Corn Belt farmers already know that the region – the midwestern U.S. roughly covering western Indiana, Illinois, Iowa, Missouri, eastern Nebraska, and eastern Kansas – has some of the most fertile soils on Earth. The amount of corn harvested in this region annually has increased by +400% since 1950. But perhaps there is more to the story…
Interestingly, the region’s climate has not followed the patterns predicted by climate change researchers. Whereas the rest of the world has warmed, the corn belt region’s summer temperatures have dropped as much as a full degree Celsius, and rainfall has increased up to +35%, the largest spike anywhere in the world. Due to farming practices and the natural influence of shallow groundwater, “precipitation recycling” has increased by nearly 30% in the Corn Belt. According to a new study, this feedback loop has helped boost rainfall during the crucial growing season.
In the new study, the research team used high-resolution climate models coupled with an explicit water vapor tracer algorithm to quantify the impacts of shallow groundwater, dynamic crop growth, and irrigation on regional precipitation recycling in the US Corn Belt. The results showed the precipitation recycling ratio — or fraction of precipitation that fell as a result of local processes — reached 18% because of the combination of shallow groundwater that fed moisture to the surface, leafy corn plants that released moisture to the atmosphere, and evaporation from irrigation systems. Without such factors, the modeling showed the precipitation recycling ratio would be just 14%, or about 29% less.
However, the role of precipitation recycling varies from month to month and year to year, the research found. It peaks in summer months with the maturing of the corn crop, and in dry years when little moisture arrives from other regions. Importantly, this enhanced precipitation recycling is stronger in a dry year than normal and wet years.
Previous research by scientists at the University of California (UC), Irvine, found evidence that corn production can cause increased rainfall and decreased temperatures in Midwest states. They theorized that it has to do with photosynthesis, which leads to more water vapor in the air. Zhang and his colleagues wanted to quantify the impact of precipitation recycling.
Zhang and his team say their new research could help improve rainfall predictions for the Corn Belt and provide useful insights for water resource allocations and planting strategies. “In an agricultural region like the U.S. Corn Belt where rainfall is critical, it’s important for both farmers and water resource managers to understand where the rain comes from,” notes Zhang. The team now plans to examine how these changing precipitation patterns may impact agricultural productivity.
The findings from the Corn Belt may also provide valuable insights for other important agricultural regions. By understanding these localized climate interactions, the researchers say it could allow for a global framework for managing water resources in a warming climate. The full research paper is HERE.