Ruth Underwood, Fruition Horticulture (First seen in The Orchardist, June 2016)

Winter is a busy period in kiwifruit orchards. Some of the work has flexible timing but there are a lot of tasks to complete before the spring growth starts. In this article, I’ll talk about the winter tasks, fitting them together and a few reminders of what is important. The late harvest in 2016 may squeeze winter activities and the weather is another factor altogether!

Winter pruning
Winter pruning is your key winter activity. The quality of work done at winter pruning sets up your crop for the 2017 harvest and affects your income through to at least mid-2018. You need a quality job done, not just a job done in time. Peter Mulligan’s article in the April Orchardist covered kiwifruit winter pruning specifically so I won’t go into detail here. There is some flexibility about timing of pruning but it can be a scramble to get the job done as there’s limited fine weather. Pruning dry vines is an important Psa prevention strategy. Set priority areas for pruning – usually varieties with earliest likely budbreak to be done first; with contingencies of choosing older vines and varieties more tolerant to Psa to be done if the weather is marginal but time is running out. Plan to do varieties in frosty areas likely to lose their leaves first if lack of leaf-fall is delaying a start.

Communication with pruning teams
Ensure you have clear instructions about how you want the pruning done and regular communication about which blocks are the next priority, especially if it changes as the winter progresses. Keeping up with mulching will help to maintain the work rate of the pruning team.

Budbreak
Timing of budbreakers is very important. It is best to apply them to pruned and tied down vines. However, calibration, timing and weather are also important. Satisfactory results have been achieved on unpruned vines or vines pruned but not tied-down where the application is directed to cover the canopy as it is presented on the day of application.

Establishing New Varieties
Growers who’ve applied for the additional Gold3 license available by tender this year will find out results on 20th June. If you’ve put in a bid, you’ll need to plan the operation side of implementing the re-development, including which part of the orchard you’ll use and booking in specialist grafters. It’s crucial you don’t presume success by cutting back vines before you know tender results! Stump grafting is easier to manage through the first season but notch grafting may provide a better financial result if the vines are managed well.

Looking after younger vines including male vines
One key to sustained orchard performance is reducing variability. If you have replacement vines among the orchard, male or female, check them over separately before pruning that block. Similarly, if you have a whole block of young vines, use the dormant period in winter to do any fine tuning you missed during the growing season. This is your chance to make adjustments like replacing the end of a weak leader, cutting out any Psa cankers, reducing the number of trunks or leaders, removing constricting ties or trimming back a neighbouring vine to give them some space and priority. Timing for this is flexible but where younger vines are among older ones, it works best to go through ahead of the pruning to give them their special attention. These vines often miss any special attention by contract pruners so it is useful to separate the task from general winter pruning of the block.

Looking after the soil
The soils most Bay of Plenty kiwifruit are grown on are so good for the crop we really can forget how forgiving they are. In some other regions protecting the soil is much more ‘in your face’ as machinery access is limited to dry periods. Activities like mulching and spreading fertiliser may have to be delayed, sometimes for weeks, because machinery would get stuck driving into the block. We still should look after all soils though by avoiding driving heavy machinery on them when they are wet, returning organic matter through mulching and diverting run-off from tracks so it doesn’t scour off the topsoil. The reward is well-aerated soil that also stores water well, provides good physical access for roots and a hospitable environment for beneficial soil organisms, plant root functions and nutrient cycling.

Orchards where the soil has been recontoured provide less favourable growing conditions, even when the contouring was done well and many years ago. They tend to be too wet after rain, but don’t hold the moisture for drier periods and roots may be short of aeration. These areas benefit from special attention to avoid further compaction, add organic matter, ensure they don’t receive surface run-off from other areas and provide drainage. Ripping in wheel tracks may help reduce surface run-off and is best done in drying soil conditions.

If you’re planting new vines, avoiding wide-spread cultivation preserves soil organic matter and natural drainage. Also check mechanically-dug planting-holes don’t have smoothed, smeared walls which restrict root access to the soil beyond the planting hole. Running a sharp spade down the walls of the hole to make vertical slashes will help roots of the new vine to spread out into the soil.

Soils are wetter in winter even if monthly rainfall occurs evenly, as there isn’t high plant water uptake, especially from dormant vines! Vines are most susceptible to waterlogging in spring because the soils haven’t cleared their usual winter water-load but the vines have ended their dormant period. If your orchard is drained, winter is the time to check and maintain the drains before the new season. Outlets need checking and clearing; including checking any system preventing backflow in tidal areas or where drains feed into a river with variable water level.

Photo 1: The wheel track to the left of this photo has become a route for water run-off after rain.  Diverting run-off, adding organic matter and encouraging sward growth by opening up the vine canopy will help this area improve.

Fertiliser
Timing to apply most fertiliser materials has some flexibility. If lime is recommended to raise the soil pH, aim to spread it as soon as you can. Next comes the base fertiliser and any bulky material being applied, such as compost or chicken manure. Side dressings that include nitrogen are best applied close to budbreak and in the early growing season when the vine is becoming active. Access for fertiliser spreaders is an issue as they are under time pressure too. Some only need to drive down every second row so check with them if your work is behind, as mulching alternate rows may be enough before the fertiliser is spread.

Pest and Disease Control
Winter can be important for control of cicada, scale and passion-vine hopper insects. Increased pest pressure can occur when the autumn or winter have been mild. Take account of your previous control strategies and packout results when deciding how to approach this winter. Psa disease control continues all year in response to weather conditions and orchard activities. Always check your information is up to date about what material, rate, date and crop stage to apply it at in terms of both providing effective control and meeting export standards. There is good information on-line which is regularly updated. Don’t forget the cultural aspects of control such as what vegetation is around the orchard that may help or hinder pest control.

Existing armillaria sluicing holes may need to be cleared or new vines sluiced. If a vine appears doomed, remove it, taking as much of the infected root system as you can. The canopy can be filled by extending the neighbouring vine in close plantings or replanting. If you replant, use plenty of compost in the planting hole and gently spread the roots of the young vine.

Photo 2: This kiwifruit vine has been sluiced to control armillaria root-rot.  The sluicing hole has been kept clear of leaves and debris so is readily visible to people working in the orchard. 

Frost control

If you have a frost control system, it needs to be operational by a few weeks before budbreak, and checked again regularly during the frost-risk period. If you rely on passive frost measures like air circulation instead or as well, get them up to date before budbreak. The might mean trimming up shelter bases or maintaining gaps in shelter for air-flow; weed control or mowing to keep the sward low.

Photo 3: Ensure frost protection systems are maintained and working before budbreak.

Photo 4: Drains need to be cleared during winter to avoid damage to vines from water-logging in spring.   

In summary, the end of one season quickly runs into the start of the next. At times, work will be behind due to weather, high demand for labour or equipment problems, so tasks will need regular re-prioritising. Getting all the winter activities completed is a challenge but it is important tasks are not just done, but are done to the quality standards you want to get good results for the coming season.