Researchers reveal the growing sensitivity of the US corn crop to drought

Like a baseball player whose home runs increase despite losing more curves each season, the prodigious production of the US Corn Belt hides a growing vulnerability. A new Stanford study reveals that while yields have increased overall, possibly due to new technologies and management approaches, the staple crop has become significantly more sensitive to drought conditions. The research, published on October 26 in Natural food, uses a new approach based on large differences in the ability to retain moisture between soils. The analysis could help lay the groundwork for accelerating the development of approaches to increase the resilience of agriculture to climate change.

“The good news is that new technologies are really helping to increase yields, in all kinds of weather conditions,” said lead author David Lobell, director of Gloria’s Center for Food Safety and the Environment. and Richard Kushel. “The bad news is that these technologies, which include some specifically designed to withstand drought, are so useful in good conditions that the cost of bad conditions is rising. So there is still no sign that they will help reduce the cost of change. climatic “.

Corn production in the United States is a seemingly unstoppable behemoth. Despite concerns about hardy weeds, climate change, and many other factors, the industry has set record yields in five of the past seven years. Probable drivers of these extraordinary crops include changes in planting and harvesting practices, such as the adoption of drought tolerant varieties, and changes in environmental conditions, such as reduced ozone levels and higher concentrations of atmospheric carbon dioxide which generally improve the efficiency of crop water use.

As climate change intensifies, however, the cost of maintaining crops is likely to increase.

Using county soil maps and satellite-based yield estimates, among other data, the researchers examined fields in the corn belt, a nine-state region of the Midwest that accounts for about two-thirds of corn production in the United States. . By comparing fields along drought stress gradients each year, they could identify how sensitivity to drought is changing over time.

Even within a single county, they found a wide range of soil moisture retention, with some soils being able to retain twice as much water as others. As might be expected, there were generally higher yields for soils that held more water. They found that yield sensitivity for soil water accumulation in the region increased by an average of 55% between 1999 and 2018, with greater increases in the driest states.

The results made it clear that the soil’s ability to hold water was the main reason for the loss of yield. In some cases, the soil’s ability to hold more moisture was three times more effective in increasing yields than an equivalent increase in rainfall.

So why have crops become more sensitive to drought? A variety of factors may be at play, such as the increased water requirements of crops due to the higher planting density of plants. What is clear is that, despite robust corn crops, the cost of drought and global demand for corn are increasing simultaneously.

To better understand how climate impacts on maize are evolving over time, researchers are calling for greater access to field-level yield data measured independently of meteorological data, such as government insurance data that was previously publicly available but not. I am more.

“This study shows the power of satellite data, and if necessary, we can try to track things from space on our own. It’s exciting,” Lobell said. “But knowing whether farmers are adapting well to climate stress and which practices are most beneficial are key questions for our nation. In today’s world, there is really no good reason why researchers shouldn’t have access to. all the best data available to answer these questions. “

Lobell is also Professor of Earth System Science at Stanford’s School of Earth, Energy & Environmental Sciences; the William Wrigley Senior Fellow at the Stanford Woods Institute for the Environment and a senior fellow at the Freeman Spogli Institute for International Studies and the Stanford Institute for Economic Policy Research. Co-authors of the study include Jillian Deines, postdoctoral researcher at Stanford’s School of Earth, Energy & Environmental Sciences, and Stefania Di Tommaso, research data analyst at the Center on Food Security and the Environment.