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How sensors in space can help scientists know if crops have enough water to grow

"What we think we should see from space is that in the morning we should see juicy plants and in the evening we should see plants that have dried out a little bit, if they're happy," said Iowa State University agronomy professor Brian Hornbuckle. "If they're not happy, we're expecting to see no change in plants from morning to evening, because they were not able to open their stomata and therefore didn't lose any water because they couldn't afford to do that."
Graphic by Deb Berger/Iowa State University.
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Photos provided by NASA and Brian Hornbuckle.
"What we think we should see from space is that in the morning we should see juicy plants and in the evening we should see plants that have dried out a little bit, if they're happy," said Iowa State University agronomy professor Brian Hornbuckle. "If they're not happy, we're expecting to see no change in plants from morning to evening, because they were not able to open their stomata and therefore didn't lose any water because they couldn't afford to do that."

NASA satellites can provide critical information to farmers about the condition of their plants.

One satellite, called ECOSTRESS, measures the temperature of plants. Another, called SMAP, measures the amount of water in the soil, and takes measurements in the morning and evening each day.

Using a $536,000 NASA grant, Iowa State University researchers are collecting data from sensors on these two NASA satellites to get a more accurate picture of what crop stress looks like across the Corn Belt. The data they collect could serve as an early warning system for crop stress, ultimately helping farmers make important decisions during harvest.

“In the past, if we see hot crops, that means they don’t have enough water in the soil,” said Iowa State University agronomy professor Brian Hornbuckle, who is leading the research. “The new approach is to actually look at the water in the plants, how that water in the plants changes over the day.”

See, plants that are thriving and “happy” have enough water in the soil. They open tiny pores in their leaves called stomata to take in carbon dioxide from the atmosphere and release oxygen. It’s part of their photosynthesis process that helps them grow.

“What we think we should see from space is that in the morning we should see juicy plants,” Hornbuckle said. “And in the evening, we should see plants that have dried out a little bit, if they’re happy.”

If they’re not happy, Hornbuckle said there should not be any changes in the plants from morning to evening. If they don't have enough water, they won't open their stomata so they can preserve that water. “They’re not putting mass on grain,” he said. “They’re not adding anything to the yield that we’ll harvest at the end of the season.”

Initial results are promising, Hornbuckle said, providing insight into plant stress that coincides with an area’s drought status.

“Our initial results are showing that yes, there is a significant difference in these measurements between the morning and the evening in areas that are less affected by drought,” Hornbuckle said.

Understanding if plants are water-stressed can give farmers a better idea of what their crop yields will look like. The data from the research could be an early warning system for crop stress, helping farmers make key financial decisions.

“It will help them decide what to do in terms of economics: ‘should I sell more of the grain that I’ve stored from the previous season? Are prices going to go up? Are they going to go down because maybe we’re going to have less yield than we expected because of water stress?’,” Hornbuckle said.

The team could also share the data with weather and climate forecasters to help them improve weather and climate predictions.

Katie Peikes was a reporter for Iowa Public Radio from 2018 to 2023. She joined IPR as its first-ever Western Iowa reporter, and then served as the agricultural reporter.