Correlation Between Soil Fertility And Nut Quality In Shaanxi Walnut Producing Areas

Due to the differences in site,climate and soil conditions in different walnut producing areas,and the nutrients required by trees of different planting years are different,it is necessary to clarify the nutrient profit and loss of walnut trees and their site soils in actual production.It is of great significance to provide scientific nutrient management for walnut orchards and to achieve high quality,high yield and high efficiency of walnuts.In this study,’ Xiangling ’ walnuts with different planting years(1-10 years,11-19 years,more than 20years)in three main walnut producing areas of Shangzhou District of Shangluo City,Linwei District of Weinan City and Huanglong County of Yan ’an City in Shaanxi Province were taken as the research objects.The indicators were measured from three aspects: soil quality characteristics,walnut leaf nutrition and walnut quality.The nutritional status of soil and tree and their effects on fruit quality were studied in order to provide theoretical support for optimizing nutrient management of walnut orchards with different planting years and different regions.The main results are as follows:(1)The soil fertility characteristics of walnut orchards in different producing areas and different planting years were revealed.The soil p H of walnut orchards in each producing area was between 7.42 and 8.45,and the soil was mainly slightly alkaline,which was more suitable for walnut planting.Except for soil p H,the coefficients of variation of other soil fertility indexes were medium or high,with strong spatial and temporal heterogeneity.According to the average value of soil physical and chemical indexes in each producing area,the soil organic matter,water content,total nitrogen,nitrate nitrogen,ammonium nitrogen,available phosphorus,available potassium,available iron,available manganese and available copper of walnut orchard in Linwei production area were significantly higher than those in other production areas(P<0.05),which were 21.64 g/kg,22.54%,0.75 g/kg,6.67 mg/kg,12.28 mg/kg,57.93 mg/kg,95.73 mg/kg,35.87 mg/kg,26.08 mg/kg and 1.95 mg/kg,respectively,and the overall fertility was better.The contents of soil total potassium,exchangeable calcium,exchangeable magnesium and available zinc in Shangzhou were significantly higher than those in other producing areas(P<0.05),which were 10.36 g / kg,3312.44 mg / kg,200.77 mg / kg and 3.19 mg / kg,respectively.The total phosphorus content of walnut orchard soil in Huanglong production area was significantly different from that in other production areas(P<0.05),which was 1.24 g / kg,respectively.The results of principal component analysis also showed that the comprehensive evaluation score of soil fertility in Linwei was the highest,and the scores were ranked as follows :Linwei,Shangzhou and Huanglong.From the perspective of planting years,the planting years had significant effects on the contents of soil organic matter,total phosphorus,ammonium nitrogen,available potassium,exchangeable magnesium and available iron(P<0.05).(2)The nutrient characteristics of walnut trees in different producing areas and different planting years were revealed.The coefficient of variation of leaf nutrient indexes was between 6.87 % and 79.43 %.Among them,the coefficient of variation of total organic carbon and nitrogen content in leaves was below 10 %,which was weak variation,and other indexes were moderate variation.From the average value of leaf nutrients in each production area,the average contents of phosphorus,potassium,iron,copper and zinc in walnut leaves in Shangzhou were higher than those in other producing areas,and the contents of macroelements and trace elements were abundant.The contents of nitrogen,magnesium,calcium and total organic carbon in leaves of Huanglong production area were higher than those in other production areas,and the contents of large and medium elements were rich.The average manganese content in leaves of Linwei was 320.69 mg / kg,which was significantly higher than that of Huanglong and Shangzhou.On the whole,the content of mineral elements in walnut leaves in Shangzhou and Linwei is relatively more abundant,and only manganese content in Linwei has a prominent advantage.From the perspective of planting years,the contents of potassium and manganese in leaves showed significant changes,while the contents of other nutrients did not show significant changes.(3)The abundance and deficiency of soil fertility and leaf nutrients in walnut orchards in three main walnut producing areas were clarified.The content of soil organic matter and available potassium in walnut orchards in the main producing areas of walnut in Shaanxi is generally at a lack level.The contents of total phosphorus,available iron,available manganese and available copper were abundant,and the content of exchangeable calcium was extremely rich,and there was nutrient surplus.Total nitrogen and total potassium belong to the lack of level;available phosphorus and available zinc are distributed in all content levels,and exchangeable magnesium is at an appropriate level.It can be seen from the NBIm value that the nutrient balance of trees in different walnut producing areas is the best in Linwei producing area.The nutrient imbalance index of Huanglong and Shangzhou producing areas is higher than the average value of the producing areas,and the nutrient balance of trees is poor.The order of fertilizer requirement of walnut trees in Linwei,Huanglong and Shangzhou was Zn > K > Fe > N > Mg,Mn > Zn > Cu > K > P,Mn > Mg >Ca > N,respectively.(4)The characteristics of walnut nut quality in different producing areas and different planting years were revealed.The comprehensive quality of walnut nuts in Linwei production area have the best comprehensive quality and the most promotional value;the walnut shell in Huanglong production area is thin,the kernel rate is high,and it is easy to eat,which may be more popular with consumers.Walnut nuts in Shangzhou are rich in minerals and other nutrients,which can be further processed and utilized based on their health effects.From the perspective of planting years,walnut samples with different planting years in the production area did not show aggregation.The comprehensive quality score trends of walnut samples with different planting years in the same production area were different.The quality score of walnut nuts in Linwei production area showed a trend of first increase and then decrease.The Huanglong and Shangzhou production areas showed a trend of first decrease and then increase.Compared with the planting years,the spatial heterogeneity of walnut nut quality is more prominent.(5)The correlation between soil fertility,leaf nutrients and fruit quality were studied.There were different degrees of correlation between soil fertility indexes,and the overall correlation was mainly positive.Soil p H was significantly positively correlated with exchangeable calcium,and both were significantly negatively correlated with other indicators.There were many significant or extremely significant correlations between soil fertility indexes and leaf manganese,nitrogen,zinc,copper and potassium.The fruit size,shell thickness,single fruit weight,kernel weight and nutritional quality indexes of walnut nuts were affected by soil fertility indexes.Among them,soil total potassium,nitrate nitrogen,ammonium nitrogen,available phosphorus,available zinc and water content are important indicators affecting leaf nutrients and fruit quality.The comprehensive effect of leaf zinc on nut quality was the most significant,which was significantly negatively correlated with the index of nut size,nucleolar crude protein and amino acid content,and significantly positively correlated with magnesium,potassium,linolenic acid,palmitic acid and stearic acid.