A pilot study into the effects of fertilizer applied at planting on branching inPinus patula

Abstract

SYNOPSIS This study aimed to investigate the effect of fertilizer applications on the early branching dynamics of trees that were fertilized with 25 g P tree.1 at planting compared to unfertilized trees. The study took place at two sites where significant positive growth responses to the nutrient additions had been found immediately after planting. The branching was assessed at the time of the first pruning operation. The results of the study indicated that the application of fertilizer does not change the branching morphology of the trees in terms of branch length, number of branches per whorl, number of whorls per pruned length of stem or branch diameter (the latter measured at the point where the branch joins the stem). However, significant differences were found in the diameter over the stubs (DOS). Differences between the DOS in the fertilized and unfertilized trees was much greater towards the bottom of the stem. The maximum DOS within the pruned length of stem, which provides an indication of the extent of the knotty core, was significantly higher in the fertilized trees and greater than the target set by the saw timber industry in the area. Thus it appears that the greater initial volumes are being achieved in the fertilized stands at the expense of wood quality. The results indicate the importance of site-specific pruning regimes which take the initial growth rates of the trees into account, particularly if these growth rates are influenced by other silvicultural operations.