This article examines the influence of intrinsic and extrinsic motivations, as well as the interplay between the two, on the adoption intensity of soil conservation agriculture (SCA). It seeks to understand the drivers of SCA among annual crop farmers using three conservation practices subject to be financed by an economic incentive for degraded soils in Chile; namely conservation tillage, stubble incorporation, and use of organic manure. The incentive to conservation represents an extrinsic motivation, while intrinsic motivations was represented by several beliefs about SCA based on the Planned Behavior Approach. To account for selection bias on unobservable factors between the incentive and behavior, a two-step model was performed to estimate the intensity of SCA adoption. Farm/farmers characteristics and control variables were also included in the model. Results of the econometric analysis show that attitudes and the exogenous incentive are both significant, but also the interaction with each other. Farmers with low intrinsic motivation are heavily dependent on extrinsic motivation to adopt SCA, while those intrinsically motivated seem to act in a sustainable way regardless the existence of external rewards. Finally, soil degradation was also found to play a key role on the intensity of SCA adoption. Acknowledgement : This work was supported by the Chilean National Commission for Scientific and Technological Research (CONICYT), through its Programme Becas Chile for Phd studies 2016.