Our primary goal here is to answer the question (and title of the proposal): do soil health promoting practices make soybean production more climate resilient?

We will leverage the ISA-funded (FY 2022) precipitation exclusion, application systems (PEAS) to test specifically soybean physiological response to future climate scenarios. Climate models predict wetter springs (>15 %) and more variable summer precipitation that will include more droughty summers (NOAA National Climate Assessment, 2023). Our intent is to add 20% precipitation to ambient rainfall between months of April through June 21, and thereafter remove 50% precipitation until end of September. This will simulate a ’worse-case’ future precipitation (FP) scenario with wetter springs making it more difficult to get in the field, and drier summer mimicking soybean-limited soil moisture conditions that may occur more frequently in the future. We will have an ambient precipitation (AP) and FP sub-plots within a long-term (22 years), randomized, replicated trial crop rotation experiment – the Marsden Agricultural Diversity Experiment (MADE) – that has three rotations: corn-soybean plus synthetic N fertilizer (2-year), corn-soybeans-oat/redclover (3-year), and corns-soybean-oat/alfalfa-alfalfa plus composted cattle manure (4-year). Prior research from PI-McDaniel’s group, Soil Health Institute, and others have documented the many soil health benefits from the 4-year rotation compared to the 2-year. We will focus on comparing whether these increases in soil health translate to more climate resilience in 4-year rotation compared to the 2-year. In other words, does improving soil health buffer soybean yields against these changes in precipitation?

1. Determine if long-term adoption of soil health promoting practices (e.g., diversified crop rotations and manure) increase soybean resilience to drought.
2. Determine effects of future precipitation in Iowa - wetter springs drier summer - affects soils and crops more generally.

- Peer-reviewed publications
- Field days
- Extension/outreach presentations
- Contacts with farmers using similar practices

Updated September 9, 2025:
The second year of Precipitation Exclusion and Application Systems (PEAS) research continued in the summer of 2024. This season, the soybeans (Pioneer P22A67E) were planted on May 30th, 2024, and the PEAS was deployed on June 6th, 2024. Water application for the season began on June 18th, 2024, and continued until September 24th. The irrigation protocol included two treatments: AP- Ambient Precipitation and FP-Future Precipitation. The AP shelters received the total amount of precipitation the previous week, and the FP shelters received 20% more water than last week's total precipitation until June 20th,2024, and 75% less water for the rest of the cropping season. Rotations were similar to the previous year: 2-year rotation and 4-year rotation. In addition to these rotations, we observed a preliminary outside plot (identical to the area covered by PEAS but without a rainout shelter) to compare the shelter effect to our collected measurements.

During the season, soil moisture was measured at 12 depths using Sentek Drill and Drop soil moisture sensors. These sensors provided insight into moisture distribution along the vertical profile and root activity in various depths. We also conducted manual root samples showing us the root biomass at three different depths (0-15 cm, 15-30 cm, and 60-45 cm). These root samples are currently being processed to separate roots. In addition, we collected PAR and net radiation data to get an energy balance inside and outside of the rainout shelters and to understand the microclimate differences created by shelters. We also collected N2O emissions bi-weekly and stomatal conductance once during the season. All the data is still under analysis, pending graphs and statistics.

View uploaded report

Springs are getting wetter and summer precipitation is more variable making growing soybeans more difficult for farmers.
Wetter springs reduce the days of operation and drier summers can hinder crop yields.
We're testing whether long-term management - in this case including small grains and forages plus animal manure as source of nutrients - can help buffer some of these changes.