© 1971 by Institute of Chartered Foresters
EDITORIAL |
The Effect of Form, Rate, and Position of Phosphatic Fertilizers on Growth and Nutrient Uptake of Sitka Spruce on Deep Peat
Chemical and Animal Nutrition Research Division Ministry of Agriculture, Northern Ireland
The effects of superphosphate, ground rock phosphate, and basic slag, each applied in three positions, on the growth of Sitka spruce (Picea sitchensis Carr.) were compared up to the eighth year after planting on deep oligotrophic blanket peat in Northern Ireland. Broadcast application was initially the most effective, but after eight years there was no significant difference in mean tree height between this method and placement on top of the planting ribbon. Application of fertilizer below the ribbon gave consistently poorer results but with the previously used method of placement in the planting hole growth was almost 40 per cent less even than this. At equivalent rates, superphosphate and ground rock phosphate were equally effective and both were significantly better than basic slag.
Fertilizer position had little effect on foliar nutrient concentration in either the fifth or eighth growing seasons. In both seasons, foliar N concentration increased with amount of slag applied but N levels were higher with superphosphate and G.R.P. in both the fifth and eighth seasons. At the lower rates of applied slag, foliar N concentrations were below the accepted optimum in the eighth season. Foliar P concentration also decreased significantly with time and, except where 100 Kg P per ha had been applied as slag, the P nutrition of the trees after 8 years was becoming critical. Fertilizer treatment had no significant effect on foliar K concentration in the fifth season but by the eighth season foliar K levels were inversely related to growth rate. This suggests an imminent K deficiency.
It is concluded that the broadcast application of ground rock phosphate at not less than 50 Kg P per ha is an effective fertilizer regime for the establishment of Sitka spruce on deep blanket peat, but that supplementary fertilizing with K, and possibly P, may be necessary about 8 years after planting.