Contrary to conventional wisdom, irrigated corn in Nebraska is highly efficient in the use of energy, water and fertilizer, according to University of Nebraska-Lincoln scientists whose research found that increased yields more than offset the energy cost of these inputs.
This research has important ramifications for agriculture’s efforts to meet increasing global needs for food, feed, fuel and fiber on existing farmland, says Ken Cassman, a UNL agronomist who holds the university’s inaugural Robert B. Daugherty Professorship. Cassman and Patricio Grassini, a UNL research professor in agronomy and horticulture, co-authored a paper about their research that appears in this week’s Proceedings of the National Academy of Sciences.
“If the goal is simply to reduce greenhouse gases or to have the highest possible energy efficiency, you’d do that producing crops without any inputs at all, or by getting rid of agriculture entirely,” Cassman says. “Of course that’s not a tenable position. The challenge, therefore, is how to produce enough food in a way that also protects the environment, conserves natural resources and minimizes the greenhouse gas emissions from agriculture.”
The UNL research shows that modern, irrigated, high-input agriculture, though it uses more fossil fuels and generates more climate change-causing greenhouse gases than dryland systems, also produces much higher crop yields.
At a glance
• UNL scientists say irrigated corn is efficient and high-yielding.
• Management gains produce lower inputs per unit of production.
• Nebraska irrigated corn is a benchmark for future cropping systems.
The widely held perception of irrigated agriculture as wasteful of energy fails to take into account crop management changes in recent decades that have increased yields without requiring more fertilizer or irrigation, Cassman says.
Those changes have steadily boosted the energy efficiency of irrigated corn grown in the western Corn Belt and High Plains, including Nebraska, Colorado, South Dakota, North Dakota, Kansas, Oklahoma and parts of Texas, which accounts for about 15% of U.S. corn production.
“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 dryland systems with much smaller input levels and lower yields,” Grassini explains.
The findings are based on several years of field data collected from a large number of commercial production fields in Nebraska. This “rigorous on-farm assessment” is a first, Grassini explains.
Previous research used secondary data gathered and extrapolated by the USDA through producer surveys.
“In our study, each field has its own database. We could go back to the same field in 10 years and see how things have changed,” Cassman adds.
It’s important to assess energy efficiency and GHG emissions of cropping systems on a yield basis, not a land-area basis, Grassini says.
To illustrate that point, Grassini says it would be possible to achieve a large decrease in GHG emissions in the three Nebraska counties included in this study — Gosper, Phelps and Kearney — by converting irrigated cropland into dryland agriculture, but to make up for the estimated 50% decrease in grain yield would require 308,000 additional acres of dryland corn production in Nebraska.
Penny-wise and pound-foolish
“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 adds.
“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 says. “This paper sets standards on how you can do that using real-world farm data.”
“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.
The findings do not mean irrigated corn systems can’t be made even more energy efficient, Cassman says. 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 plowing, and fine-tuning applications of nitrogen fertilizer and irrigation water.
UNL scientists now are conducting similar research on soybean production in Nebraska.
The article in the Proceedings of the National Academy of Sciences is titled “High-yield maize with large net energy yield and small global warming intensity.”
Source: University of Nebraska-Lincoln
CONTINUED IMPROVEMENT: Better crop management and technology have steadily boosted the energy efficiency of irrigated corn in the High Plains, says Ken Cassman, an agronomist and professor at teh University of Nebraska-Lincoln.