Leaf Nutrition Diagnosis Of ‘Xuxiang’ Kiwifruit Orchards At Different Growth Stages In Central Shaanxi Province

Leaf nutrient diagnosis is an important basis for fruit orchard fertilization decision.At present,the established nutritional diagnostic standards for high-quality orchards are almost based on yield performance,with little consideration for fruit quality and tree growth.However,fruit trees are perennial economic crops,and their high yield,high quality and stable yield are equally important for high-quality orchards.In addition,it is of great application value for precise fertilization of fruit trees to diagnose leaf nutrition at different growth stages and establish its standards.Therefore,this study took‘Xuxiang’kiwifruit as the material,collected 114‘Xuxiang’kiwifruit samples of leaves and fruit in the central Shaanxi province,and established kiwifruit fruit yield,fruit quality related indicators,tree growth and leaf mineral elements.All the samples were divided into the high-efficiency orchards and the low-efficiency orchards by analyzing the functional relationship of content and calculating its inflection point value.Based on the leaf nutrient characteristics,the leaf nutrition diagnosis of low-efficiency orchards was carried out by using the comprehensive method of diagnosis and recommendation integrated System（DRIS）,the method of compositional nutrient diagnosis（CND）and the method of deviation from optimum percentage（DOP）,and the leaf nutrient content was proposed by the probability classification method.The normal range provides a theoretical basis for the scientific fertilization of‘Xuxiang’kiwifruit in central Shaanxi province.The main research results are as follows:1.Based on the indicators related to orchard yield,fruit quality and tree growth,a scientific and reasonable standard for efficient group division was proposed.Principal component analysis was performed on fruit quality-related indicators（single fruit weight,fruit shape index,dry matter content,soluble solids,titratable acid,solid-acid ratio,and vitamin C content）,and the comprehensive score of fruit quality was calculated.The CND inflection point method was used to construct the functional relationship expression of the yield,fruit quality comprehensive score,tree growth and leaf nutrient element analysis parameters,so as to realize the scientific division of high-yield,high-quality,and stable-yield orchards.2.Through the three methods of DRIS,CND,and DOP,fertilization suggestion of‘Xuxiang’kiwifruit annual leaf nutrition diagnosis in central Shaanxi province was put forward.The order of fertilizer requirement of‘Xuxiang’kiwifruit in central Shaanxi province during the leaf spreading period is Ca>K>Fe>N>Cu>B>S>Mg>P>Zn>Mn（DRIS）,Ca>Fe>K>N>Cu>B>S>Mg>Zn>P>Mn（CND）,and Ca>Fe>K>N>B>Cu>Mg>S>P>Zn>Mn（DOP）,so the central Shaanxi province needs to increase the application of Ca,K and Fe fertilizers;the sequence of fertilizer requirements during fruit expansion period is Ca>N>Fe>S>Mn>P>K>Cu>Zn>Mg>B（DRIS）,Ca>N>P>Mn>Fe>S>K>Zn>Cu>Mg>B（CND）,and Ca>N>P>S>Fe>Mn>K>Mg>B>Cu>Zn（DOP）,so the central Shaanxi province needs to increase Ca and N fertilizer;the order of fertilizer requirement for late fruit development is Ca>Fe>K>Zn>B>Mg>Cu>S>N>P>Mn（DRIS）,Ca>Fe>Zn>K>B>Mg>Cu>Mn>S>P>N（CND）,Fe>Ca>Zn>K>B>Cu>Mg>N>P>S>Mn（DOP）,so Ca and Fe fertilizers should be applied in central Shaanxi province at the later stage of fruit development.3.Based on the probability classification method,the annual normal range of mineral elements for the leaves of‘Xuxiang’kiwifruit in central Shaanxi province of Shaanxi was proposed.Through the normal distribution test of the nutrient content of kiwifruit leaves in the leaf spreading stage,fruit expansion stage and late fruit development stage,and based on the DRIS results,the measured values of high-efficiency orchards and the existing standards of the predecessors,the normal ranges for annual nutritional diagnosis of‘Xuxiang’kiwifruit in central Shaanxi province was made.Among them,the normal range of leaves in the leaf spreading stage is N(34-40 g kg^-1),P(2.8-3.5 g kg^-1),K(21-29 g kg^-1),Ca(18-24 g kg^-1),Mg(2.5-3.1 g kg^-1),S(1.6-2.4 g kg^-1),Fe(85-182 mg kg^-1),Mn(37-67 mg kg^-1),Cu(13-19 mg kg^-1),Zn(18-26 mg kg^-1)and B(32-44 mg kg^-1);the normal range of fruit expansion stage is N(29-34 g kg^-1),P（1.4-1.8 g kg-¹）,K(9-16 g kg^-1),Ca(38-46 g kg^-1),Mg(5-8 g kg^-1),S(1.9-3 g kg^-1),Fe(160-242 mg kg^-1),Mn(86-180 mg kg^-1),Cu(8-14 mg kg^-1),Zn(15-32 mg kg^-1)and B(53-68 mg kg^-1);the normal ranges for late fruit development are N(20-24 g kg^-1),P(1.0-1.4 g kg^-1),K(6-11 g kg^-1),Ca(46-52 g kg^-1),Mg(7.1-9.7 g kg^-1),S(1.6-2.4 g kg^-1),Fe(216-270 mg kg^-1),Mn(80-140 mg kg^-1),Cu(7.6-10.6 mg kg^-1),Zn(19-41 mg kg^-1)and B(46-63 mg kg^-1).The results of nutritional diagnosis of low-productivity orchards were consistent with DRIS,CND and DOP,indicating that the optimum range was reasonable.