Evaluation of soil testing methods for predicting early growth and responses to phosphate fertiliser of Pinus radiata at Heywood.  P. Hopmans, D. W. Flinn and B. C. Aeberli.  July 1977.  7 pp. (unpubl.)

SUMMARY

The object of this study was to identify a soil test for predicting early growth, and response to phosphate fertiliser, of Pinus radiata D. Don planted on the soil type Gorae gravelly loam near Heywood. This soil is known to have low total and extractable phosphorus levels and high phosphate sorption properties.

In 1970 an experiment was established at ten sites within the proposed plantation area at Heywood to study response of P. radiata to phosphate fertiliser (0 and 280 g/tree of 1:1 mixture of agricultural lime and superphosphate) and site preparation method (control, ripping and ploughing). Simultaneously, composite soil samples were collected from unfertilised portions of each site and tests were then carried out to determine phosphorus sorption maximum, total soil phosphorus and extractable phosphorus using citric acid, bicarbonate, EDTA and acidified (0.025N and 0.1N hydrochloric acid) ammonium fluoride (Bray No. 1 and Bray No. 2 methods respectively). Using two-year height growth data from the field experiment, correlation coefficients for relationships between soil test values and both mean height of unfertilised trees and height response to fertiliser were computed for each site preparation method.

Bray No. 2 extractable phosphorus was shown to be the only soil test significantly correlated with early height growth of unfertilised P. radiata on ripped sites and on unprepared sites with low mortality. Height response to the phosphate fertiliser is strongly correlated with Bray No. 2 extractable phosphorus for all site preparation methods. For the soil type of Gorae gravelly loam, this relatively simple soil test can therefore be carried out on soil samples collected prior to planting to predict response to phosphate fertiliser, and this provides a useful basis for efficient use of fertiliser.

Also published:

Hopmans, P., Flinn, D.W. and Aeberli, B. C. (1978)  Evaluation of soil testing methods for predicting early growth and responses to phosphate fertiliser of Pinus radiata at Heywood, Victoria.  Aust. For. Res. 8: 57-61.