Effects Of Density,Biochar–based Organic Fertilizer And Nitrogen Fertilizer Interaction On Light Energy Utilization And Sucrose Metabolism Of Sugar Beet(Beta Vulgaris L.)

Sugar beet is the second largest sugar crop in the world.Both density and fertilizer have an important influence on the yield and quality of sugar beet.Too much of density or fertilizer can reduce the yield and quality of sugar beet.Due to long-term excessive application of nitrogen fertilizer,the environment is gradually destroyed,soil physical and chemical properties deteriorated,and crop yield and quality also decreased.Biochar–based organic fertilizer is a kind of ecological and environmental protection fertilizer made by combining biochar and organic fertilizer with a reasonable proportion.Many studies showed that the biochar–based organic fertilizer could effectively increase organic matter amount of soil and diversity of microorganism,also improve soil fertility,enzyme activity and soil physicochemical properties.It could effectively alleviate the negative effects caused by long-term excessive application of nitrogen fertilizer.Therefore,in order to explore the technical cultivation measures of the application of biochar–based organic fertilizer in sugar beet planting,and understand the influence of density,biochar–based organic fertilizer and nitrogen fertilizer and their interaction on the radiation use efficiency,sucrose metabolism,yield and quality during the growth of sugar beet.In this experiment,three factors and four levels saturated D-optimal design was adopted,with a total of 10 treatments,the effects of different factors in each period on sugar beet’s growth were simulated by linear regression.The results are as follows:(1)In single factors,in the early growth stage of sugar beet,applying more nitrogen fertilizer could significantly improve the dry matter accumulation of aboveground;proper density could improve the dry matter accumulation of aboveground;increasing the density could improve the leaf area index,reduce the canopy transmittance and improve the radiation interception rate of sugar beet.In the late growth stage,biochar–based organic fertilizer had the greatest influence on the dry weight per unit area of aboveground,and with the increase of the amount of fertilizer,the dry matter of aboveground increased at the same time.The application of nitrogen fertilizer could reduce the radiation use efficiency of sugar beet.In two-factor interactions,in the early middle growth stages of sugar beet,treatment of the interaction between nitrogen fertilizer and density had the greatest influence on the radiation use efficiency,while in the late growth stage,the treatment of the interaction between density and biochar–based organic fertilizer had the greatest influence on the radiation use efficiency of sugar beet.(2)Biochar–based organic fertilizer had the greatest influence on the activities of sucrose phosphate synthase(SPS)and the synthesis direction of sucrose synthase(SS)in sugar beet root after the rapid-growth stage of leafage,with the increase of application of biochar –based organic fertilizer,both of the activities firstly increased and then decre ased.The decomposition direction of SS,acid invertase(AI)and neutral invertase(NI)in different stages were mainly affected by biochar–based organic fertilizer.The total soluble sugar amount of sugar beet root was most affected by density from late stage of rapid-growth of leafage to sugar accumulation stage,while the sucrose amount of root was most affected by the application rate of biochar –based organic fertilizer in every stage.The interaction of the two factors(biochar–based organic fertilizer and nitrogen fertilizer)which had the greatest influence on SPS and the synthesis direction of SS was same in the sugar accumulation stage.In sugar accumulation stage,the sucrose in root was greatly affected by treatment of the interaction between biochar–based organic fertilizer and nitrogen fertilizer,while soluble sugar amount was closely related to the interaction of density-nitrogen fertilizer and densitybiochar–based organic fertilizer.(3)The influence of density on sugar beet yield and sugar yield was greater than that of biochar–based organic fertilizer and nitrogen fertilizer,and nitrogen fertilizer had the greatest influence on sugar content.In the interaction of two factors,sugar beet yield and sugar content were most influenced by the interaction between density and nitrogen fertilizer,and sugar yield was most influenced by the interaction between density and biochar–based organic fertilizer.Proper density and amount of biochar–based organic fertilizer could improve sugar content and sugar yield of sugar beet,and the application of nitrogen fertilizer could reduce sugar content of the sugar beet.When the three factors interacted,the maximum yield was 93.83 t/ha,while the density,biochar–based organic fertilizer application and nitrogen fertilizer application were 90000 plants/ha,3.17 t/ha and39.71 kg/ha,respectively.When the density,biochar–based organic fertilizer application and nitrogen fertilizer application were 84500 plants/ha,2.83 t/ha and 15 kg/ha,respectively,and the maximum sugar content was 18.69%.When the density,the application of biochar–based organic fertilizer and nitrogen fertilizer application were 85900 plants/ha,3.07 t/ha,and 29.31 kg/ha respectively,the maximum sugar yield was 16.64 t/ha.