| Yuxi city of Yunnan province is one of the important high-efficiency citrus producing areas in China.For a long time,there is seldom research on citrus soil and plant nutrient status in Yuxi.This dissertation studied the soil and leaf nutrient status and distribution characteristics of 101 representative citrus orchards in 4 ecoclimatic zones in Yuxi,i.e.,Yuanjiang dry-hot valley,Huaning mountain hills,Xinping mountain hills and Huaning Nanpanjiang valley.The fruit quality of 50 representative Bingtangcheng orange orchards was analyzed,and the fertilization application rates of 60 orange orchards in Huaning county was also investigated so as to provide basis for high yield,good quality and high efficiency production and fertilizer application reduction guidance for Yuxi citrus industry.1.Soil nutrient status in Yuxi citrus orchardThe soil pH value was 3.98?8.07 with an average of 6.42,and 67.33% samples were suitable or basically suitable for citrus growth?pH 4.5?7.5?.The strong acid soil accounted for 4.95%?pH<4.5?,and the alkaline soil accounted for 27.72%?pH>7.5?.The soil organic matter content was 1.02?38.31g·kg-1 with an average of14.62 g·kg-1.Among all the samples,59.4% were low(<15 g·kg-1)and 4.95% were rich(>30 g·kg-1)of organic matter content.The content of soil alkali-hydrolysis N was 23.75?377.52 mg·kg-1 with an average of 78.64 mg·kg-1,and 0.99% of the samples were high and 78.22% in insufficient?low and deficient,the same below?level.The N content of 91.67% soil samples in the Yuanjiang dry-hot valley was insufficient,and more than 60% of the soil samples in the other 3 ecological areas were insufficient.The soil available P content was 0.52?530.46 mg·kg-1,and with an average of 53.95 mg·kg-1,31.69% of the samples were insufficient,and 18.81% were high.The Huaning mountain hills were 100% insufficient of soil available P,and the other 3 ecological areas were suitable or high of soil available P.Soil available K content was 77.28?774.95 mg·kg-1,and with an average of 273.15 mg·kg-1,64.36% soil samples were high.In Yuanjiang dry-hot valley,25.00% soil samples had high content of soil available K,and in the other 3 ecological zones this proportion was greater than 65%.The soil available Ca content was 322.70?18577.98 mg·kg-1 with an average of 3243.37mg·kg-1.However,22.77% were insufficient and 51.48% were excessive?high and excess,the same below?of soil available Ca.In Huaning mountain hills 100% soil samples had excessive available Ca,however in Xinping mountainou hills 63.34% soil samples were insufficient of available Ca.The soil available Mg content was 21.38?702.13 mg·kg-1 and its average was 233.39 mg·kg-1.For all the soil samples,35.64% were insufficient and 33.67% were excessive of available Mg.Xinping mountain hills had 83.33% soil samples with insufficient of available Mg,however Huaning Nanpanjiang valley had 58.33% soil samples with excessive available Mg.The content of soil available Fe was2.37?179.60 mg·kg-1 with an average of 23.21 mg·kg-1,44.55% of the samples were excessive and 24.76% in insufficient level.The Fe content of 75% soil samples in Yuanjiang dry-hot valley was insufficient,and the other 3 ecological areas were suitable or excessive of soil available Fe.The soil available Mn content was 3.95?155.08mg·kg-1,and with an average of 43.82mg·kg-1,1.98% of the samples were insufficient and 56.44% were excessive.More than 76.67% of the soil samples in Yuanjiang dry-hot valley and Xinping mountain hills were excessive of soil available Mn,however the other 2 ecological areas were suitable.Soil available Zn content was 0.28?50.00mg·kg-1,and with an average of 5.67mg·kg-1,39.61% soil samples were insufficient.Insufficient samples of soil available Zn in the Yuanjiang dry-hot valley and Xinping mountain hills were 91.67%and 