Wheat production in controlled environments

Abstract

Our goal is to optimize conditions for maximum yield and quality of wheat to be used in a controlled-environment, life-support system (CELSS) in a Lunar or Martian base or perhaps in a space craft. With yields of 23 to 57 g m −2 d −1 of edible biomass, a minimum size for a CELSS would be between 12 and 30 m 2 per person, utilizing about 600 W m −2 of electrical energy for artificial light. Temperature, irradiance, photoperiod, carbon-dioxide levels, humidity, and wind velocity are controlled in state-of-the-art growth chambers. Nutrient solutions (adjusted for wheat) are supplied to the roots via a recirculating system that controls pH by adding HNO 3 and controlling the NO 3/NH 4 ratio in solution. A rock-wool plant support allows direct seeding and densities up to 10,000 plants per meter 2. Densities up to 2000 plants m −2 appear to increase seed yield. Biomass production increases almost linearily with increasing irradiance from 400 to 1700 μmol m −2 s −1 of photosynthetic photon flux (PPF), but the efficiency of light utilization decreases over this range. Photoperiod and temperature both have a profound influence on floral initiation, spikelet formation, stem elongation, and fertilization. High temperatures (25 to 27°C) and long days shorten the life cycle and promote rapid growth, but cooler temperatures (20°C) and shorter days greatly increase seed number per head and thus yield (g m −2). The life cycle is lengthened in these conditions but yield per day (g m −2 d −1) is still increased. We have evaluated about 600 cultivars from around the world and have developed several breeding lines for our controlled conditions. Some of our ultra-dwarf lines (30 to 50 cm tall) look especially promising with high yields and high harvest indices (percent edible biomass).