An increasing number of papers analyse the inclusion of collective/spatial conditionality constraints in agricultural policies dealing with natural resource management. In this article we theoretically assess the conditions in which employing collective conditionality constraints linked to incentives better reach the social preferences on PG provision by agriculture. We deal with this issue by using a coalition formation model to endogenize the size of the group of farmers cooperating, and investigate how it is affected by different policy schemes. We analyse and compare the following policy schemes: (1) a homogenous payment that target the whole population of farmers, (2) a coalition bonus, that incentivizes only the contributions by the c...