Harvesting Sun Light — Canopy Management Field Day Report
By Jim Patch and Kevin Quinlan, MPC
A successful canopy management field day on July 12th 2012 reviewed four different strategies used by growers.
Ninety growers took part and the field day concluded with a BBQ lunch at Charlie Sultana’s farm.
Many in the macadamia industry believe lack of light penetrating trees in mature orchards is having detrimental impacts upon production, pest and disease management ,whilst increasing soil erosion.
On the day, four options were examined:
- Row removal and replanting – Colin & Fay Worner’s Clunes orchard;
- Row removal – Guido & Claudette Conte’s orchard;
- 50% tree removal (every second tree) – Tony & Lena Kempnich’s orchard;
- Limb removal – Charlie Sultana’s orchard.
Considerable industry research on canopy management has found there isn’t a ‘silver bullet’ – each strategy has its pros and cons.
Growers have observed, as macadamia trees mature, they become denser, the tree centre and lower limbs die-out and the crop moves to the top of the tree. This may coincide with canopies becoming externally dense (one cause may be continual hedging) and limited light reaching the centre of the tree which limits leaf, fruiting and fruiting wood growth.
Limbs may also grow more vertically as competition for light increases in mature orchards and fruit production on vertical limbs is often less than that on horizontally angled limbs.
Row removal and replanting at wider spacings
Jamie Greenhalgh manages Colin & Fay Worner’s orchard and explained the row removal and replant strategy used on the farm.
“The Clunes orchard was planted in 1987 – 88 with varieties 344,741, 333 & A16 at 7 x 4m spacings. The trees grew well and produced good crops in the early years but as they have aged, the orchard has become very cramped for space”, said Jamie.
Jamie has found insect management has become difficult (as it is hard to spray to the tops of the trees, let alone monitor the orchard), grass in the inter row has become non-existent, soil erosion has increased and production has decreased.
“It was very difficult to harvest from under the tree canopy as the orchard floor remained wet for extended periods because sunlight didn’t reach the ground and there wasn’t air movement to dry it out either” he said.
Nut quality had the potential to be compromised, as nuts on the ground remained wet for long intervals between harvest rounds in wet harvest seasons. Nut set was also reduced as a result of the damp/dark conditions in the orchard.
Jamie had seen the effect of removing trees. “In 2002 on one of our other farms, we removed every second row from a block of 2000 trees after harvest . The production was 27t from 2000 trees before we started row removal. Wiith half the number of trees (1000) the block we produced 34t of NIS in 2004”.
Jamie devised a replanting strategy for the farm. The process involves removing two rows and leaving one. In the centre of where the rows were removed a new row is planted.
To assist with cashflow, on a bare section of the orchard a new block of 1,000 trees was planted before tree row removal in the mature trees commenced.
The aim of this new planting was to produce an improved cash flow during the period of time where replanted trees were not producing a commercial crop.
In 2006 the first block had trees removed and a row replanted. During the next two years, all the A16 trees were removed from the farm. Jamie said the A16’s had been a problem to manage in the orchard due to husk spot and the stick-tights they have in them.
A bulldozer was used to remove trees. Trees to be removed in one row were pushed towards other rows to be removed, to limit damage to the remaining tree rows.
The dozer then pushed batches of up to 10 trees from the site at a time. Jamie said, “tree pushing was quick and efficient”. The problem they faced after removing the trees was finding a place to stack them.
The wide inter-row created was replanted with one row of variety 246 trees. The tree spacings are now 10.5 x 4m. The varieties that remain following tree removal and row replanting in the first block will be 246 and the existing mature 333s. The 333’s have been kept as Jamie has found they bear consistently well and are easy to manage, suffering little insect damage.
The work is ongoing as there is still another block of 344/741 trees to be removed and rows replanted. In the first completed block the new 246 replants are about to commence production and the existing 333s have now started to spread outwards, with branches becoming more horizontal.
The results Jamie has observed are:
- An increasing yield per tree for remaining mature 333 trees;
- Grass cover on the orchard floor;
- Reduced soil erosion;
- Removal of a tree variety that caused costly management problems (A16);
- Reduced insect pressure;
- Increased coverage/efficiency of insect/disease management spray applications;
- Improved harvesting conditions from faster drying of the orchard floor and increased quality due to the shorter harvest intervals now possible;
- An opportunity to plant a variety that has performed well on their farm.
Row removal at Guido Conte’s orchard
Guido owns and operates a 4,100 tree orchard at Tregeagle. He planted the first 2.1ha block of 1000 trees in his orchard in 1988 at 7 x 3m. The trees grew rapidly and by year 14 the trees had merged across the inter row.
Hedging was commenced at year 14 to allow light to penetrate to the orchard floor and machinery access.
Guido found the ground cover had disappeared, soil erosion was becoming a problem and the trees had started to hollow out with few effective leaves left inside the canopy.
