Search Results

Rice (Oryza sativa L.) is a candidate crop for use in Controlled Ecological Life-support Systems (CELSS) proposed for a lunar or Mars outpost. `Ai-Nan-Tsao' is a promising semi-dwarf cultivar because growth volume is limited and HI (percent edible biomass) is high. Yield efficiency rate (YER: g grain/m³ per day [g nonedible biomass]-) combines edible yield rate (EYR: g grain/m³ per day) and HI to quantify edible yield in terms of penalties for growth volume, cropping time, and nonedible biomass production. Greenhouse studies indicate EYR increases with plant density from 70 to 282 plants/m². YER and shoot HI are stable across this density range because nonedible biomass accumulation keeps pace with edible. Tiller number and panicle size per plant decreased with increasing plant density, but total tiller and panicle number per unit area increased to compensate. Density trials in rigorously controlled environments will determine if higher plant densities will produce even greater YER. This research is supported by NASA grant NAGW-2329.

Mineral resources will be recycled in a controlled ecological life-support system (CELSS) deployed in space. N typically is supplied to crops as ${\text{NO}}_3^{-}$ or ${\text{NH}}_4^{+}\hspace{0.17em}+\hspace{0.17em}{\text{NO}}_3^{-}$ mixtures. In a CELSS, ${\text{NH}}_4^{+}$ will be abundant, but nitrification will require energetically costly chemical or biological ${\text{NH}}_4^{+}$ oxidization. Rice is tolerant of ${\text{NH}}_4^{+}$ and preferentially absorbs ${\text{NH}}_4^{+}$ if provided a 1 ${\text{NO}}_3^{-}$ : 1 ${\text{NH}}_4^{+}$ ratio in hydroponics. Hybrid rice absorbs more N as ${\text{NH}}_4^{+}$ than does inbred rice. To determine how much and in what proportion to ${\text{NO}}_3^{-}$ rice will tolerate ${\text{NH}}_4^{+}$ and how varying N sources will affect grain yield, semi-dwarf hybrid rice cultivar `Ai-Nan-Tsao' was grown hydroponically in a growth chamber. Nutrient solutions supplied 5 mm N as 40%, 60%, or 80% ${\text{NH}}_4^{+}$ , the remainder as ${\text{NO}}_3^{-}$ . Periodic analysis of solutions tracked mineral uptake, and solutions were modified to maintain proper concentrations. Treatment stands were harvested 84 to 86 DAP. Across all treatments, yield characteristics were similar but were highest for the border plants, presumably due to greater light absorption. Yield-efficiency rate (YER: grams of grain·per cubed meter per day·[grams inedible shoot biomass]) was 0.09 for all treatments (border) and ranged from 0.03 to 0.05 (interior), Harvest index ranged from 0.28 to 0.30 (border) and 0.26 to 0.39 (interior). Edible yield rate (EYR: grams of grain per cubed meter per day) ranged from 20.97 to 26.45 (border) and 8.52 to 14.96 (interior). The sector provided with 80% ${\text{NH}}_4^{+}$ had the highest YER, HI (interior), and EYR (interior), indicating that rice productivity was not limited by high percentages of N supplied as ${\text{NH}}_4^{+}$ . Supported by NASA grant NAGW-2329.