Optimising your harvest outcomeIndustry Best Practice
The 2021 harvest will be challenging. Many growers may find it necessary to rely on a new labour pool as access to foreign workers, who have formed a significant part of the harvest labour pool in the past, is impacted by COVID-19 travel restrictions.
Compared to the experienced pickers that have been available from offshore, this season’s labour pool may be less experienced, less fit, and likely to find fruit picking very demanding, so may rapidly lose motivation.
Good training programs will be necessary, particularly where it is necessary to use ladders. Ladder positioning and good picking technique are the keys to efficient picking. Instructions on which fruit to pick need to be clear to your pickers. Make sure they can confidently identify which fruit is to be picked. Picking colour can be a problem when fruit is being selectively picked by colour.
Often your picking team will have a range of capability, so those that are experienced with using ladders could team up with a less capable ground picker. Your experienced person is then responsible for the upper tree, while the other picks the lower tree.
It may be necessary to be flexible with hours of work. For instance, workers with school age children may only be available from 9am to 3pm to fit in with their family commitments. Incidentally, as fruit picking is physically very demanding, there may not be much benefit to be had pushing hours much beyond six hours until the workforce becomes fit and better suited to the job.
Picking will be less fatiguing for some workers if they are given smaller picking bags rather than the large picking bags that are usually used for pomefruit harvest. Shorter shift rotations may also help with fatigue.
Picker retention may be a problem. Many growers and contractors have overcome this problem by building a bonus payment into their pay structure for pickers who see out the season and report for work when required.
Harvest labour requires very good supervision to ensure that the correct fruit is being picked and harvest injury such as stem punctures and bruising is minimised. Most of this injury comes from fruit to fruit contact, either from placing the fruit in the picking bag, or emptying the picking bag into the bin.
The potential for pickers to damage fruit is miniscule compared to what rough tracks, fast tractor drivers and rough forklift drivers can cause.
Should harvesting rates begin to fall behind fruit maturity, it may be necessary to bypass later picks and low value, difficult to harvest blocks.
Manage colour and fruit maturity
Obtaining adequate fruit colour ahead of internal maturity parameters is the key to an efficient harvest.
Firm, well coloured fruit picked during the first half of the maturity window is much more robust than later harvested fruit. It is less prone to bruising and usually has much higher potential for storage and quality out of storage.
It is crisp, juicy, flavourful apples that get repeat sales. Attractive colour may be the incentive to buy, but if these apples do not eat well, consumers will not be back for more.
There are a number of tools we can use to improve fruit colour.
These include getting crop loads correct early in the growing season. Crop load has a huge effect on fruit colour. Over cropped trees give poor fruit colour, small fruit, poor flavour and delayed harvest. Fruit on over cropped trees will size at more or less normal rates, then at around 90 days after full bloom sizing will slowdown. If there is a sudden falling off in the rate of fruit size proactive thinning – by removing small fruit and those fruit in shaded areas – will rectify the situation and fruit will begin to grow again.
Fruit requires adequate light exposure for good colour development. Where the canopy is too dense it needs to be thinned out to improve fruit light exposure. There are a number of ways to achieve better light levels in the canopy. These include summer pruning to remove unwanted annual shoot growth, leaf blowing or plucking and lifting of branches which have lodged on lower branches. Tying up branches to improve light penetration into the lower tree is an easy way to improve fruit colour. The optimum gradient for branches is around 30 degrees below the horizontal. Fruit on very pendant branches, below 450, colours poorly due to fruit-to-fruit shading.
Red and partially red varieties colour better when fruit nitrogen levels are relatively low. Leaf nitrogen levels need to be in the lower half of the optimum range for the January/February samples.
Compared to foliage, fruit will continue to accumulate nitrogen in situations where there are high levels of nitrogen available, so a small lift in foliar nitrogen levels will indicate a much larger lift in fruit nitrogen content.
Forcing tree roots to tap deep soil water reserves during the growing season has been shown to lower nitrogen uptake and improve fruit colour development. It takes about six weeks for nitrogen to go from the roots into the fruit, so irrigation near harvest which wets the top soil will not influence fruit nitrogen content to the same extent as regular irrigation that keeps the top soil moist through to earlier part of the growing season.
Where there are problems with fruit colour due to excess nitrogen it is necessary to try and limit nitrogen uptake during the growing season. This can be done by increasing the width of the grass sward between the rows so the grass will compete more for soil nitrogen.
Trunk girdling is another method which can be used to lower nitrogen levels in the tree. Trunk girdling can be effective as late as six weeks before harvest. Trunk girdling may also advance maturity, so check maturity to make sure that maturity is not getting out of control.
In recent years reflective mulch has become a very important tool for lifting fruit colour and pack outs. Experience indicates that reflective mulch will be more effective on blocks with a history of good colour than on blocks with a history of poor colour.
