Nitrogen Nutrition of Containerized Ternstroemia gymnanthera

Abstract

Rooted stem cuttings of Japanese ternstroemia (Ternstroemia gymnanthera Thunb.) were grown in 3.8 liter (#1) plastic containers utilizing a substrate of pine bark: sand (8: 1 by vol) amended with micronutrients and dolomitic limestone. Plants were fertilized every other day with a solution consisting of P (K2H2PO4) at a constant rate of 30 mg/liter (ppm), K (K2SO4 and K2H2PO4) at a constant rate of 60 mg/liter (ppm), and a variable rate of N (NH4NO3) at 0, 10, 20, 40, 80, 160, or 320 mg/liter (ppm). Leaf area and shoot (stems and leaves) dry weight increased with increasing N application rate (NAR) until a plateau was reached at 117 mg/liter (ppm). Root: shoot ratio was 0.8 in non-fertilized plants, and decreased to ≈0.1 with N ≥ 104 mg/liter (ppm). Root dry weight and root area increased in response to increasing NARs, reaching a plateau with N at 86 and 70 mg/liter (ppm), respectively. Leaf weight ratio (leaf dry weight ÷ total plant dry weight) increased from 0.2 with N at 0 mg/liter (ppm) to a plateau of ≈0.6 with N ≥ 109 mg/liter (ppm). Stem weight ratio (stem dry weight ÷ total plant dry weight) was 0.4 with N at 0 mg/liter (ppm) then leveled off at ≈0.3 with N ≥ 52 mg/liter (ppm). Root weight ratio (root dry weight ÷ total plant dry weight) decreased steadily from 0.4 with N at 0 mg/liter (ppm) to ≈0.1 with N ≥ 117 mg/liter (ppm). Shoot N, P, K, and S concentrations increased with increasing NARs, reaching plateaus at 117, 23, 124, and 183 mg/liter (ppm), respectively, while Mg was unaffected by NAR. Calcium concentrations increased to 0.75% with a NAR of 40 mg/liter (ppm), and decreased to 0.6 % with N ≥ 107 mg/liter (ppm). Root mineral nutrient concentrations of N, P, K, and S increased with increasing NARs, reaching plateaus of 287, 53, 39, and 195 mg/liter (ppm) respectively, whereas Ca and Mg were not affected by NAR.