Study On Soil And Leaf Nutrient Status Of Citrus Orchards In Northern Guangxi

Guibei is a major producing area of citrus in Guangxi,and is also an important part of the citrus predominance-area of southern Jiangxi-southern Hunan-northern Guangxi.The citrus producing area center of Lipu is currently the largest ?Shatangju? Tangerine producing county in China.However,there has been a lack of systematic research on soil nutrients and tree nutrient status in the citrus producing areas of northern Guangxi.In this study,102 representative orchards in 7 main producing counties(cities)were investigated,measured and analyzed for fertilization status,soil nutrients,tree nutrients and fruit quality by questionnaire,field sampling and lab analysis.The soil nutrient and tree nutrient status of citrus orchards were studied,which provided a basis for the high yield,high quality and fertilizer reduction and efficiency improvement technology of citrus in northern Guangxi.The main results are as follows.1.Soil nutrient status of citrus orchards in northern GuangxiSoil acidification in orange orchards in northern Guangxi is serious,the range of soil pH value was 3.95-8.02,and the average value is 5.26.Among them,strong acid(pH<4.5)soil occupied 24.51%,acid(pH 4.5-5.5)soil occupied 48.04%,alkaline(pH>7.3)soil accounted for 9.80%,and acid soil was the most widely distributed.There were 64.70% soil samples with suitable or appropriate pH value(pH 4.5-7.0)for citrus growth,but only 14.71% soil samples had pH value range(pH 5.5-6.5)suitable for citrus growth.The soil organic matter content was rich,with an average of 24.96 g/kg,the proportion of suitable or above suitable content levels reached 83.33%.Soil alkali-hydrolyzable N content was 49.11-290.43 mg/kg,with an average of 115.81 mg/kg.The percentages of orchards with insufficient(deficient and low,the same below),suitable and over-standard(high and excessive,the same below)N contents were 36.27%,58.83% and 4.90%,respectively.Available P content ranged from 1.18 to 261.46 mg/kg,with an average of 53.98 mg/kg.Insufficient,suitable and over-standard levels were 33.33%,45.10% and 21.57%,respectively.Available K content was 15.04-556.54 mg/kg,with an average of 152.80 mg/kg.Insufficient,suitable and over-standard levels were 30.39%,46.08% and 23.53%,respectively.The effective Ca content ranged from 36.67 mg/kg to 29689.34 mg/kg,with an average of 2407.01 mg/kg.Insufficient,suitable and over-standard levels were 31.37%,53.93% and 14.70%,respectively.The effective Mg content ranged from 11.92 mg/kg to 373.08 mg/kg,with an average of 103.89 mg/kg.Insufficient,suitable and over-standard levels were 59.80%,31.38% and 8.82%,respectively.The available Fe content was rich,ranging from 1.55 mg/kg to 222.02 mg/kg,with an average of 43.83 mg/kg.The insufficient,suitable and over-standard levels were 15.68%,19.61% and 64.71%,respectively.The available Mn content was sufficient,ranging from 1.68 mg/kg to 230.74 mg/kg,with an average of 31.80 mg/kg.Insufficient,suitable and over-standard levels were 6.86%,37.25% and 55.89%,respectively.Effective zinc deficiency was serious,ranging from 0.21 mg/kg to 24.28 mg/kg,with an average of 2.09 mg/kg.Insufficient,suitable and over-standard levels were 92.16%,5.88% and 1.96%,respectively.The content of available copper in the orchard ranged from 0.43 mg/kg to 9.99 mg/kg,with an average of 2.58 mg/kg.The contents of insufficient,suitable and over-standard levels were 56.86%,39.22% and 3.92%,respectively.Effective B content ranged from 0.15 mg/kg to 1.78 mg/kg,with an average of 0.56 mg/kg.Insufficient,appropriate and over-standard levels were 50.98%,44.12% and 4.90%,respectively.Most of the analyzed citrus orchard soils were characteristics of rich and deficient of some elements,which indicated poor balance of soil element nutrient status.The proportion of soil effective P and K contents below suitable range were 33.33 % and 30.39 %,respectively,and those above suitable ranges were 21.57% and 23.53%,respectively.The soil available N and effective Ca contents were mainly within the suitable levels,however 36.27% and 31.37% were in insufficient levels,respectively.The soil available Fe and Mn contents were rich,and 64.71% and 55.89% exceeded suitable level,respectively.The deficiency ratios of available Mg,Zn,Cu and B in soils were 59.80%,92.16%,56.86% and 50.98%,respectively.The correlation analysis of soil pH,organic matter and available nutrient elements showed that soil pH was positively correlated with organic matter,alkali-hydrolyzed N,available Ca and available Mg(P < 0.01);organic matter was positively correlated with alkali-hydrolyzed N,available K,available Ca and available Mg,and positively correlated with available B(P < 0.05).There were also significant or extremely significant positive or negative correlations between most mineral nutrient contents in soil,but generally these correlations were mainly positive correlations.Therefore,the synergistic effect of soil nutrients was obvious and the antagonistic effect was weak.2.Nutritional status of citrus leaves in northern GuangxiThe citrus leaf N content in northern Guangxi ranged from 2.33% to 4.01%,with an average of 2.97%.Orchards with insufficient,suitable and over-standard leaf N contents acounted for 11.76%,48.04% and 40.20%,respectively.Leaf P content ranged from 0.10% to 0.16%,with an average of 0.13%.Orchards with low and suitable leaf P contents acounted for 30.39% and 69.61%,respectively.Leaf K content ranged from 0.40% to 3.58%,with an average of 1.45%.Orchards with