ASHS 2024 Conference

Soilless growing systems (SGS) integrated into controlled environment agriculture (CEA) offer a viable solution for increasing food production in densely populated areas with limited land, water, and nutritional security. The design, components, inputs, and nutrient management of alternative SGS along with the plant genotype, directly impact crop yield, nutritional value, and resource use efficiency. As the adoption of CEA and SGS continues to expand, there is a growing need to compare and evaluate the performance of alternative SGS in terms of resource use efficiency, crop yield, and impact on crop nutritional quality. To this purpose, a study was undertaken to assess the performance of five alternative SGSs including Deep Water Culture (DWC), Nutrient Film Techniques (NFT), Ebb and Flow, Drip irrigation, and the Kratky system concerning yield, nutritional quality, and resource use efficiency, using green and red stripe amaranth cultivar as test crops. As expected, the Kratky system had the lowest dissolved oxygen levels in the nutrient solution compared to other SGSs. Among the growing systems, DWC and NFT exhibited higher fresh and dry biomass production compared to drip irrigation, ebb and flow, and the Kratky system. There was no distinct difference in leaf fresh and dry weight between cultivars, but green amaranth displayed higher stem fresh and dry weight than red stripe amaranth. Dry matter content remained unaffected by the SGS, while red stripe amaranth exhibited higher dry matter content compared to green amaranth. The Kratky and DWC systems utilized 34.2% and 25.6% less nutrient solution, respectively, compared to the ebb and flow system, which had the highest nutrient solution consumption compared to other methods. DWC had the highest water use efficiency (WUE, dry biomass produced per liter of water used). Nitrate content in amaranth leaves was higher when grown in NFT compared to drip irrigation, DWC, and ebb and flow, but was similar to Kratky. The red stripe cultivar displayed higher nitrate content than the green one. Regarding bioactive compounds, green amaranth exhibited higher total antioxidants and flavonoids, whereas DWC and NFT led to lower total phenols and flavonoids compared to the Kratky, ebb and flow, and drip irrigation systems. In conclusion, the DWC and NFT systems maximized yield, with DWC having higher water use efficiency, while Kratky, ebb and flow, and drip irrigation system resulted in higher nutritional quality of the amaranth grown as a summer leafy vegetable.