2019 ASHS Annual Conference

Astronaut diets on the International Space Station (ISS) depend on resupplied packaged food. However, missions to Mars of 3-5 years will not accommodate re-supply. In addition, many human macro and micro nutrients degrade during long-term storage. Thus, growing nutritional plants aboard ISS is essential for providing astronauts with fresh, healthy produce. NASA is usingan experimental vegetable production unit called VEGGIE to grow fresh salad crops aboard ISS to provide astronauts with healthy diets. VEGGIE is a small plant-growth chamber designed as a garden for astronauts that is low in mass and has a low power requirement. Veggie is equipped with light-emitting diodes (LEDs) but is exposed to the ISS cabin environment. Plants are grown with roots in a baked-ceramic substrate (arcillite) incorporating controlled-release fertilizer and wicks delivering water by capillary action from a reservoir.

The fertilizer capsules release nutrients to plants slowly over time. Different slow-release types have the same amount of fertilizer but release it over different time periods. The Purdue Mitchell lab in collaboration with NASA is testing growth of salad crops within VEGGIE analogs under ISS-like environments in a growth chamber. Specifically, we are evaluating effects of different fertilizer treatmentson “cut-and-come-again” harvest scenarios, comparing productivity and quality of Lettuce as well as anAsian salad crop called Mizuna.

ISS environments being mimicked include temperature: 24/21°C D/N, CO2: 2800 PPM D/N, RH: 45-50% D/N and photoperiod: 16hours.Arcillitemedium contained one of two different fertilizer mixes: 7.5g18-6-8 T 70 + 7.5g 18-6-8 T100, or 7.5g18-6-8 T70 +7.5g 18-6-8 T180fertilizer/liter medium. LED Light treatment provides total PPFD of 330µmol m^--2s^-1 PAR; with 270µmol m^--2s^-1Red(R), 30µmol m^--2s^-1Blue (B), and 30µmol m^--2s^-1Green (G). Plants are grown under those conditions for 8 weeks, and harvested three times at 28, 42, and 56 days from planting. At each harvest, yield parameters as well as tissue mineral content have been measured for optimum fertilizer treatment selection.

Lettuce plants grown underT70+T100 fertilizer treatment had significantly higher yield than those grown underT70+T180 treatment. In addition, lettuce plants grown under both fertilizer treatments had significant increases in yield from harvest to harvest. In contrast to lettuce, first-harvest data for Mizuna indicated that plants grown under the mix of T70+T180 had significantly higher yield than those grown under the mix of T70+T100. The Mizuna experiment is still in progress and data for second and third harvestsas well as mineral composition for all species and treatments will be presented.