Evaluation of invasive Acacia species compost as alternative horticultural organic substrates

The physical and chemical characteristics of composts of invasive Acacia longifolia and Acacia melanoxylon shrubs were evaluated to identify compost limitations as a substrate component. The bulk density was <0.4 g cm and the total pore space was >85% of the total volume. Air capacity, the easily available water and buffering capacity were also within acceptable recommended values for horticultural substrates. With increased composting time the physical characteristics of the composts improved, but the same was not true for chemical characteristics. It is recommended to use these Acacia composts in mixtures with peat which increases the content of organic matter and the C/N ratio, and decreases the pH and the electrical conductivity, of the final substrates.