Wireless sensor network is an autonomous network which consists of resource constraints sensor motes which are used to capture various events of interest such as temperature, humidity and pressure. These networks are used in many areas like agriculture monitoring, health care monitoring, forest fire monitoring, environmental monitoring etc. These networks are used to monitor various agriculture products or various parameters in agriculture such as the quality of fruits, vegetables, the amount of oxygen and nitrogen required. In this paper we aim to present the existence studies of wireless sensor networks which are used for agriculture monitoring. We will explain in details the advantages and dis advantages of the existing studies and we present our own analysis and conclusion.