Effects of root puddling with standard and fertiliser-fortified root slurries on mortality and early growth of Pinus radiata outplants.  G. Minko.  September 1974.  10 pp. (unpubl.)

SUMMARY

1. Puddling of roots of radiata seedlings in fertiliser-free clay slurries slightly reduced first-year height growth of outplants, but did not significantly increase mortality.

2. The growth retarding effect of clay slurries was not of sufficient magnitude to justify rejection of root puddling as a technique for preventing root damage or exposure.

3. Superphosphate and lime superphosphate, unless used in minimal quantities in root slurries, produced inconsistent effects on early survival and growth of radiata outplants. Their use in this way is not recommended.

4. radiata was highly tolerant to powdered rock phosphate applied directly to the roots in clay slurries. Thus root puddling in a mixture of clay and rock phosphate is worthy of further investigation for seedlings planted on phosphorus-deficient sites.

5. Low rates of the slow-release fertiliser Osmocote 18-6-12 (9.1 kg clay, 5.3 kg water, 2.4 kg fertiliser) consistently resulted in improved first-year height growth of outplants with no significant increase in mortality. However, this height-growth response was not substantial, and at this stage the fertiliser cannot be recommended for operational use in clay slurries.

6. The fertilisers Hygold 12 and Osmocote 18-9-9 were also tried as clay-slurry additives, and found to be unsatisfactory.

Also published:

Minko, G. (1975)  Effects of root puddling Pinus radiata seedlings with standard and fertiliser-fortified clay slurries.  For. Comm. Vic., For. Tech. Pap. 23: 3-6.