Over
the past few decades there has been ongoing research throughout
the international industry regarding the most viable tree spacing
for irrigated olive groves. However, as more and more trials
are coming of age and results are being published, it is
becoming increasingly accepted that the most effective spacings
for an irrigated, mechanically harvested olive grove range
from 250 to 300 trees per hectare.
The
tree spacing in these irrigated groves ranges from 8m x 5m
(250 trees/ha) to 7.5m x 4.5m (296 trees/ha). Although some
irrigated trials have shown increased crops from more densely
planted groves in early years, researchers generally agree that
the 250-300 tree/ha groves are more economically viable in the
long term. Growers looking at shorter term (10 years or less)
olive groves and/or dynamic plantings with increased crops per
hectare in the early years can gain further information
on the denser plantings from Australis Plants. Research is being
conducted for densities from 400 to 1,250 trees per hectare
in Spain, Italy and Argentina using a range of mechanical harvesting
equipment.
Recommended
spacing for olive trees is the traditional 5m x 8m (250
trees/ha). Although not quite as dense as the 300 trees/ha,
the 8 metre row spacings give enough room for the movement of
whatever size mechanical harvesters are available at the time
of harvesting, and the 5 metre tree spacings give room for
the opening of a fruit catching umbrella. Following is a list
of factors which need to be assessed when deciding on a tree
spacing for your grove.
Irrigated
or Non-irrigated?
The majority of olive groves being planted outside of
the Mediterranean have some form of irrigation system. The main
advantages of irrigation are improved tree health and resulting
increased crops which make the grove economically viable. Irrigation
allows trees to be planted closer together as they are not competing
with each other for natural rain water. If you are not planning
to irrigate your grove, you will generally need to plant your
trees on a spacing of approximately 9m x 9m (120 trees/ha). Naturally
this spacing will vary depending on the amount and season of rain
received in the region, but broadly speaking, 9m x 9m is a satisfactory
spacing for non-irrigated groves. This gives each tree 81m2 of
land from which to source its necessary water and nutritional
needs.
Mechanically
Harvested or Hand Picked?
Your choice of harvesting method directly affects the
site and spacing of your trees. As mentioned above, Olives
Australia recommends an 8m x 5m spacing to allow for mechanical
harvesters such as an Enviroharvester or Orchard Machinery
Corporation's Catchall III to work efficiently in the rows. There
are also smaller tractor-mounted shakers which can work
in narrower rows but don't forget that increased light and air
penetration into a tree will improve the tree's health and crop.
There are also some harvesters which actually consist of two machines
and two operators, one machine drives down each side of
the tree row. The first machine shakes the tree while the
other is a catching machine which collects the fruit. These machines
can also work in narrow rows. However, just because there are
harvesters that can work in a narrow, say 6m x 3m tree spacing,
doesn't mean that your trees will necessarily produce their best
long term crops at this spacing or that such a machine will
be locally available at your harvest time. Unless you are planting
many hundreds of hectares and will purchase your own harvester,
you need to consider the type and availability of the mechanical
harvester/s most likely to be working in the density of
groves near yours.
The
slope of the ground in the grove also effects the efficiency
of mechanical harvesters. According to OMC in California, a slope
of up to 25 degrees (maximum) is suitable for their Catchall III
harvesters if there is a firm surface underneath. Groves on slopes
greater than 25 degrees currently need to be hand picked.
If
you are planning to hand pick fruit for table olive processing
then you may choose to plant your trees closer than a mechanically
harvested grove. A spacing of 6m x 4m (416 trees/ha) could be
planted. However, it is still recommended that you plant on approximately
8m x 5m to allow for the invention of non-fruit-bruising mechanical
harvesters suitable for table olive picking in the future, and
again, to allow light and air penetration. Also, after eight or
ten years of growth, a row spacing of 6 metres will not allow
room for the movement of normal sized vehicles for carrying the
harvested fruit in most varieties.
Drainage
Although grove drainage is not the topic of this sheet,
there are two main points to consider. Firstly, too much
water is the worst enemy of the olive tree. Your soil type and
drainage system must allow water to get away efficiently both
above and below the ground surface. Secondly, you need to protect
against erosion in the grove. Make sure your grove layout
balances all of the points on this OLIFAX without causing
extensive erosion to your property.
Which
Pruning Method?
The shape to which you prune your tree is naturally
going to effect how close your trees can be planted together.
If, as most growers choose, you are pruning in the vase
shape then about 250 trees per hectare is fine. If on the other
hand you are planning to prune monoconically (Christmas
tree shape), then you may choose to plant slightly closer together.
(See OLIFAX 9 for more details on this monoconical method).
Many
people wonder what is the easiest method to mark the actual
tree sites onto a paddock. Although we've planted over 28,000
trees on our own nursery property for propagation purposes and
many thousands more in a private grove, we've also consulted
to a number of our large commercial clients.
Remember
that your initial marking of the rows and tree sites is
not the final one. It is simply a rough marking to show where
to spread your manure, crusher dust and possibly lime on each
site, after which you will be deep ripping the rows and
thereby destroying any accurate marking you may have done. However,
it is worth having fixed end-of-row markers which are positioned
out of the way of ripping machinery as they will be a permanent
row guide through all stages of land preparation and planting.
There
are many ways of marking tree sites. In reality it comes down
to how accurate you want to be. Some growers mark their 8 metre
row spaces with brightly coloured stakes at each end of the row
and then simply rip backwards and forwards between them.
Others do the same but run a stringline between the stakes
to mark various points along the row with additional stakes
to guide the ripping machine even more accurately. Large groves
are designed by surveyors able to give perfect tree and
row placements.
Once
the land is ripped, some growers simply pace out the 5 metre
tree sites along the centre of the ripped area (This method will
not give you an accurate and tidy grove). Others will again
run a string line or use surveyors to get the rows exactly straight.
Some use a tape measure to accurately pinpoint each 5 metre tree
site (Generally a two person job). Another option is to use a
long length of light gauge fencing wire or multi-strand stainless
steel cable on which you have already marked the 5 metre spaces
with a bright paint or electrician's tape. If the row is
very long, this wire can be pulled tight with a tractor or winch.
The 5 metre paint/tape marks could expand and contract a
bit with different tensions on the wire but it does save a lot
of measuring.
When
fixing tree positions on hill country, the rows will often
not line up due to the distances gained or lost over the undulations.
You may then choose to sight your rows by eye from a fixed point
on the row. A second option is to use a surveyor or surveying
techniques and equipment to fix the exact tree positions, despite
the terrain.
Most
growers find it best to use their permanent stake to mark each
site prior to planting. The trees can then be planted in the hole
beside the stake in such a way that they are growing towards and
up the stake. Once the irrigation and stakes are in place, four
people should be able to plant at about 150 trees an hour. Start
with two people putting the trees at each site with a vehicle
and trailer, one person digging holes and one person planting.
When the two with the vehicle have placed a few hundred
trees they too can start planting. This team with one person
digging holes and three people planting works quite efficiently.
It is then essential to thoroughly water the tree very soon
after planting.
While
your final method is up to you, we hope this summary sheet has
given you some helpful hints.
