The Internet of Things (IoT) relates to many billions of various applications and devices scattered around the world talk to each other and can exchange data and perform cooperative tasks without the intervention of humans. Towards efficiently realizing this, many things are needed to be achieved in advance, such as common language, basis of work and cooperation, roles distribution, resources availability, and security. Here comes the role of humans to build a reference architecture represents the common communication framework among the Internet things. There is no doubt that in order for the IoT to meet expectations, it needs to follow standardization; therefore, this paper addresses the IoT standardization by formulating the basis of an IoT reference architecture for the agriculture domain. The proposed Agricultural IoT Reference Architecture (AITRA) is based on a defined architecture generation process incorporates analysis of the IoT and the application domain ecosystems. AITRA is composed of three tiers: Device, Cloud, and Business, described in the paper including architectures, conventions, frame format, applications and services, and illustrative examples for utilizing the architecture at its highest abstraction level. The proposed design resulted in a foundation for a reference architecture combines the three main required features: best practices, common vocabulary, and reusable designs; characterized over the other architectures by its efficient low abstraction level meanwhile giving design freedom, lower timeto-market, standardization in its interfaces and communication protocol. It connects to its outside world with authorization rules and at any scale: individual, company, government(s), and global levels.