Effect of struvite on the growth of green beans on Mars and Moon regolith simulants

When humans are going to live on the Moon or Mars, food production and reusing waste products as manure will be essential for their survival. This calls for a circular sustainable agricultural ecosystem for food production. Earlier experiments have shown that crop growth is possible on simulant regoliths though there are several challenges. One of them is the shortage of nitrate or ammonium in the regoliths. Moreover, phosphate is not easily available. This could be solved by the application of human feces as manure. The goal of this experiment was to test if human urine-based struvite (MgNH4PO4) could fertilize Mars and Moon regolith simulants and lead to a higher yield of green beans. Three "soils" were examined: Mars regolith simulant (MMS), Moon regolith simulant (JSC 1A), and Earth potting soil with and without struvite. Forty grams of struvite were added, besides 10% (volume) organic matter. The experiment was conducted in tenfold. Length of plants was recorded, and beans were harvested when ripe and at the end of the experiment, three and a half months after the start. The struvite treatment yielded a significantly higher bean harvest. Plants on potting soil and Moon soil simulant with struvite addition reached the same height and were higher than the control plants. The plants on Mars soil simulant were smaller but still taller than the control. It can be concluded that the addition of struvite had a significant positive effect on the production of green beans on potting soil and Mars and Moon soil simulant.