Diversified cropping systems enhance soybean resilience to extreme drought

Extreme precipitation threatens global agriculture production. In the Midwest U.S., drought-prone summers can lead to crop yield losses. Agricultural diversification has been touted as a climate-resilient management practice that can buffer against drought-induced crop yield decline; however, few studies have tested this hypothesis. Our objectives were to: 1) synthesize previously published and new unpublished soil physical data from a long-term experiment (>20-years) that might provide mechanistic evidence for climate-resilience, 2) measure soybean physiological response to an experimentally imposed drought. Across both objectives, we compared a business-as-usual maize-soybean rotation (2-year) to a more diversified maize-soybean-oat/alfalfa-alfalfa rotation with manure inputs (4-year). Across the 20-year experiment (Objective 1), the 4-year decreased bulk density by 3 %, decreased overall penetration resistance by 23 %, and increased water content at field capacity by 16 % compared to the 2-year. After imposing drought in both rotations (Objective 2), the 4-year reduced drought-induced decline in stomatal conductance by half compared to the 2-year. According to response ratios, the extreme drought decreased the 2-year soybean yield by 11 %, while the 4-year had no detectable yield loss. Diversified cropping systems can improve soil physical properties, and this is the most parsimonious factor explaining observed drought resilience in soybeans. Our data support the notion that diversified cropping systems can buffer against negative consequences of extreme drought – a likely scenario for future growing seasons. • > 20 years of agricultural diversification improved soil’s crop water access. • We tested if soybeans in diversified systems were more resilient to imposed drought. • Diversified soybeans had lower decrease in stomatal conductance and crop yield. • Long-rotations+manure improve soil health and increase soybean drought resilience.