Abstract
This study assessed the long-term effects of tillage and crop rotation on physical, chemical, and biological soil health indicators in two contrasting agroecosystems in Nebraska, Haskell Agricultural Laboratory (HAL) and South Central Agricultural Laboratory (SCAL). Treatments included three tillage systems: no-till (NT), reduced till (RT), and conventional till (CT), and two crop rotations: continuous corn (CC) and corn-soybean (CS). At HAL, conservation tillage practices (NT and RT) significantly improved soil organic carbon (SOC) by ∼40%, total nitrogen (TN) by ∼47%, and water extractable C and N (HWC, HWN) fractions by 75–82% relative to CT. Enzymatic activities (acid phosphatase, β-glucosidase, arylsulfatase, and urease) were also 40–60% higher under NT, indicating enhanced nutrient cycling potential. Microbial biomass carbon (MBC) increased by 9–28%, and mean weight diameter (MWD) improved by up to 59% compared to CT. Crop rotation effects were modest but CS increased urease activity by ∼49%, while CC enhanced arbuscular mycorrhizal fungi and gram-negative bacterial abundance by 33% and 28%, respectively, at HAL. The NT×CC combination led to the greatest gains in mean weight diameter (MWD), water-stable aggregates (WSA), and aggregate-associated SOC and TN, highlighting the importance of surface residue retention and minimal disturbance. At SCAL, tillage effects were generally smaller, although NT still enhanced β-glucosidase by 59%, urease activity by 58%, and MBC by 28%. Principal component analysis revealed strong associations between NT×CC systems and improved soil C and N pools, aggregate stability indicators, and biological activity indicators, while biological and aggregation responses were stronger at HAL than SCAL. These findings demonstrate that conservation tillage practices enhance soil biological activity, nutrient cycling, and structural stability, although the magnitude of these responses varies between sites. The results emphasize the importance of site-specific soil properties and management conditions in determining long-term soil health outcomes in Midwestern U.S. agroecosystems.