Growth and nutrient relationships of juvenile Pinus pinaster grown on ex-farmland in Western Australia

Abstract

Summary The action and interaction of N, P and K on the growth and nutrient relationships of young Pinus pinaster were examined on three sites with dissimilar soils and land use histories in Western Australia. The three sites were a fertile gravelly loam (ex-pasture), a deep fertile sand (ex-pasture) and a deep infertile sand (newly cleared banksia woodland). Mean annual rainfall over the 3 y of the experiment was 615 mm, concentrated from May to September, with mean annual evaporation of about 2150 mm. Phosphorus was the key nutrient limiting growth on the infertile sands. Tree height was significantly increased on this site by the application of 140 kg P ha−1. No effect was found on the other two more fertile sites. The addition of 276 kg N ha−1 and/or 250 kg K ha−1 did not increase height growth on any site. There was a negative N × P interaction at all sites, such that the application of N in combination with P significantly reduced tree height growth and lowered P concentrations in the foliage. Foliar P concentrations below 0.07% were found to be deficient for optimum early growth of P. pinaster on all sites. Three years after the treatments were applied, a mean concentration of plant- available P (Olsen bic-P) as low as 0.75 mg kg−1 in the surface soil was sufficient for adequate early growth of P. pinaster, but a mean bic-P of 0.04 mg kg−1 was clearly inadequate. Therefore, while P is the critical element in the optimal early growth of P. pinaster, the amount required is very small.