A novel prototype NB-IoT-based quasi-smart water management platform for irrigation is proposed. The prototype has been deployed in a vineyard in Peta village, Greece, as part of the AREThOU5A project. An IoT framework for regularly and accurately tracking the status of soil hydration and reporting it to a centralized entity for further processing since water needs are directly related to soil moisture is proposed. The framework is based on specialized IoT hardware that includes low-cost microcontrollers with integrated sensor interfaces and telecommunication modems, open-source applications, open and standardized data transfer protocols, with low capital and operating costs. In the vineyard, an IoT end-node have been placed. Each node: i) collects soil moisture and temperature samples at a depth of 20 cm, ii) is battery-powered and has a battery life of several months on a single charge, and iii) connects to the system back-end via NB-IoT. The sensor measurements from the IoT nodes are forwarded to a cloud-based infrastructure using the Constrained Application Protocol (CoAP)/IPv6 protocol using a public mobile network. Data is maintained on a cloud backend and can be accessed in real-time via dashboards from any Internet-connected individual. In terms of hardware integration, operating solutions, networking and connectivity support, the proposed platform offers numerous novel features.