Jun 2, 2011
Usage, population, sprawl push advancements in irrigation

Plants need water to grow, but as global demand for quality fruit has increased in the last 50 years, the need to have the proper amount of water for successful plant growth has increased, too.

Waste not

No irrigation system will apply water without some waste or losses, because the cost to prevent all losses is prohibitive, according to a study published by the University of Florida’s Institute of Food and Agricultural Sciences (IFAS). Some water losses are expected and accepted in proper irrigation system design, installation and management.

Water is a finite resource and is always in the wrong place, according to Mark Huntley, director of the Irrigation Association. As the world’s population continues to grow, the demands on water continue to grow. It’s a global issue, not just limited to the United States.

Technological advancements have reduced water usage and waste, which ultimately lowers the costs to growers and consumers, Huntley said.

“In the early 1970s, growers started to see the benefits of going away from overhead irrigation systems for strawberries to drip-tape delivery systems,” Huntley said. “It was much more efficient and better for the plant and fruit. The popularity of drip tape grew from strawberries in southern California and Florida to other crops.”

It wasn’t just with strawberries that growers saw the benefits of precise water management. As they moved away from flood irrigation and inefficient sprinklers, technology allowed for more control – and research showed how much water was used versus what was actually utilized, Huntley said.

“I think we’re on the technological verge of being able to tailor irrigation to our point source and have individual emitters right down to the tree, plant or vine,” he said. “Soon, you’ll see water usage tailored to respond to each individual plant’s needs.”

What kind of technology? Most of it has to do with information gathering, according to David Zoldoske, director of the Center for Irrigation Technology. Information-gathering systems in the field that monitor weather, soil, ground water and plant intake are all part of the modern picture for irrigation decision-making.

“Ag has been flying blind all this time without having these inputs available,” Zoldoske said. “Growers now can access real-time, meaningful data and log that data for historical comparison, which helps make informed decisions.”

For growers in the mid-Atlantic region, not a lot has changed in irrigation and water management, according to Robert Crassweller, a horticulturist with Penn State.

“Yes, a few growers have installed trickle systems, but by and large most are still relying on natural rainfall,” he said. “There is a greater awareness of the fickle nature of rainfall, but as of yet few growers are trying to alleviate the problem.”

Besides economics, there are legal issues to consider, Zoldoske said. With the information systems and controls available today, a grower can verify good irrigation practices, as more and more water sources are legislated to force reporting of all water usage.

“Having good records is becoming more and more important,” he said. “It will be imperative to have a system in place on your farm that collects and stores all of that data for you.”

Irrigation efficiency

One of the major changes in irrigation has been the scientific research that has been done to see what different plants need. It has allowed irrigation specialists to tailor systems and make them more efficient than ever before.

Maintaining a good system became very important, according to IFAS. Irrigation efficiencies vary with the type of irrigation system and with other factors such as soil, crop and climate characteristics – as well as with the level of maintenance and management of the irrigation system. The type of irrigation system used and the intended level of irrigation efficiency will partially depend on the availability and value of water for irrigation.

Crop coefficients are used to estimate specific crop evapotranspiration rates. The crop coefficient is a dimensionless number that is multiplied by the value to arrive at a crop estimate. The resulting estimate can be used to help an irrigation manager schedule when irrigation should occur and how much water should be put back into the soil.

“I have been working on understanding water use and thus the need for irrigation for apples in our humid climate,” said Alan Lakso, a horticultural physiologist with Cornell University. “We found out that apples don’t need as much water in cooler years as is estimated by the standard crop coefficient from arid climates. The explanation is technical, but the bottom line is that the standard method can overestimate the actual required water use by sometimes 100 percent.”

Researchers at Michigan State University (MSU) are looking at irrigation and fertigation as an important part of new plantings and research in high-density tart cherries, said Nikki Rothwell, an MSU horticulturist. Greg Lang, also with MSU, is working on irrigation and fertigation for fresh-market sweet cherries, she said. Growers in northern states also use irrigation systems for frost protection, with sprinklers installed as well.

