Double-season production of hops (Humulus lupulus L.) with photoperiod manipulation in a subtropical climate
Aleyda Acosta-Rangel, Shinsuke Agehara, Jack Rechcigl
Abstract
Hops (Humulus lupulus L.) have an ancient history of cultivation in temperate climates primarily as an ingredient of beer. However, growing hops in subtropical or tropical climates has been challenging because of non-optimal day length conditions. We examined the potential of subtropical hop production with photoperiod manipulation. ‘Cascade’ hops were grown in Florida, United States with extended day length (>16.5 h) using light-emitting diode (LED) bulbs to inhibit flowering until sufficient vegetative growth was achieved. Phenology, plant growth, yield, and cone quality data were collected during the first two years after planting. With as little as 0.47 μmol m–2 s–1, photoperiod extension was effective in inhibiting flowering, while promoting vegetative growth. Uniform flowering was induced upon the discontinuation of photoperiod extension. As a result, plants achieved two growing cycles per year, with the spring and fall growing seasons running from February to July and July to December, respectively. Yield increased by 92 % from Year 1 to Year 2 but decreased by 37 % from the spring to fall growing season. The maximum yield was 465 kg ha–1 in Year 2 Spring. Cone quality was greatly affected by both year and season, with α acid, β acid, and total oil concentrations ranging from 2.7 % to 6.2 %, 1.9 % to 3.2 % and 0.14 to 0.53 mL/100 g, respectively. These results demonstrate that, with an aid of photoperiod manipulation for flowering control, ‘Cascade’ hops exhibit high phenological plasticity and acclimation capacity to subtropical climatic conditions. This study provides a foundation for developing the double-season hop production system in a subtropical climate.