IrriSmart is a cloud service that implements FAO-56 guidelines for computing crop water requirements from meteorological data and crop coefficients, a key foundation component in decision support systems for irrigation and fertirrigation practices. FAO-56 guidelines provide a standardized guidance to project managers, consultants, irrigation engineers, hydrologists, agronomists and meteorologists for computing crop water requirements for both irrigated and rainfed agriculture and water consumption by agricultural and natural vegetation, allowing a model-based approach in critical business processes. IrriSmart takes full advantage of FIspace platform capabilities, allowing the integration and the processing of weather data from inhomogeneous sources (e.g. IoT-enabled sensor system and 3rd party services), and providing multi-parameter results to the end-users via customizable widgets as well as to 3rd party software components in collaborative workflows: IrriSmart computes FAO-56 parameters, shows them in a convenient way for end-users, and shares them with 3rd party mashed-up apps allowing further analytics and complex autonomous architectures in irrigation and fertirigation practices.