Correlation between the contents of carbon and nitrogen and ratio of C/N and the yield of Kuerlexiangli pear

Abstract: 【Objective】Nitrogen (N) is one of the most important mineral nutrients for plants, and ade-quacy of N is directly related to the photosynthesis, growth and development of plant, thereby affecting the yield and quality of crops. Therefore, nitrogen fertilizer management has become one of the impor-tant means to regulate crop growth. The application of nitrogen fertilizer affects the contents of carbon and nitrogen in plant organs, and thus carbon-to-nitrogen (C/N) ratio. It is vital to investigate the carbon and nitrogen nutrients in plant organs under different nitrogen application levels and their distribution in plants. The cultivation of Kuerlexiangli pear has been expanding rapidly. However, excessive applica-tion of nitrogen fertilizer in order to gain high yield not only causes harmful effect on productivity but also increases production costs. There have few reports about the correlation between the contents of N and C and C/N in Kuerlexiangli pear trees and the yield under different nitrogen treatments. In this pa-per, we investigated the effects of different nitrogen application rates on carbon and nitrogen contents, C/N value and yield of each organ of Kuerlexiangli pear trees, analyzed the correlations between nitro-gen application rate and C/N ratio and yield of new organs, and proposed suitable nitrogen application range and C/N ratio range for new organs.【Methods】Six-year-old Kuerlexiangli pear trees were used as the materials. Whole plant excavation and organ dissection of Kuerlexiangli pear trees under different nitrogen application treatments of N0, N1, N2, and N3 (corresponding to 0, 150, 300 and 450 N kg·hm-2,respectively) were carried out at the new shoot growing stage, fruit swelling stage and fruit maturity stage. Total carbon and total nitrogen in each organ were determined by potassium dichromate-sulfuric acid oxidation method and Kjeldahl method, respectively. The yield of per plant measured by multiply-ing the total number of fruit per plant with average fruit weight, and then