Pea and Lettuce growth in Martian regolith and light conditions : How do different soil amendments and fertilizer affect the growth of lettuce and peas in Martian regolith simulant under Mars habitat light and environmental conditions?

One of the biggest problems humans face trying to reach our neighbouring planet Mars is how humans would cultivate food. Martian soil, known as regolith, is not only extremely nutrient poor and void of organic matter, but it also has poor water retention abilities and contains compounds such as perchlorates which are toxic to both humans and plants. Further inhospitable environmental conditions like radiation and weaker sunlight make growing plants on Mars an extreme challenge. Transporting large amounts of food to Mars would neither be economically nor logistically viable for a long-term Martian colony. The objective of this experiment was to investigate the effect of Martian regolith simulant (without perchlorates due to safety hazards) and Martian light strength on plant germination and growth. Additionally, the study aimed to determine what impact different amendments such as universal fertilizer and terrestrial soil would have on the growth and germination rate of plants. In this experiment peas (pisum sativum) and lettuce (Lactuca sativa var. capitata) were selected as test species due to their relatively short growth period and low maintenance. Seeds were grown in both Martian regolith and all-purpose soil, exposed to either Martian or terrestrial light strength. Various treatment strategies were applied, including universal fertilizer and combining all-purpose soil and Martian regolith in different ratios, as well as using layering techniques where seeds were placed between Martian regolith and all-purpose soil layers. The results indicate that universal fertilizer alone provided only a minimal increase in germination rates and was observed to be insufficient to support healthy plant growth. In those samples the plants often died shortly after germination, suggesting that the nutrients couldn’t properly reach the roots of the plant due to the cement-like layer of salts and Martian regolith’s poor water absorption ability. In contrast soil amendments were found to be more effective in promoting the germination rate of plants and their survival. Mixtures with a higher soil content demonstrated significantly higher germination rates than Martian regolith dominant mixtures. A mixture of ¼ soil and ¾ regolith proved insufficient for any plants to grow successfully in Martian light strength. All amendments with a 100%, 75% and 50% soil content were found to be successful and so were samples where seeds were placed between a layer of soil and Martian regolith. These findings highlight the importance of soil-like properties for Martian agriculture and suggest that combining Martian regolith and all-purpose soil would be a possible solution for growing crops in Martian habitats, though using bacteria has been proven successful as well. While this experiment ignores all external factors apart from light strength, future research should explore the possibility of a greenhouse that shields the plants form cosmic radiation and how said bacteria would behave in Martian conditions.