Aims Eucalyptus grandis is an excellent, fast-growing timber species. It is important to understand the effect of nitrogen and phosphorus addition on E. grandis growth, nutrient limitation and stoichiometric characteristics. Our objectives are to test 1) biomass of organs (roots, stems and leaves) and allocation proportion, 2) C, N and P content and allocation in different organs and 3) elements that restrict the growth of E. grandis as well as N and P use efficiency and C:N:P stoichiometry.
Methods We grew E. grandis clone tissue culture seedlings using a pot experiment with acidic purple soil and N and P fertilizer additions. We measured the biomass and C, N and P content of roots, stems, leaves and soils.
Important findings Roots, stems, leaves and total biomass of E. grandis seedlings were significantly affected by application of N, which increased the aboveground biomass ratio and significantly reduced the root biomass ratio. Total biomass was not significantly affected by application of P, root biomass allocation ratio increased significantly and stem and leaf biomass allocation were not significant affected. N or P fertilization significantly changed N and P content and the stoichiometric ratio, as well as significantly affected the soil and plant N:P relationship. N fertilization can promote N uptake and inhibit the absorption of P in acid purple soil, and then P fertilization can promote P uptake of E. grandis seedlings. C, N and P distribution in roots, stems and leaves were significantly affected by N fertilization while not significantly affected by P fertilization. N-use efficiency was reduced and P-use efficiency improved significantly by N addition; however, P-use efficiency was reduced significantly by P addition. N:P of roots, stems and leaves can be significantly improved by N fertilization to alleviate the phenomenon of lack of N, but it is further exacerbated by the lack of N element by P fertilization.