Effects of N exponential fertilization on nutrient loading and photosynthesis of Betula platyphylla seedlings

In order to improve Betula platyphylla seedling quality, the biomass allocation, nutrient (N, P, K) content dynamics, nutrient loading and leaf photosynthesis of B. platyphylla container seedlings under constant (CF), exponential (EF), half exponential (HEF) and doubled exponential fertilization (DEF) regimes and control (CK) were studied in the first year growing. Results showed that: 1) at the end of the growing season, EF treatment improved the biomass of seedlings and the biomass proportion of root. The total biomass of seedlings under EF treatment was greater than that under CK (P 0.05) in 23.87%. The biomass proportion of root under EF treatment was greater than that under both CF and DEF treatment (P 0.05) in 26.09%. 2) EF treatment improved the nutrient loading of seedling with no significant difference from that under DEF treatment. However the nutrient content of seedling under EF treatment was greater than that under CF, HEF and CK treatment in 29.65%, 33.42% and 113.74 respectively. 3) During the peak periods of seedlings growth, EF treatment promoted photosynthetic characteristics of seedling leaf. Chlorophyll concentration and photosynthetic rate of B. platyphylla seedlings under EF treatment was greater than that under CF treatment in 15.2% (P 0.05), 7.3% (P 0.05) respectively. Meanwhile, seedling leaf area under EF treatment was greater than that under CF treatment in 14.3%. 4) The concentration of N, P and N, K nutrient under 5 fertilization treatments was linear correlation. Exponential fertilization improved the P, K uptake efficiency (EF DEF HEF CF CK) in seedlings. EF reffectively promoted biomass accumulation and improved nutrient loading, meanwhile, significantly increased P, K utilization. EF is the best fertilization regime for B. platyphylla seedlings.