Hunan Citrus Orchard Soil Rhizosphere Microbial Community Research

Citrus is an important commercial crop over the world.The citrus industry is developing rapidly,but there are many problems during the development.One of the main problem is the unscientific fertilization,include few kinds of fertilizer were used,give priority to inorganic fertilizer,fertilization is not fixed,meanwhile lack of labor and sources of oganic fertilizer reduced,further aggravated the adverse effect of this problem.Long-term implementation of unscientific fertilization system and methods,resulting in soil hardening and fertility decline,acidification,the diversity of soil microbial communities and microbial activity decreased,and further lead to nutrient imbalance of fruit tree and fruit quality deterioration,also resulting in fertilizer waste,utilization rate reduced,fertilizer loss serious,and further aggravated a series of problems such as agricultural pollution.Therefore,some urgent things must be done to improve citrus production such as finding suitable citrus fertilization systems,improveing soil fertility,reducing soil acidification,increasing soil microbial community and vitality,improveing fruit quality and so on.In order to to provide technical guidance for finding a reasonable orange orchard fertilization systems,increasing soil fertility,improving fruit quality,the effects of fertilization systems on soil moisture content,soil bulk density,soil nutrition,tree nutrition and fruit quality were analyzed by investigating the status of citrus orchard nutrition in the main producing areas of citrus,and further explored the relationship of soil microbes and soil nutrition,tree nutrition with fruit quality.The main results are as follows:1,The overall nutrient profile of citrus in Hunan isas follows: thecontent of alkali-hydrolysable nitrogen,available phosphorus,available potassium,available iron,exchangeable calcium and effective manganese are excessive,but the content of effective zinc content is lower in soil.The content of phosphorus and iron in the leaves were excessive,and the content of nitrogen,potassium,copper,calcium and magnesium were slightly lower in the leaves.In fruits,nitrogen is the highest levels of mineral nutrients,the level of potassium second,and the level of phosphorus lowest.Citrus fruit peel thickness of larger diameter fruit was significantly higher than that of smaller diameter,while the TSS,Vc and total sugar content of smaller diameter fruit significantly higher than larger diameter,showing good comprehensive quality.2,Through the investigation for ten citrus orchards in four major citrus producing areas of Hunan province,we found that the soil nutrient elements in the fertilization systems of inorganic fertilizer plus organic fertilizer is better than only application inorganic fertilizer.The soil bulk density under the condition of single use of chemical fertilizer is lower than that of inorganic fertilizer plus organic fertilizer,and the water content is low.For fruit quality,organic fertilizer plus inorganic fertilizer can effectively improve fruit quality,including increase fruits weightVitamin C content and total sugar content,decrease total acid content.The results of analysis the sugar and acid compositions in fruit show that,sucrose content in organic fertilizer plus inorganic fertilizer systems higher than that of single chemical fertilizers systems,since the sucrose concentration was the dominant factor in the sugar content,fructose and glucose content on the influence of total sugar is weak.So,the fruit quality under the system of organic fertilizer plus chemical fertilizer better than system of only chemical fertilizer,result from sucrose concentration is higher and the acid concentration is lower in fruits.3,Through the survey of orange orchards in Hunan,we found that the pattern of microbes in soil after planting citrus was significantly changed,69% of the fungal community was promoted,and 55% of the bacterial community was also promoted.,And the change of fertilization systems also have significant effects on microbial community,of which 58% bacteria community richness in the soil that applicate organic fertilizer was enhanced,and 57% of the fungal community richness was also improved.4,Through the investigation of the relationship between soil microorganisms and soil nutrition,tree nutrition,and fruit quality in the citrus producing region of Hunan province,we found that the correlation between bacteria,fungi and soil nutrition,tree nutrition,and the correlation of fruit quality are high.The correlation between bacterial Georgfuchsia and effective copper is the highest in soil.And fungi Colletotrichum had the highest correlation with available potassium in soil.Bacteria Janthinobacterium and fungi Volutella,Cladosporium in soil have the highest correlation with total manganese in whole tree.Bacteria Edaphobacter had the highest correlation with fruit sucrose,and Janthinobacterium had the highest correlation with fruit weight.Fungal Volutella and Cladosporium were highly significant correlated with a variety of fruit qualities and most were positively correlated.