Animal wastes, especially pig manure, are the main sources of stream pollution in Hong Kong. Recycling of the waste material will ease the disposal problem. In this experiment, pig manure compost and horse manure compost were applied to tree seedlings (Acacia confusa). Both pH and concentrations of N, P, K, Mg, Ca, Na and organic C in the treated soil increased with increasing application rates of manure compost. Higher productivities of tree seedlings were obtained under the treatments with 10%, 20%, 30% (v/v) horse manure compost. However, higher death rate and lower productivity of tree seedlings were noted at higher application rates of the manure compost. Soils treated with pig manure compost supported better growth than horse manure in terms of oven-dry weight according to the results of the present investigation. Although the trace metal concentrations of soils increased as more compost was added, the concentrations in plant tissues did not increase correspondingly. Copyright © 1985 Published by Elsevier Ltd.