This literature review on Internet of Things (IoT) in agriculture and food, provides an overview of existing applications, enabling technologies and main challenges ahead. The results of the review show that this subject received attention by the scientific community from 2010 on and the number of papers has increased since then. The literature on IoT in agriculture and food is very much dominated by Asian scientists, especially from China. In other continents, the concept of IoT was up to recently mainly adopted by non-agricultural scientists. The application area of food supply chains is addressed most frequently, followed by arable farming. Most papers report the results of explorative studies or they present IoT systems that are designed or implemented in prototypes and pilots. The literature reviewed focuses on sensing and monitoring, while actuation and remote control is much less addressed. The findings indicate that IoT is still in its infancy in the agriculture and food domain. Applications are often fragmentary, lack seamless integration and especially more advanced solutions are in an experimental stage of development. Important challenges to overcome this situation include (i) integration of existing IoT solutions by open IoT architectures, platforms and standards, (ii) upscaling the usage of interoperable IoT technologies beyond early adopters especially by the simplification of existing solutions and make it more affordable for end users, and (iii) further improvement of IoT technologies to ensure a broad usability in the diversity of the agri-food domain.