Effects Of Different Fertilization On Growth And Physiological Characteristics Of Castanopsis Tibetana Seedlings

Castanopsis tibetana Hance, an evergreen hardwood tree species, belongs to the family of Fagaceae Castanopsis tibetana is a valuable and economical timber species in subtropical areas with broad prospect. "3414" orthogonal test design was conducted in the experiment.The variance of C.tibetana seedlings’ growth, biomass, main physiological and biochemical characteristics and photosynthesis indexes under different fertilizer ratio was studied in this research by using two-year C.tibetana seedlings as plant materials.The best fertilizing plan was selected by diagnosing the nutrition of C.tibetana seedlings using DRIS index method.The study provides the theoretical and practical foundation for scientific fertilization technology of C.tibetana seedlings. The main results are listed as follows:1. All the two-year C.tibetana seedling’s growth rhythm under all fertilization treatment were characterized by "slow-fast-slow" and basically showed S-shaped curve. However, there were significant differences in seedling growth and biomass under different fertilizer ratio. Treatment 3(N1P2K2) performed the best while treatment 7(N2P3K2) performed the worst. Considering the growth index, the optimal fertilization treatment for C.tibetana seedling’s growth was treatment 3(N1P2K2).2. The content of soluble protein and soluble sugar of C.tibetana seedlings were significantly different under different fertilizer ratio. As the seedlings grew, the total content of soluble protein and soluble sugar was on the rise.However, the soluble protein showed small decline in July. Among all the treatments,the highest content of the soluble protein was in treatment 9(N2P2K1) and the lowest was in treatment 10(N2P2K3); the highest content of the soluble sugar was in treatment 6(N2P2K2) and the lowest was treatment 11 (N3P2K2).3. The seasonal photosynthesis test of C.tibetana seedlings under different fertilizer ratio presented that there were significant differences in net photosynthesis rate, stomatal conductance, transpiration rate and intercellular CO2 concentration among all the treatments. Ci value showed the highest in treatment 7(N2P3K2), and all other photosynthetic parameters displayed the highest in treatment 3(N1P2K2).This results demonstrated that the photosynthetic capacity of C.tibetana seedlings in treatment 3(N1P2K2) was the strongest. The chlorophyll content of two-year C.tibetana seedlings under all the fertilization treatments showed the rising trend until July with the maximum,then declined.However,fertilization ratio significantly affected,the chlorophyll content of C.tibetana seedlings.Treatment 3(N1P2K2) performed the highest chlorophyll content while treatment 7(N2P3K2) performed the lowest.4. DRIS index nutrition diagnosis was used to diagnose the nutritional condition of the two-year C.tibetana seedlings. The results showed that the best nutrient equilibrium condition expressed ratio range of N, P, K nutrient in P/N, K/N, K/P were 0.1164～0.1124,0.4788～0.5290,3.9637～4.4269. Using the graphic method and index method, we concluded that the NPK nutrient ratio of treatment 3(N1P2K2) was in a balanced state and treatment 9(N2P2K1) became the second. Therefore, considering the seedling growth,physiological index and the DRIS index nutrition diagnosis, we concluded that the treatment 3(N1P2K2) was the best choice to promote the growth of C.tibetana seedlings.In treatment3(N1P2K2), the fertilizing amount of N,P,K were 3g, 6g and 6g per plant. Overall,for two-year C.tibetana seedlings,among N,P and K.P was relatively large demanded, followed by K, and N was relatively low demanded.