Agriculture increases nutrient loading to freshwater ecosystems, particularly in tile-drained landscapes. In these systems, increasing hydroclimatic variability raises questions about how agricultural conservation practices alter carbon and nitrogen availability and, in turn, regulate denitrification rates and biogeochemical resilience. While nitrate (NO₃⁻) runoff is a primary target for conservation practices, dissolved organic carbon (DOC) fuels heterotrophic metabolism and nutrient processing, including denitrification. Accordingly, we focus primarily on patterns of DOC export across field and watershed scales, and use DOC:NO₃⁻ ratios to assess responses to a common conservation practice. Winter cover crops (CC) can reduce NO₃⁻ losses, yet their influence on DOC export and DOC:NO₃⁻ stoichiometry remains unclear. We measured DOC and NO₃⁻ concentrations from 2017–2022 across field and watershed scales in two northern Indiana watersheds (>80% row crops) with variable CC coverage. We quantified how hydrologic variability and CC interact to shape DOC export and DOC:NO₃⁻ stoichiometry. Watershed-scale DOC yield was largely controlled by hydrology rather than CC, ranging from 5 to 36 kg C ha⁻¹ yr⁻¹ and peaking during the wettest years. One watershed exhibited episodic DOC export linked to antecedent rainfall, suggesting mobilization from near-surface soils, while the less flashy watershed showed lower variability and reduced sensitivity to high flows, likely reflecting groundwater contributions, soil texture, or management differences. Although CC sometimes reduced subsurface tile flow and DOC export, field-scale DOC responses to CC were inconsistent, and high CC years coincided with high precipitation and DOC yields, potentially masking CC effects at the watershed scale. In contrast, CC effects on NO₃⁻ consistently reduced field-scale NO₃⁻ losses (65% on average). Molar DOC:NO₃⁻ ratios generally remained carbon-limited for denitrification (<2:1 C:N) at both field and watershed scales. Significant differences in field-scale DOC:NO₃⁻ were observed in only one watershed, with higher ratios in tiles draining CC compared to conventional management, particularly during spring and summer. These results indicate that cover crops can transiently increase DOC availability, reduce NO₃⁻ loss, and modestly increase DOC:NO₃⁻ ratios. However, DOC export remains hydrologically controlled and ratios suggest carbon-limitation for denitrification, potentially constraining gains in biogeochemical resilience in tile-drained agricultural systems.