Agriculture unquestionably is one of the traditional occupations, which feeds all mankind in the world. Continuous changes are happening in the agricultural field to increase production. Researchers are applying various techniques to improve farming methods. To monitor plants even from remote places and to improve the yield of plants, Internet of Things (IoT), which is a boon in today's world, is applied in farming, in general, known as smart farming. Smart farming is a way where the farmers can monitor their field and manage farming activities from remote places. This reduces man power and increases resource utilization in farming. In this article, we have studied the architecture of smart farming and studied different smart farming techniques, also we have classified smart farming techniques into three categories, namely, IoT-based agricultural monitoring and controlling system, automatic irrigation system, and plant disease monitoring system. The review for the article is selected based on the systematic literature review method, and articles published from 2011 to 2019 are considered for review. Different IoT technologies such as sensors, gateway, communication system, user interface and experiment nature, plant type, disease type, advantages, and limitations are also reviewed. Future research direction and challenges in smart farming techniques are also discussed. Trans Emerging Tel Tech. 2020;31:e3958. wileyonlinelibrary.com/journal/ett Atzori et al 16 presented a survey on IoT techniques. In this article, the architecture, applications, and challenges of IoT technologies were discussed. Various environmental and agricultural monitoring applications were discussed. Zhang et al 17 projected various agricultural data transmission methods in his review article, namely, voice information transmission, short message service (SMS) information transmission, online information transmission, video conference information transmission, and multichannel-based information transmission techniques. Case studies, features, applications, examples, and limitations of various information transmission techniques were discussed. Kamilaris et al 18 projected survey on big data analysis in agriculture. In this article, 34 agriculture works were considered for the study and different features such as tools applied, big data algorithm used, problem and proposed solution implemented, and data used were discussed. The type of plants and experimental duration and advantages and limitation of algorithms were missing. Talavera et al 14 reviewed IoT applications in environment and agroindustrial system. The authors discussed about various IoT techniques involved in monitoring, communication, logistics, energy and resource management in environment monitoring, and agroindustrial system. In this study, the authors approached all the IoT techniques with following two questions: what is the primary technical solution of IoT in environmental monitoring and agroindustrial system and which methodology and IoT components such as sensors, actuato...