Effect of Fertilizer On Growth and Physiological Response of Zanthoxylum Ailanthoides Sieb.Et Zucc. Seedlings

Zanthoxylum ailanthoides Sieb.et Zucc., a native plant in Hunan, China, has a great potential for an ornamental plant or timber plantation. To better manage its seedling production, nine fertilizer combinations of urea (0, 3, 6 g/pot), calcium superphosphate (CP; 0, 2, 3 g/pot) and potassium chloride (PC; 0, 2, 3 g/pot) were applied to potted seedling plants.  Fertilizers significantly influenced the seedling growth (measured by plant height (cm) and caliper size (mm)). All plants received fertilizer(s) were significantly taller and bigger than that (19.6cm and 4.6mm) of the control. The height reached 76.9cm and caliper diameter was 11.9mm under the fertilizer treatment of 3g urea + 3g CP per pot. Regression analysis indicated that nitrogen had much stronger influence than that of phosphorous and potassium. The proper nitrogen level should be 3g urea per pot. Too higher (6g/pot urea) greatly reduced seedling growth, especially with increased phosphorous levels from 0 to 2 to 3g/pot CP.  Regardless of P or K levels, caliper sizes ranged from 11.5 to 12.4mm under application of urea for 3 or 6 g/pot. Total dry weight, root weight, leaf area index had the similar trend as the plant growth.  The ratio of root to shoot was higher in the lower concentrations of N, P, and K. It was clear that shortage of nutrient should increase in root/shoot ratio, which led to more roots to take nutrients from soil. Chlorophyll content (CC) and photosynthesis rate (Pn) increased significantly as the N-P-K concentrations went up. Both CC and Pn doubled under the highest combination of three fertilizers. Seedlings could be much higher and stronger if we applied 3g urea + 2g CP + 3g PC per pot during their growing season.