Effects of different fertilization season and nutrient on the growth and physiological characteristics of Tsoongiodendron odorum at seeding stage

In order to investigate the effects of different fertilization and season on the growth and stress resistance of Tsoongiodendron odorum seedlings, we examined the 10-month-old Tsoongiodendron odorum seedlings with single fertilization(N, P, K) and mixed fertilization(NP, NK, PK, NPK) in spring and autumn respectively. The seeding growth, antioxidant enzyme activity of leaves and soil available nutrients were measured under different fertilization and season. The results showed that single fertilization had no significant effect on the growth of Tsoongiodendron odorum seedlings, while mixed application of NK, NP and NPK significantly increased the seedling height and ground diameter. Fertilization effectively regulated the available nutrients in the soil and improve the antioxidant activity of the seeding leaves. For example, applying NK fertilizer in spring has the best growth-promoting effect on the Tsoongiodendron odorum seedlings, significantly increased the activities of PAL, POD and SOD in the leaves, and the soil available potassium content reached 56 mg/kg, which was 17.48% higher than the control. Application of NP in autumn significantly increased PAL, POD, SOD and PPO enzyme activities, but had no significant effect on seedling height and ground diameter. The soil alkalohydrolytic nitrogen and available phosphorus increased by 14.88% and 34.78% compared with the control, reaching to 55.79 and 29.07 mg/kg, respectively. The application of NP and NK both significantly increased the content of soluble protein in the leaves. but had no significant effect on soluble sugar. Mantel test showed that there was a significant positive correlation between fertilization season and soluble sugar in the Tsoongiodendron odorum leaves. In conclusion, application of NK fertilizer in spring effectively promoted the growth and antioxidant capacity of Tsoongiodendron odorum, and application of NP fertilizer in autumn effectively improved the antioxidant capacity.