Thanks to bigger yields, irrigated corn is more energy efficient

Irrigated corn in Nebraska is highly efficient in the use of energy, water and fertilizer, as the increase in yields more than offset the energy costs of inputs, according to researchers at the University of Nebraska-Lincoln.

The research paper "High-yield maize with large net energy yield and small global warming intensity," was published online in the Proceedings of the National Academy of Sciences. You can view the abstract and view the entire paper here.

The paper was co-authored by Ken Cassman, a UNL agronomist, and Patricio Grassini, a UNL research professor in agronomy and horticulture.

As noted in North Platte Bulletin (click here for the article), the research shows that modern, irrigated, high-input agriculture, even though it uses more fossil fuels than rainfed systems, also produces much higher crop yields. The perception of irrigated agriculture as "energy wasteful" fails to take into account crop-management changes in recent decades that have increased yields without more fertilizer or irrigation, Cassman said in the paper.

"In fact, 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," Grassini told the paper.

Research findings are based on several years' field data collected from a large number of commercial production fields in Nebraska.

In the Wisconsin Ag Connection (click here), Grassini said that it's important to assess energy efficiency and greenhouse gas (GHG) emissions of cropping systems on a yield basis, not a land-area basis. For example, it may be possible to achieve a large decrease in GHG emissions in the three Nebraska counties included in the study by converting irrigated cropland into rainfed-only agriculture, but to make up for the estimated 50 percent decrease in grain yield would require an additional 308,000 acres of rainfed corn production.

"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 told the publication.

"At some point, in a world with limited resources and confronted with emerging challenges such as climate change and limited supplies of fresh water, understanding how all of the world's agriculture performs in terms of net energy yield, greenhouse gas emissions intensity and water and nitrogen productivity is going to be important," Cassman said. "This paper sets standards on how you can do that using real-world farm data."

Yet progress can still be made – as farmers continuously adopt improved management practices, adopt advanced irrigation systems, take advantage of conservation tillage practices, utilize improved hybrids and fine-tune applications of nitrogen fertilizer and irrigation water. (It's sustaining innovation!)

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Cassman, if you recall, published some research in 2009 that examined modern production methods for corn and ethanol – and the results were impressive. One of the best points of that work (see the links below) was that between 10 and 19 gallons of ethanol are produced for each gallon of petroleum used in the entire corn to ethanol production life cycle.

Some have a hard time grasping this – especially after doing a Google search and coming up with some very (very!) dated work by Pimentel that continues, despite being out of date and inaccurate by today's standard, to be repeated by the anti-ethanol crowd.

• University report slams corn ethanol myths
• Ethanol reduces greenhouse gas emissions, oil use