Remote Sensing-based Indicators for Evaluating Impact of Micro-irrigation Systems on Tea Canopy Growth

Water scarcity is emerging as a critical constraint for tea plantations in the Dooars region of West Bengal, India, where irrigation largely relies on groundwater resources and conventional overhead sprinklers often lack precision and uniformity. This study employed remote sensing techniques in sprinkler-irrigated and drip-irrigated plots in the Dooars during the pre-monsoon and post-monsoon seasons over a three-year period (2018-2020) to determine how the two different irrigation systems (sprinkler and drip) influence tea canopy growth. Correlations between canopy cover and its influencing factors, i.e., normalized difference vegetation index (NDVI), leaf area index (LAI), soil moisture content, and land surface temperature (LST) were assessed. Results showed that the mean NDVI increased by 11.14% in the pre-monsoon season and 6.17% in the post-monsoon season. These changes in the mean NDVI in the drip-irrigated plot indicated higher tea canopy growth due to adequate water availability in the root zone. The values of NDVI (0.47 to 0.55), LAI (2.79 to 3.14), and soil moisture (0.09 to 0.17 m³ m^-3) were higher under drip irrigation system. Also, strong correlations among NDVI, LAI, LST and soil moisture parameters demonstrated that water availability in the root zone of the tea plantation under drip irrigation improved canopy growth driven by favorable soil-plant-water interactions. Therefore, drip irrigation outperformed sprinkler system in improving soil moisture retention and promoting tea canopy growth, making it a sustainable long-term solution for tea estates in the region.