Specialist consultant and owner of Advanced Macadamia Consulting Kobus van Niekerk details the best way to plant macadamia trees in a newly prepared orchard.
Marking tree positions (pegging)
Once the land has been prepared, the tree positions can be marked by pegging sturdy wooden pegs into soil. Reference points such as a road or a wind break can be used to create a base line for the rows, or base lines can also be referenced on the irrigation design, the land contour or a fence.
Row direction must be decided upon according to soil types, erodibility, topography or access to light. Where the slope gets steeper than between 5% and 8 %, row direction should follow the contour as closely as possible.
Tree spacing that balances the health of the orchard and pragmatic economic sense is 8m between the rows and 4m between the trees in the row. This will eventually allow for a 2m to 2.5m work area, where tractors and implements can move between the rows with ease. This distance limits the tree growth to between 6m and 6.5m.
By keeping the tree at a height of 75% to 80% of the row width using pruning, light is allowed on to the entire tree length, as well as on to the soil. It also helps to maintain a ground cover of grass or similar suitable plants.
Pegging the land must be done accurately and with assistance from GPS, a dumpy level or a theodolite. Farmers are now making more use of GPS-guided tractors with a single tine tooth implement, drawing shallow furrows at regular intervals (8m or 16m) in a grid.
When the base line is decided on, peg out the tree rows at an 8m distance every 100m. Take care to maintain the distance accurately at 100m. Over a ridge or through a gully, it is more accurate by sight than by using a measuring tape or a marked cable/rope. A hill or a slope pulls the distances closer. Each tree position should be accurately marked using a level distance.
Diagram 2 shows how measuring along the slope actually pulls the tree positions closer, compared with the distance measured at perfectly level. These small differences over a few hectares pull the tree rows askew and out of square, especially diagonally. This is less likely to happen using GPS equipment.
In Picture 1, the tree position pegs can also be seen in straight lines in all directions.
Picture 1: Tree positions pegged on a soon-to-be-planted orchard.
Reference pegs to retain exact tree position
Once all the tree positions have been pegged, making sure the exact positioning is maintained, put in two reference pegs using a wooden plank jig as illustrated in Diagram 3.
Diagram 3: Planting jig
The planting jig is a plank measuring about 1.2m, with a notch cut in the middle and two notches cut exactly the same distance from the centre notch.
The jig is placed with the tree position peg in the centre notch. Then two reference pegs are driven into the ground, resting in the two side notches.
Picture 2: The planting jig with two reference pegs at both sides of the tree position peg.
Four or more identical jigs are necessary: two for the workers putting in the pegs and those digging the holes, and one with each planting team (at least two jigs per team).
Behind those putting in the pegs, workers will dig a hole for planting.
The reference pegs remain in place. Those who dig the holes can also install the reference pegs.
Applying fertiliser in planting holes
Once the holes have been dug, fertiliser is dropped into the base and then covered with topsoil before being well mixed. This can be done by workers doing the planting. Once the soil and fertiliser are well mixed, follow up with another spade of topsoil to fill the hole to the same depth as the medium in the bag holding the young tree.
Picture 3: The tree is positioned exactly where the tree position peg stood.
Once that is done the planting team can remove the bag. At this stage the planter should hold the open root ball with one hand at the bottom while placing the other hand on either side or top of the root ball. If a very strong root is detected at the very bottom of the medium, with a sharp bed or kink, it can be pruned. This is the only stage where any root pruning needs to be done between germination, and planting the tree.
Few trees need root pruning or trimming due to a bent tap root. At no stage during planting should the young tree be held by the stem. Once the tree is in the hole the jig can be positioned with the two outside notches snugly fitted around the reference pegs. The tree is then positioned in line with the middle notch, and the hole filled with topsoil from around the planting hole.
The soil around the tree can now be lightly compacted.
Building a dam around the base of the tree
The planting team is followed by a worker who builds a dam at the base of the tree for watering purposes. The best method is to place a small car tyre over the tree before gathering soil from the outside rim, which is then built up to the height of the tyre. The soil removed from the hole before planting can be used to build the dam. Slow release fertiliser can also be sprinkled around the tyre before it is covered with soil.
Picture 4: Building a dam around the base of a tree using a tyre
Watering the newly planted tree
Staking the tree
After filling the dam with water, one of the reference pegs should be used to stake the tree. The stake should be placed at a 45˚ angle. This keeps it out of the root zone, and prevents the twine used to secure the young tree from slipping down. Raw sisal twine should be used. Tie the tree by binding it twice or three times around the stake before looping it around the tree.
The irrigation system can also be placed into position.
Once all the trees are planted the tractor can hook up the water bowser and fill each base-dam with water. This is to ensure proper soil root contact as soil washes into the plant medium and air is removed from the immediate soil volume around the tree and the plant medium.
