It’s long been assumed that diversified cropping systems, which involve growing a variety of crops in one area with manure as a nutrient source, can assist climate change mitigation efforts by increasing the amount of carbon stored in the soil. But a recent study coauthored by assistant professor and extension specialist Steven Hall counters this perspective.

Published in Nature Sustainability in January 2025, the study finds that adding organic matter to the soil stimulates microbial activity, which boosts decomposition and causes an uptick in carbon dioxide emissions that counteracts the increased carbon input of diversified crops. Based on data from a long-term field trial at Iowa State University, the study also indicates that, as organic matter breaks down faster in these systems, it releases more of the nitrogen that crops need to thrive. This decreases the need for synthetic fertilizer applications, likely reducing emissions of the heat-trapping gas nitrous oxide.