Study On The Correlation Analysis Of Soil And Leaf Mineral Nutrients With Fruit Quality Of Lemon

Lemon contains many bioactive substances,which are good for the health of human.Lemon is widely planted in the world,with 1.0845 million hm² of plantation and 17.2182 million tons of annual production to 2017.The abundance or deficiency of mineral nutrients have great effect on growth,fruit yield and quality of lemon.At present,there many studies have been conducted on extraction,detection and application of bioactive components of lemon fruit in China,but less research on study of the effect of mineral nutrients to fruit quality of lemon.In order to understand the status of soil nutrients and leaf nutrients in lemon orchards,and the effect of nutrients on fruit quality,to provide scientific reference for cultivation and management of lemon tree,to promote the healthy and sustainable development of lemon industry,93samples including soil,lemon leaves and fruits,were collected in Anyue and Tongliang county in 2019 for this study.All samples are collected from Eureka lemon variety.Soils were analysed for p H,organic matter,alkali-hydrolyzable nitrogen（N）,available phosphorus（P）,available potassium（K）,exchanged calcium（Ca）,exchanged magnesium（Mg）,available iron（Fe）,available manganese（Mn）,available zinc（Zn）,available copper（Cu）and available boron（B）contents.And the leaves were determined the nitrogen（N）,phosphorus（P）,potassium（K）,calcium（Ca）,magnesium（Mg）,sulfur（S）,iron（Fe）,manganese（Mn）,zinc（Zn）,copper（Cu）,boron（B）contents.Fruits samples were analyzed for single fruit weight,peel thickness,fruit shape index,juice yield,the total soluble solid content,titratable acid content,solid to acid ratio,vitamin C content,peel brightness,color difference and other parameters.The main results are as follows:（1）The soil p H of lemon orchards in Anyue and Tongliang are obviously different.The soil in Tongliang lemon orchard is acidic,with average p H value of 5.41,and the p H of 75.00%of orchards are lower than 5.5.The soil in Anyue is alkaline,with average p H of 7.14,and the p H of 77.78%of orchards are higher than 6.5.The soil in Anyue is more suitable for the growth of lemon.The distribution of soil nutrients is imbalance.The contents of alkali-hydrolyzed nitrogen,available phosphorus,available potassium,exchanged calcium,exchanged magnesium,available iron and available copper in the most of orchards in Anyue are too high or excessive,and the alkali-hydrolyzable nitrogen,available phosphorus,exchanged magnesium,available iron and available copper of the soil are high or excessive in Tongliang.The available manganese and available boron are deficient in both soils of Anyue and Tongliang county.（2）The contents of most nutritional elements of lemon leaves are in the best ranges.In Anyue,the content of P,Ca,S,Fe,Mn,Cu and B elements in 80%of orchards are in the suitable range,and N,K,Mg and Zn elements are in the low or deficient range.In Tongliang,the concentration of K,Zn and B in lemon leaves are low or deficient.The N,P,S,Fe,Cu elements are in suitable ranges in more than 80%of orchards.The Ca,Mg,Mn in 50%orchards are suitable.（3）According to the probabilistic grading method,the suitable range of N,K,Zn of lemon leaves is 22.01-24.59g·kg^-1,7.96-10.06g·kg^-1 and 17.78-23.93mg·kg^-1respectively.Those levels are slightly lower compared to the standard level of citrus leaves in Chongqing.（4）Contents of different nutrient elements are varied among different tissues of lemon.In general,the order of most of nutrients is leaf>peel>pulp,but that of Cu and P elements are peel>leaf>pulp,and K element is peel>pulp>leaf.The contents of Ca and Mn are higher in fruit pulp than in fruit peel.（5）Overall,the fruits tested in this study are good in quality.The quality of fruits produced in different regions is slightly different.The single fruit weight of lemon is158.02g and185.91g,in Anyue and Tongliang orchards,respectively,and the number of fruit seeds is 15.89 and 19.65,the peel thickness is 6.34mm and 7.00mm.The fruit longitude is 8.13cm and 6.46cm in Anyue,8.23cm and 6.86cm in Tongliang.The fruit shape index is 1.26 and 1.20 in Anyue and Tongliang orchards,respectively,the yield of fruit juice is 32.55%and 29.48%,the total soluble solid is 8.21%and 7.39%,the acid content is 5.96 mg·100m L^-1 and 5.80 mg·100m L^-1,vitamin C is 49.81mg·100m L^-1 and 42.92 mg·100m L^-1,the ratio of solid to acid is 1.37 and 1.27,the peel brightness is 80.08 and 76.56.The degree of redness and yellowness are-5.88 and47.35 in Anyue,-3.83 and 46.77 in Tongliang.（6）According to the results of correlation analysis,Soil organic matter and available B have the greatest influence on fruit quality of lemon.Available B is significantly positively correlated with juice yield,TA and vitamin C are significantly negatively correlated.In addition,soil alkali-hydrolytic N and available K have a great influence on fruit quality.Leaf element B has the greatest effect on fruit quality,which is significantly positively correlated with fruit weight,transverse diameter and juice yield,and negatively correlated with fruit shape index,content of TA and vitamin C and brightness of peel.（7）In Tongliang lemon orchards,organic fertilizer should be applied in time,and boron fertilizer,zinc fertilizer,potassium fertilizer should also be sprayed on the foliage to control the single weight of lemon fruit and improve the juice yield of lemon fruit.In general,the soil p H of Anyue lemon orchard is suitable,while the soil of Tongliang lemon orchard is acidic,which should be corrected in time.Based on the diagnosis of citrus nutrition,the soil nutrients in the orchards of two regions are generally too high.The leaf nutrients are in the suitable range,but the N,K,Mg and Zn are lower than the recommended levels,which is related to the lower level of nutrition in lemon leaves and the higher demanding of N and K by fruit.Quality of lemon fruit is good,relatively speaking,the quality of Tongliang lemon still has the room for improvement.