Low tunnels increased early-season yield of organic June-bearing strawberries in southeastern United States

Out-of-season strawberries are profitable in the southeastern US. However, cold temperatures cause significant yield loss if plants were not protected. Our objective was to evaluate the efficacy of low tunnels in the annual plasticulture system on harvest times, yield and frost protection. This 2-year study took place in an organically managed field at North Carolina A&T State University Farm in Greensboro, North Carolina. The experimental design was a completely randomized design conducted as a splitplot treatment design with three replications. Main plots were black plastic mulched beds with low tunnels (LT) or without LT. Split plots were four June-bearing cultivars. LT (Dubois Agrinovation) were wire frames (71 cm × 20.5 m) covered with clear 0.038 mm polyethylene plastic film. Strawberries were planted in early September of both years (2016/17 and 2017/18). Row covers of 51 g m^‑2 were used to cover LT during periods of prolonged freezing temperatures. In the 2017/18 season, frost damages to flowers and fruits were 22.7 and 8.7% with LT, and 41.3 and 57.2% without LT, respectively. Strawberry harvests occurred in February 2017 and December 2018, respectively. Harvests steadily increased and reached the peak in April, which was earlier by about one month than the normal field harvest in North Carolina. LT significantly increased early marketable yield; for example, it was 122 g plant^-1 with LT in April 2018, compared to 51.6 g plant^-1 without LT. As temperatures in the field began to rise significantly in May, yield started to decline, suggesting the necessary removal of LT. Cultivars varied in yield, bloom times, early season fruit quality and cold hardiness. 'Benicia' had the highest marketable yield, followed by 'Florida Radiance', 'Winterstar' and 'Camino Real'. Our research results suggest that LT protect plants, flowers and fruit from frost damage and result in early harvest and yield of June-bearing strawberries.