Managing the season you are in
As first seen in the Orchardist, October 2018
Ruth Underwood, Horticultural Consultant, Fruition Horticulture (BOP) Ltd
Every kiwifruit growing season is different. What happened last season is often top of mind and we set out ready to solve or prevent the problems of last season. The real success comes when we are able to solve or prevent the problems of this season!
Many of you will have come off one of your best kiwifruit yields in recent years at the 2018 harvest. How do you avoid a dip in yield for 2019? In this article, I’ll describe some strategies through the rest of the season to increase the chance of the next harvest being as good as the last one, by focussing on the season we’re in.
Put on your fertiliser to support spring growth
Support canopy growth in spring. Spring is when most of the nutrients required for the season are taken up by kiwifruit vines. Supply from cycling of nutrients in the soil may be limited by cool soil temperatures, so the fertiliser component of nutrient supply is especially important in this spring period. We have to be judicious with fertiliser quantities, to conserve limited world-wide resources, so part of using them efficiently is applying them in good time for peak vine uptake.
Minimise canopy interference in spring
Kiwifruit has a relatively long period between budbreak and flowering compared to other deciduous fruit. This period is a great opportunity for the vine to build resources in the canopy before the demands of flowering and fruit growth start. Canopy work in this period should be minimal and aiming to direct where growth occurs, but only removing a small portion of the developing leaf area. Crushing tips or tipping are good strategies. Leaves take over a month of development before they are contributing to vine resources, so we need to get this leaf-area workforce up and running as quickly as possible. Rapid canopy development in this pre-flowering period is particularly helpful if a high crop the past season or other stresses like a dry autumn have depleted vine resources.
In spring, keeping the sward short and ground fairly bare helps to prevent frost damage
Minimise soil compaction
It’s been pretty wet recently, and running heavy equipment across soggy soils creates compaction damage that impairs soil storage and supply of water and nutrients, and doesn’t fix itself quickly. Compaction can make the soil too dense, poorly aerated and slower to warm up. Avoid excess trafficking of heavy equipment on wet soils and consider reducing weights such as by working on the better areas when the sprayer tank is full or using partly-filled sprayer tanks (although check the measurements are accurate for part-filled tanks), or even accessing tracked equipment if that can be used for the activity needed. Also identify areas that may benefit from adding localised drainage or diversion of run-off next year after harvest. If there are areas where the ground has dried into ruts, spreading some soil or metal on the area will make it safer working in that area too.
Be ready for frosts
If you have frost protection equipment, make sure it is ready to operate and the alerts are in place. The latest damaging frost I can recall was in mid-November, so you wouldn’t want to bring down over-under sprinklers until late November. All spring growth stages are vulnerable to effects from frosts and low temperatures. Because these often occur over several consecutive days, check the system is ready to go again for the next night after each use.
Remember the passive frost measures like keeping the sward short, shelter trimmed or bases cleared. These activities help air movement which reduces the chance of cold air collecting and causing frost damage. Having relatively bare soil helps too, such as after mulching and weed control, as the dark soil absorbs heat during the day which provides a bit of warming overnight.
If it does get dry, it is the areas with more challenging soil conditions that are likely to be affected first. They tend to have a narrower band between being too wet and being too dry. If you have over-under sprinklers that are still in their ‘up’ position but it’s getting dry, apply any irrigation at a time of day when the canopy won’t stay wet for too long, as a prolonged wet canopy can promote disease including budrot. Even being next to a dense shelter belt can keep the canopy wet for longer, so watch for this and note to trim or thin such shelters if it is a problem.
Young shoots take some time to develop before they add to the vine resources
How do we recognise what this season is providing?
Counting flower buds and fruit is almost no-ones favourite job but it is one of the most important jobs in managing the orchard. These counts enable you to know how numbers are tracking compared to targets as well as to previous seasons. If numbers are down, try to figure where the drop has occurred. Is it lower winter buds to start with or fewer flowers being produced on a similar quantity of wood? Sometimes you can see if there are flowerbuds that have stopped growing or aborted – it’s useful if they were doubles and triples but a problem if you have too few flowers left on each fruit shoot or too many blind shoots.
Spring can be a volatile time on the orchard – things can look grim but only a few warmer weeks later it can be hard to find the problem areas that were so concerning earlier! Our eye is drawn to imperfections, which can seem negative, but these observations can be useful. For example, late budbreak on individual vines can be an early sign of a disease problem – watch for this in areas where you have had Armillaria root rot previously.
