The Responses Of Growth And Physiology Of Populus×euramericana Cv.’74/76’ Seedlings To Different N Treatments

Rational fertilization techniques is one of the key factors that can be used to promote the quality of Populusxeuramericana cv.’74/76’seedlings. Pot exponential fertilization experiments under sand culture combined with field fertilization experiments were conducted in this paper. We analysed the morphologic parameters (height and ground diameter), biomass, nitrogen concentration and photosynthesis parameters of Populus×euramericana cv.’74/76’seedlings at various experimental treatments, and besides, revealed its annual growth rule and nitrogen-fertilizer requirement feature. On this basis, we calculated the reasonable fertilization time and fertilizer amount. The main results were showed as follows:(1) The height and ground diameter growth principle of Populusxeuramericana cv.’74/76’seedlings was characteristic by rhythm of slow-fast-slow. The growth period in one year of Populusxeuramericana cv.’74/76’seedlings was divided into four phases, which were survive time (April), seedling stage (May to June), fast-growing stage (July to August) and hardening stage (September to October), respectively.(2) Under the condition of exponential fertilization of pot stand culture, different degree of increase were observed in height, diameter growth, biomass accumulation and seedling photosynthetic parameters when nitrogen supply level increased from0.0to6g-seedling-1year-1.However, when the nitrogen supply exceed10mg-seedling-lyear-1, the plants’morphologic parameters, biomass (gseedling-1), photosynthesis parameters declined, compared with N2level (6g-seedling-1-year-1). It was detected that the seedlings under N2treatments had the optimal growth status within all the four experimental treatments, with172.38cm height,13.64mm ground diameter, and94.783g biomass gain in the end of year.(3) The results of sand culture and Held fertilization experiments were in accord with each other. No significant differences were recorded between treatment1(15gseedling-lyear-1) and treatment2(6gseedling-l·year-1)(P>0.05).For the purpose of fertilization economization,6gN-seedling-l year-I can be applied for the cultivation of one-year old Populusxeuramericana cv.’74/76’seedlings. Reasonable fertilization period was June in seedling stage, July and August in fast-growing stage, and the fast-growing period (August) was the key phase for nitrogen supply, fertilization should be implemented within15days before seedling growth peak. Fertilization should be implemented in the middle of June.