(CN) – A warming climate and bigger corn yields mean Midwestern corn growers who today rely on rainfall to water their crops will need to switch to irrigation by midcentury if current trends continue, possibly setting off a battle royale for dwindling water supplies, new research released Monday suggests.
Trends toward hotter, drier weather in the Midwestern United States stemming from climate change and bigger, more productive corn plants will draw more moisture out of the plants, resulting in increased water use and water loss through plant leaves, according to the study published Tuesday in the journal Ecosphere.
Without comparable increases in rainfall, corn growers who currently water their fields with rainwater will have to irrigate them, which could deplete aquifers, disrupt streams and rivers, and exacerbate already tense water disputes between farmers, cities and wildlife, say researchers.
"In California and much of the arid west, battle lines have been drawn between agriculture (irrigation) and the needs of urban centers," lead study author and University of Illinois plant biologist Evan DeLucia wrote in an email. "This has not historically been a problem in much of the Midwest where irrigation currently is minimal. It is concerning that the challenges faced by the western U.S. over water could be moving east."
DeLucia and his team calculated how much water corn plants would lose through evaporation at the hotter temperatures expected by the middle of this century in the Midwest, where much of the country's corn is grown.
They found that increases in "vapor pressure deficit" – the difference between the amount of moisture in the air and how much moisture the air can hold – will require triple the amount of irrigated water used today to maintain current corn yields in areas where farmers use rainfall on their crops.
But that's only one piece of the puzzle. Since the 1990s, corn plants have been bred or genetically engineered to be bigger and more productive – and bigger plants need more water, DeLucia said.
Average corn yields in the Midwest today are about 170 bushels per acre, a 50-bushel increase since 1990. Researchers say if the trend continues, Midwestern corn yields could jump to an average 230 bushels to 240 bushels per acre, which would require more water. But hotter weather alone will increase water demand, they say.
Planting fewer acres of corn to avoid a water fight may be unrealistic. According to DeLucia, much of the corn grown in the United States is fed to livestock to satisfy an increasing demand for meat - typically more expensive than vegetables or grains - from a growing and more affluent population, a trend that will likely continue.
Researchers instead suggest combating drier weather by using minimum tillage and mulches to reduce the rate of water loss from the soil, and breeding or genetically modifying plants to capture more chlorophyll in their lower leaves. This would make photosynthesis more efficient closer to the ground, where it's more humid. And it would reduce moisture loss when plants open the pores in their leaves to take in carbon dioxide during photosynthesis, they say.
"There are a number of physiological strategies that could be bred or engineered into crops to make them more efficient in water use. This has not been a priority in the past, but perhaps should be a higher priority to prepare us for the future," DeLucia said. But he said agricultural techniques like these alone aren't sufficient for dealing with a warming climate.
"We really need to move rapidly away from fossil fuels as an energy source and toward renewable energy to slow the rate of climate change," DeLucia said. "This should be a national priority."
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