Ag Weather Forum

The month of July is prime time for the U.S. corn crop. The crop moves into the reproductive phases of pollination and grain fill -- when this year's yield is determined. Timely precipitation is critical to the success of these phases. Research on the subject of "precipitation recycling" by scientists at the U.S. National Science Foundation National Center for Atmospheric Research (NSF NCAR) has found the large amount of acreage in the central U.S. devoted to corn has indeed made a big difference in precipitation patterns -- notably, during the summer.

Research findings were published earlier this year in the Proceedings of the National Academy of Sciences, the peer-reviewed journal of the National Academy of Sciences. The subject -- precipitation recycling -- is defined as a process in which the moisture released to the atmosphere by plants, soils, lakes, and other features of the landscape returns to the same area in the form of rain. The NSF NCAR research team used advanced computer modeling to determine that Midwest agriculture, combined with shallow groundwater, increases the precipitation recycling ratio by almost 30%. That is a significant increase in moisture during the growing season.

Precipitation recycling is not a constant over the growing season. It varies from month to month and year to year, the research found. Precipitation recycling shows a maximum in summer months with the maturing of the corn crop, and in dry years when little moisture arrives from other regions.

That recycled moisture is not a minor amount. University of Illinois energy and environmental stewardship educator Duane Friend noted in a 2021 "All About Weather" post that one acre of corn can add up to 4,000 gallons of water to the atmosphere in a day. This "corn sweat" is also cited as a big factor in higher humidity values during midsummer both in the day and night.

Regarding the influence of recycled moisture, the NSF NCAR scientists used the NSF NCAR-based Weather Research and Forecasting (WRF) model, which can simulate the atmosphere at a very high resolution of four kilometers (about 2.5 miles). They also used another NSF NCAR-based computer model, known as Noah-MP, which allows specific analysis of the interactive system of groundwater, crop growth and irrigation. They applied a physically realistic algorithm to trace the movement of water vapor in the simulations. Then, they compared scenarios that included crops, irrigation and groundwater with other scenarios that lacked one or more of those factors. Project lead author, scientist Zhe Zhang, said in a news release on the project: "We were able to truly distinguish how different processes contribute to changes in precipitation. Since agriculture relies on rainfall, this understanding can inform agricultural management as well as lead to a better understanding of freshwater availability."

The Precipitation Recycling research was funded by the National Science Foundation (NSF). Scientists from the Hong Kong University of Science and Technology and the University of Santiago de Compostela in Spain also joined the project.

More details on the Precipitation Recycling research project are available here: https://www.pnas.org/….

Bryce Anderson can be reached at bryce.anderson@dtn.com

(c) Copyright 2025 DTN, LLC. All rights reserved.