Enhanced Plant Growth on Simulated Martian Regolith via Water Chemistry Optimisation: The Role of RONS and Nano/Micro-Bubbles

Development of sustainable agriculture on Mars is a critical step towards its colonisation. However, Martian regolith is coarse-grained, and its mineral profile differs significantly from that of terrestrial arable soil, resulting in poor seed germination success and stunted plant development. This study investigates whether germination success and plant growth can be improved by exposing seeds and plants to water enriched with either i) biochemically active reactive oxygen and nitrogen species generated by atmospheric pressure plasma (PAW) or (ii) nano-/micro-bubbles and minerals such as potassium and calcium extracted from Aquapulse^® feldspar (APW), a type of rock that is readily available on Mars, at different stages of the crop lifecycle. As a crop model, microgreen crops of B. oleracea and M. sativa are chosen for their short growth cycle, low resource requirements, and high nutritional value. For B. oleracea crops, soaking of seeds in PAW followed by irrigation with APW led to an increase in germination by ~566.7%, in biomass by 412.4%, and in chlorophyll content by 17.7% compared to crops grown using normal water for seed soaking and irrigation. For M. sativa crops, the use of APW for soaking and irrigation yielded an increase of 41.7% in seed germination and 45.2% in crop biomass, whereas the use of PAW for both soaking and irrigation resulted in the greatest improvement in seed germination, 41.7%, when compared to control. These results suggest that, with further optimisation, a regiment of treatment with PAW and APW in place of normal water can be used to address stage-specific challenges of the crop lifecycle in Martian regolith. As amending Martian regolith with a minimum of 1% organic matter is required to promote healthy plant development, further studies should investigate the use of plasma-mediated reforming of biowaste for in situ production of e.g., biochar.