In every stage of the agricultural process, fertilizers and various chemicals such as pesticides, herbicides, insecticides, etc. have long been applied to crops, plants, and vegetation to protect them against pests. Even though pesticides are beneficial to crop yields and the world economy, their widespread and ineffective use raises serious health and environmental concerns. Moreover, the use of nanotechnology in agriculture has resulted in substantial advances in fertilizer and various chemical detection methods. Nanosensors, which are small in size and have great sensitivity, play an important role in these applications because they allow for the rapid and exact detection of these toxic chemical agents in groundwater, soil, and plants. In this chapter, we discuss about critical function of nanosensors in agriculture, concentrating on their concepts, kinds, and applications in detecting these toxins. Nanosensors have various advantages over standard detection methods, such as higher sensitivity, selectivity, and portability. They provide real-time monitoring and exact application of agrochemicals, increasing efficiency, lowering environmental impact, and ensuring food safety. Scalability, cost-effectiveness, and integration into existing agricultural techniques are among the challenges addressed.