Development of colour sensor based low-cost hand-held device for crop nitrogen management

In this study a low-cost sensor based device was developed for the measurement of Chlorophyll content in leaves. This device consisted of Arduino based red-green-blue (RGB) sensor, battery and outer casing. It measures the reflectance of the green pigment chlorophyll from the leaves when the light from the LED is allowed to fall on the plant leaf surface. The greenness of the leaves is an indicator of the chlorophyll content in the leaves & thus indicates the plant health & vigour. RGB values obtained from developed device were used to calculate vegetation indices such as Green Ratio vegetation Index (GRVI), Visible Atmospherically Resistant Index (VARI) and Normalized Pigment Chlorophyll Ratio Index(NPCI). Vegetation indices derived from the developed device was compared with Chlorophyll content meter (CCM) readings obtained from CCM-200for tomato crop grown under protected cultivation conditions. VARI and GRVI obtained with developed sensor were positively correlated with the CCM-200 readings with an R² of 0.85 and 0.86, respectively. As VARI and GRVI showed positive correlation with the CCM-200 readings thus it can be used to indicate crop health. Also as developed hand held device is low cost (Rs. 3500 only) it can be suitable for small holder farmers for nutrient management.