Jul 26, 2016

Irrigation evolves from cumbersome sprinkler applications

Irrigation of vegetable crops has a lengthy history, driven by the reality that water is a finite resource. The emphasis on having the proper amount of water for successful plant growth continues to increase.

According to the Fairfax, Virginia-based Irrigation Association, irrigation began in 6000 BC. It began at about the same time in Egypt and Mesopotamia (present day Iraq and Iran), using the water of the flooding Nile or Tigris/Euphrates rivers. The flood waters, which occurred July through December, were diverted to fields for 40 to 60 days. The water was then drained back into the river at the right moment in the growing cycle.

In 1800 AD, irrigated land worldwide reached nearly 20 million acres. This compares to an estimated 600 million acres today.

The potential of portable sprinkler irrigation in crop production was recognized after World War II. The catalyst was the growing availability of aluminum. The lightweight metal began to replace heavy steel tubing and fittings made of cast iron or steel.

The significance of aluminum is evident in statistics for the period. U.S. government figures reveal that 1.25 million pounds of tubing were installed in the United States in 1946. By 1955, the figure had risen to 50 million pounds.

There are four main types of irrigation: surface (flood and furrow); sprinkler; drip; and subsurface. Surface methods generally lose the most water to evaporation, and have been declining in popularity for several decades as efficient drip systems take their place.

The vegetable world has seen a shift to drip irrigation in the last several decades.

Drip irrigation (also known as trickle, or micro- irrigation) allows for a precisely controlled application of water and fertilizer by allowing water to drip slowly near the plant roots through a network of valves, pipes, tubing and emitters. Plasticulture is the combined use of drip irrigation, polyethylene mulch and raised beds. Greatest productivity and earliness may be achieved in vegetable production by combining plasticulture with the use of transplants, according to industry experts.

“Most vegetable growers I deal with have some form of irrigation,” said Ron Goldy, senior Extension educator at Michigan State University.

Goldy initiated and operates the Southwest Michigan Irrigation Network, a pay-for-service soil moisture monitoring program that provides growers with weekly readings and advice on irrigation application.

“Depending on the crop, most have gone to drip,” Goldy said. “Some crops don’t lend themselves to drip, such as corn, carrots, celery, onions, beans, potatoes, pickles, peas and others that are planted at high densities.”

Other advantages offered by drip systems, according to Goldy, include:

• Drip irrigators also use the drip lines to fertilize
• Pressure-compensating tape has allowed the use of drip on hilly sites
• Drip is much better when it comes to food safety
• Drip provides for more efficient use of water and nutrients
• Drip can work off lower pressure and volume, and is therefore better for those with low well output
• Drip minimizes disease pressure by not wetting the leaves and fruit
• Growers can irrigate with drip and still carry on other field activities
• Drip is easier to automate

“Irrigation is one of the best ways to reduce risk in high-value crops, even in a high water state like Michigan,” Goldy said. “I would encourage every grower of high-value vegetables to irrigate in some manner, preferably with drip.”

A survey of irrigation methods in California by the American Society of Civil Engineers collected information on the methods used by growers to irrigate their crops in 2010. The results were compared with earlier surveys to assess trends.

According to findings, from 1972 to 2010 the planted area increased from 15 to 30 percent for orchards and from 6 to 15 percent for vineyards. The area planted with vegetables has remained relatively static, whereas that planted to field crops has declined from 67 to 41 percent of the irrigated area. The land irrigated with low-volume (drip and micro- sprinkler) irrigation has increased by approximately 38 percent, whereas the amount of land irrigated by surface methods decreased by approximately 37 percent.

According to USDA, despite hopes for a drenching from El Niño, California farmers are facing another drought year in 2016. Even after four years of the worst drought on record, California farm output was a record $54 billion in 2015, accounting for more than half of the nation’s fresh produce. Groundwater has helped compensate for California’s lack of rainfall, but groundwater overdraft cannot be continued indefinitely.

California farmers have responded to the drought by fallowing land; switching to crops that yield higher value per unit of water; and switching irrigation technologies. Almost all California cropland is irrigated, so continued improvements in irrigation efficiency are key to weathering drought.

Production, efficiency

David Zoldoske, director of the Center for Irrigation Technology (CIT) at California State University, Fresno, has been working with growers on irrigation issues for 35 years.

CIT was established in 1980, following one of the worst droughts in California’s history (prior to the current one) in 1976-77.

Zoldoske said the state legislature was determined to do more to refine irrigation practices in California, just as drip irrigation use was coming into its own. The center has evolved its testing lab work along with the development of irrigation products.

“We’ve sort of led the way in the testing of irrigation equipment for the past 35 years,” he said.

“We work with drip emitters, drip tape for vegetable growing, and we also do a lot of field research and training to take what we learn and share that with growers,” he said. “We’ve grown to the point we’re now actually promoting innovation with irrigation companies and products.”

Zoldoske recalls the days prior to drip technology when “all things were irrigated with sprinklers. Vegetables were grown for a long time with sprinklers. Precision agriculture changed all of that.”

He said initial challenges using drip include figuring out the depth of its effectiveness and how long to leave the system running. Working with the size of holes in emitters and keeping insecticides from damaging the drip tape were also encountered.

“The technology allowed us to improve significantly our production and efficiency with the use of drip tape in vegetable production,” Zoldoske said.

He noticed reluctance on the part of growers who were comfortable with sprinkler irrigation, before they understood how to work around the plastic for planting and harvesting needs.

“With drip, we can really manage applied water and fertilizer in general,” he said. “There is a good understanding of the management of depth, the use of better plastics and emitters to get the right flow rate and spacing in order to achieve improved filtration.”