When the trees reached 18 years of age (2006), Guido noticed the production had been reduced to 4.5t/ha, from a high of 6.5t/ha. Guido put this down to there being very little effectively lit canopy left per tree.
As a result, in 2007 Guido decided removing trees was his best option, and decided to remove whole rows. Trees in the first block thinned were var.333, 508 & 344. All trees were about 8m tall at the time of row removal.
Guido decided to remove every second tree row (with the exception of the outside row on the southern side) from his front block in August 2007, to produce a 500 tree block at a spacing of 14 x 3m.
Guido remembers growers telling him that at the time of removal, this spacing appeared to be excessive.
Removed trees were prepared for removal by being heavily hedged on both sides for two years. This provided extra growth space for the retained trees.
Trees to be removed, although heavily hedged, provided some crop/cash flow in those two seasons before being removed.
Guido used a contractor with an excavator and chipper to remove the trees and have them chipped on-site.
The removal method lifted trees out of the ground with an excavator, positioning them on the ground with all trunks facing the same direction.
The site where trees had been removed was then ripped by the excavator to remove surface roots. A second excavator picked up trees and fed them into a radio controlled, self propelled 800h.p. chipper that reduced a tree to chip in about three minutes.
Guido said this operation cost $25.00 per tree in 2007 and was effective, producing a fine chip.
The entire chip produced was spread evenly across the orchard floor by Guido using a ‘Bobcat’. He then mulched it to level the chip and introduce soil into it to increase its breakdown rate.
Smother grass was then planted to protect the orchard floor from soil erosion. Guido has found the retained trees have not increased in height since thinning.
Yield from the block decreased the year following removal but has been increasing steadily every year since.
In 2011 the block produced over 4.5t/ha (which was a disastrous year for most growers). In 2012 production dropped slightly to 4t/ha and Guido believes this was because of poor nutset caused by rainfall at flowering.
Trees in this block have now spread-out, with limbs becoming more horizontal and there is leaf, flowers and nutset from the bottom to the top of the tree canopy. Guido believes significant hedging may never be required.
Guido is now preparing other blocks on his farm for row removal. His system involves hedging both sides of the row he wishes to remove, allowing the remaining rows to grow into the space created. After hedging the row back for several years, Guido will then remove the row. The aim is to maintain production in the orchard, allowing remaining trees to spread and take advantage of the increased space.
Guido has continued removing entire rows of trees in the oldest /close planted blocks of the orchard and has observed the block of 344s he recently thinned is also improving in production and kernel recovery.
Guido beleives row removal has had many benefits:
- Trees expanded rapidly into the inter row as limbs ‘drooped’ towards the horizontal;
- Tree height contained through lack of competition for light;
- Many new shoots/fruiting wood appeared inside trees;
- Light entered right through trees to ground, with leaves and nuts to bottom of trees;
- Soil health improved by the addition of organic matter from the wood chip from chipped trees.
- Improved light/airflow decreases pest and disease pressure;
- Trees are easier to spray effectively;
- Production is returning towards what had been produced by that block in three years since thinning was completed and is expected to continue increasing;
- Improved harvest conditions from a faster drying orchard floor;
- Trees now have productive limbs from skirt to apex;
- Kernel recovery has improved due to increased sunlight in trees.
Forestry Mulcher for clearing/chipping macadamia tree demonstration.
Simon Richens from S&G Agricultural Contractors demonstrated his 160HP Fendt powered ‘Berti’ forestry mulcher at Guido Conte’s orchard for the field day.
S& G Agricultural Contractors own multiple units and these range in size, from 160HP to 300HP.
Normally for macadamias the forestry mulcher is mounted on the front and a second mulcher is carried on the rear. This second mulcher is used to chip the material even finer to produce a small chip size.
During demonstration the machine felled the tree, ground the stump to ground level and reduced a tree to small particles in short order. If a grower wishes, they can fell trees and have the resulting material mulched.
The chip produced was very fine and considering the secondary mulcher was not used, the size could be made even smaller. Many growers remarked that they thought after passing their orchard mulcher over the chip, they would have a good harvesting surface.
Simon said as macadamias were something they had only just started working in, they could only give a wide range for the cost per tree. So far the cost has been between $10-$20 per tree, with it expected that on average it will be around the $14-$16 per tree mark. Simon has also found that more trees may be mulched per hour if they are first felled by the grower. This also allows a grower to better direct where a tree falls, reducing potential damage to remaining trees.
50% Tree removal (every second tree) Tony and Lena Kempnich’s orchard
Tony and Lena have taken every second tree out in one block and are currently removing 25% of trees in another.
These blocks were planted at 8 x 3.5m in 1989 with varieties 344 and 741. Early on the trees grew quickly, competed with each other for light and were later hedged in an attempt to provide light and operating space between tree rows. The orchard became dark within the blocks and trees lost limbs and production in the lower portions. Production also fell as a result. Grass no longer grew in the inter-row space and soil erosion became a problem in steeper parts. The cool dark environment produced by the crowded trees provided an ideal habitat for insects – lace bugs in particular.
