Human urine may be Number 1 for fertilizing plants on Mars
Shipping fertilizer to colonies on Mars could be quite a hassle – it would certainly be better if the colonists were able to grow crops using whatever's on hand. The continuation of an existing study now indicates that urine might in fact serve as a perfectly good fertilizer.
It was back in 2016 that we first heard how scientists at The Netherlands' Wageningen University were trying to grow food plants in simulations of both lunar and Martian soil. At the time, it was found that while the plants didn't fare well in nothing but the soil, they did better when a fertilizer made of fresh-cut grass was added.
Unfortunately, though, the Red Planet isn't known for its lush lawns – and growing grass in Martian greenhouses would use up a lot of water and space. With that in mind, the researchers more recently looked to struvite – it's a phosphate mineral, which they obtained from human urine in wastewater treatment facilities.
In greenhouse tests, they planted string bean seeds in a total of 60 pots that were filled with either simulated lunar or Martian soil, or with regular Earth-type potting soil. Half of the pots additionally contained 15 grams of struvite, while the others had no added fertilizer. All of the plants were automatically watered daily, with the greenhouse being kept at a temperature of 20º C (68º F) at day and 18º C (64º F) at night.
As the bean plants sprouted, their length was monitored. The scientists noted that all of the struvite-fertilized plants showed the strongest growth, by quite a wide margin – particularly those grown in the lunar and potting soils.
The Martian-soil struvite plants did ultimately produce harvestable beans, although they did so a week later than the other two. That said, their growth rate might be boosted substantially if fertilizer obtained from human feces was also used.
Source: Wageningen University