Effects of exponential fertilization on seedling growth and nitrogen uptake and utilization efficiency of Catalpa bungei clones

In order to study the regularity of the growth and nitrogen absorption and utilization of different Catalpa bungei clones, an exponential fertilization trial was conducted with four nitrogen dose levels (applying a total of CK, 6 ,10, 14 g/plant), and used two-year-old C. bungei clones 1-4,7080 and 015-1 tissue culture seedlings as experimental material to research the effects of exponential fertilization on seedling growth and nitrogen uptake and utilization efficiency of C. bungei clones from March to August 2011 in Xiaolongshan Mountain Forestry Science and Technology Research Institute, Tianshui City of Gansu Province, northwestern China. Results showed that: 1) The height of seedling, ground diameter and total biomass of C. bungei clones first increased and then decreased with increasing amount of nitrogen, peaking in the urea 10 g/plant. The height of seedlings was 142.1, 120.0, 142.0 cm, rising by 49%, 67%, 67% than CK. The ground diameter was 16.94, 16.13, 18.28 mm, rising by 18%, 36%, 30% than CK. The total biomass was 193.13, 188.91, 230.71 g/plant, rising by 65%, 57%, 66% than CK. 2) The nitrogen concentration and nitrogen content of three C. bungei clones were expressed as leaf root stem. The maximum of nitrogen concentration and nitrogen content were 13.45-27.87 g/kg,0.72-2.07 g/plant, and increased by 100%-145%, 133%-390% respectively compared with CK. 3) The apparent absorption efficiency , fertilization efficiency, biomass harvest index and nitrogen harvest index of clone 015-1 were 56.92%, 43.23 g/g, 52.62 g/g and 86.05%, which were 1.09-1.26 times of clones 1-4 and 7080. Nitrogen uptake and utilization parameters were significantly reduced with increasing amount of nitrogen. Comprehensive analysis showed that the effects of exponential fertilization on growth, nitrogen concentration and nitrogen content of C. bungei clones had a significant role in promoting. The growth and nitrogen uptake and utilization efficiency of clone 015-1 were greater than clones 1-4 and 7080. The optimum fertilization of three clones was urea 10-14 g/plant.