The “Optimizing Continuous Soybean Production” project funded by the ISRC and led by ISRC faculty research affiliate Sotirios Archontoulis has concluded, and a final report may be found on the ISRC’s website. Note, this project will continue with funding from the Iowa Soybean Association. Co-PIs on the project include PhD student Carolina Freitas and faculty research affiliates Mark Licht and Michael Castellano, agronomy.
The project has generated a lot of interest as continuous soybean is generally frowned upon in the Midwestern U.S. to keep soybean pests at manageable levels. Rotating soybeans with corn and other crops have generally been the norm.
According to the report, “Iowa soybean farmers could potentially benefit economically from planting soybeans after soybeans in time periods when input prices are high or in the scenario of higher soybean demand to meet crushing capacity. Soybeans do not require nitrogen fertilizer inputs and have lower production costs compared to corn. Also, current policies that aim to offset the cost of increasing biodiesel production while adopting conservation practices could increase demand for more soybean production.”
The continuous soybean project was established in 2023 at locations near Boone and Sutherland, Iowa. The study explores seven cropping system treatments, with two soybean cultivars (PI88788 and Peking resistance, subplots), each replicated four times. Plots are 16 rows by 100 feet to allow for extensive data collection and collaboration across multiple labs. The cropping systems explored are: 1) soy-soy in 30” rows, 2) soy-soy in 15” rows, 3) soy-rye cover crop-soy, 4) soy-rye cover crop-soy + manure, 5) corn-corn, 6) corn-soy, and 7) soy-corn. The data collected covers a wide range of agronomy research areas including drone imagery, hydrology, crop physiology, soil and soybean pathology.
While field experiment results have not yet shown a yield gap associated with growing soybeans for four consecutive years, in 2025, researchers did observe a trend of increased soybean cyst nematode (SCN) pressure in plots where soybeans were grown continuously. Large variability in the measurements and differences amongst treatments varied by location.
In addition, hydrology data collected from sensors used in the study has provided valuable information on the importance of water tables to crop production, and patterns of water use for both corn and soybeans. While in-season rainfall is the main water source, it cannot support crop water demand alone. More detailed information can be found in the report.
With funding from ISA, this experiment is continuing in 2026, and similar data to the ISRC-funded project will be collected to build capacity and gain confidence in conclusions and recommendations.