insufficient,suitable and over-standard leaf K were 35.29%,43.14% and 21.57%,respectively.Ca content in leaves ranged from 1.39% to 4.99%,with an average of 3.13%.The percentage of insufficient orchards,suitable orchards and over-standard orchards were 43.14%,56.86% and 0.00%,respectively.The leaf Mg content ranged from 0.12% to 0.47%,with an average of 0.26%.Orchards with insufficient and suitable leaf Mg were 44.12% and 55.88%,respectively.Leaf S content ranged from 0.21% to 0.47%,with an average of 0.29%.Orchards with suitable and over-standard leaf S were 98.04% and 1.96%,respectively.The leaf Fe content was 38.34-223.82 mg/kg,with an average of 88.68 mg/kg.Orchards with insufficient,suitable and over-standard leaf Fe were 17.65%,71.57% and 10.78%,respectively.Leaf Mn content ranged from 13.45 mg/kg to 228.44 mg/kg,with an average of 67.86 mg/kg.Orchards with insufficient,suitable and over-standard leaf Mn were 7.84%,72.55% and 19.61%,respectively.Leaf zinc content ranged from 5.42 mg/kg to 51.04 mg/kg,with an average of 19.10 mg/kg.Orchards with insufficient and suitable leaf Zn were 63.73% and 36.27%,respectively.Cu content in leaves ranged from 1.20 mg/kg to 42.61 mg/kg,with an average of 6.96 mg/kg.Orchards with insufficient,suitable and over-standard leaf Cu were 54.91%,35.29% and 9.80%,respectively.Leaf B content ranged from 32.88 mg/kg to 281.05 mg/kg,with an average of 115.00 mg/kg.Orchards with insufficient,suitable and over-standard leaf B were 0.98%,39.22% and 59.80%,respectively.In general,the citrus leaf N was abundant,and leaf K coexisted with exceeding the standard.The contentS of P,Ca and Mg in leaves were insufficient,and leaf S content was optimal.The Fe and Mn contents in leaves were mainly in suitable levels.The contents of Zn and Cu in the leaves were mainly insufficient,and leaf B content was mainly exceeded.Analysis of the correlation between leaf nutrient contents showed that the N,P,K,Ca,Zn contents in leaves was significantly correlated with other nutrient elements.Therefore,the contents of leaf N,P,K,Ca,Zn were significantly affected by the antagonism or synergism effects of other elements.3.Fruit quality of ‘Shatangju’ Tangerine in northern GuangxiThe average fruit weight of ?Shatangju? Tangerine was 21.64-49.53 g,with an average of 39.71 g.The fruit average longitudinal diameter was 3.45 cm,with an average transverse diameter of 4.53 cm.The fruit peel thickness was 0.14-0.34 cm,and average seed number and average carpel were 0.54 and 9.45 respectively.Fruit edible rate was 72.14%,and TSS content was 11.80-17.40%,with an average of 14.32%.The TA content was 0.30-1.04%,with an average of 0.56%.The solid-acid ratio was 14.00-44.66.And vitamin C content was 3.97-26.78 mg/100 mL,with an average of 20.44 mg/100 mL.Reducing sugar was 2.21-5.99 g/100 mL,with an average of 4.65 g/100 mL.And total sugar was 9.09-15.92 g/100 mL,with an average of 13.08 g/100 mL.4.Correlation among soil nutrition,leaf nutrient status and fruit quality in citrus orchard of northern Guangxi(1)The correlation between soil nutrition and leaf nutrients statusSoil pH valus was negatively correlated with leaf N,K,Mg,Mn and Zn content,and positively correlated with leaf Ca content.Soil organic matter was positively correlated with leaf Ca,Mn and Zn contents,and negatively correlated with leaf Mg content.The contents of available N,P,Ca and Mg in soil were significantly or negatively correlated with some elements in leaves,while the contents of available Ca,Fe,Mn,Zn,Cu,B in soil and their corresponding nutrient elements in leaves were significantly or positively correlated.(2)The correlation between soil nutrition and fruit qualitySoil pH value,soil available P,Ca and Mg contents had a significant correlation with fruit appearance quality and internal quality.(3)The correlation between leaf nutrient status and fruit qualityThe correlation between nutrient elements in leaves and fruit quality was mainly reflected in the contents of N,K,Ca,S,Mn and B in leaves.5.Current status and suggestions on fertilization in citrus production areas in northern GuangxiThe fertilier types in the citrus production area in northern Guangxi were mainly chemical fertilizers and organic fertilizers.The chemical fertilizers were mainly compound fertilizers,urea,potassium sulfate,etc.,and the organic fertilizers were mainly farmyard manure,cow dung,peanut cake,rapeseed cake,yellow humic acid potassium and commercial organic fertilizer.The average annual application rate of pure NPK per hectare was 512.02 kg,420.71 kg and 581.21 kg,and their ratio was 1: 0.82: 1.13.The application rates of NPK had great difference among orchards.The applied pure NPK in each hectare from chemical fertilizer were 376.38 kg,336.09 kg and 466.70 kg,respectively,which accounted for 73.51%,79.89% and 80.30% of the total application of NPK.Based on the results of leaf diagnosis and supplemented by soil determination data,combined with the status of fertilization in the citrus production area in northern Guangxi,some reasonable suggestions were put forward.First,adjust the pH value of the soil for acidified soil,it is necessary to apply lime,fused calcium-magnesium phosphate regularly.The second is to reduce the application of NPK.The third is to increase the application of magnesium fertilizer,zinc fertilizer,and control the application of cupric fungicide.The fourth is to increase the application of organic fertilizer.The fifth is the rational application of foliar fertilizer,especially control the boron application.Sixth is to promote grass cultivation.