70.00%,respectively.The soil available Cu content was 0.39?10.16 mg·kg-1 and its average was 2.89 mg·kg-1.For all the soil samples,2.97% were insufficient and 83.17% were excessive of available Cu.On the whole,For all the ecological areas were mainly excessive of available Cu.Soil available B content was 0.11?3.09 mg·kg-1 with an average of 0.50 mg·kg-1.However,66.34% samples were insufficient and 5.94% were excessive of soil available B.In Yuxi citrus orchards,the soil pH 67.33% samples were suitable or basically suitable for citrus growth,organic matter were low.Soil alkali-hydrolysis N and available B contents were insufficient,available K,Ca,Mn and Cu contents were excessive.The available Zn consistency was poor,and the insufficient ratio was relatively high,and available P and Fe contents were rich.Orchards with insufficient,suitable and excessive available Mg each accounted for about 1/3.Regional characteristics of soil nutrients in citrus orchards:Huaning is better than Xinping,and Xinping is better than Yuanjiang.Correlation analysis among the soil nutrient elements indicated that pH was significant positive correlation with available Ca,Mg,Zn and B,but significant negative correlation with available Mn and Cu;Organic matter was positive correlation with available N,K,Ca,Zn,B,P,Mg and Fe,especilly N,K,Ca,Zn,B;Available Mn and Cu was negative correlation with most elements,and most of the other elements are positively correlated.2.The status of leaf nutrient in Yuxi citrus orchardThe leaf N content was 2.34%?3.62%.With an average of 2.96%,17.83% of the samples were insufficient and 46.53% were excessive.Excessive samples of leaf N in Yuanjiang dry-hot valley and Xinping mountain hills were 58.34% and 73.33%,respectively,however the other 2 ecological areas were optimal.The leaf P content was0.11%?0.21% with an average of 0.15%,and 9.90% samples were insufficient and 67.33% samples were in optimal P level.In Yuanjiang dry-hot valley 33.33% leaf samples had insufficient P content,however in Xinping mountainou hills 43.33% leaf samples were excessive of P.Leaf K content was 0.46%?2.48%,and its average was 1.22%.However,30.70% was insufficient,46.53% was optimal and 22.77% was excessive of leaf K.There was no K insufficient orchard in Yuanjiang dry-hot valley,and in Xinping mountainou hills 43.33% leaf samples were excessive of K.The Ca content was 3.35%?5.79%,with an average of 4.32%,and 91.09% leaf samples were optimal of Ca.Leaf Mg content was 0.06%?0.64%,with an average of 0.29%.For all the leaf samples,67.59% were insufficient and 6.21% were excessive of Mg.In Huaning mountain hills 100% leaf samples had insufficient Mg content.Leaf S content was 0.20%?0.54%,with an average of 0.31%.However,0.99% samples were insufficient and 86.14% samples were optimal of leaf S.Leaf Fe was 33.20?292.88mg·kg-1,with an average of 135.66 mg·kg-1,which 4.95% leaf samples were insufficient and 50.49% were excessive of Fe.The samples with excessive leaf Fe in Yuanjiang dry-hot valley and Xinping mountain hills were 100% and 86.67%,respectively.Leaf Mn content was 14.05?687.98 mg·kg-1,with an average of 95.14 mg·kg-1.For all the leaf samples,7.92% were insufficient and 65.35% were optimal of Mn.Samples with excessive leaf Mn in Yuanjiang dry-hot valley and Xinping mountain hills were 91.67% and 43.33%,respectively.Leaf Zn content was 3.48?39.18 mg·kg-1,and its average value was 16.21 mg·kg-1.89.11% samples were insufficient and 10.89% samples were optimal of Zn.All leaf samples collected in Huaning county were insufficient of Zn.Leaf Cu content was 1.00?65.83 mg·kg-1,with an average of 23.33 mg·kg-1.15.85% samples were insufficient and 61.38% samples were excessive of Cu.Huaning Nanpanjiang valley had 87.50% leaf samples with excessive Cu.leaf B content was 32.21?163.25 mg·kg-1,with an