Retractable roof greenhouse production of basil (ocimum basilicum) and lemon grass (cymbopogon citrates) in a semi-arid climate

Production of high quality herbs for fresh culinary markets was evaluated in a retractable roof greenhouse (RRGH) under semi-arid climate conditions. Two basil cultivars, 'Genovese' and 'Purple Ruffles' and lemon grass were grown in a RRGH under 35% and 50% shade, and in the field. Basil was grown using two production systems in the RRGH, hydroponic rockwool culture and peat-based media in containers. Lemon grass was grown in containers only. Environmental and physiological parameters were monitored throughout production. Lemon grass showed greatest biomass accumulation under 35% shade, producing 0.7 times more than in the 50% shade and 7 times more than in the field. Overall, 'Genovese' produced 91% more than 'Purple Ruffles'. Biomass accumulation of basil was affected more by media than by shade. During full production with weekly harvests, 'Genovese' and 'Purple Ruffles' in hydroponic rockwool culture produced 45% and 44%, respectively, more biomass than plants in containers and 106% and 160%, respectively, more than plants in the field. The quality of basil and lemon grass was superior in all RRGH treatments compared to the field. These results indicate culinary herb production in a RRGH can optimize biomass and quality of basil and lemon grass in a semi-arid climate.