Rain Exclusion eXperiment (REX)

The Rainfall Exclusion eXperiment (REX) is a manipulation study within the Main Cropping System Experiment (MCSE) established in 2021 to test mechanisms of resilience in response to induced growing-season drought and episodic rainfall across a variety of land uses. Temporary rainout shelters (14 ft ◊ 18 ft) are installed within the Conventional (T1), No-till (T2), and Early Successional (T7) treatments over the growing season to control rainfall. Under each shelter footprint, soil resources (soil carbon) and microbial diversity (fungi and nematodes) are manipulated in four subplots (4.9 ◊ 6.6 ft) using organic additions, fungicide, or nematicide. Subplot manipulations differ slightly between treatments: Conventional has only soil carbon inputs (biochar, sorghum, and switchgrass), whereas No-Till and Early Successional each have soil carbon (sorghum), fungicide, and nematicide inputs; and all footprints have a control subplot. 

Each year Control and Variable footprints are covered with rainout shelters during the growing season, while the Drought Soy, Drought Wheat, and Drought Corn footprints are only sheltered in that respective year of crop rotation and are left ambient in other years. Control footprints receive the growing season 30-year mean for weekly rainfall once a week. Variable rainfall footprints receive the same amount of total rainfall, but redistributed to be episodic – three weeks-worth of rainfall is applied over two days, with none applied for the remainder of that three week period. These three-week cycles are implemented three times in succession during each growing season in the Variable rainfall footprints. Drought footprints receive the same weekly rainfall application as the Control, outside of a six-week period during the height of the summer (July-August) when no rainfall is applied at all.

The Early Successional treatment has two additional rainout shelters that use open-top chambers (OTC) to examine the combined effects of warming and rainfall on resilience mechanisms. 

The experiment is replicated in 4 blocks for the Conventional and No-till treatments and in 6 blocks for the Early Successional treatment.