Agriculture is one of the drivers for societies and economies worldwide. There are several challenges to be addressed in this sector, such as food security and climate change. Agriculture 4.0 and the Internet of Things (IoT) technology paradigms aim to address these challenges, allowing for sustainable usage of natural resources and application of novel farming practices. This paper introduces an innovative smart IoT-based prototype system that supports precision irrigation of crops and enables real-time exploitation of data for minimization of errors, as well as forecasting. It is based on microprocessors and a Single-Board Computer (SBC) for data logging using various sensors that monitor soil moisture, air humidity, air temperature and UV light. Farmers’ Intelligent Actuation systems have full access to all relevant raw data, in order to choose when, where and how much to irrigate. The respective precision irrigation prototype system has been evaluated over series of experiments and the respective findings are presented in this paper.