We use propensity score matching to estimate the level of additionality from enrollment in federal cost-share programs for six agricultural conservation practices. We analyze farmer conservation adoption decisions based on survey data of farmers in southwest Ohio. We also develop a new methodological approach to decompose the average treatment effect on the treated (ATT) according to the relative contributions of adopters and non-adopters. Our results indicate that enrollment in federal conservation programs achieves positive and significant levels of additionality for each of the six practices. But the percent additionality varies dramatically between practices types. Specifically, the percent additionality is highest for filter strips (92.0%), hayfields (91.0%), and cover crops (86.7%), while it is lowest for conservation tillage (18.0%).