In My View
Viticulture in Australia
Precision viticulture, and the research efforts to study vineyard spatial and temporal variability, did not start in Australia. However, research towards understanding vineyard variability and implementation of measuring and monitoring vineyard variability with "precision agriculture tools" has advanced more in Australia than anywhere else.
Former Washington State University -Prosser viticulturist Dr. Bob Wample initiated efforts in precision viticulture in the mid 1990's through work with yield monitoring in both wine and juice grapes. While efforts at Prosser and several other locations in the United States have dabbled in precision viticulture, in 1999 Australian scientist Dr. Rob Bramley took on the challenge and developed a strong research program addressing spatial and temporal variability in vineyards.
For those interested in a more detailed view of some of Bramley's efforts, many of his publications can be located at this Web site: www.clw.csiro.au/staff/ BramleyR/publications.html.
For me, I had the privilege of spending from October 2004 through April 2005 working in Bramley's lab in Adelaide, South Australia, on a professional leave from WSU. The rest of this article will talk a bit about the highlights of what I saw and learned about precision viticulture, Australian style.
As mentioned above, yield monitoring was the first area where forays were made into the use of precision agriculture tools for viticulture. Interestingly enough, the initial yield monitors codeveloped by Wample's WSU lab and Ron Campbell of HarvestMaster used load cells and fruit weight measurement to monitor yield. There was a shift from load cells to ultrasonic sensors when Wample and Campbell found that low-yielding areas of a given vineyard did not always have enough fruit to register weight.
Bramley's group, working with Australian industry partners, has redeveloped a loadcell, fruit weight approach to yield monitoring in Australia that is currently being commercialized.
But why bother with yield monitoring? What can it tell us? Yield monitoring a vineyard for one single harvest certainly can give insights into the variability of yield within the vineyard in a given year. Yes, that is all it tells us. However, if used in conjunction with repeated, multiyear measurement of yield or other precision viticulture tools, more can be learned.
Once better understood, yield variability in a field can be mapped to determine if there is any advantage to differentially harvesting high vs. low vigor areas of the field. This is an approach that has been taken by several vineyards in Australia where Global Positioning Systems guide differential harvest, using separate gondolas for fruit from high vs. low vigor areas. The differential harvest has proved to be economically advantageous to the grower since the higher returns on the high quality fruit, averaged together with the lower returns on the lower quality fruit, averaged out to be higher overall than if the fruit from both areas of the vineyard were combined.
Another technology for measuring variability in vineyards that has more widespread use in Australia than in North America is nondestructively monitoring soils for apparent electromagnetic conductivity (EM mapping), using EM-38 equipment, manufactured by Geonics. In comparison with Washington vineyards, saline (salty) soils are a more widespread problem in Australian viticulture.
An EM-38 map of a vineyard can show soil variability in the vineyard. Bramley's group has worked extensively with this technology and uses it, in conjunction with extensive soil sampling, to determine sources of soil variability in vineyards. Through this work, they have identified a level of between 0.6 to 0.7 dS/m as being soils where high salts can adversely affect grape yield. There is still a strong interest to determine the impacts of salinity on grape quality, but that is research waiting to be conducted.
Of course, EM-38 maps are not flawless, and there are challenges with the technology. Metal posts and, possibly, wires can interfere with this measurement, although the exact amount of metal that causes interference is not conclusively documented. In addition, as alluded to earlier, the variability in EM-38 readings across a map must be accompanied by soil sampling for "ground truthing" to determine the cause of variability, which could come from a difference in salinity, soil texture, soil depth, or another related factor.
Aerial photography and remote sensing
Another approach used in South Australia that is not commonly seen in Washington viticulture is the use of multiple wavelength aerial imagery for measuring vineyard variability. In South Australia, much of this imagery has been collected for monitoring the potential spread of phylloxera. However, vineyard managers and researchers alike use these images as another source of monitoring vineyard variability.
The images are geo-referenced, meaning that they can be imported into a Geographical Information System and analyzed with a clear view to where the variability is located. The data can be analyzed using different indices, coupled with other data sources (e.g., EM-38 data) and again, used to determine sources of the variability. Sometimes, the information gained from these images is as simple as locating a break in an irrigation system to as complex as an issue of variability of one or more soil issues.
Precision agriculture is partly about measuring variability and partly about responding to it. Due to support of research efforts in precision viticulture, through federal and state funding as well as industry collaboration, the Commonwealth Scientific and Industrial Research Organisation Precision Viticulture program under Bramley has made great strides. Techniques to measure variability as well as steps that need to be taken to verify findings have been established.
The aspect of responding to variability truly relies on first developing economically viable monitoring techniques. However, differential harvest of fruit from high vs. low vigor areas is one way of responding to variability. Other techniques to reduce variability are still the subject of research. As the area of precision viticulture grows, and as we begin to take some of the learnings from Australia and implement them here, more tools to manage variability can be developed, and more advanced methods to measure variability can continue to evolve.
Dr. Joan Davenport is associate soil scientist at Washington State University, Pullman, Washington.