Study On Leaf Mineral Nutrition Diagnosis And Fertilization Decision Based On Nutrient Balance For High Yield And Good Quality Of Citrus

Leaf nutrition diagnosis is an important basis for fertilizer application in citrus production.To explore and establish the orange orchard leaf nutrient diagnosis of high-yield,high-quality production guiding fertilization decision-making scheme automatically generated method,the8-year-old‘Dekopon’citrus was chosen as the research subject,and the contents of mineral nutrients in the leaves of each experimental plot in the physiological fruiting stage and fruit enlargement stage,as well as the fruit quality factors in the fruit ripening stage were tested and analyzed.Principal component analysis was used to construct the comprehensive evaluation model of‘Dekopon’citrus fruit quality.The compositional nutrient diagnosis（CND）inflection point value method was used for the automatic generation of the suitable nutrient standard of high-yield leaves in the physiological fruiting stage and the suitable nutrient standard of high-quality leaves in the fruit enlargement stage.In addition,the feasibility of the correction of the recommended fertilization scheme based on the deviation from optimum percentage（DOP）method diagnosis results of the low-yield and low-quality plots of‘Dekopon’citrus was discussed,and the effect of the recommended fertilization scheme was verified.It is expected to provide a new method and data support for the establishment of comprehensive diagnosis of nutrient and automatic generation of fertilization decision for high-yield and high-quality leaves of orange orchard,and facilitate reduction of fertilizer application,improvement of quality and increase in yield.The main research results are as follows:1.The scoring algorithm model for comprehensive evaluation of‘Dekopon’citrus fruit quality was established,which facilitated the comprehensive evaluation of fruit quality of orange orchard and the automatic scientific division of low-quality plots by CND method.The per fruit weight（PFW）,height（H）,diameter（D）,total soluble solid（TSS）,titratable acid（TA）,TSS/TA（T/A）,juice rate（JR）,edible rate（ER）,peel thickness（PT）and comprehensive color index（CCI）were evaluated.Principal component analysis（PCA）was used to construct a comprehensive evaluation score model of fruit quality based on six selected key evaluation factors:FQ=0.13PFW+0.16D+0.11TSS+0.16TA+0.18T/A+0.12JY（R²=0.87）.The function model can optimally describe the overall characteristics of fruit quality.Based on the comprehensive evaluation score of fruit quality,the‘CND inflection point value method’can be used to achieve automatic scientific division of high-yield plots in the physiological fruiting stage and high-quality plots in the fruit enlargement stage.2.The optimum nutrient value standard for high-yield and high-quality leaves of‘Dekopon’citrus was established,which provided an important basis for the nutritional diagnosis of orange orchard in different stages to improve the yield and quality of oranges.According to the leaf nutrients of the high-yield plots at the physiological fruit drop stage,the appropriate value of mineral element content in the high-yield leaves of‘Dekopon’citrus was determined as:N（15.5-19.4）g.kg^-1,K（4.1-8.6）g.kg^-1,P（0.9-1.1）g.kg^-1,Ca（36.0-63.7）g.kg^-1,Mg（1.0-1.7）g.kg^-1,Cu（34.0-63.0）mg.kg^-1,Fe（27.0-53.0）mg.kg^-1,Mn（123.0-238.0）mg.kg^-1and Zn（48.0-65.0）mg.kg^-1.According to the leaf nutrients of the high-quality plot at the fruit expansion stage,the appropriate value standard of mineral element content in the high-quality leaves of‘Dekopon’citrus was:N（23.1-32.4）g.kg^-1,K（4.9-12.8）g.kg^-1,P（0.8-1.5）g.kg^-1,Ca（30.7-62.2）g.kg^-1,Mg（1.6-2.1）g.kg^-1,Cu（30.0-65.0）mg.kg^-1,Fe（32.0-96.0）mg.kg^-1,Mn（116.0-150.0）mg.kg^-1and Zn（106.0-214.0）mg.kg^-1.3.The leaf nutrition diagnosis results by the DOP method in low-yield and low-quality plots of‘Dekopon’citrus experimental orchard were presented,which provided data and theoretical support for recommending fertilization scheme for orange orchard.Based on the above findings,the leaf nutrition diagnosis of‘Dekopon’citrus at the physiological fruiting stage and the fruit enlargement stage was studied based on the DOP method.In the low-yield plots of‘Dekopon’citrus at physiological fruiting stage,the deficiency limiting factors were Fe and Ca,the excess limiting factors were K and Mn,and the order of fertilizer needed was Fe>>Ca>>Mg.In the low-quality plots during fruit enlargement stage,the deficiency limiting factors were Ca and Fe,the excess limiting factors were K and P,and the order of fertilizer requirement was Ca>>Fe>>Mg>Mn.This study also discussed the measurement of the content deviation of unbalanced elements based on the DOP method,and the diagnostic results were helpful for the automatic quantitative adjustment of the subsequent recommended fertilization scheme.4.The automatic generation of recommended fertilization correction scheme based on DOP diagnosis results was proposed,and the effectiveness of fertilization scheme was verified.According to the results of leaf nutrition diagnosis by the DOP method in the low-yield plots at the physiological fruiting stage and low-quality plots at the fruit enlargement stage of‘Dekopon’citrus,the recommended fertilization schemes of spring fertilizer and summer fertilizer for orchards were corrected.Compared with the conventional fertilization treatment,the fruit yield and the high-yield plots population in the recommended fertilization treatment were increased by 27.5%and 50.0%,respectively,while the comprehensive score of fruit quality and the high-quality plots population in the recommended fertilization treatment were increased by 141.7%and 50.0%,respectively.