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Field Day at David Jones’ Farm

An informative “ orchard walk” style field day was conducted at David and Ann Jones ‘Tweebreena’ property in October 2012 and was well attended by sixty five people.

Part of the MPC field day group at Tweebreena orchard discussing gully erosion management

Part of the MPC field day group at Tweebreena orchard discussing gully erosion management

Featured topics were:

  • Working safely near overhead power lines in orchards
  • Canopy management – tree removal at ‘Tweebreena’
  • Nut in shell drying using a ‘Bungay style drying system’
  • Erosion control

Working safely near overhead power lines

Michael Dall from WorkCover addressed the danger to macadamia growers when working near power lines in their orchards.

There is a Code of Practice – Work Near Overhead Power Lines available to macadamia growers, setting out the permitted safe working distance which must be maintained from power lines.

The Code illustrates various voltages of power lines and the critical factors which apply. The code is available from the local office of WorkCover or on line at www.workcover.nsw.gov.au

Canopy Management

Using tree removal the Jones family embarked on a canopy management plan to introduce light back into their mature trees and onto the orchard floor.

The orchard has two plantings with two different densities. The first in the early 80’s was on a 10 x 5 metre spacing and has 246, 508, H2, 344 and 741 varieties. The second planting in the early 90’s was planted at 8 x 5 metres with 344 and 660.

The close spacing of this second planting caused trees to compete for light, creating tall trees with hollow centres and little canopy growth near the base due to lack of light penetration.

These trees have expanded to cover the inter-row space which introduced problems of loss of ground cover, soil erosion, and an orchard floor that remains wet through harvest with a subsequent major reduction in yield.

Greg Jones said: “Work to remove every second tree in every second row (25% tree removal) in the 8 x 5 blocks began in 2010.Thinning of the remaining rows will take place at a later date. Little sunlight reached the orchard floor in the 8 x 5 blocks and production was very low. These areas did not dry-out during harvest and harvesting was very difficult in the wet conditions. ”

“Since the tree thinning” said Greg, “we now have a lot more sunlight in the trees and on the orchard floor, ground cover is returning in the form of weeds and some grass and the ground dries out much better. We have planted smother grass in these areas as there is now plenty of light to allow it to grow. The trees are producing new shoots and are opening up and filling in the space from where the trees were removed.”

The removed trees were stacked up and then taken away by Surfmill contracting for free as part of the co-generation power plant at Broadwater Sugar Mill.

This first stage of tree removal was a big job, with trees cut and tractors used to haul the felled trees out. To make the job easier and to retain the wood chip as a mulch on the farm, David Jones recently bought an 18 inch self powered chipper and a medium sized excavator with a grab to feed it. The remaining 8 x 5 blocks will have 25% of the trees removed by felling with chain saws. After felling it will be chipped, with the wood chip spread under the remaining trees.

“After we finish the 8 x 5 metre blocks we will probably start on the 10 x 5 blocks. We will see how this work goes and then make our decision based on the results”, said Greg Jones.

Nut in Shell drying.

David Jones (centre) describes his Bungay style macadamia drying system and how it has assisted in post harvest quality retention

David Jones (centre) describes his Bungay style macadamia drying system and how it has assisted in post harvest quality retention

Tweebreena a 40 tonne ‘Bungay style’ macadamia drying system

“We had to hold the nuts in the outside blowdown silos for far too long before we could resort during wet weather. As a result of the nuts stored and remaining wet, we had a reduction in quality from brown centres, discolouration and mould. This new system dries the nuts quickly and efficiently and we can get them to the factory for processing with the original quality retained. The bins hold about a week’s harvest” said David.

Air recirculated through the four by ten tonne bins is sourced from just under the roof in the dehusking/machinery shed. Dry air is pumped by fan in the base of each bin through the nut bed where it accumulates moisture from the nuts.

When the circulated air accumulates to a pre determined moisture level, an exhaust fan purges some moisture laden air from above the nut bed. During purging new dry air is introduced and the cycle re-commences. If the introduced air is not sufficiently dry to be effectively used, a bank of electrical elements in the intake duct is turned on by the system. Heat expands the air which can carry a higher level of moisture. The elements may be in use for as little as 60 seconds in this process. When the nuts reach a pre determined moisture level the computer controlled system closes down.

The original ‘blow down’ silos are now only used for pre delivery storage of dried nut in shell.

Erosion Control.

Trees had been planted across a steep gully at the rear of the orchard prior to purchase by David. This gully traverses the tree rows for some 250 metres and carries a lot of water during a heavy rainfall event. Trees planted in the gully shaded the ground and as a result, grass died out.

With no protection, the gully eroded and the area became very difficult to manage and caused problems for harvesting.

The gully restored following damage created by soil erosion

The gully restored following damage created by soil erosion

With assistance from Gerry Ryan of the Catchment Management Authority (CMA), a plan to reconstruct the gully was formulated.

In 2009 trees were removed from the gully allowing sufficient light to reach the gully base so grass could regrow.

Large chunks of crushed rock were spread across the gully to revert the base shape from a ‘V’ to a dish shape. Rocks were then covered with soil.

The area was rolled and seeded with millet, which grew rapidly and held the soil in place. Straw bales were fixed in place across the gully at 24 metre intervals on tree lines to slow the flow rate of water during rainfall. Then on June 3rd 2010 the area was drenched by a rainfall event which delivered 200mm in a few hours. Much of the work held firm. There was however a trench formed down the centre of the gulley and several holes formed that corresponded with the tree rows where the soil may have been less compacted.

To fix the damage the holes and small trench were filled with soil using a tracked ‘Bobcat’, re-rolling the area, laying a jute mat and sowing a grass mix to stabilise the soil.

The jute mat was used because it gives temporary protection to the soil surface until the grass establishes. If there is heavy rainfall while the gully is regressing, the run off water will flow over the upper surface of the mat and not scour out the soil.

The jute mat covering is 4.0metres wide (two widths of 2.0m mat were used) and runs for the length of the gully. At the time of the field day the grass mix had started to germinate and there were grass shoots starting to protrude through.

The jute mat and seedlings emerging through it

The jute mat and seedlings emerging through it

The jute mat and seedlings emerging through it

Gerry Ryan from the CMA said “the mat has to be well pinned down to a smoothed soil surface to ensure that the grass seed germinates and grows through the mat, thus holding the mat in place. If the soil surface isn’t smooth, the seed germinates and grows under the loose mat, not through it. This causes the mat to be lifted by the grass and may become less effective in stopping soil erosion”. The jute mat should rot away in about six months, leaving the grass to hold the soil in place.

The block of trees that the gully runs through may now be harvested without the difficulty that has been experienced.

Did you know that the Northern Rivers CMA has grants available for works such as repairing this gully? To find out more contact Gerry Ryan at the CMA on 02 6627 0170.

MPC would like to thank the Jones Family for hosting this field day and showing us the changes they have been making on the farm. We also thank them for sharing their experiences and knowledge with all of us