Seasonal Dynamics of Soil Biological Properties under Long‐term Cereal Rye Cover Cropping in a No‐till Corn–soybean Rotation in Southeastern Indiana

Abstract Cover crops are widely used in corn ( Zea mays L.)–soybean ( Glycine max ) systems to improve soil health, yet seasonally dynamic responses of soil biological properties to long‐term cover cropping remain not fully understood, particularly in the low‐organic matter Alfisols of the eastern Corn Belt. We evaluated the effects of more than a decade of cereal rye ( Secale cereale L.) cover cropping on soil biological properties in a no‐till corn–soybean rotation in southeastern Indiana in a field experiment established in 2011. Soil samples were collected at two depths (0–10 and 10–20 cm) during fall, spring, and summer in 2023–2024 and analyzed for microbial biomass carbon and nitrogen (soil microbial biomass carbon [SMBC] and soil microbial biomass nitrogen [SMBN]), potentially mineralizable carbon (PMC), permanganate‐oxidizable carbon (POXC), autoclaved citrate‐extractable (ACE) protein, and enzyme activities associated with carbon (C), nitrogen (N), and phosphorus (P) cycling. Cover cropping increased SMBC, SMBN, and PMC, with treatment effects varying by season and soil depth. Cover crop effects on microbial biomass and PMC were most pronounced during spring and were largely confined to the 0–10 cm. In contrast, POXC, ACE protein, and enzyme responses were indicator‐specific; acid phosphatase activity increased under cover cropping and peaked in summer, whereas POXC, ACE protein, and activities of β‐glucosidase and N‐acetyl‐β‐glucosaminidase showed limited overall treatment effects. These findings indicate that long‐term cereal rye cover cropping enhances biologically mediated C and nutrient cycling in no‐till systems, with effects expressed in a seasonally and vertically stratified manner rather than as uniform, sustained increases.