Study Finds U.S. Yield Trends Vary By Crops and Regios

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Study Finds U.S. Yield Trends Vary By Crops and Regios

A 65-year comparative analysis between U.S. yields of irrigated and rain-fed crops has sounded a message to farmers, land managers and policymakers: Mind the gap.

By Scott Schrage | University Communication

The University of Nebraska–Lincoln’s Suat Irmak and Meetpal Kukal analyzed the annual yields of nine crops — corn, soybean, spring wheat, winter wheat, sorghum, cotton, barley, oats and alfalfa — on a county-by-county basis from 1950 to 2015.

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Representative image source: Pixabay, labeled for reuse

Irmak and Kukal found that the yield gaps — differences in food produced with irrigation vs. rainfall alone — generally widened over that span, a trend they suspect stems partly from climate change and technological advances in irrigation management.

But the rates at which those gaps widened, and how consistently they did so over time, differed substantially among the crops and the regions that grew them.

“You get more yield from irrigated than rain-fed (agriculture), but the magnitude of yield increase is a function of several variables,” said Irmak, Eberhard Distinguished Professor of Biological Systems Engineering. “It’s not surprising that as precipitation increases, the yield gap decreases. But that also has spatial and temporal attributes, so it’s not really constant in all regions or for all crops.”

Irrigation most benefited corn yields, according to the study, boosting them 270% nationally over the 65-year span. The unique growing season of winter wheat meant that its yields rose only 25% with irrigation, the smallest gain among the nine crops. Yet even crop-specific yield gaps varied noticeably by location. Two corn-growing areas separated by about 700 miles, for instance, saw a seven-fold difference in irrigation-related yield gains.

Having mapped such differences across roughly 80% of the United States’ cultivated land, the researchers said they hope the findings can help guide future crop production while calibrating water management and irrigation use nationwide.

Reference:

Meetpal S. Kukal, Suat Irmak, "Irrigation-limited yield gaps: trends and variability in the United States post-1950", Environmental Research Communications, July 2019, DOI: 10.1088/2515-7620/ab2aee

Meetpal S. Kukal, Suat Irmak, "U.S. Agro-Climate in 20th Century: Growing Degree Days, First and Last Frost, Growing Season Length, and Impacts on Crop Yields", Scientific reports, May 2018, DOI: 10.1038/s41598-018-25212-2

Meetpal S. Kukal, Suat Irmak, "Climate-Driven Crop Yield and Yield Variability and Climate Change Impacts on the U.S. Great Plains Agricultural Production", Scientific Reports, February 2018, DOI:  10.1038/s41598-018-21848-2

Read the full report by Scott Schrage on Nebraska Today

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