ASHS 2024 Conference

Nutrient solutions play a crucial role in determining crop yield and quality, with optimized quantities offering sustainability benefits. However, there is a lack of comprehensive research regarding the optimal nutrient application quantity for various leafy green vegetables in recirculating hydroponic cultivation. To address this research gap, we proposed a project on different nutrient application quantities using the nutrient film technique (NFT) hydroponic system in a greenhouse with three replications during the fall (air temp: 24.22°C, RH: 31.2%), winter (air temp: 15.5 °C, RH: 73.3%) and early spring (air temp: 13.7 °C, RH: 72.4% ). The project focused on exploring different nutrient solution quantities of Low (76 liters), Medium (114 liters), and High (151 liters) nutrient regimens for six different leafy green vegetable species and cultivars common in Kansas including red butter lettuce (Lectuca sativa), green butter lettuce (Lectuca sativa), arugula (Eruca sativa), kale (Brassica oleracea), red malabar spinach (Basella alba), and basil (Ocimum basilicum). Our results showed that green butter lettuce and basil remained unaffected by the treatments throughout the study. Additionally, plant height, leaf count, and SPAD value for all species remained consistent across treatments and seasons. However, during the fall, the shoot fresh weight of red butter lettuce and kale increased by 7.11% and 21.1%, respectively, in the high-nutrient regimen. Moreover, the dry shoot weight of kale increased by 18.7% in the high-nutrient regimen, while the dry shoot weight of the red malabar spinach increased by 10.3% in the low-nutrient regimen. In contrast, during winter, the shoot fresh weight of red butter lettuce increased by 18.9% and 25.0%, respectively, in medium nutrient regimens compared to low and high nutrient regimens. Similarly, the shoot fresh weight of red malabar spinach increased by 15.3% and 25.0%, respectively, in low-nutrient regimens compared to medium and high-nutrient regimens. During early spring, the shoot fresh weight of red butter lettuce increased by 17.9-18.0% and that of arugula increased by 17.8% in the high-nutrient regimen, compared to low and medium nutrient regimens. In summary, the high-nutrient regimen benefited red butter lettuce and kale in fall and arugula in early spring. Conversely, during winter, the medium nutrient regimen benefited red butter lettuce, while the low nutrient regimen benefited red malabar spinach. The results from this experiment identified the optimal nutrient application quantity which helps to reduce nutrient waste for vital leafy vegetables in Kansas for different seasons and offers valuable production guidelines for local growers.