Minimizing energy utilization for growing strawberries during long-duration space habitation Gioia D. Massa a, * , Judith B. Santini b , Cary A. Mitchell a a NASA Specialized Center of Research and Training in Advanced Life Support (ALSNSCORT), Department of Horticulture and Landscape Architecture, Purdue University, West Lafayette, IN 47907-2010, USA b Research Statistical Analyst, Department of Agronomy, Purdue University, West Lafayette, IN 47907-2054, USA Received 29 October 2009; received in revised form 12 February 2010; accepted 22 February 2010 Abstract Strawberry is a candidate crop for space that is rich in protective antioxidants and could also have psychological benefits as a com- ponent of crew diets during long-duration space habitation. Energy for electric lighting is a major input to a controlled-environment crop-production system for space habitation. Day-neutral strawberry cultivars were evaluated at several different photoperiods to deter- mine minimum lighting requirements without limiting yield or negatively impacting fruit quality. The cultivars ‘Tribute’, ‘Seascape’, and ‘Fern’ were grown at 14, 17, or 20 h of light per day, and fruit yield was evaluated over a 31-week production period. This amounted to a difference of 2418 kWh m 2 in energy usage between the longest and shortest photoperiods. All cultivars produced similar total fresh weight of fruit regardless of photoperiod. Volunteer tasters rated organoleptic characteristics including sweetness, tartness, texture, and overall appeal as measures of fruit quality. Generally, organoleptic attributes were not affected by photoperiod, but these attributes were somewhat dependent upon cultivar and harvest time. Cultivars under different photoperiods varied in their production of fruit over time. ‘Seascape’ was the most consistent producer, typically with the largest, most palatable fruit. ‘Seascape’ plants subsequently were grown at 10-, 12-, or 14-h photoperiods over a treatment period of 33 weeks. Photoperiod again had no significant effect on total fruit weight, although there were periodic flushes of productivity. Fruit under all photoperiods had acceptable approval ratings. A large- fruited, day-neutral strawberry cultivar such as ‘Seascape’ remains productive under shortened photoperiods, allowing reductions in energy and crew labor while maintaining flexibility for mixed-cropping scenarios in space. Ó 2010 COSPAR. Published by Elsevier Ltd. All rights reserved. Keywords: Controlled environment; Daily light integral; Life support; Light energy; Organoleptic characteristics; Photoperiod 1. Introduction 1.1. Controlled-environment production Strawberry is a “small fruit” valued for its flavor charac- teristics and antioxidant content that has great potential for crop production in controlled environments such as space life-support systems (Massa et al., 2006b). Cultivars have been developed throughout the world to accommodate vary- ing climatic conditions, regional markets, and pathogen pressures (Hokanson and Finn, 2000). For production in a controlled environment that is part of a space life-support system, different selection criteria will apply. Space straw- berries will lack pest pressure and natural pollinators, and have space and energy constraints, but still must be highly productive over long durations. Growth environments will need to provide the temperature, humidity, and light required to maintain crop productivity with minimal labor inputs. These characteristics are equally relevant for con- trolled-environment production scenarios on Earth ranging from plant “factories” in urban areas (Walsh, 2008) to growth habitats in extreme environments such as Antarctica (Morlocki, 2003) to off-Earth, plant-based life-support systems (Wheeler et al., 2003). In addition, many of the same criteria apply to out-of-season production in greenhouses 0273-1177/$36.00 Ó 2010 COSPAR. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.asr.2010.02.025 * Corresponding author. E-mail address: gmassa@purdue.edu (G.D. Massa). www.elsevier.com/locate/asr Available online at www.sciencedirect.com Advances in Space Research 46 (2010) 735–743