Commonwealth Forestry Review

34 COMMONWEALTH FORESTRY REVIEW
TABLE 5
TOTAL HEIGHTS (M) AND FRESH WEIGHTS (G) OF Eucalyptus grandis SEEDLINGS GROWN IN
POTS ON A MAMBILLA PLATEAU SURFACE AND SUBSOIL
Treatment
I
Surface Soil I Subsoil
0-6 inches (0-0.15 m.) 12-18 inches (0.30-0.46 m.)
I
Fresh Weight Total Height I Fresh Weight Total Height
(g) I (m) (g) (m)
I
Control
4.5 0.175 0.15 0.034
N I 8.8 0.247 0.45 0.065
P 14.9 0.283 3.67 0.148
K 11.6 0.270 0.19 0.034
NP 13.0 0.305 1.81 0.187
NK 8.1 0.240 0.06 0.029
PK 15.1 0.314 3.15 0.151
NPK 13.7 0.300 2.01 0.092
CaMg 14.3 0.326 0.44 0.047
I
NPK, Ca Mg 17.2
0.379 7.05 0.216
NPK, Ca Mg, Micro* 15.1 0.325 10.65 0.290
NPK, Micro 16.7 0.336
6.49 0.225
B, NPK, CaMg 19.5 0.387 8.99 0.337
Boron 7.8 0.218 0.47 0.047
*Micronutrients are tnanganese, zinc, copper, molybdenum and boron
Plants receiving only CaMg were about the same size as those receiving P alone
or in combination with Nand K, and were significantly larger than the controls.
No tissue tests were made so it was not possible to tell, as planned, if :CaMg increased
the availability of soil P to the seedlings. 'Seedlings receiving B alone were
about 75 per cent heavier than the controls but the difference was not quite significant
at the 5 per cent probability level. T'here is no evidence that the see'dlings
responded to the other micronutrients-manganese, zinc, copp1er and molybdenum.
The evidence as a whole points to P as the principal limiting element with the
suggestion that B may also be re'quired and that liming may help, increase P
availability in the less acid surface soil. Because of the rather large variations in
treatment response between replicates a more detailed discussion of the interactions
of various treatments does not seem warranted. The' need for field fertiliser trials
employing at least P. B, Ca and N alone and in combinations, is indicated.
I