|By Joshua Kato|
The Ministry of Agriculture Animal Industry and Fisheries (MAAIF) has selected macadamia as one of the money crops. According to Dr Samuel Mugasi, NAADS Executive Director, the nut has been selected because of its high value especially to the dollar markets. However, just like other crops, losses are made during harvesting and postharvest. In this article, we look at how to properly harvest macadamia.
In the month before the start of mature nut drop, ensure grass or weeds are under control and remove or use offset flail mulchers to chop up to ‘cornflake’ size pieces any significant quantities of unsound, old or immature nuts, leaf or foreign matter.
Old, immature and pest or disease-damaged nuts left on the ground will reduce the quality of the harvest. To minimise the amount of material on the orchard floor requiring removal or chopping up, undertake pruning operations (side trimming and skirting) as soon as possible after the previous season’s harvest is complete.
This ensures that prunings are well broken down by the time of the next harvest. When herbicides are used to control weeds, avoid spraying fallen mature nuts. Where it is necessary to use herbicides during the harvest season, spray where possible immediately after nut pick-up.
Nuts are harvested after they have fallen to the ground. Farmers can use mechanical harvesters. Hand harvesting off the ground is practised on some smaller orchards and where steep slopes preclude the safe use of mechanical
harvesters. It may also be necessary on occasions during extended wet weather. Most mechanical harvesters are of the finger-wheel type—a range of these is available to suit different orchard sizes and conditions. Clean mechanical harvesters before use to reduce contamination of harvested nuts. Also, clean harvesters before shifting to a different orchard to avoid spread of diseases and weed seeds.
Harvest nuts at least every four weeks, particularly during extended wet weather or where nuts are exposed to direct sunlight.
The less time the nuts are on the ground, the less the deterioration from mould, rancidity and early germination, and the better the kernel quality. Ensure pick-up is efficient to avoid nuts being left on the ground until the next harvest round. These may deteriorate and reduce the quality of the next pick-up.
Keep nuts from different harvest rounds separate, particularly with early season harvests that often have high levels of immature nuts. It may be an advantage in the future to harvest, store and consign varieties separately. Where possible, harvest varieties with different processing characteristics separately.
Provided they are mature, nuts can be harvested directly from the tree. Tree harvesting is necessary with sticktight varieties such as Own Choice and Beaumont, unless ethephon is used to promote nut drop. For tree harvesting, the nuts are knocked, dropped or shaken from branches onto a mat spread below the tree. An indication of nut maturity is when the inside of the husk changes from white to brown. However, it is recommended that a sample of the nuts be first tested for maturity using the flotation test.