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Automatic Spraying is Coming

by Dr. Andrew Landers 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 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 grapegrowing 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 coverag e 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.

Limiting airflow on the air intake is attainable by using a "Cornell doughnut" system. Simple doughnuts are made and fitted to the air intake, and the intake hole is changed as the canopy develops. Field trials showed a considerable reduction in drift and improved deposition in grapevines.

In 2007, trials were conducted with a Rears sprayer (Rears Sprayers Inc.) fitted with a louver to adjust the airflow as it leaves the tower on an apple sprayer. Drift can be virtually eliminated, and therefore deposition considerably improved, but the operator has difficulty in monitoring any adjustments on the move. A canopy-sensor system would solve this important challenge.

Pressure/nozzles

A number of devices currently are available for growers to use on their sprayers. Air induction nozzles have a proven ability to reduce drift, and this is particularly useful near the boundary of vineyards, near susceptible crops, neighbors and watercourses. Wilger and Lechler both manufacture pneumatic nozzle actuators, which allow the operator to switch from a hollow cone nozzle to an air induction at the press of a switch in the tractor cab. This could be automated using the wind speed sensor and GPS locator mentioned above.

Liquid flow

For two decades, field crop sprayers have been able to buy electronic controllers to adjust the output of their sprayer according to forward speed and desired application rate. A small number of grapegrowers have fitted such devices to their canopy sprayers. With real-time sensing of the crop canopy, and using sensor technology described previously, the application rate could change automatically.

Direct-injection techniques can be used to change rate and product together.

There is a need for real-time sensing of canopy size and shape to allow a constant monitoring of the growing canopy over the season. The current use of a field scout is a limiting factor in the adoption of precision spraying systems.

Autonomous sprayers

At the best of times, spraying is a task that needs to be done--preferably by someone else. It is potentially dangerous to all concerned and requires constant attention to detail to minimize mistakes. For many years, we have seen the use of autonomous vehicles in dangerous situations such as mines, quarries and the other land-based industries. Robotics are commonplace in certain industries. As U.S. grapegrowers face the uncertainty of a labor force--let alone a trained labor force--then there is a need to remove the operator from the dangers associated with crop spraying.

Conclusions

Much needs to be done to combine existing knowledge on canopy spraying in vineyards with existing knowledge on precision farming in field crops. We may be years behind European researchers in developing an automatic fruit sprayer in certain respects, but we also may be closer than we think, if we choose to adapt existing proven technology. Researchers need to join with sprayer manufacturers to develop such techniques if we are to remain competitive.

Putting together a fully automated vineyard sprayer       The ultimate fully automatic vineyard sprayer may comprise many of the aspects shown below. The sprayer could drive along the rows of vines, monitoring the canopy for both canopy volume and absence or presence of vines. Sensors will allow us to monitor the dimensions of the canopy and thus alter both airflow output from the fan and liquid flow (application rate/acre) according to the variable canopy. Patches of diseases or insect activity may have been located previously by scouting the crop, their exact location recorded on a hand-held GPS device. Research at Cornell University has shown how the application rate of spray varies considerably with canopy volume and growth stage in Riesling and Cabernet Franc on VSP trellis. For example, the application rate varies from 16 gallons per acre in early season to 50 gallons per acre in full canopy. A.L.

Dr. Andrew Landers is a member of the faculty at Cornell University and is based at the New York State Agricultural Experiment Station in Geneva, N.Y. He directs the application technology program and his teaching/extension/research appointment involves the use of engineering solutions to provide safer spraying. Landers is author of the textbook, Farm Machinery: Selection, Investment and Management. Contact him through edit@winesandvines.com.

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