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The R esponse of Sitka Spruce to Sulphate of Ammonia 21TreatmentPoPIP2P aMeanTABLE 4Effect of Treatment on Foliar N concentrations, 1967-1969Mean Foliar N Concentration ( % DM)No Nl N219670.70 1.30 1.391.18 1.58 1.851.34 1.63 1.821.26 !1.57 1.731.19 1.52 1.70CV = 2.90%Mean No NI N2 Mean19681.13 0.83 0.94 1.00 0.921.54 1.08 1.16 1.27 1.171.59 1.22 1.27 1.25 1.251.52 1.27 lAO 1.32 1.581.10 1.19 1.21CV= 2.62%Mean19691.01 1.23 1.161.12 1.60 1.341.27 1.42 lAO1.29 1.60 1.361.17 1.46 1.31CV= 2.03 %Significant Comparisons1.131.35 No vs (NI+N2) '67** '69**1.37 NI vs N2 '67* '69*1042 Po vs (PI+P 2 +P a ) '67** '68**'69**Significance level: *0.05, **0.01.CY : Coefficient of variation.On this basis, a condition of N deficiency existed under the NoPotreatment in 1967 and 1968.Both fertilizers produced significant increases in foliar N concentrations(Table 4). The effect of G.N.A.P. was highly significantin all three seasons. As in height increment, there were no significantdifferences above the 55 kg P/ha level. The effect of S/A wassignificant only in the season of application. The 1969 applicationproduced a significantly higher foliar N concentration at the N Ilevel of application over the N 2 level.The increase in foliar N concentrations with phosphate applicationwas not accompanied by a significant increase in dilute H 2S0 4extractable N in the peat (Table 5). This may have been due to theextreme variation in peat N concentrations within plots. Kaila(1958) has measured increased N mineralization in acid peat withsuperphosphate application. The evidence suggests that the causativefactor is calcium (Forestry Commission, 1967; Atterson, 1969).This is present in all commercial phosphatic fertilizers (G.N.A.P.