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For the aim of achieving the modernization of citrus production and ensuring high yield, high quality and low environmental pollution, reasonable fertilizer has become one of the most important section in citrus production.In many developed countries, using leaf nutrition diagnosis standard on the basis of basic researches of nutrition to guide fertilization is now already a common sense. Through several years’study on sweet orange leaves, the scientists in Florida formulated a relatively perfect Nutrition diagnosis standard for sweet orange leaves. And in our country many researches on Citrus nutrition diagnosis have also been done, and several leaf nutrition diagnosis standards for Ponkan, Satsuma Mandarin, Guanximiyou, Jincheng orange and some other varieties have been put forward.In the Three Gorges Reservoir district of Chongqing, one of the most important citrus planted area of China, however, the fertilization of citrus orchards there are mainly not guided by the leaf nutrition diagnosis standard, and there are only occasional reports on macroelements or one element analysis. Therefore, Our study, based on the quantitative analysis of leaf nutrition elements, is to analyse the content of N, P, K and other 6 elements in some Jincheng orange and Hamlin sweet orange leaves in the Three Gorges Reservoir district with the purpose of providing some basis for rational fertilization.1. Distribution of nutrient contents in sweet orange leavesLeaf nutrient element levels of N, P, K, Ca, Mg, Fe, Mn, Cu and Zn were analyzed in Jincheng orange and Hamlin sweet orange. Results showed that the average content of these 9 elements was 2.99%,0.16%,0.89%,4.20%,0.28%,85.66mg-kg-1, 28.71mg-kg-11,7.43mg-kg-1 and 13.59mg-kg-1in Jincheng orange respectively. And the average content of these 9 elements was 2.89%,0.15%,1.41%,4.08%,0.23%, 83.34mg-kg-1,20.24 mg-kg-1,6.82mg-kg-1 and 14.08mg-kg-1 in Hamlin sweet orange respectively.2. The influence of different types of soils on sweet orange leaf nutrient element levelsAccording to the relationships between soil types and leaf nutrient status, the content of N in Jincheng orange leaves from high to low is alluvial soils> Shaximiao purple soil>Suining purple soil, but the content of Ca showed the opposite result. The results of N and Fe content in Hamlin sweet orange leaves showed that their contents in Shaximiao purple soil are both higher than in the Suining purple soil; However, the Ca content in Suining purple soil is higher than Shaximiao purple soil.3. The contents of sweet orange leaf nutrient element levelsIn Jincheng leaves the content of N, Ca, Mg, Fe were adequent, the content of Cu was much higher, and Zn content were seriously deficient. Results of Hamlin sweet orange showed that the content of N in the leaves was much higher, the contents of P, K, Ca, Cu and Fe were in optimum range, while Mg, Mn and Zn contents were seriously deficient.4. Correlation Analysis among these 9 netrient elementsIn Jincheng orange leaves, correlation analysis indicated N was negative correlation with P, Ca and Cu, especially with P and Mg; Ca was positive correlation with P, but negative correlation with other 7 nutritional elements.The correlation analysis of Hamlin sweet orange leaves showed N was significant positive correlation with Mn and have Synergy effects with most elements. K was only positive correlation with Zn; Ca was positive correlation with N, P, Cu and Zn, but negative correlation with other 4 nutritional elements, especially with K.
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