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College of Food, Agricultural, and Environmental Sciences


Field Crop Irrigation May Work For Some Ohio Growers

September 23, 2002

COLUMBUS, Ohio - When it comes to production practices, irrigating field crops usually does not make an Ohio grower's list of necessary agricultural investments.

However, during growing seasons like this year, when corn and soybeans struggle amidst drought conditions and farmers ponder alternative money-making uses for their crop, an irrigation system may not be so far-fetched.

"Ohio normally tends to get enough rainfall during the summer months that investing in an irrigation system for field crops does not work out to be economically feasible over the long term under traditional irrigation approaches," said Larry Brown, an Ohio State University Extension agricultural engineer and professor of Food, Agricultural and Biological Engineering. "But if we continue to experience dry conditions year after year, then there are cases where it could work for the grower under the right conditions." According to the most recent statistics available to Brown - a limited survey he conducted in 1989 - less than 40,000 acres of Ohio farmland is irrigated. The actual amount of irrigated farmland today is possibly twice that, said Brown, but no comprehensive survey has been conducted recently.

Irrigation systems in Ohio are used mainly for fruits and vegetables, where benefits of the crops' high-value and the smaller acreages tend to outweigh the costs of the system.

"You are talking about an irrigation system that can cost anywhere from a few thousand to upwards of $200,000 depending on the system to be used on 30 to 200 acres of corn or soybeans. A grower might need the system for parts of only two months in two to three years out of five, and that's a difficult proposal to justify," said Brown.

Regardless of the economics, Brown said that there are often a few weeks in almost every growing season where corn and soybeans could use a little extra water. And, after this crop season, many producers may seriously start to consider irrigation. The June-August months were considered the eighth driest Ohio summer since 1895, according to the National Oceanic and Atmospheric Administration (NOAA).

"Using irrigation on field crops is doable, but a number of factors need to be considered before making such an investment," said Brown.

One such factor is the amount of precipitation an area receives. Precipitation as rainfall varies throughout the state, with about 10 inches more rainfall occurring in southern Ohio than in northern Ohio on an annual basis. However, in most Ohio counties the maximum monthly rainfall usually occurs during the growing season. The potential amount of rainfall during the growing season helps to determine the need for supplemental irrigation, said Brown.

Growers should also consider an available water supply, such as a river, creek, pond or well, which can be used for irrigation purposes.

"The water supply needs to be of a sufficient volume and flow rate to be able to help meet the irrigation needs of the growing crop during dry times," Brown said. The potential water supply needs to be reliable during drought periods, and Brown noted that "many streams are dry during drought times, and therefore are not the most reliable sources of water." A well or stream flow of six to 15 gallons of water per minute is generally required for each acre to be irrigated. For frost protection, the flow rate increases three to 10 times per acre. When using a pond as a water source, one to one and a half feet of water should be stored for each acre to be irrigated.

Brown said many farmers along the Ohio River bottoms in the southern half of the state use irrigation systems on their field crops because ground water is close enough to the surface and the river is in close proximity, and in high enough amounts where it may be more economical to use irrigation systems that tap into these readily available water supplies.

"If a grower has an available and sufficient water supply, the potential may be there for irrigation," said Brown, because of the energy costs associated with pumping water.

The amount of irrigation water required to grow a crop depends largely on the soil type and how well that soil can hold onto water or easily drain water away. Water flows easily through sandy soils, and drains away quickly because sandy soils are made up of large-sized particles that cannot hold on to the water very well. Silt-loam and silty-clay soils, on the other hand, are made up of smaller-sized particles, which hold on to water better, but make it harder for excess water to drain away.

"With an irrigation system, the goal is to try to maintain the soil's water content midway between the plant's wilting point (a water content where the plant can no longer extract available water from the soil) and the soil's field capacity water content," said Brown. "The amount of water in a soil between the wilting point water content and the field capacity water content is the plant available water, and this is the water that the plant can generally use. With sandy soils a grower might have to irrigate every two to three days; with silt loam and clay soils, every four to six days, depending on the actual crop being grown." Some crops, such as corn, are more water-dependent than others, and tend to perform poorly when adequate water is unavailable.

"The daily water-use requirements may range between one-tenth of an inch to a half-inch depending on the crop and its stage of growth," said Brown. For example, average water use of a corn crop during pollination and grain fill is about 1/3 inch per day.

Brown said that growers should consider the type of irrigation system they might need for their commercial production, as several are available that range in price and require different management and labor requirements. Brown noted that a farmer's operation and management time would increase under an irrigation system.

"The traditional overhead sprinkler systems are the most popular and are used largely in mid-western states like Kansas, Nebraska and Michigan," said Brown. "But there are alternative systems out there that a grower might find more efficient and economically feasible." Micro-irrigation systems, including trickle irrigation and drip irrigation, are widely used in commercial horticultural crops and home gardens, and are gaining popularity for other agricultural uses. For growers who are seeking to rent equipment on a short-term basis, a reel-type of irrigation system, known as a big gun, may be a viable option. The system is used on golf courses and turf-grass production areas.

Above all other factors to consider when evaluating an irrigation system, Brown emphasized, is the economic feasibility of the investment.

"In my opinion, a grower needs to do a detailed economic analysis, which includes all of the other factors involved, what the grower needs and how long that grower may need to use the system," he said. "Do your homework. For short periods in a typical Ohio growing season the return on the investment may not be there."

Candace Pollock
Larry Brown