The growing number of unmanned aerial vehicles (UAVs), typically referred to as drones, poses new challenges on how to manage their operations in various internet of things (IoT) use cases such as surveillance and monitoring, weather prediction, agriculture, etc. The latter includes a massive number of devices that sometimes produce invalid messages due to lack of energy or system shutdown and needs to be autonomously monitored with drones in rural areas. In this paper, we develop a blockchain-based platform for managing drone IoT operations while maintaining trust and security. The test-bed consists of IoT devices, a drone and blockchain-enabled gateways through which drones are controlled to replace malfunctioning devices. The latter are detected using Z-score observation algorithm which launches a smart contract and sends the drone with clear operation order. The results obtained in realistic agriculture use case highlight the utility of our proposition in decreasing signaling and operation time, improving the percentage of successful maintenance operations and providing trust and security when managing drones in an autonomous manner.