Do fruit thinning early – at flowerbud stage where possible
It is great we can see fruit shape features at the flower bud stage. Thinning them off before flowering saves vine resources that are then available to fuel the fruit you will carry through to harvest. Flats and fans missed for removal before flowering are sometimes not as clearly seen again until well into January.
If your counts show high flowerbud numbers, work through what potential crop that is and decide if that is feasible to carry through or whether some should be removed to a more feasible cropping level. Comparison to counts at the same time in previous seasons can be very useful here. For example, on some orchards last year we found there were about 30% more flowers than carried the best-ever crop on a high-yielding orchard. It made complete sense to remove enough to bring cropload back similar to previous, good seasons rather than carry so much and risk problems. It’s still important to leave a margin of well-shaped flowers to allow room to remove defects that show up later in the season, but not too great a margin.
When flower buds are well developed but not opening, fruit shape flaws, doubles and trebles can be readily identified and thinned off
Thinning is costly but worthwhile if your numbers are high. It allows you to space the fruit you keep across the canopy – removing more in areas where leaf-cover is sparse and matching fruit numbers to the strength of shoots – indicated by their leaf number. Where numbers are really high, ripping off weak shoots carrying many flowers will improve vine leaf to fruit ratios and may be quicker to do. Similarly, if the high flower density is mostly in the middle of the bay, just working in the centre few wires of each bay may work well and is faster. Keeping thinning instructions simple also helps to get a good job done. I’ve found a technique like only thinning shoots shorter than a handspan, and reducing them to a specified number of flowers (usually between 2-4) works well. We’ve all got different sized hands but most handspans are 15-25cm so you will be directing people to thin from the weak shoots.
If your counts show flower numbers are down, still thin off flats and fans unless there are so few of them it’s not worth putting a team through the block. When numbers are down, each fruit is precious. A gain in fruit size can help to offset lower numbers and spacing out the fruit you have may help reduce losses to pests and diseases. If numbers are down, also pay special attention to activities that reduce rejects like tying up the ends of shoots that will hang below the canopy and get battered by machinery driving through the block.
For young vines that won’t produce a commercial crop, remove flowers to direct the vines resources into growing the vines permanent framework. The purpose of leaving any flowers on these vines is to check the vine layout is as intended, such as placement of male and female vines. The other information they provide, such as timing of flower opening, is probably different to timing on mature vines, so is only useful for a new and distinctly different site or variety where all new information is valuable. Otherwise, these fruit are taking away vine resources that you want put into growing the permanent parts of the vine for commercial-scale cropping in future seasons.
If you’re spending lots on thinning, don’t necessarily plan to prune harder next winter! Thinning is expensive, but worthwhile in the crop quality as you have the ability to selectively remove the dud or excess fruit. When you prune harder in winter instead, you lose some of those options. If you’ve pruned too hard and reduce your crop, that affects your income for well more than a year.
Good canopy development before flowering provides fuel for fruit growth
Good pollination is a function of weather, pollen availability from male vines or purchased pollen, pollen ploidy and bee preparation. Keep in touch with your beekeeper about hive numbers, sugar feeding and likely dates. Don’t skimp on hive numbers if flower numbers are down. It’s still a relatively modest cost in the scheme of things and you want enough well-prepared beehives that the bees will pollinate the crop even if there are only short bursts of good foraging weather.
Pollen availability is likely a constraint. Harvesting the early male flowers for pollen won’t impair your pollination and provides a resource for bad weather or next season if stored correctly.
Always keep bee-safety top of mind, and access for trucks arriving with hives in the night. Providing water bees won’t drown collecting can help if conditions are dry, as the bees won’t have to travel too far to get the water they need.
It can be hard see enough detail to thin fruit well for quality between flower-bud stage and January
Follow-up results of winter activities
Follow up results from budbreak applications to add to your knowledge. Was the most successful timing best because of weather conditions at application time, stage of vine dormancy or amount and timing of chilling during the winter? Was it mostly to do with the conditions around budbreak time arising from those applications? It is worth thinking these things through to figure how strongly this years results are indicating the best timing for future seasons.
When we’ve had a good last season, we can be a bit unalert to the potential problems or perils ahead! What makes each season different is the combination of seasonal conditions, the growing technologies we use and the condition of the vines we are working with.
Managing an orchard is complex – conditions can differ markedly from season to season, but you can use your tools to counteract the unhelpful ones and keep track of the features and impact of the season as it develops. You won’t be able to eliminate differences between seasonal results, but should aim to minimise drops in production after high yielding years.