Optimizing rainwater utilization for lettuce cultivation in smart greenhouses for sustainable agriculture in tropical Indonesia

This study examines the integration of a rainwater harvesting system with a smart greenhouse for hydroponic lettuce (Lactuca sativa L.) cultivation to improve water-use efficiency and support sustainable precision agriculture. The system incorporates IoT-based environmental monitoring and automated irrigation using real-time data on temperature, humidity, light intensity, water quality, and nutrient conditions. A 30-day comparative experiment was conducted using two irrigation sources: filtered harvested rainwater and groundwater. Measurements included environmental parameters, water use, and plant traits such as leaf number, leaf size, biomass, root length, and chlorophyll content (SPAD). Independent Sample T-Test results showed that groundwater significantly enhanced vegetative growth, increasing fresh weight by up to 62.5% and root length by 44.45% compared to rainwater treatment. In contrast, rainwater-grown plants exhibited 16.67% higher SPAD values, suggesting greater chlorophyll concentration and physiological quality. Laboratory analysis indicated that filtration improved rainwater pH and TDS but increased turbidity and total hardness, while groundwater demonstrated more stable quality across all parameters. These findings highlight the potential of integrating smart irrigation and alternative water sources to support climate-resilient agriculture. Future work should optimize filtration processes and investigate nutrient uptake and physiological responses under varying water qualities in hydroponic systems.