An economic evaluation of superphosphate for established stands of Pinus radiata at Scarsdale.  L.J. Bren and F.G. Craig.  April 1972.  17 pp. (unpubl.)

SUMMARY

This report evaluates the results of superphosphate trials established in 1963 and 1965 in four P. radiata stands aged 9 to 18 years at Scarsdale.

The results indicate that for stands of up to 18 years of age, at least an additional 800 ft³/acre can be expected at 30 years of age; this being approximately equivalent to an additional $80 per acre in royalty at present values.

Economic analysis of the growth responses showed clearly that 5 cwt/acre is generally a more profitable and reliable application rate than 10 cwt/acre. Even if no further responses occur, compound interest returns of between 9.0 and 16.4 percent should be realised at age 30 years, or between 4.8 percent and 9.8 percent at age 40 years from 5 cwt/acre of superphosphate.

However, if responses continue, as is expected from the results of similar trials in Australia, returns should be between 13.1 and 19.5 percent at 30 years, or between 8.7 and 11.5 percent at 40 years.

Thus, application of superphosphate at 5 cwt/acre to P. radiata stands of up to 18 years of age at Scarsdale can be recommended as a sound investment. Techniques for the aerial application of superphosphate to these stands have been investigated and are to be reported shortly in this series.