On-the-go plant scanner helps fine-tune vineyard management
By Vicky Boyd
With the help of a global positioning system linked to a plant scanner, Sander Scheer isn’t limited to managing winegrape grape blocks based on arbitrary boundaries.
Instead, he can customize cultural recommendations within a block for management zones with similar plant vigor based on the data he collects from the Green-Seeker scanner.
“Sometimes it’s difficult to stand out in a large block when some of the vines are in excess of 7 feet tall and identify where we have weak areas,” says Scheer, viticulturist for Jack Neal & Son vineyard management in St. Helena, Calif. “If we can use the system to pick up some of these weak areas more quickly, we hope to keep every vineyard block as balanced as possible,” he says.
Keeping vines in optimum condition has taken on new meaning as wineries become increasingly picky and will only select the highest quality fruit to go into super- and ultra-premium wines.
But as Scheer and Jack Neal & Son geographical information systems manager Walden Grindle are quick to point out, the plant scanner doesn’t eliminate the need for somebody to scout the vineyard and ground truth the information. What it does is make him or her more efficient and highlight the areas needing attention.
The technology behind the GreenSeeker is nothing new. Growers around the world have used sensors to recognize vegetation and help apply herbicides only to weeds and not the ground. What is new is the application.
The machine’s manufacturer, NTech Industries in Ukiah, Calif., introduced the vineyard-mapping version in 2004.
The GreenSeeker, designed to attach to an all-terrain vehicle or tractor, emits red and near-infrared light into the crop or canopy.
A photodiode on the sensor head measures how much light is absorbed or reflected. The data is collected automatically and in real time.
Plant chlorophyll absorbs red light. So, healthy plants absorb more red and reflect more near-infrared light waves than unhealthy ones.
The results are reported as a normalized difference vegetation index, or NDVI, says Ted Mayfield, NTech chief operating officer.
As an indicator of vegetation with active photosynthesis, NDVI can be related to plant stress as well as canopy structure. Unlike aerial remote sensing images, which only show relative values, the sensor puts out an exact number with the NDVI value, Mayfield says.
Because GreenSeeker uses its own light source, it can operate day or night. The sensor can view the plant canopy from either the top or sides.
Horizontal or side scanning allows for the image to only contain information about the vine canopy, excluding the soil or cover crop.
Side scanning also allows you to image a vineyard early in the season with minimal plant growth, Mayfield says. If you can identify limiting factors in the spring, you may be able to correct or minimize them before they affect the crop.
If you were to have a satellite or plane image an early-season vineyard on a vertical trellis, you’d see very little canopy because the craft is shooting straight down.
Aerial images, whether from satellites or airplanes, also can vary depending
on weather conditions, time of day and time of year. Because the GreenSeeker sensor is about 3 inches from the canopy and has its own light source, Mayfield says it provides data that can be compared from year to year.
The GreenSeeker sensor is simple to operate and requires only a few set-up steps. And even if the ATV or tractor operator forgets to turn off the unit, the data isn’t lost.
Data is stored and can be written later to a CompactFlash card. The card can be removed for easy data transfer to a laptop or desktop computer.
From data to useful maps
Grindle used the ArcView program from Environmental Systems Research Institute Inc. in Redlands, Calif., to take the data and make maps showing relative plant health.
To make the information useful, Grindle says he and Scheer had to go to the vineyard and interpret the values.
“This color means this for this variety for this location on this type of soil,” Grindle says. “It really gets down to that level of detail.”
During 2004 and 2005, he also compared maps created from the GreenSeeker data to remote sensing images taken from airplanes flying the vineyard during the same timeframe. The data correlated well, he says.
Getting picky about grapes
In addition to helping make decisions about cultural practices, the data was used in 2005 to selectively harvest grapes and divert the fruit into specific wine programs.
“We were looking initially at vigor and trying to understand whether or not that translates into different levels of maturity from one color scale to the next across the block,” Scheer says.
In general, higher vine vigor indicates lower maturity. Based on that theory, Scheer says crews were directed to pick the more mature fruit first.
Those grapes, primarily cabernet, were kept separate and currently are undergoing fermentation, so Scheer and Grindle won’t know the results until later this spring. But Scheer says the winemakers have been supportive.
“This way, we can give the winemakers a sense of where we think the quality fruit is on the map,” Scheer says.
“Grape sampling efforts can then be altered to back up where we think differences in maturity may exist. We hope to use this more and more as an aid in making harvest decisions.”
Benefits spur expansion
During 2005, Grindle had the operator collect the data while driving 5 to 7 mph through the vineyard on an ATV.
He hopes to mount the sensor and GPS unit on a tractor in the coming season so the operator could conduct routine vineyard maintenance operations, such as disking, mowing or spraying, at the same time as scanning.
Despite not knowing yet how management changes prompted by the plant scanner have affected the 2005 vintage, Scheer says the company is expanding its use
“We’re looking to apply this to more and more acres as we start ‘06. We think it’s definitely a benefit,” he says.