ASHS 2025 Conference

Efficient nutrient management is critical for optimizing hydroponic production. However, limited research exists on optimizing nutrient solution volume for various leafy green vegetables in recirculating hydroponic cultivation. To address this gap, we evaluated the growth and nutrient responses of four leafy green vegetables: butterhead lettuce (Lactuca sativa ‘Salanova Red Butter’), arugula (Eruca sativa ‘Standard’), kale (Brassica oleracea ‘Red Russian’), and red Malabar spinach (Basella alba ‘Rubra’). These crops were grown in a nutrient film technique (NFT) hydroponic system under two nutrient solution volumes, Low (76 liters) and High (151 liters), in a greenhouse during both summer and fall. Electrical conductivity (EC) of 1.8 mS/cm was maintained across treatments. Results indicated that leaf nitrogen (N) and potassium (K) content significantly increased with High nutrient solution volume while phosphorous (P) and K followed a similar trend in the fall. Low nutrient solution volume reduced nitrate levels in arugula tissue during both seasons, suggesting that lower volume may help minimize excessive nitrate levels in plant tissues. In summer, nitrate levels in red Malabar spinach (Low volume) and red butter lettuce (High volume) slightly exceeded recommended limits, while kale consistently surpassed safe nitrate levels regardless of treatment. Additionally, nutrient solution volume influenced key postharvest attributes such as color, texture, vitamin C, and anthocyanin content, with species-specific responses. These findings highlight the importance of crop-specific nutrient solution management to optimize plant health, improve nutrient use efficiency, minimize nitrate accumulation and nutrient waste, and support sustainable hydroponic production.