Increasing growth in high production Radiata Pine stands by nitrogen fertilizers.

Authors: R. C. Woollons, G. M. Will
Publication: New Zealand Journal of Forestry, Volume N.Z.J.For. 1975, Issue N.Z.J.For. 20(2) 1975, pp 243-253, Aug 1975
Publisher: New Zealand Institute of Forestry

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Abstract: The recent dramatic increases of fertiliser usage in world-forestry are reviewed. Contrast is made between fertiliser responses in overtly deficient and in apparently healthy stands of radiata pine in New Zealand. For the latter, growing on pumice soils, it has been found in a series of experiments that:
(1)   Following thinning, the application of a mixed fertiliser in two successive years boosted the growth of naturally regenerated 13-year-old radiata pine. A sustained response has lasted seven years to date, with substantial gains of 61 m'/ha at 540 stems/ha and 36 m3/ha at 320 stems/ha.
(2)   If fertilisers are applied more than three years after thinning the response is inconsistent or transient; no response al all has been detected in unthinned stands.
(3)   The only nutrient to give a consistent response is nitrogen.
(4)   The rates of nitrogen needed to give a sustained response have been partially defined; evidence to date suggests that two annual applications of urea at 250 kg/ha in successive years is the most productive.
The data show that the stem volume increases caused by such applications of nitrogen fertilisers occur partially through a change in stem form. There is no evidence of height increases through fertiliser application

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