Residual fertiliser and liming impacts in a long-term Acacia mearnsii trial

Sixth rotation growth measurements of an Acacia mearnsii fertiliser trial established to test the effect of nitrogen (N), phosphorus (P), potassium (K) and lime application on growth and bark production, showed that residual P and lime effects are present. First established in 1951, the trial was re-established a further five times. The sixth rotation was planted in late 2003 without the application of fertiliser or lime, but with treatment plot identities maintained to test the residual effects of these treatments into the sixth rotation. Soil properties, stocking, height, basal area, volume and bark yield were determined at rotation-end. There were significant positive effects of residual P on height, basal area and volume and significant negative effects of residual lime on stocking, basal area, volume and bark yield. The responses were significantly, though weakly, related to soil properties associated with residual treatment effects. Liming is not advocated in wattle plantations, while there are residual benefits of applied P. The lack of strong relationships, however, does not permit adjustment to current wattle fertiliser guidelines.