The Iowa Nutrient Reduction Strategy is a statewide effort that aims to encourage voluntary adoption of conservation practices by farmers to reduce the loss of nitrogen and phosphorus that contribute to water quality impairments in the Upper Midwest and drive hypoxic conditions in the Gulf of Mexico. This work is an analysis of the first 2 years (2015–2016) of a 5‐year survey of Iowa farmers. We employ causal mediation analysis to examine the direct and indirect effects of key explanatory variables (e.g., information sources, nutrient management influences, involvement in watershed management activities, and conservation technical assistance) and two causally ordered mediators (farmers' awareness of and attitudes toward the Nutrient Reduction Strategy) on cover crop use. Results showed that participation in watershed activities and receipt of cost share or technical assistance had positive direct effects on cover crop use, while low levels of perceived nutrient loss mitigation self‐efficacy had a negative direct effect. Information and influence of public sector soil and water conservation entities had positive indirect effects on cover crop use through awareness and attitudes, while influence of private sector agribusiness entities had negative indirect effects through those mediators. These results suggest that current strategies such as engaging farmers in watershed management activities and public sector cost share and technical assistance are increasing adoption of cover crops, but the data also point to a need to increase engagement with private sector actors to help them improve their effectiveness as conservation technical assistance providers.