Reducing the drip, drip, drip
A shorter version of this article first appeared in the Drinks Business, January 2013.
Water is one of our most precious resources, and irrigation is vital to much vineyard growth around the world, but how are growers reducing its use?
Much of the typically unirrigated old world, gets off lightly here, because deliberately turning on a tap is a highly visible and measurable thing, and strictly controlled by local and/or national authorities. In Chile, for example, said Patricio Parra, sustainability consultant to Wines of Chile, whether water is from groundwater or the Andes it is “nationally regulated, and privately administered” with water rights issued to growers. Flow meters keep a tally of the amount of water being used. In South Africa, dams must be registered or licensed, and all water extraction from rivers or groundwater is registered.
But it is Australia that arguably leads the innovation field of water-reduction strategies. The country spent much of the first decade of the new millennium in prolonged drought; necessity has forced the rate of change, such that Peter Clingeleffer, a senior research scientist at CSIRO (Commonwealth Scientific and Industrial Research Organisation) said “viticulture in Australia is highly water efficient, producing a greater dollar value per unit of water consumed than almost any other irrigated crop, far greater than irrigated annual crops. However, viticulture in Australia is almost entirely reliant on irrigation with 85% of vineyards being irrigated, not just those in the warmer climate regions. Supplementary irrigation is essential even in cool climate regions.”
Complex issues
There’s enough research out there that shows a certain amount of water stress at certain times during the growing season can actually enhance fruit quality. This would suggest that high quality fruit, which must surely be part of the irrigation question, emerges more reliably and more consistently from regions where water input can be totally controlled, i.e. those very areas that must be irrigated.
Irrigation strategies have moved into the realm of detailed understanding of vine phenology and physiology and how these are affected by soil moisture rates, evapo-transpiration, stress and its effects. Wendy Cameron, head of winemaking at Brown Brothers said “irrigation is all about matching water application to the vines’ requirement. This will vary depending on the vines growth stage, soil type, variety, rootstocks, climate, weather conditions and the end yield and quality that is being aimed for.” So, she added “water infrastructure is very important – variable speed pumps, lines, emitters and soil moisture monitoring to ensure the minimum amount of water is applied, differentially to different parts of the vineyard and different varieties for the desired result.”
These complex issues are being integrated into the new Chilean wine industry sustainability code. Parra said the basic requirement is to “protect water resources from over-exploitation and pollution” and at this stage is to confirm whether a company “has an inventory of their water sources with water rights, a program for conservation and water efficiency, a record of the annual volume used and a map of the water source locations.” He added that while “the code is new, the idea is to compare after some years if we really are reducing water use.”
At the opposite end of the industry sustainability code spectrum, New Zealand, which started in 1997, and where about 85% of the industry uses irrigation, mostly drip, water usage data has been collected for the past few years. Philip Manson, general manager for sustainability at New Zealand Winegrowers, said “irrigation decisions are being based on increasingly detailed incoming data, not just weather and rainfall data, but evapo-transpiration and soil moisture measurement as well as having a good old-fashioned look at the vines.”
Methods and strategies
Different irrigation methods use different amounts of water. Flood and furrow irrigation may remain common in Argentina, but just 3% of the Aussie vineyard still uses these heavy options, and even overhead sprinklers are becoming appropriately unfashionable. At Yalumba, vineyard manager Fred Strachan said “reducing vineyard water use without affecting crop yield/quality is something that Oxford Landing has been working strongly at for over 20 years. This began with the replacement of inefficient overhead irrigation practices to modern drip irrigation systems. This not only saved water but also reduced the variability within our vineyards and increased our yield and quality. The quality results and improvements to water use efficiency, water used per tonne of grapes harvested, were so outstanding – it almost halved – that all our contracted growers chose to do the same.”
All things being equal, drip irrigation evidently uses less water than flood, furrow and overhead sprinkler. But even drip has been subject to tweaking. RDI (reduction deficit irrigation), which restricts water at certain times during the growing season uses less water than conventional drip, and PRD (partial rootzone drying) uses less again. Both strategies are typically delivered via drip irrigation systems, and both strategies were developed in water-scarce Australia. Strachan said RDI “is just how we grow grapes. We aim to regulate the water use at specific growth stages of the vine to maximise grape quality and maintain commercial yields.”
The newer PRD strategy effectively irrigates one half of the rootzone only, alternating each half, to reduce total water used. It has not yet been widely adopted, even in Australia. Cost is a big thing – it requires two irrigation drip lines for each vine row. Clingeleffer said “PRD can be difficult to implement, with a greater infrastructure cost also. It requires a high evaporative demand environment and freely draining soils to be effective and the timing of ‘switching’ between sections of the root system must be specific to a variety and the weather conditions.” Research suggests that water use can be halved with PRD.
Strachan thinks its time may yet come, saying PRD’s “use has remained small as its infrastructure costs and management creates some small complications in a large scale situation. This technique is well published and is very successful at optimising water used per tonne of grapes. I suspect as water becomes more costly the conversion to PRD systems will be more advantageous.”
It’s not just a question of water volume. Electricity costs to pump the water have to be factored in to the overall sustainability index of a wine producer. The cost of pumping water increases the carbon footprint, creating a double whammy of business reasons not to do it. But water is essential. Manson said “growers recognise the significant cost of applying water. Every time they turn on the irrigation system, they are not only using up water allocation they may have a right to, but they are also consuming electricity to pump that water around. They irrigate to achieve a quality outcome, and hesitate where possible to incur the cost.”
