Agriculture Reference
In-Depth Information
with dif erent growth vigour and habits. Varieties can be compact compared
to the traditional size, or their canopy shape can vary from wide to narrow.
Rootstocks will also play a vital role in tree vigour, varying from very vigorous
to dwarfi ng rootstocks. Sexually propagated plants are normally larger than
their asexually propagated counterparts. Another factor that can modify
distances is how large the tree will be allowed to grow and the pruning and
shaping carried out during initial growth. For example, a tree pruned into
a vase shape will be wider than a tree left with a central leader, while a tree
trained in a palmette system will be wide only in one direction. The severity of
pruning also plays a role.
Soil quality infl uences fi nal tree size, with trees grown in poorer soils
being smaller. Rainfall pattern and its amount in non-irrigated areas can also
reduce tree size. Sometimes the harvest practices, irrigation or the spraying
system can modify certain distances or at least make it necessary to leave some
broader spaces among certain tree rows. The exact distance will be dii cult
to establish if the crop has never been grown in that area. An approximate
distance can be established, sometimes with the help of an expert (Table 3.3).
In the middle of the last century, orchards were planted at densities of
less than 250 trees per hectare; today, tree density ranges from 200 to 2000
plus trees per hectare. In the past, tree spaces were based upon the distances
required for the adult trees; this meant a lot of wasted space before the ground
area was covered by the canopies. This practice led to a higher cost of weed
control and spraying and increased harvest cost, as tall trees (>3 m) are more
expensive to collect fruit, requiring ladders and mechanical platforms. This
adult-form concept has now changed, with a more pressing need to recover
your initial investment as soon as possible and reduce your overall management
cost associated with large, tall trees. One system being used is to plant at much
shorter distances, and as the trees become larger, the so-called temporary
or fi ller trees are pruned so as to reduce interference with the growth of the
permanent trees. Finally, the temporary trees are removed completely to avoid
further competition. A second thinning of the remaining trees is sometimes
performed once they have grown larger, in order to leave the fi nal number of
trees per area. This system will require larger early investments in trees and
maintenance, which will need to be balanced against the larger returns and
income during this early orchard development period. In some situations, this
practice may not be worth the extra cost and alternatives such as short-cycle
vegetable crops or even widely spaced banana or papaya may be alternatives.
PLANTING
In a good soil with irrigation and which has been properly prepared, a planting
hole slightly larger than the container holding the root-ball can be used. This is
normally a 30 by 30 cm or a 50 by 50 cm hole made using shovels or augers.
