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Irrigation boost crop energy efficiency -- study

Jeff Caldwell 01/19/2012 @ 1:27pm Multimedia Editor for Agriculture.com and Successful Farming magazine.

Irrigated corn on the Plains is energy-intensive, high-cost and high-risk, right? Wrong.

That's the theme of a recent portfolio of research by University of Nebraska agronomists Ken Cassman and Patricio Grassini. What's sometimes seen as an energy-hogging way to net huge corn yields can actually do so with high levels of efficiency and low impacts to the surrounding natural environment. The researchers say these are based on "several years' field data collected from a large number of commercial production fields in Nebraska" as well as other USDA data and farmer surveys.

"We found that irrigated corn had substantially larger net energy yield and less greenhouse gas emissions per unit of grain produced than corn from rainfed systems with much smaller input levels and lower yields," says Grassini, adding that a crop's energy efficiency should be measured on a yield basis, not on land area used.

Irrigation does use more resources -- namely water -- at the outset. But longer-term, the resource balance makes irrigation a more balanced system than dryland production in a state like Nebraska. Grassini says converting irrigated land to dryland would yield a per-acre decrease in greenhouse gases. But, on the other side of the equation, it would require twice as many acres in production to raise the same amount of grain.

"Thus it is penny-wise and pound foolish to convert irrigated agriculture back to dryland production for the sake of reducing greenhouse gas emissions," Grassini says.

Cassman and Grassini's research doesn't ignore the issue of water scarcity in the nation's midsection. But, it does illustrate how the availability of resources like water can work together with a production system like center-pivot irrigation to maximize yields in a given environment under a given production system.

"The story of irrigated corn in Nebraska can be taken as a benchmark for other current and future irrigated cropping systems because it shows that achieving high yields, high energy efficiency, and low global warming potential are not mutually exclusive goals in real-world commercial farming," Grassini says.

Adds Cassman: "The findings do not mean irrigated corn systems can't be made more energy efficient. Continued progress can come with use of best management practices, including rotation of corn with soybeans rather than continuous corn, replacement of surface irrigation with pivot irrigation systems, use of conservation tillage practices rather than conventional disc-plowing, and fine-tuning applications of nitrogen fertilizer and irrigation water."

What about cost?

If raising an irrigated corn crop is more efficient when it comes to natural resources, what about the cost of the systems? Irrigation obviously carries additional costs, but can a new system justify itself on the balance sheet? That depends on a lot, says Agriculture.com Crop Talk frequent contributor Nebraska Sandhiller.

"If you are in a area where you would not need to run it many hours to get a big bump in yield it would be like having an insurance policy," he says. "What will it cost to get water? You may be able to get fairly cheap interest on a new center pivot. Do yuo have electricity or natural gas available, or would you be using diesel? In my area diesel cost several times as much as electric. If electric, would it get shut off at times of high demand, and if so would you have enough water to make it through those times."

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