Effects of P fertilisation on productivity and nutrient accumulation in a Eucalyptus grandis x E-urophylla plantation in southern China

Phosphorus deficiency is the main constraint to productivity of eucalypt plantations in southern China, but knowledge of P application on nutrient utilisation by eucalypt plantations in China is limited. This study, therefore. investigates the impacts of P fertiliser rate on biomass production, nutrient uptake, partition and use, efficiency of a 75-month-old clonal plantation of Eucalyptus grandis x E. urophylla on a high P sorption oxisol near Kaiping, southern China. Results show that P application significantly increased tree growth, biomass production, N, P and K uptake, and decreased understorey biomass and litter dry weight. Application of 208 kg P ha(-1) was adequate for tree growth. The proportion of stem-wood was increased and the proportion of root biomass was decreased as the quantity of phosphorus applied increased. The application of P also increased the proportion of tree biomass:total biomass of tree, understorey and litter. The N and K use efficiencies for tree biomass and stem-wood production increased with P supply. The P use efficiency was highest in the 13 kg P ha(-1) treatment, and decreased at higher rates of P. The P recovery by tree uptake was between 7.6 and 25.3% and decreased as the quantity of P applied increased. It is suggested that harvest residue, as well as understorey and litter should be retained on the site after harvest so that the accumulated P in these components following P fertilisation can benefit tree growth in the next rotation. The study also indicated that N is likely to limit productivity after P due to the high uptake of N by the understorey. (C) 2002 Elsevier Science B.V. All rights reserved.