In strawberries, a critical stage of growth is the establishment period of the transplants, said Marvin Pritts, a small-fruit horticulturist from Cornell University. The two-week period after transplants are set is when they are most susceptible to water stress. This vulnerability is mainly because plants have not developed a strong root system to maximize water absorption. The results are often yield reductions of roughly 33 percent, and size reductions of 17 percent. These results have been documented under only moderately dry conditions without irrigation.

When determining when to irrigate blueberries, said Elsa Sanchez, a professor of horticultural systems management from Penn State, growers need to know what the soil can do. One way is to look at the water-holding capacity of the soil.
Growers will also have to determine the plant water use and the amount of rainfall daily, then subtract the daily plant water use and add the daily amount of rainfall to the available water-holding capacity of the soil. Irrigate the plants when the available water-holding capacity of the soil drops to 50 percent of capacity. Check the soil moisture content periodically to verify the water usage and availability.

Irrigation system application efficiencies can vary widely, depending upon how well a system is designed and managed, according to IFAS. Application efficiencies also vary with other factors, including stage of crop development, time of year and climatic conditions. However, the average seasonal application efficiencies of systems scheduled to maintain adequate soil moisture levels to meet crop water requirements for evapotranspiration will be much less variable.

Drought, run-off

Drought is another issue for irrigation technology to solve. The maps show drought regions across the country from 2000 to the present day. They show that regions experiencing drought have moved around the country.
Growers have to adapt, and that is where irrigation comes in. In times of sufficient rainfall, irrigation is an insurance policy against drought. One area Huntley knows well is the Colorado River Basin, a very dry region with a high agricultural output.

It isn’t just drought that impacts irrigation, according to Huntley. In the Northeast, there are demands on water for economic and cultural impact, as well as concerns over fisheries and wildlife. The Chesapeake Bay, for example, has strict run-off restrictions that limit the amounts of water growers can use, he said. The water is used for more livelihoods than just agriculture.

But how serious of a problem is run-off?

One thing that has changed is the amount of regulations relating to water and potential contamination, Crassweller said. Pending legislation relating to pesticide application and water contamination is of concern to growers.

“It seems to me that pesticide contamination of waterways is very minor compared to the contamination and degradation of water resources due to fracking with the development of Marcellus shale natural gas,” he said. “There have already been more major spills from the natural gas drilling procedures than any pesticide contamination incidents.”

Another major issue is salt, Zoldoske said.

“Salt contamination is lowering the groundwater quality in many areas,” he said. “It is forcing some growers to switch to more salt-tolerant crops. It’s another area we’re going to have to accommodate. Groundwater management is the biggest threat to irrigation.”

Sprawl

Urban sprawl plays a major role in water usage. When land and water sources are converted to urban usage, the higher-quality water is taken away as a source for agriculture and cannot be replaced, Zoldoske said.

How does agriculture come in balance with a shortened water supply? This is a burning question, Zoldoske said. Does a grower retire acreage and use what water he or she can on the most profitable crops that require the most water? Does the grower look at different forms of irrigation that reduce water consumption? How do growers plan for change and integrate irrigation systems to adapt to that change?

“We used to be able to take water from thinly populated areas for agricultural uses,” Huntley said. “That just isn’t possible anymore because of the local populations. Good agricultural land has been replaced with housing developments now, which pushes the growers away from water sources even further.”

The future is now

There are many tools available to manage irrigation, more than even dreamed of 50 years ago. Modern irrigation systems can be managed by computer systems, and even through the use of cellular phones. Technology has made irrigation systems more efficient than ever, and research is showing growers the best practices to use for individual plant species.

“I truly believe that farmers are the best caretakers of the land,” Huntley said. “The future may be a little rough, but it is bright. We can solve all of our problems, we just have to give our farmers the incentives and all the tools available for them to take advantage of.”

By Derrek Sigler





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