Many modern technology solutions, such as smart irrigation systems, may be utilized to boost agricultural crop productivity by optimizing irrigation water volumes depending on crop demands, soil conditions, and environmental variables, therefore saving time, effort, water, and agricultural space. However, in the literature, there are not enough studies on the usage of smart irrigation systems that examine the type of sensors, software, environmental conditions, and the impacts of these systems based on field trials. This study aims to locate, collect, and synthesize works from numerous studies that employed smart IoT irrigation systems that rely on web or mobile applications to improve the productivity of agricultural crops based on systematic literature review methodology. The study followed the PRISMA selection procedure covering research from four major scientific databases between 2012 to March 2023. It offers a systematic analysis of 33 scientific studies to comprehend, compare, and reflect on current initiatives to use IoT irrigation systems across the following dimensions: Environmental factors used by the smart irrigation system, data collection technologies, data analysis techniques, and the impact of using these systems on the productivity of agricultural crops. The valuable result in this study is that IoT-based smart irrigation systems effectively contributes towards the provision of measurable economical water irrigation by data collection and analysis of environmental factors affecting the area under experiment. This study will serve as a guide to farmers on the use and importance of smart irrigation systems with implementation of IoT applications for the improvement of their agricultural products.