivar KW S0143 was chosen as materials,Na Cl,Na2SO4,Na2CO3 and Na HCO3 were mixed together.Saline alkali soil environment was simulated by a pot experiment.Pot experiments totalled 6 treatments including CK(no fertilizer),S(saline alkali),SF1(saline alkali+1500kg/ha biochar-based organic fertilizer),SF2(saline alkali+2250kg/ha biochar-based organic fertilizer,SF3(saline alkali+3000kg/ha biochar-based organic fertilizer),SF4(saline alkali+3750kg/ha biochar-based organic fertilizer).Study on photosynthetic fluorescence parameters,key enzymes of nitrogen metabolism,Protective enzymes,biomass,yield and quality of root,microorganism and enzyme activity in sugar beet rhizosphere soil of biochar-based organic fertilizer.The results of study show:(1)Under saline alkali stress,the application for biochar-based organic fertilizer could significantly(P<0.05)improve fresh dry biomass,root shoot ratio,yield,gas exchange parameters(Pn,Gs,E and Ci),chlorophyll content,Fv/Fm,Yield(II),q P,and ETR,decrea se NPQ of sugar beet.With an increase of organic fertilizer concentration,the above indexes of sugar beet leaves.firstly increased and then decrease,except for NPQ.All indicators of 3000kg/ha organic fertilizer treatment performed best.The correlation between dry biomass,Chla,Chlb,Car,Gs,Fv/Fm,Yield(?),and ETR was significantly higher than that of Pn and E.(2)Four levels of fertilization increased the activities of nitrogen metabolizing enzymes and antioxidant enzymes and decreased the content of MDA in sugar beet leaves under saline alkali stress.The NR,GOGA,.and GS activity increased first and then decreased with the increase of SF3 treatment activity.had the highest.The four fertilization levels were significantly different from those of saline-alkali treatment(P<0.05).Activities of SOD,POD,and CAT increased with the increase of the amount of fertilizer,showing that SF1 < SF2 < SF3 < SF4,but the content of MDA in leaves changed in reverse.The activity of SOD,POD,CAT,and t he content of MDA in the four fertilization levels were significantly higher than those in the saline-alkali treatment.(3)The application of organic fertilizer had a significant effect on the rhizosphere soil of sugar beet.The activities of bacteria,actinomycetes,fungi,urease and catalase in soil increased with the application of biochar-based organic fertilizer,and the difference of the four fertilization levels was significant compared with the control(CK)and saline-alkali treatment(S)(P<0.05).However,alkaline phosphatase activity and root activity increased first and then decreased with the increase of fertilization.The conductivity of soil decreased with the increase of the amount of organic fertilizer,but the p H value of soil decreased slight ly,but reached a significant level with saline-alkali(S)treatment.Correlation analysis showed that the number of rhizosphere soil microbes,enzyme activity,nutrient content and root activity were positively or extremely correlated,but negatively correlated with soil p H and electrical conductivity.(4)Fresh biomass,dry biomass,and root shoot ratio firstly increased and then decrease.About 3000kg/hm2 organic fertilizer treatment,between 2017 and 2018 year,the root yield was 110.56% and 121.30% than CK;the sugar yield was 136.96% and 150.66% than CK;the root yield was 157.70%,and 173.83% than saline treatment;the sugar yield was 208.84% and 220.4 2%than that of saline-alkali treatment.(5)The root yield of sugar beet was significantly positively correlated with NR,GS,and GOGAT(P<0.01)or positively correlated with SOD,POD,and CAT(P<0.05),but negatively correlated with MDA.Applying organic fertilizer at different levels can reduce the content of reducing sugar in root.The content of reducing sugar,amino acid,betaine and nitrate in root decreased with the increase of fertilizer.the content of reducing sugar,amino acid,betaine and nitrate in root in SF4 treatment was the lowest.