MOST mature macadamia plantations suffer from die-back as their spreading branches shade the forest floor and decades of sweep-style nut harvesting scours the soil from atop sensitive root hairs.
However there are ways to improve productivity, which can fall drastically from the tonnage rates when trees were young.
Dymocks Group, owners of three macadamia plantations near Macksville on the Mid North Coast, are investing heavily in a simple curative: Mulch.
Using the inventive skills of manager and second generation macadamia grower Chris Cook, biological mulch made from municipal waste – treated first in an autoclave to kill pathogens – is being applied at the rate of half a metre per tree.
It is sourced at a very reasonable cost of $23/m and spread with a custom-made side-throwing spreader. Mr Cook envisages the treatment will have to take place at least every seven years.
Already the results are showing improved growth in root hairs and reduced die-back with a return to previous productivity taking place after two growing seasons.
Nevertheless the investment is a sizeable one, considering the three plantations contain 75,000 trees.
Being one of the southern-most macadamia plantation in Australia – only one other is further south: at Kew – it is unusual that Mr Cook has started harvest before May and after just three weeks the shed has processed 70 tonnes of nut in shell. Mr Cook expects 350t by the end of October
The oldest trees used to produce 6t/ha at their peak and some have fallen to 1.5t/ha. With an industry average of 3.5t/ha Mr Cook’s goal is to bring production back to 5t/ha using a combination of biological approaches – primarily mulch.
Insect control using beneficial bugs is also part of the program as well as a push towards more condensed harvesting periods which while reducing wasted product and labour will also minimise fungal attack on nuts that fail to drop from the tree.
Mr Cook currently buys mulch because the cost imposed by his supplier is only a $1.50 dearer than making it himself – which he previously did using sawmill waste, chicken manure and nut husk, turning it three times during its maturation.
