Agriculture, being the vital sector, contributes to India's GDP by 18%. It is necessary to enhance the production in this sector with minimal need of resources to get the good yield of crops. It in turn boosts up the necessity of automation in the field of agriculture. This paper discusses about the experimental study which includes the invasive/non-invasive method to sense the approximate supply of macro nutrients such as Nitrogen, Phosphorous & Potassium to the plants. The nutrient content of leaf is sensed by the usage of optical sensors. The results have been obtained based on the sensor data carried out for the sample test leaf. Thus, the level of the estimated nutrient contents is indicated by three different ranges such as Low (L), Medium (M) and High (H). A mathematical model is developed for nutrient measurement especially for nitrogen and validated with SPAD meters for the measurement of nitrogen content. The other macro nutrients were also estimated, and the entire system is tested at different test conditions with the support of UASD in the field of University of Agricultural Science.