Does replacing fallow with winter crops affect corn yield and soil carbon retention in a Florida cropping system?

Abstract Cropping systems in the southeastern United States established on sandy soils and subject to a subtropical climate with heavy rainfall often lose nutrients and carbon during winter fallow periods. While cover crops can mitigate these losses, their adoption is limited because they are not harvested for profit. Replacing winter fallows with a cash crop may offer economic and environmental benefits, but benefits may take years to emerge. Crop simulation models, such as those within the Decision Support System for Agrotechnology Transfer (DSSAT), can complement short‐term field trials to assess longer term responses. This study assessed the impacts of replacing winter fallows with chickpea ( Cicer arietinum L.) or rye ( Secale cereale L.) on soil carbon and nitrogen in a corn ( Zea mays L.) rotation system, using a combination of experiments and crop modeling. Two years of field data were used to calibrate and evaluate DSSAT‐cropping system model (CSM) models, which were then used to simulate 10‐year responses under North Florida conditions. Chickpea and rye had limited short‐term effects on corn responses and soil conditions compared to fallow. Model calibration achieved acceptable accuracy across crops, despite challenges due to disease and extreme weather during the second experimental year. Soil organic carbon (SOC) simulations were moderately accurate due to low variability, while predictions of soil nitrogen dynamics were less accurate. Despite these limitations, DSSAT captured biomass and soil trends, supporting its use for long‐term simulations. Ten‐year simulations showed that chickpea and rye helped retain SOC but did not improve corn yields, highlighting how long‐term soil benefits might be the primary advantage of integrating a winter crop in these systems.