average of 82.21 mg·kg-1.72.28% samples were optimal and 25.74% samples were excessive of B.No leaf sample was found all nutrient elements in optimal level.Leaf N,Fe and Cu contents were mainly excessive.The consistency of K was poor,and it was mostly optimal,and leaf P,Ca,S,Mn contents were mainly optimal.Leaf B was mainly based on optimal and partly high.However,and most leaf Mg and Zn contents were insufficient.In the leaf of Yuxi citrus orchards,correlation analysis indicated most of the leaf elements were positive correlation.The elements with significant positive correlation were:N with Fe,K,P,S;K with P,Fe,Mn;Ca with S,Zn;Mg with Zn,S;S with Zn;Fe with Mn;Mn with Zn.The elements with significant negative correlation were:K with Ca;Ca with Cu;S with Cu;B with S,Fe,Mn,Zn.However there were no correlation between other elements in leaf.3.Fruit quality of Bingtangcheng orangeThe indexes of Bingtangcheng orange fruit were as follow:single fruit weight was 121.56?253.98g,with an average of 177.05g;The average fruit shape index was 1.01;Peel thickness was 2.86?7.80mm,with an average of 4.00mm;Edible rate was70.60?79.65%;TSS was 8.80?13.00%,and the TA content was 0.28?0.73%.TSS/TA was 12.34?40.96;Vc content was 31.81?47.57 mg/100 ml.4.Correlation between soil nutrition,leaf nutrition and fruit quality?1?Correlation analysis among soil and leaf nutrient elementsSoil pH was significant negative correlation with leaf N,Mg,S,Fe,Mn and Zn,but positive correlation with other elements.Soil organic matter was significant positive correlation with leaf P,K,Cu and B,but significant negative correlation with other elements.There were significant positive correlations between leaf and soil nutrient contents:N with Mn,Cu;Mg with Cu;S with Cu;Fe with Cu;Mn with Mn and Cu;B with Ca,Mg,Zn and B.There were significant negative correlations between leaf and soil nutrient content:N with Ca,Mg,Zn;Mg with Ca and B;S with Ca,Mg,Zn,B;Fe with Ca,Mg,Zn,B;Mn with Ca,Mg,Zn,B.?2?Correlation between soil and leaf nutrients with fruit qualitySoil nutrients that were significant correlations with fruit quality were as follows:B,Mg,Cu,Zn,and Ca.The correlation between leaf nutrient elements and fruit quality were slightly stronger than that between soil nutrient elements and fruit quality.Leaf nutrients with significant correlation with fruit quality included Cu,Fe,S,K,and N.5.Fertilization of citrus orchards in Huaning CountyThe applied fertilizers in Huining citrus was mainly urea,compound fertilizer,calcium superphosphate,potassium sulfate and organic fertilizer.The average annual applied fertilization rate per hectare orchard was 6642.15 kg organic fertilizer,2418.79kg calcium superphosphate,823.99 kg urea,308.70 kg compound fertilizer,270.70 kg potassium sulfate,which acounted pure N,P and K per hectare were 425.30 kg,336.60kg and 181.70 kg,respectively.There were many kinds of organic fertilizers were applied,some of which were added with chemical fertilizers,and the nutrient contents vary greatly.Supposed the average N,P and K contents in organic fertilizers were 3%,0.5% and 1.5%,the application of organic fertilizers per hectare were equivalent to 199.30 kg,33.20 kg and 99.60 kg of pure N,P and K.The total pure N,P and K applied in orange orchards per hectare were 624.60 kg,369.80 kg and 281.30 kg per year,which had a ratio of N,P and K of 1:0.59:0.45.In theory,the proportion of K application was low,but because of excessive N application,the actual amount of K was sufficient.For all the investigated orchards,the yield increased as the amount of fertilizer applied increased.The application rates of N,P and K fertilizers in high-yield citrus orchards were 2.42 times,9.35 times and 1.12 times that of low-yield citrus orchards,respectively. |
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