Where there is a history of poor colour in a block the best way to overcome the problem is to pull the block out or graft it over to a high colour strain.
Reflective mulch needs to be put out four to six weeks ahead of expected harvest. In Australia it is also important to try and avoid the heat waves with reflective mulch. If you encounter an unexpected heat wave and the mulch is out, it is wise to pull it back so that the grass sward can help to keep the ambient temperatures lower.
Managing reflective mulch can be quite labour intensive so it is necessary to seek out efficient ways of dealing with the mulch.
Colour development is best when there is reflective mulch on either side of the tree. An efficient way to use mulch is to lay it in half row lengths, then after two to three weeks pull it through to the other half of the row. With this approach, lay it at one end in every alternate row, with it laid down at the other end of the in between rows. The objective is to have reflective mulch on one side or the other side off the trees all the time the mulch is out.
Managing fruit maturity
Retain® and Harvista® are tools which can be used to manipulate fruit maturity, so it is now possible to spread harvest to reduce peak labour requirement.
Retain® needs to be applied four to five weeks ahead of the anticipated harvest date. When used correctly, a maturity delay of ten to fourteen days is possible. Provided crop loads are optimum, fruit will continue to size during this delay period so the increase in fruit size and yield will usually more than cover the cost of the Retain® application.
Harvista®, a sprayable form of MCP, is applied closer to harvest, usually within 21 days of picking and up to three days pre-harvest.
The mode of action of these two products differs so it is possible to use them in sequence to lengthen the harvest delay period.
Retain® is sometimes used closer to harvest to hold up maturity of later pick fruit. This use pattern enables harvest to commence at the normal time and is useful to give more time for later picks.
While Retain® is used for harvest management, watch fruit maturity because once the impacts of Retain begin to wear off, fruit maturity can advance quite rapidly.
There is now several years commercial experience with Harvista® use in Australia for harvest delay so the industry should be building up its knowledge base on the product, including how various cultivars respond to it.
In regard to Retain® there are large differences in cultivars response depending on their levels of endogenous ethylene build up in the pre-harvest period. Cultivars such as the Gala group and Red Delicious are particularly responsive, as are Scifresh (trademarked as Jazz®) and Scilate (Envy™). Low ethylene producers such as Fuji are less responsive.
Both Retain® and Harvista® are also excellent for minimising pre-harvest drop problems.
With careful planning, and utilisation of all of the tools available for manipulating fruit maturity, it is possible to extend a cultivar harvest from two to three weeks out to six to seven weeks. These tools include rootstocks, use of dormancy breakers on blocks destined for early harvest and harvest delay strategies for blocks that will be later harvested.
Among rootstocks M26 is generally the earliest to ripen, closely followed by other dwarfing rootstocks, then with increasing rootstock vigour fruit maturity becomes progressively later with M793 among the latest to ripen.
There is a spread of two to three weeks in harvest timing over this rootstock range, so planning for spreading harvest by using a range of different rootstocks is a practical way to extend the harvest period where an orchard business is overweight in a single variety. Dwarf rootstocks are usually grown as single leaders, whereas the more vigorous rootstocks are multi-leader along the row to give a similar canopy form to the more intensively planted dwarf rootstocks.
Picking platforms and other harvest aids
In recent years there has been a lot of interest in picking platforms and there are now many starting to appear on Australian orchards.
Their main value is their ability to improve access to fruit to be harvested. In the absence of subsidies or taxation write-off provisions, picking platforms are capital intensive. Their main advantage is that by taking ladders and picking buckets out of the harvest, less-fit workers can be utilised, expanding the available labour supply. We estimate that in a normal working population, the proportion of the population that can pick for three months with a bag and ladder may be as low as 10 per cent. Platform technology allows the business to expand that up to maybe 70 per cent which is a big advantage in a labour supply crisis.
Because platforms are capital intensive, it is good to try and utilise them for more than the usual 8 to 10-hour day. This may mean running several shifts a day to maximise their utilisation.
They are not suited to all orchard terrains and canopy designs. For instance, they are unsuited to hilly orchards, old-style three-dimensional trees or orchards where the orchard floor in uneven.
ooking to the future I think we may see the development of hybrid systems in which the lower tree that can be easily reached from the ground is picked with a ground crew, while the upper tree is designed for platform picking.
There is a lot of design effort going into orchard platforms at present so there will be continual improvement going forward.
As a picking aid they are capital intensive, however many of them can be adapted to other orchard cultural tasks such as tree training, pruning and thinning, which will spread their capital outlay over more than just picking.
Watch this space.
As it can be wet during harvest, orchards need to be well drained for platform use and the soils capable of taking heavy machinery without becoming a quagmire.