Performance of hop cultivars (Humulus lupulus L.) under the annual double harvest system under artificial light supplementation in a subtropical climate

Abstract

We compared growth performance, yield, and cone quality of hops cultivars grown under a double annual-harvest scheme under artificial supplementary light in a subtropical region. The experiment was conducted in Palotina, Paraná, Brazil (24°17’40.05” S; 55°50’23.16” W, at 332 m elevation). Plants were trained on a 5,5 m high vertical trellis, “V” shaped tutoring system. The experiment was laid in a randomized complete-block design in a factorial arrangement (2 × 4) to evaluate the following factors and levels: a) harvest (Conventional Summer Harvest 2022/23, CSH; Off-season Fall Harvest 2023, OFH); and b) cultivar (Hallertau Mittelfrüher; Mapuche; Northern Brewer; Spalter). In both harvests, plant growth, expressed as plant height and fresh weight, yield components (number of cones per side branch, number of cones per plant, cone fresh weight, weight of fresh cones per plant, and estimated productivity), and chemical components of the cones (alpha- and beta-acids and essential oil) were evaluated. Plant growth was analyzed using nonlinear log-logistic regression. The remaining data were subjected to analysis of variance and means were compared using Tukey's test at the 5% probability level. Plant growth, yield, and chemical components of cones differed between harvests, with the summer crop showing faster vegetative growth and yield, while the fall crop showed greater cone mass and quality. At both harvests, cultivars Mapuche and Spalter showed faster vegetative growth, and greater biomass accumulation and yield. Therefore, vegetative growth was considered a major factor influencing yield components, while comparing cultivars and harvests. Hops cultivation for two harvests per year (summer and fall) seems feasible in subtropical climates with the use of supplementary artificial light.