The Response of Pinus radiata and Pinus pinaster to N, P and K Fertilizers Applied At Planting

SUMMARY

P. radiata and P. pinaster fertilized with N. P and K at planting responded positively to phosphate and negatively to potassium. Nitrogen increased the height growth of P. radiata during the first year only. Significant volume increases when the fertilizer treatments were compared with the controls were not sufficient to cover the cost of the fertilizer compounded at an interest rate of 9% for eleven years. It is recommended that in forests which have achieved a “normal” cutting cycle the increment derived from fertilizer application be cut from mature forests from the time that fertilizer is applied and that all compound interests charges be waived. The experiment has shown that:

1. P. radiata can be grown on sites previously thought suitable only for P. pinaster.

2. Inorganic fertilizers can significantly improve the growth of P. radiata and P. pinaster on the T.M.S. sand soils of the Western Cape.

Where timber production is regarded as in the national interest there appears to be a bona fide case for the use of inorganic fertilizers in State plantations on these soils types.