Effect of Cultivation and Fertilizing On Potential Yield of Pulpwood from Loblolly Pine

Abstract

SUMMARY On the lateritic podzolic soils of southern Queensland, the response of loblolly (Pinus taeda L.) to phosphorus fertilizers depends on its nitrogen status, as affected by cultivation of the site and the addition of nitrogen fertilizers. The longevity of the nitrogen and cultivation effects is examined and the economics of site amelioration by these means discussed. Loblolly pine responded very rapidly to added phosphorus on cultivated sites, but to guarantee an immediate response nitrogen must be added also. The effect of cultivation on current annual increment did not persist for more than two or three years, nor was any advantage gained by continuing the application of nitrogen fertilizers after the first growing season. The usefulness of these establishment techniques depends on whether their extra cost can be recouped by higher and earlier thinning yields. A stand of 900 stems per acre could sustain a pulpwood thinning at age 7 years when established with the aid of cultivation and nitrogen fertilizer. The benefit/cost ratio for this plantation was 1.33 compared to a ratio of 1.03 for a stand of 400 stems per acre planted without site amelioration.