| Qiongzhong green orange grows in Qiongzhong Li and Miao Autonomous County which located in the mountain area of middle part of Hainan Province, planting of green orange is the most important economic pillar of the county now. However, under the background of generally low production technology, currently the growers of green orange are lack of knowledge about the soil fertility of the orchard. Most of them carry out production and fertilization based on their experience, which results in some problems like unbalanced fertilization, excessive fertilization, insufficient organic fertilizer, etc. that to some degree have limited the improvement of quantity and quality of green orange and have constrained the development of the green orange industry. This paper is in connection with the issues mentioned above. After investigation on the fertilization practices of the growers and identification of current fertilization situation and the problems existing, we have carried out "3414"field manure trial on nitrogen, phosphate, and potash. The paper not only establishes functional equation of fertilizer effect according to the data of production quantity which put forward recommended fertilizing amount suitable to orchard of different ages and provides theoretical basis for the improved fertility of green orange orchard soil, but also explores the optimum nutrient management model and nutrient control measures on the basis of analysis on variation trend of soil and leaf nutrients in different periods and the influence of fertilization on nutrient content, and through the soil and leaf nutrient data acquired by lab analysis and detection of green orange of different growth periods.The main content of this study includes:variation trend and comparison analysis of main nutrient in soil and leaf in green orange orchards of different ages; the effect of different fertilization on the harvest and economic benefits of green orange; analysis of relationship between nutrient content of orchard soil and leaf and the harvest of green orange; the establishment of function of nitrogen, phosphorus, potash for green orange orchard of different ages and the identification of fertilization parameters; the influence of nitrogen, phosphorus, potash of different levels and their mixture ratio on the quality of the fruit of green orange; and relevance analysis between nutrients in nitrogen, phosphorus, potash and indicators of fruit quality. The results we obtained are as follows:(1) The influence of different levels and ratios of nitrogen, phosphorus and potassium fertilization on the soil nutrient content roughly the same in different orchards. From the flowering period to fruit swelling period, the content of soil hydrolytic nitrogen, soil available potassium and soil organic matter gradually declines and reaches the lowest value, the content of soil available phosphorus increases. From fruit maturing period to the picking period, the content of soil hydrolytic nitrogen, soil available potassium start to go up, and soil available phosphorus and organic matters declines. The pH variation of soil generally goes down first and then up in the entire growth period, fertilization has significant impact on soil pH, and the influence of nitrogen and potash is larger than that of phosphorus.(2) Variances generally exist in the leaf nutrient contents of different ages green orange tree. The total content ranges of nitrogen, potash and phosphorus for leaf of different trees are respectively1.76%～2.81%,0.11%～0.25%and1.41%～2.41%. The amount of fertilization has relatively large influence on the variation of leaf nutrient of green orange, while that of the mixed application of fertilizer is relatively small.(3) Fertilization has a heavy effect on the green orange orchards in the full fruiting period (six-year and ten-year) with similar fertilizing effect. No matter how different the fertilization standards of single factor or of the double factors is, their influence on green orange harvest are both obvious. Fertilization of nitrogen, phosphate and potash in green orange orchards at different ages may bring increasing of economic returns, with nitrogen fertilization bringing the best production increasing. The effect of phosphate and potash is a bit different for the production of green orange orchards during beginning period and full fruiting period; generally, adding phosphate and potash can help increase the production of green orange. Compared with fertilization, the proportioning of fertilizers has less effect, so the fertilization of green orange should focus on the effect from the amount of the fertilizers used.(4) The production, cultivation and fertilization parameters of Qiongzhong green orange are developed in this study by creating ternary quadratic fertilizer effect equation. It shows that the major limiting factor of yield is potassium content in the abundance and deficiency. And the target yield for orange trees of4years,6years and10years is respectively19.71per plant,58.94per plant and80.62per plant, and the recommended annual rate of fertilizer application of azophoska is0.53kg per plant,0.578per plant, and0.865kg per plant respectively, superphosphate0.38kg per plant,0.568kg per plant, and0.392kg per plant respectively, and potassium chloride0.406kg per plant,0.519kg per plant and1.206kg per plant respectively. The annual fertilization is divided into3times. The rate of fertilizer application for fruit picking, before anthesis, stabilization and strengthening is with urea accounting for40%,25%and35%, superphosphate accounting for75%,25%and0%, as well as potassium chliride accounting for25%,10%, and65%respectively.(5) The application rate of azophoska, superphosphate and potassium has an important impact on the apperrance quality and flavor quality of green orange. Rational fertilization can increase the single fruit weight, transverse diameter and longitudinal diameter, improve the flavor quality, but excessive fertilization might lead to some negative effects. The influence of the fertilizer and its proportion on fruit-shape index is relatively small.Potassium and phosphorus are the two major nutrients that affect the flavor quality of green orange. Potassium mainly has effect on the soluble solids content and soluble total sugar content, while phosphorus mainly affects the soluble solids content and titratable acid content, and nitrogen just can improve the edible rate, soluble acid ratio and sugar acid ratio. With the increase of the use of potassium, so does the index value of flavor quality like the content of soluble solids, while excessive nitrogen and phosphate will lower soluble solids content, titratable acid and soluble sugar content. So nitrogen and phosphate fertilizer must be controlled within a certain range to get fruit of higher quality. The proportioning ratio of the three nutrients mainly influences soluble solids content and soluble total sugar content, and has little effect on eating quality and the content of titratable acid.(6) The results of principal component analysis (PCA) shows that the influencing factors on the harvest and fruit quality of green oranges mainly contain two parts, i.e. the nutrient in the soil and that in the lamina. During the growth and the developmental phase of the green orange, the influence of the effective phosphate content and the organic content in the soil are comparatively higher, hydrolysable nitrogen/available phosphorus in the soil cast important influence on the fruit expanding stage, the fruit maturation stage and the harvest stage of the fruit, the available phosphorus/available potassium cast important influence on the eflorescence and harvest period, the effect of the available potassium content in the soil is obvious during the fruit maturation stage; the full lamina phosphorus content and full lamina phosphorus/full potassium cast higher influence on eflorescence, fruit expanding stage and fruit maturation stage, full lamina potassium content mainly effects the eflorescence and harvest stage, and the full lamina nitrogen/full potassium mainly play a role in the fruit maturation stage and harvest stage.(7) For the four-year, six-year and ten-year green orange orchards, both the VCR value and net profit is comparatively higher with nitrogen fertilization, followed by normal local fertilization treatment, adding potash fertilization and phosphate fertilization treatment. Therefore, on the basis of local fertilization, adding adequate amount of nitrogen fertilizer, phosphate fertilizer and potash fertilizer may help enhance economic returns. |
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