Where’s the Water?
Today’s crop models–our primary tools for predicting yields and how crops respond to climate change–ignore the contribution of groundwater, a substantial source of water for agriculture. In part, this is because there is a lack of data on groundwater in agriculture to inform crop model improvements. As a result, future climate change predictions on grain yield are uncertain, especially in environments with wet soils, such as areas of the Midwest Corn Belt.
Most crop models are capable of simulating drought stress but not excess moisture stress, including flooding. A major assumption of these models is that there is no water table–the subsoil layer that is fully saturated with water–in a soil profile. Rather, the models take for granted that water enters the top of the soil profile as rain or irrigation and leaves from the bottom of the profile as drainage. With a $300,000 FFAR grant and matching funds from the Iowa Crop Improvement Association, Iowa State University’s Dr. Sotirios Archontoulis and his research team addressed this problematic assumption in two steps.
First, the team carried out research to enable simulations of excess moisture in crop models. Second, they linked excess moisture stress to soil-root-plant processes so the model can simulate excess moisture’s impacts on grain yields. The researchers not only found that water balances change, but they also determined how the excess moisture stress affects grain yields.
With the results of these breakthroughs, the research team released web-based tools to inform growers and agronomists about soil water and also how this affects the soil nitrogen. A major advantage to growers and researchers is they can use these data to better predict crop yield based on soil water availability.
Better Predictions of Future Yields
To develop excess moisture simulations, the researchers gathered data on water table fluctuations and soil moisture from field experiments. They then used the Agricultural Production Systems sIMulator (APSIM), a commonly used platform for modelling agricultural systems, to simulate soil moisture at scale.
The team also carried out further field experiments and literature review to link excess moisture stress to crop growth and grain yield. In addition, the experiments examined crops’ root functionality in response to crop management, and environmental settings.
“What makes this research exciting is that we are able to more accurately represent the real-world system across scales and see how plants and soil processes respond to the full spectrum of water stress—from too little water to too much water induced by shallow water tables,” explained Dr. Archontoulis. “The simulated grain yield response to precipitation better matched real-world observations, which is a major step towards more accurate future climate change yield predictions and agronomic assessments.