Agriculture Reference
In-Depth Information
Table
.
The effects of rootstock
planting density combinations on
yields following planting in
×
Average yields per year (tonnes ha
−
)
Rootstock
Seedling
'M'
'M'
Trees per ha
Tree form
Standard
Spindlebush
Hedgerow
Cultivar
'GD'
'S'
'GD'
'S'
'GD'
'S'
-
.
.
.
.
.
.
-
.
.
. .
. .
-
.
.
.
.
.
.
'GD', 'Golden Delicious'; 'S', 'Starking' ('Red Delicious').
Data from Hungary, abstracted from Gyuro ().
by discounted cash flow analysis ( Jackson,
) to evaluate overall orchard
system profitability. Moreover the prices which will be obtained in the distant
future are always uncertain. Precocious cropping, i.e. cropping early in the life
of the tree, therefore has a value much greater than might be inferred from
its effect on accumulated yield over the life of the orchard. There are direct
effects of rootstock on the precocity of flowering and fruiting at the individual
tree level. Tubbs (
) concluded that precocity may occur independently of
a dwarfing influence and there are precocity-inducing rootstocks within each
vigour class. 'M.
' has long been regarded as outstanding in this respect but
'MM.
' also induce early crops. However, the most important
effects of rootstock on precocity are at the orchard level. As a result of the
much greater number of trees per hectare which can be planted with trees on
dwarfing rootstocks, the early yield per hectare is much higher even if yields per
tree are similar or lower (Table
' and 'M.
). This effect is accentuated when the trees
on the more vigorous rootstocks are pruned relatively severely in their early
years and defruited to facilitate development of a strong branch framework.
.
Effects on yield to tree size ratio
The ratio of fruit yield to tree size reflects the efficiency with which the products
of photosynthesis are partitioned between crop and vegetative growth, i.e. it
is similar to the harvest indexof annual crop plants. This ratio, for apple
trees, is partly dependent on tree size so the effects of rootstocks on it are not
independent of their effects on size itself. This is because once a canopy is
of more than a certain depth any further increase in canopy depth does not
increase the volume which can produce good quality fruits: it simply increases
the amount of excessively shaded and unproductive volume. It is therefore
to be expected that trees on dwarfing rootstocks or with dwarfing interstocks
