Sustained growth responses to superphosphate applied to established stands of radiata pine.  D. W. Flinn, I. Moller and P. Hopmans.  April 1979.  11 pp. (unpubl.)

SUMMARY

Growth responses to superphosphate broadcast applied at 630 and 1260 kgha^-1 to established, unthinned stands of radiata pine at three sites in the Scarsdale plantation (Victoria) have been measured for up to 13 years after treatment. A substantial basal area response was found for both rates of superphosphate and there is evidence that the responses will continue through to rotation age with a commensurate increase in site productivity. Sectional measurements showed that form factor of the co-dominant and partly suppressed trees was not significantly influenced by fertiliser addition.

Basal area response curves together with favourable soil P retention characteristics and differential soil and foliar P levels between treatments indicated that the higher application rate of superphosphate will provide substantially higher yields at rotation age than the lower rate. Responses to the higher rate represented an increase in standing volume of at least 100 m³ha^-1 at all sites over the 11-13 year period after treatment and reduced the time taken to obtain the equivalent basal area growth on unfertilised sites by over four years.

Foliar and soil analyses showed that the sites were not only P deficient but also low in Ca and high in Al. Correction of mild Ca deficiency and alleviation of the adverse effects of Al on the P nutrition of radiata pine by the application of superphosphate probably contributed to the substantial responses obtained.

Also published:

Flinn, D.W., Moller, I.M. and Hopmans, P. (1979)  Sustained growth responses to superphosphate applied to established stands of Pinus radiata.  N.Z. J. For. Sci. 9 (2): 201-11.