Viticultural Practice

  1. Trunk Diseases
  2. Canopy Management
  3. Subsurface Irrigation and mowing
  4. Intensive use of Legumes as a way of introducing Nitrogen organically into the Vineyard

Trunk Diseases

Henry Manufacturing has undertaken very little work in the area of grape trunk diseases.

At the 2017 New Zealand Organic Winegrowers Conference, the following presentation (listed with permission of its author) was given by Francois Dal. It provides an unusual degree of insight into how trunk diseases (short and long term) can be dealt with by well planned and executed pruning.

We list this presentation here as we wish to support good viticultural practice.

View the presentation Pruning to limit trunk disease, Francois Dal

Canopy Management – as it pertains to High Vigour Sauvignon Blanc

Within the New Zealand context, canopy management/canopy density may have a profound impact on how well agrichemical products perform on the various grape diseases. Good coverage is particularly important for contact fungicides, largely determining their effectiveness regardless of whether organic or synthetic.

Over the decades within New Zealand, Henry Manufacturing has undertaken many trials, including independent machine sprayed trials comparing its products in full season programmes against what was regarded as the best industry synthetic standard at that time.

In most instances, regardless of variety or location, performance equivalence was achieved; the exception being highly vigorous Sauvignon Blanc grown on a 4 cane VSP system in the upper South Island. This production system accounts for the majority of New Zealand’s Sauvignon Blanc production and in many respects these vines are not grown in a conventional manner – referred jokingly with the New Zealand industry as the ‘anti grape’.

The issues confronting Henry Manufacturing in obtaining good commercial efficacy of its products within this particular industry segment, are not about Sauvignon Blanc, but simply multiple layers of leaves that prevent spray coverage through critical periods; the most critical period being pre-flowering to perhaps 4 weeks after fruit set.

In the 2019-20 season, Henry Manufacturing supported research into various shoot thinning strategies within 4 cane VSP trained Sauvignon blanc vines looking at the impact of the changes to canopy management on canopy cover, spray penetration and vine fruitfulness. Research will likely need to continue for a number of years.

The trial was conducted on a commercial vineyard in the Dillons Point area of Blenheim, Marlborough, where deep, fertile silt soils and a high water table produce a dense canopy. Seven shoot thinning treatments were used in an attempt to modify the canopy density.

The full report can be found here.

To summarise that report - overall, the thinning treatments did not produce the differences in the canopy that were hoped for. Various assessment methods did not disclose a significant improvement in spray penetration that would lead to acceptable disease control, except in the head of the vine where any shoot thinning delivered improved coverage.

While the Late Full Monty treatment showed the best result for spray penetration in the wettable papers assessment, the timing of this treatment was considered to be too late as the growth was too far advanced for easy removal.

Yield assessment of the various treatments was not undertaken due to Covid-19 lockdown, but it was certainly observed by the advisory group that the number of bunches in the Full Monty treatments were lower compared to the other treatments. The overall yield for the block was 22 tonnes per hectare and that was after the powdery mildew outbreak in December resulted in significant amounts of diseased fruit being removed.

Any improvement to fruitfulness would only be seen in the following season.

In the 2020 -21 season, research will be undertaken using an alternative trellising system - ‘splitting the canopy’, ultra early specific leaf removal and a regime of different machine leaf plucking timings on a 4 cane VSP trellis.

Research and Trials

Sauvignon Blanc Canopy Management Trial, Giesen Vineyard, Dillons Point Rd, Blenheim, Marlborough, 2019-20

Subsurface Irrigation and mowing

Wherever Chris Henry has seen mowing as a sole strategy of weed control, significant loss of yield / de-vigouring of vines occurs in the seasons following. Getting economic yields back is very difficult, particularly if trying to do it organically. See also section below on introducing nitrogen organically into the vineyard.

With subsurface irrigation, mowing alone might work. Mark Allen and Chris Ireland presented at Bragato 2019 (view here) showing the success of subsurface irrigation and technology advances. The principle is simple, bury the irrigation pipe to water the vines and deprive weeds of water and allow summer to desiccate them. Reliability is high, checking is simple. Another approach more suitable for mature vineyards has been developed at Amisfield, Central Otago involves a formed 100mm deep trench in the centre of the interrow which irrigates both the vines and legumes (view here).

For organic growers the economic advantages are there to move away from cultivation. For conventional growers with glyphosate resistant weeds, this provides a far better long-term solution than moving to residual herbicides.

Intensive use of Legumes as a way of introducing Nitrogen organically into the Vineyard

Maintaining and enhancing fertility in the vineyard is a particular challenge for organic vineyards. Use of legumes as a means of fixing nitrogen is well researched in many farming systems but less so in the vineyard environment.

Early practical research in a vineyard setting has been undertaken by Andre Lategan, the manager of Amisfield’s vineyards in Central Otago New Zealand. Amisfield’s vineyards are organically certified. Andre combined the attributes of sub-surface irrigation with the cropping of legumes to assist YAN levels in juices – see photograph for innovative implement to sub-surface irrigation. Andre has monitored adjacent blocks in comparison to where this practice is undertaken and has noted improved YAN juice levels, season on season out of the legume enriched block.

Dr Richard Smart wrote about this in an Australian wine magazine ‘Grapegrower’ (view here). As the author of this introduction, I recognise the value of overcoming fertility challenges (particularly in an organic setting) and the need for practical research in this area to help all growers.

On November 20th 2020 a seminar was held at the Renwick Sports Centre regarding the use of legumes in the interrow to improve vine nutrition, with an emphasis on nitrogen. There were three speakers, all expert in various aspects of this concept. Here is a summary of their contribution and a link to their presentations:

Dr Mike Trought:- Mike has a long and distinguished science career as a plant physiologist (specialising in grape vines), both here in New Zealand and overseas. He is recognised by both the New Zealand wine industry and his science peers. His presentation (view here) covers changes in interrow practice in Marlborough from the early 1980’s to the present day, some thoughts on useful legume species and finishes with what occurs when there is a nitrogen deficiency in the vine, and the effects on juices/wine quality.

Professor Derrick Moot:- Derrick is a Professor at Lincoln University and his work within New Zealand’s dry farming and arable farming sectors on the benefits of incorporating legumes is highly acknowledged. He has demonstrated that the inclusion of legumes improves resilience, performance and yield. His presentation is titled ‘Legumes for Vineyards?’ (view here) It is an interesting wide-ranging presentation of applied research covering various agricultural settings. It canvasses New Zealand’s historic nitrogen use and water use, their relationship to productivity and climate change predictions. He makes a good case for inclusion of subterranean clovers and other legumes to be incorporated into the vineyard interrow with relevant research from Chile, Australia and Italy. He estimates the likely vine nitrogen uptake from a legume dominant sward, as well as discusses the various sward mixes, the date of sowing and the outcomes on dry matter and weed ingress.

Bruce Clark:- Bruce is the manager of Kiwi Seeds Limited in Marlborough. In his presentation (view here), he draws on decades of experience regarding legumes and offers comments and a pictorial presentation of annual clovers, perennial clovers, subterranean clovers and lucerne – included are specific varieties and their sowing times.