He said the use of drones for remote sensing gives a better view of the effectiveness of irrigation in the field.

“We can identify leak spots, plants under stress and identify early where we might have a problem with irrigation, fertility, soil and bugs. It can help correct problems during the growing season and give you that information early.”

As early as several years ago, Zoldoske was involved in work that used sensors to monitor the vegetative index of large fields of melons.

“A week or 10 days out, you could look at the different areas in the field with some ground truthing and go out and estimate the yield and size of the product. This helped the marketing folks pre-sell the field before it’s harvested. Some of this information that can be provided we knew 15 to 20 years ago.”

Use of new technology “has been a process of evolution,” he said. “Just because one person is doing it doesn’t mean it’s widely adapted. We’re starting to see growers injecting air into the drip lines, and it helps with water aeration in the root zone leading to increased yield. We’ve seen an increase of 15 percent in marketable melons in the last five years.”

Zoldoske said growers are using more no-till or minimum-till management practices, “so the soil isn’t worked up as much. That will have benefits in both the cost and emphasis on soil health. People are paying more attention to assure the soil is as healthy as possible. Some are growing vegetables with more salinity in them, causing some of that ground to shift away from soil-sensitive crops.”

He said labor shortages continue to be a problem, particularly with more skilled labor needed to understand and operate the latest technological tools.

“You need fewer but more skilled labor with drip irrigation than with sprinklers,” he said. “You used to hand- move sprinklers around. Now there is more information. The whole wireless communication has been a big plus. It gives you information about irrigation pressures and flows, soil moisture status, along with wind and water readings.

“Growers today have a lot more data at their fingertips to make decisions. Going forward, we’re going to see a lot more data being collected from the field on a regular basis, driven through an iPhone or something.”

Drip’s practical approach

John Nye, president and co-founder of the St. Joseph, Michigan-based Trickl-eez, has been involved in the irrigation business for more than 40 years. He has worked with grower Jim Demski, one of the first growers in southwest Michigan to use drip.

“They were growing tomatoes a long time with sprinkler irrigation over the top of them,” Nye said. “What would happen is they would have a certain amount of scars on them. He’d been growing tomatoes a long time – 15 years or more. He was just turning dollars, not making any money. He was excited about the prospects of raised beds, film, drip plastic, feeding water and nutrients into that system. It was a big step to do that all at one time. That was actually the best way to do it.

“I worked on several fields. His production being on flat ground, he was getting about 700 boxes of No. 1 tomatoes to the acre. When he converted to raised beds, using film, the yields went to 1,500 bushels to the acre. He more than doubled the yield and quality increased a lot. He couldn’t keep up with the orders. Other growers in the area saw it and wanted to utilize it.

“(Drip) is practical for peppers, eggplant and various other vegetable crops,” he said. “Now everybody in the vegetable industry except in muck ground is using the technology. With yields on tomatoes of over 2,000 boxes an acre, it’s a pretty exciting story.”

Drip use has been aided by better quality tubing and knowing more about nutrient feeding, Nye said.

“It’s been a bit of an evolution – an exciting one. Everybody in the industry has gone to it and never gone back, once they see how good it can be.”

Nye said there was some grower resistance to drip installation early on.

“It seemed like a lot of expense – a lot to change over. For those who tried it, the rewards were there and the whole industry has fallen in line. It’s quite an investment of cost in doing this. The production and quality is that much higher, with lower per-unit costs in the end.”

He said improvements in tubing have made it “so dependable it is unlikely to plug up. It works the way we want them to. It’s pretty much a sure thing if the growers put the right filtration in and follow what we know how to do. It’s been tweaked and improved. Now the system is so dependable and so widely used a new grower can start right in and can easily understand and develop (a system) and use it for themselves. It’s been a real evolution.”

With the newer systems, the growers turn the pumps on and off with cell phones, and are able to monitor what the flow and fertilizer injections are doing.

“Today’s technology can monitor if a rain storm comes up and the phone can be used to turn the system off – and you can do it from far away,” Nye said.

Nye said the next significant development will be widespread recycling practices to “reuse the materials we’re pulling out and recycle them.”

A history of gains

Phil DeMarco of Hammonton, New Jersey, a former board member of the Irrigation Association who has been involved in irrigation work for seven decades, was born and raised on a farm in southern New Jersey. He observed the early use of portable, hand-moved aluminum irrigation approaches on his father’s vegetable farm that took hold in the 1940s.

“They were usually homemade rigs,” DeMarco said. “Factory-built pumps started in this area around World War II. Water winch-type systems were first used in about the late 1970s. When I distributed irrigation equipment in 1975, there were some portable units, but we were mostly building our own high-end diesel pumps and selling them with underground PVC. A vegetable area in Vineland, New Jersey, is still using some hand-moved aluminum. It’s the only area you still see some small farms with 8 to 10 acres using it.

“Drip has taken over the vegetable area,” he said. “It saves labor, is economical, there’s no waste of water, and you’re only using the water in a designated area. You’re also putting it underneath, along with the plant under plastic. They’re growing tomatoes, greens and everything. Sweet corn is even using a little drip – but it’s a fast-growing crop.”

“There are savings being seen putting in drip irrigation, and you’re not tending to machinery and pipe. It’s doing nothing except starting a pump or opening a valve. It’s made a big difference. As soon as (growers) saw something come up the street, something new, they jumped on it.”

He said southern New Jersey doesn’t have the water availability problem seen in other areas of the country.

— Gary Pullano, associate editor