Fan sprayer aims for higher efficiency with less water

The three most important elements in applying crop protection chemicals to orchards or vineyards are coverage, coverage and coverage.

Conventional wisdom says you accomplish that with water, water and water.

Application and design technology experts at Cal Poly, San Luis Obispo and University of California, Davis, say not necessarily.

Both water and coverage are certainly key elements to efficacy, but there are more environmentally friendly and cheaper ways to achieve coverage that can be adapted to California agriculture.

The California Department of Pesticide Regulation, both universities, Western Farm Service (now Crop Production Services), Western Plant Health Association and Western Growers are financially backing the effort to create a multi-fan, 48-nozzle orchard/vineyard sprayer to discover better ways of applying products to orchards and vineyards.

They will take the ideas to the field this summer with a sprayer engineered and constructed by students at Cal Poly and outfitted with a fluid handling system and variable rate technology by students at UC Davis. The goal of this effort is to improve on target coverage using available technology to reduce non-target applications and reduce drift.

One student, Ryan Billings who grew up in Davis, has been involved with the three-year project at both schools: first as an undergraduate at Cal Poly and now as a grad student at UC Davis.

Ken Giles, biological and agricultural engineering professor at Davis, says one of the goals in this project is to reduce the amount of water now used for a carrier.

In the practical world, growers and applicators typically treat to take care of the worst-case scenario. Sprays are historically targeted to reach disease or pest areas that are most likely to be nettlesome. This is often in areas difficult to penetrate. The solution, applicators believe, is to use plenty of water to reach those hard-to-reach areas. This is often more than necessary for much of the rest of the orchard or vineyard.

The issue is not about water. It is a lack of uniformity, says Giles, who explains a goal of the pesticide application technology project is to reduce water volumes needed, and in turn, the amout of pesticide needed.

“If we can get more uniformity with this variable rate sprayer, the worst place to spray will get the same rate as the easiest to spray. The result would be less overapplication,” said Giles.

This will not only reduce pesticide use, but will reduce water needed.

In Europe and other parts of the world, it is not uncommon for rates to be just 30 to 40 gallons of water carrier per acre for ground application. This is far less than in California where 100 gallons or more is common.

Jim Coburn, recently retired from Western Farm Service, says reducing by just 10 gallons per acre the water used to treat 500,000 acres of orchard represents a savings of 5 million gallons of water.

“Drop that 100 gallons down to just 50 gallons, and the savings are enormous,” said Coburn. This is not just a water use issue but an economic factor associated with reduced water hauling of million of gallons of water. Plus, using less water reduces the stopping time to reload a sprayer.

“Due to food safety concerns, at least some of the water used in agricultural spraying is municipal water and that is a big issue,” adds Giles.

Less water also means runoff is minimized.

Development of more efficient application technology with this new sprayer is similar to projects in Giles’ career that has lead to the development of application technologies that are now widely used commercially, like the sensor-based “Smart Sprayer” which turns off automatically when there is nothing to spray, significantly reducing non-target applications. He has also developed pulse width modulated spray activators for droplet size and flow water control; thermal spray systems for organic crop products and other similar new technologies.

Giles explains that they hope to achieve cost and product savings with the new multi-fan sprayer much like the smart sprayer.

“The smart spray technology works best when you have variable canopy like in a young orchard or vineyard. It saves less when you have a continuous canopy. We hope to bring some of savings like from the smart sprayer to when you have a continuous canopy. Uniformity is the key to that,” he says.

Doug Okamura, retired DPR administrator who helped develop the grant for the Cal Poly/UC sprayer development project, says regulators will be confronted in the future with mandates to force growers to apply fewer pesticide pounds per acre and reduce even more drift and residues. Technology developed from this sprayer project will go a long way to keeping crop protection chemicals available to growers, he adds.

The total investment in the sprayer is about $100,000, including equipment and time donations from industry and a grant from CDPR.

Giles said the unit actually is constructed with off-the-shelf components like the Quantum Mist fans and conventional nozzles; pumps and plumbing.

It is a tractor-pulled sprayer carrying a 100 to 200 gallon tank. Its hydraulic arms can reach as high as an almond orchard. Walnuts would be a stretch, says Giles. It wraps over a vineyard row. “In the future, we’ll add sensors like those used on the Smart Sprayers. The idea is that these technologies can measure such things as the thickness of the continuous canopy or maybe detect pest infestations.”

Giles says although the sprayer is industrial strength for use on the Cal Poly college farm, it also will be utilized for field trials.

“The project looks at volumes, but also will be testing spreaders, sticker and adjuvants and looking at the impact of ground speeds, orchard and vineyard sizes, as well as spray controller technology. We are combining a lot of things on it as a test vehicle for this program at Cal Poly,” he adds.

“You could call this a poster sprayer,” Giles laughs.

Cal Poly students under the guidance of engineering professor Mark Zohns, a UC Davis graduate, designed and built the spray rig frame, including its articulating arms, flexible carriage, adjustable fan position and its hydraulic system.

“Students in our department here at Davis have strengths in things like electronics and experimental development while the students at Cal Poly are especially strong in mechanical design and fabrication. Working together, we have a good match in this project.” says Giles.

Billings has worked on the sprayer at both places and he agrees the talent is different in each department. His first semester he worked with fellow Cal Poly students on the construction of the sprayer frame and arms. The next semester he worked on the hydraulics. He was encouraged by Giles to work on the next phases of the sprayer project as a graduate student at UC Davis.

“We had a lot of people come in the see the work of the students at Cal Poly, most of whom had a lot of shop and mechanical experience,” he says. Billings worked as an aircraft mechanic before he returned to school for a bachelor’s degree.

One California equipment manufacturer made a visit to the Cal Poly shop to see the students’ work. “One of the people asked who did some of the welds on the machine. It was one of my fellow students. The fellow from the company said he wanted to hire him as soon as he got out of school,” said Billing.

Testing of the rig will start this summer at Cal Poly. It will be run in trials comparing it with conventional air blast sprayers.

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