Finding the most effective ways for motivating agents to volunteer for the benefit of the community is a main concern for resource-constrained organizations. This paper tests the effects of three non-monetary mechanisms in the context of a large-scale volunteer Farmer Trainer program in rural Uganda. Farmers identified by local communities were randomly selected to become Farmer Trainers in dairy farming. To encourage their volunteer activity of trainer, three non-monetary mechanisms were randomly assigned to a subset of Farmer Trainers: (i) vouchers for accessing professional Extension Agents, (ii) sign-post advertising their trainer’s activity, (iii) extra training to learn to customize training sessions based on the farmers’ needs. Results show that connecting Farmer Trainers to professional extension agents is the most effective way to increase their training efforts and to diffuse information to a large number of farmers even outside of their social network. This evidence speaks in favor of providing cost-effective non-monetary incentives to Farmer Trainers for the diffusion of information.