In 2008, Tony and Lena decided they needed to do something, and decided tree removal was the best option.
They also wanted to control waterflow in their orchard and decided to create cross drains, spaced 40 metres apart, constructed across the slope at an angle just below the contour.
These drains have proved successful in catching water and in combination with the smothergrass have reduced soil erosion.
After drainage construction, alternate trees were removed from the first block in 2008. These trees were felled with a chain saw, towed out and chipped.
The contractor kept the chip as payment for the chipping. Tony said, “Light once again reached the ground and the planted smothergrass soon covered the orchard floor. This has provided erosion protection and we now have cropping through the entire trees again”.
Remaining trees have a profusion of new shoots bearing crop. For two years after removing trees there has been some storm and wind damage in the first thinned block, but overall this has had little impact.
Tony is now planning to do some limb removal and/or light hedging in this block to maintain the light penetration to the orchard floor.
In 2011, Tony and Lena decided to start removing trees in another block that was starting to become very dark and dense.
This time they removed 25% of the trees, deciding to take a straight line of trees out on the diagonal across rows. This year (2012) they plan to take more trees out using the same pattern, reducing the block to 50% of its original density.
So far they are seeing similar results to the first block with leaves and fruiting wood returning to the lower portion of the canopy and improved yield.
Lot 2 (50% tree removal in 2008) is now the best performing block on the farm, four years after tree removal. Tony’s crop was reduced in 2010 and 2011 by both rain and an infestation of lace bugs at flowering that could not be controlled because of the ongoing rain.
Tony is now confident a configuration of alternate tree removal suits his orchard and he will thin more blocks of trees as the need arises.
Tony and Lena believe the benefits to their orchard from tree removal have been numerous:
- Production increased in the first block thinned
- Grass cover has returned to the inter row
- Soil erosion has reduced
- Soil organic matter has increased to improve soil health
- Airflow through trees to decrease pest and disease pressure improved
- Trees are easier to spray effectively
- New shoots/fruiting wood growing within the canopy
- Orchard now a nice place to work and has a high aesthetic value
Limb Removal at Charlie Sultana’s orchard
Charlie has a 14 ha/5,000 tree orchard with14 and 15 year old trees, planted at 7 x 4m spacings and varieties A4, 849, 816, A16, A38 &741.
Production from his orchard peaked in 2009 and Charlie felt it was time to look at his canopy management program.
Charlie was concerned his trees were stopping light from reaching the orchard floor, making access down the rows difficult and the grass cover on the orchard floor was diminishing. After a disastrous season in 2011, Charlie decided he needed to open up his orchard. So after the 2011 harvest, he put in a huge effort and completed limb removal before flowering for the 2012 season commenced.
All removed limbs were chipped on site and the wood chip returned to the base of the trees.
Trees now have ‘windows’ through their canopies from the limb removal, and light has been introduced into the central and lower sections. New shoots and leaves have grown inside the trees and dormant buds in the limbs within the canopy have been stimulated and nut production has been improved.
Charlie believes the tree canopy size may be contained because there is less competition with neighboring trees for light.
He also believes his orchard had an improved nutset due to the limb removal . “There are a few rows where I didn’t get to prune, and the crop I harvested from those rows was heaps less than the pruned rows. That really showed me my pruning was worth the effort”.
The grass has returned to cover the orchard floor assisting to limit erosion. The trees now have new shoots and leaves throughout the canopy area which will, depending upon variety, produce crop within the next season or two.
Charlie now sees limb removal as a viable method to contain his orchard tree size.
He intends to continue removing a small amount of limbs from his trees after harvest each year from now on. He may not remove a limb from every tree each year but would remove limbs on an ‘as needed’ basis.
Charlie has observed many benefits from his tree limb removal:
- Production appears to have increased in the first season after limb removal;
- Grass cover has returned to the inter row;
- Soil erosion has been reduced;
- Soil organic matter has been increased to improve soil health;
- Airflow through the trees to decrease pest and disease pressure has improved;
- Trees are easier to spray effectively;
- New shoots/fruiting wood are now growing within the canopy;
- Possibility of containing the tree size;
- Machinery movement in the inter row is improved;
- The orchard floor dries quicker to allow frequent harvest rounds.
The farms visited showcased a small selection of different canopy management strategies. What was clear is each grower has a plan suiting their tree ages, varieties and management systems.
Increased light penetration into and through the tree canopy has removed the “dead heart” from the trees and there is now crop borne from tree top to bottom.
There has also been improved grass growth on the orchard floor, reduced soil erosion and orchards are easier to manage.
MPC thanks the owners and operators of the orchards visited for their hospitality and generosity in sharing their experiences and future orchard plans with their fellow MPC growers. A special thanks to all who attended and especially Charlie Sultana who made his shed available for our BBQ lunch.