Abstract:

Seedlings of slash pine (Pinus elliottii Engelm.) grown in plastic film bags(15cm ×23cm) were treated with liquid fertilizer at 4 relatively different addition rates, i.e.0, 5.3 %, 6.4 %, and 7.5 %, following the theory and technique of steady state mineral nutrition.The results indicated that the basal diameter, stem length (seedling height), and dry matter production of the seedlings under the 6.4 % treatment increased by 14.9 %, 24.5 %, and 39.6 % in comparison with the seedlings under the 0 treatment, which were significantly different at 0.05 or 0.01 level.Through quantitative analyses of the available nutrient contents in the root media and the amounts of nutrient element accumulated in the seedlings of various treatments in the beginning and at the end of the experiment, it was show n that 6.4 % treatment was of the best effects with nutrient accumulations of N, P, K elements in seedlings increased by 79.4 %, 58.5 % and 41.9 % over the 0 treatment, and the increments of N, P, K, Ca, Mg nutrient element contained in this treatment system by 32.3 %, 56.9 %, 36.1 %, 92.2 % and 25.3 %, respectively in comparison with 0 treatment.A t the same time, the soil nutrient flux density of N, P, K increased by 23.7 %, 36.3 %, 30.7 % in comparison with 0 treatment, respectively, and the enzyme activities of urease, proteinase, hydrogen peroxidase, neutral phosphatase were 403 %, 45.5 %, 40%, 144.5 %higher than those at the beginning of the experiment.It is concluded that the comparatively suitable nutrient relative addition rate not only promotes seedling growth, but also induces soil enzyme activity and soil nutrient flux density, as well as nutrient use efficiency.The mechanism of steady state mineral nutrition to promote soil mineralization, and its advantage were discussed in this paper.

Key words: Pinus elliottii, Container-grown seedling, Steady state mineral nutrition, Nutrient relative addition rate, Soil mineralization