A study of Pinus radiata nutrition at Webster’s Hill, Gellibrand.  L.J. Bren, F.G. Craig and P. Hopmans.  September 1974.  9 pp. (unpubl.)

SUMMARY

1. P. radiata plantings between windrows on a sandy podzol at Webster’s hill, show severe nutrient deficiency symptoms. These symptoms consist of short, bright-yellow needles, and resemble both P and Zn deficiencies. No such symptoms occur in trees established on burnt windrows on this soil type.

2. A 2 x 2 x 3 factorial fertiliser experiment was established on 3 sites in the area; one being on the soil type showing severe symptoms, and the others on yellow sands over clay. The treatments where a control, superphosphate at 284 gm/tree, 2.5% W/V ZnSO₄ solution spray, and the superphosphate and ZnSO₄treatments combined.

3. Serious scrub competition was experienced on all sites, but particularly on the sandy podzol. Various herbicides were used to control the scrub, which is now been eliminated.

4. Needle analysis of trees on the control plots indicated that the primary nutrient deficiency on all sites was phosphorus. However, N, S, and Zn were also deficient on the site showing severe symptoms.

5. Despite the scrub competition, uptake of P on the plots treated with superphosphate has been satisfactory on all sites, and the ZnSO₄spray together with superphosphate, has largely corrected the N, S, and Zn deficiencies on the sandy podzol. Visual symptoms of nutrient stress are no longer apparent on this site.

6. Examination of the experimental results indicates that there have been no effects of the fertilisers on mortality. However, superphosphate was found to have resulted in a significant overall increase in height growth. The effect of ZnSO₄alone was not significant overall, nor did it significantly add to the superphosphate response.

7. The indications are that superphosphate is essential for satisfactory growth of radiata on most of the sites at Webster’s hill. On sites in which the soil is a sandy podzol, it appears that fertiliser Zn may be required as well. For a fertiliser programme to be successful in the area, it is clear that effective scrub control is mandatory.