Automatic spraying is coming: growers are closer than they think to a precision vineyard sprayer

Wines & Vines, July, 2008 by Andrew Landers

The Durand-Wayland Smart Spray device uses ultrasonic waves to detect trees and vines.

For the past two decades, field crop farmers have been able to utilize precision farming techniques to apply fertilizer and pesticides and measure crop yields. GIS maps and GPS-based navigation systems have shown farmers their exact location within fields, allowing the precise application of inputs such as fertilizer, and, in many cases, allowing variable rate application. Technology such as direct-injection sprayers also exists to allow farmers to spot-spray pesticides within in the field--when patches of weeds occur, for example. Automatic steering systems allow greater implement output, due to minimum overlap of machines such as sprayers, disks and cultivators.

Very little precision farming technology, however, has transferred to the fruit industries of apple- and grapegrowing. The first North American Conference on Precision Fruit Spraying was held April 8 and 9 in Canandaigua, N.Y., with the objective of bringing delegates up to speed with current research and future projects involving technology for the precise application of pesticides to apple trees and grapevines.

Precision farming gives us information such as soil nutrient status, soil characteristics and crop health. We can use this information to manage our fields--for example, where to place production inputs. Information is of limited use if we are unable to interpret it or act upon it. In the global marketplace, technological developments for fruit growing are developing at a great pace in Europe and South America. In the United States, we face growing uncertainty about the availability of trained labor on fruit farms, and pesticides continue to be of concern to all who apply them, live near their application, and consume fruit.

There is tremendous interest in technology for agriculture and how it can be applied to fruit crops in the U.S. The tree fruit road map is one example of where the apple industry and researchers are getting together to set common goals. In the grape-growing industry, we have the National Grape & Wine Initiative discussing targets for the medium/long term. It appears the government also is interested in supporting these initiatives, and there seems to be the chance of further collaborative research among academics and companies.

In viticulture, we are in a pivotal position: We are able to take advantage of the lessons learned in precision agriculture for field crops and avoid the many expensive pitfalls that may have occurred. We also are able to build upon previous research within viticulture--applied research in vineyard spraying at Cornell University, in particular.

Sensors

In 2007, 10 progressive apple growers, farming 1,400 acres in Orleans County, N.Y., purchased 10 tower sprayers fitted with ultrasonic detectors with the assistance of a 50% EQIP grant. This research/extension project is funded by USDA NRCS.

The Durand-Wayland SmartSpray device uses ultrasonic waves that are reflected by the tree canopy. Sprayer manufacturers claim vast reductions in pesticide use and drift. The 10 growers began a two-year research project with myself and James Kingston of Orleans County Soil and Water Conservation District to monitor the actual reduction in pesticide use, drift reduction and machine reliability.

At one of the growers' orchards, we observed a savings of $8,500 in pesticide costs at a 95-acre orchard in one season. We also noted improved timeliness due to enhanced logistics. Pesticide savings depend on trellis system, growth stage of the trees, canopy development, cost of pesticides, and tree characteristics.

After one season of observing 10 sensor sprayers at work in commercial orchards, there have been no problems with the operators understanding the system controls, nor have there been any problems regarding sprayer/electronic reliability.

Location and forward speed

The location of a sprayer within a vineyard is very straightforward compared to a field crop sprayer. Using a perennial crop in rows may only require the use of transponder systems to identify row location, although GPS techniques have become very inexpensive when sold en masse, as is shown by the use of car-navigation systems and hand-held GPS systems. Techniques are available off-the-shelf.

Airflow

From 2001 to 2006, a series of tests was carried out at Cornell University to determine the airflow characteristics of airblast sprayers used in vineyards. Sets of deflectors were developed for both traditional airblast sprayers and Kinkelder-style sprayers. Field tests showed a 20% to 30% improvement in deposition and, importantly, with equal deposition throughout the height of grapevine canopies.

Air speed and volume need to be adjustable according to the growth stage of the canopy. There are a number of simple methods to do this, such as changing PTO speed, fitting an air-limiting system to the air intake or outlet, or using a variable speed hydraulic motor drive to the fan.

Field trials were conducted using an AgTec P300 (AgTec Minnesota) sprayer fitted with airshear nozzles operating at two fan speeds. Drift was detected using water-sensitive cards and analyzed using a DropletScan image analysis system software. At a fan speed of 2,076 rpm, drift was detected up to 80 feet from the target row where 10% card coverage occurred. Reducing fan speed by 25% resulted in considerably less drift, with card coverage at 20 feet and 40 feet from the target row being 16% and 0.20%, respectively. When drift is reduced, then deposition is increased, resulting in better coverage and better disease and insect control.