Optimization of trellis design and height for double-season hop (Humulus lupulus L.) production in a subtropical climate: Growth, morphology, yield, and cone quality during establishment years

Abstract

Photoperiod manipulation using supplemental lighting enables double-season production of hops (Humulus lupulus L.) under subtropical climatic conditions. In Florida, United States, the spring growing season (Spring) is from February to June, and the fall growing season (Fall) is from June to November. To develop the optimum trellis for this unique hop production system, we examined the effects of two trellis designs (straight trellis and V-trellis) and three trellis heights (3.7, 4.6, and 5.5 m) on growth, morphology, yield, and cone quality of 'Cascade' hops grown in west central Florida. The straight trellis had two twines per hill installed on a top middle cable, whereas the V-trellis had four twines per hill installed on two top parallel cables. We trained 16 bines per hill for both trellises. Data were collected during establishment years: Year 1 and Year 2. Yield showed significant season × trellis height interaction effects. Surprisingly, yield was highest in Year 1 Spring and decreased by 45–74 % in the subsequent seasons. Increasing trellis height from 3.7 to 5.5 m increased yield by 78–215 %. On average, the V-trellis produced 24 % higher yield than the straight trellis. The 5.5-m V-trellis produced the highest annual yield of 1807 kg ha^–1 in Year 1. Yield had a significant positive correlation with stem dry weight in Year 1 Spring and Year 2 Spring, but it had no significant correlation with bine number per hill, stem diameter, and internode length in any season. Cone quality showed significant seasonal variations. Total α acid concentration decreased from Spring to Fall in both years and recorded the highest value in Year 2 Spring. Similarly, total essential oil content was highest in Year 2 Spring. Except in Year 2 Fall, total α acid concentration (5.35–8.25 %) was within or above the normal range for ‘Cascade’. Compared to these seasonal variations, trellis design and height effects on cone quality were relatively small. These results suggest that, during establishment years, adopting a V-trellis design and increasing trellis height can maximize yield in subtropical hop production without compromising overall cone quality. Ongoing research will validate these findings in mature hop plants.