ASHS 2025 Conference

In-situ resource utilization at the lunar surface has been proposed for food production during human exploration missions. However, lunar regolith’s sandy texture holds less plant-available water than most of Earth's fine-textured agricultural soils. Reduced gravity at the lunar surface limits drainage from containerized media, likely causing root-zone hypoxic stress without appropriate irrigation management. Sensor-based irrigation systems may mitigate these challenges by maintaining an optimal medium volumetric water content. Evaluating the palatability of crops is also crucial, though sensory evaluation is uncommonly included in crop production studies. Hence, this research aimed to quantify the effects of sensor- and time-based irrigation strategies on the development and growth of Lactuca sativa (lettuce) grown using two continuous harvesting techniques in a containerized Turface MVP medium, a coarse calcined clay aggregates. Lettuce seeds were sown in 48 containers filled with the Turface MVP (particle sizes 0.8-3.4 mm) premixed with 15N-3.9P-10K controlled release fertilizer. Additionally, 24 containerized media were left unseeded to serve as controls. The containerized media were randomly assigned to sensor- and time-based irrigation under “pick-and-eat” and “cut-and-sow” harvesting techniques. Sensor-based irrigation maintained volumetric water content at 0.40 m3·m-3 through frequent sensor scanning and automated irrigation when sensor readings fell below the setpoints, while the media at time-based irrigation management were irrigated to saturation once per day. Under the “pick-and-eat” method, sensor-based irrigation increased the leaf fresh and dry weights, and photosynthesis rate by 81%, 39%, 61%, respectively, compared with plants under time-based irrigation at the end of experiment. The “cut-and-sow” method resulted in lower leaf fresh and dry weights than the “pick-and-eat” under both irrigation treatments. However, sensor-based irrigation led to increases in the medium’s electrical conductivity, causing plants under salinity stress because the phosphorus, potassium, and magnesium concentrations in the leaf tissue increased compared with those under time-based irrigation. Sensor-based irrigation improved overall acceptability of samples under “pick-and-eat” in sensory testing, with 50% of respondents disliking the time-based samples. However, the "cut-and-sow" samples under time-based irrigation exhibited higher overall acceptability, though 75% or more testers liked both samples. Sensor-based irrigation improved the yield of lettuce under "pick-and-eat" method but caused salinity stress. Conversely, the "cut-and-sow" method led to lower yield, but improved plant palatability under time-based irrigation. Nevertheless, with higher yield, increased mineral content, and improved consumer acceptability, the “pick-and-eat” method under sensor-based irrigation demonstrates potential for sustaining continuous crop production.