At Yealands Estate, in Marlborough’s Awatere Valley, owner Peter Yealands said “the electricity used to power the pumps and irrigation system is a significant, but necessary investment.” To offset this against other sustainability criteria, Yealands added “one of our methods to practise sustainable irrigation management is to purchase our electricity from power supply companies that only use renewable resources to generate their power.”
The Chilean wine industry’s relatively new sustainability code builds on the need for producers to measure and report water use, as well as introducing the concept of water footprints. Parra said “small farmers may use irrigation less efficiently, but there is a requirement to use it more efficiently, whatever irrigation system they have.” The implication being that once some years of water use data are collected, the industry will be in a better place to target reduction strategies appropriately.
The kiwis are already talking to growers. Manson said SWNZ “have started providing comprehensive individual reports back to all our members so they can compare their water use with others in their region. This is a very strong tool for people to evaluate their water use, and to consider modifications to their water management strategies.”
Reducing evaporation
Given that much irrigation is done in warmer climates, reducing the amount of water that evaporates from the soil surface reduces water usage. To this end, subsurface irrigation has been trialled in Australia, though the challenges of blockage problems, and root interference are more difficult to address than with surface pipe work.
At Banrock Station viticultural manager Stephen Winnall said “we have invested in more than 200km of subsurface drippers, covering about 24% of the vineyard. Sub-surface drippers are leading edge irrigation technology, they deliver water to the root-zone rather than dripping on to the soil surface as conventional drippers do. While they are more expensive to install and manage than conventional drippers they increase water use efficiency as all the water is at the root-zone” and thus not on the surface from where it can evaporate. He added that they have seen water savings of between 15 and 20%.
Brown Brothers have 116ha of vineyard at Mystic Park with sub-surface irrigation, established in 2005. Cameron said “The suggested water savings seen with subsurface irrigation are about 30% and this is pretty much what we are finding. There are some challenges with the technology such as ensuring no root growth into the water emitters but overall it is working well.”
However they have also done some work mounding the vineyard rows on conventionally drip irrigated vineyards “so that the applied water stays close to where the vine rows and roots are and doesn’t just flow out into the mid row and evaporate. We are finding the simple mounding technique we have more recently adopted has saved a similar amount of water”, without the infrastructural issues.
Mulching also reduces evaporation. Yealands vineyard stretches along the windy Marlborough coastline and to counter the evaporation this causes Yealands said “we apply compost directly under the vine rows in these more exposed areas. Our compost regime is helping retain moisture as well as promote soil health. It is applied at a rate one tonne per 100 metres, with the compost more than halving the water requirement we would need to supply to the vines via irrigation. “
In South Africa, Waverley Hills recently won a Green Wine Award, for using a shade net effectively as a mulch, or ground cover.
There are other well-known benefits of mulching: it improves soil condition, moisture retention and biological activity, and greater soil organic matter improves water penetration when it does rain.
Moisture monitors the way forward
Even with more efficient irrigation systems, augmented by mulching strategies, having a small army of real-time reporting moisture monitors offers another option to reduce water use. Winnall has more than 50 in his Banrock vineyard. He said “one of the most significant tools in our water management program is capacitance probes, which are our main method of monitoring soil moisture at Banrock. The system provides very accurate soil moisture levels, feeding back information to computers in the office. We log moisture conditions every half an hour so we know what soil moisture we have available 24/7.” He said they save about 20% on irrigation water by installing the probes.
Yealands is also an advocate, saying we have “moisture monitors placed throughout the vineyard at various depths in the soil. Moisture is measured automatically with the information radioed back to our controller who regulates water inputs to suit the needs of particular areas in the vineyard. It means we only irrigate as required, and can control the flow of water to blocks of the vineyards depending on the soil condition, reducing surplus irrigation and wastage.“
The use of continuous soil moisture measurement loggers linked to computers is also increasingly common practice in South Africa, with BWI producers leading the field. Such real time data gives vineyard managers up to the minute information and enables parcel-specific irrigation.
Vines and rootstocks
Another way to reduce irrigation is to plant cultivars better adapted to the locality. Simple options include trials with existing dry-tolerant vinifera species. The likes of vermentino and tempranillo are gaining a small amount of traction in Australia, for example.
Brown Brothers have long been known for their viticultural innovation, with grapes such as tarrango and cienna now part of the normal varietal landscape. Trials are now at an early stage with drought and heat resistant varieties bred at CSIRO. With temporary names such as C3PO and R2D2 (obviously not even their real temporary names, which await the completion of due legal protocol), these V. vinifera varieties were selected by Brown Brothers according to their “really interesting fruit profiles, good colour, good retention of acidity, sunburn resistance, water and heat hardiness and so on” explained Cameron, as observed in the CSIRO vineyards and micro-vinifications of them. Brown Bros have planted one hectare of each of six varieties, three red and three white, and the first crop is expected with the 2013 harvest.
Below ground, Clingeleffer and his colleagues are researching rootstocks, He said “there is certainly a lot of promise from adoption of rootstocks to assist industry to address these abiotic stress issues. Of the suite of standard commercial rootstocks 140 Ruggeri appears to have outstanding [drought] tolerance.”
The Yalumba nursery has also been working with CSIRO, SARDI and South Australia universities on drought-tolerant rootstocks. Strachan said of one trial “the work related to Ramsey rootstock actually reduced yield, but the quality improvements obtained were well worth the trade off and we were able to obtain good commercial yields at improved grape quality.”
Industry continues to innovate from several angles on reducing water use for irrigation, but the sustainability issue remains complex. Manson summarised “water has always been a precious material. The issue is about minimising water use and making sure that the water that you use is justified and not having a negative impact on the environment. A successful water management strategy fits hand in glove with broader sustainability aims.”
