Modern training systems for forcing sweet cherries - slender spindle or hedgerow for protected growing?

Recent climate change requires crop protection against heavy rain and hail, but also offers new opportunities for horticultural production. While polytunnels and hail nets protect the crops against adverse weather, crops can be forced and harvested, irrespective of the weather. Moreover, the modified microclimate may increase yield as well as the fruit quality. In sweet cherry, growing trees in a closed polytunnel forces the ripeness and reduces fruit cracking. This environmental-friendly approach without fossil fuel enables customers to purchase domestic products with good taste, firmness and carbon footprint as well as good returns to the grower before the field season starts. One objective of the study was to determine the influence of the modified microclimate on flowering and harvest date. Another objective was to compare different planting systems and pruning measures with regard to yield and the efficiency on small cultivation areas. In 2008-2009, three early cherry cultivars ‘Samba’, ‘Bellise’ and ‘Rita’ on dwarfing rootstock GiSelA 3 were grown at Campus Klein-Altendorf (latitude 50.5°N), University of Bonn, Germany. Each research block consisted of 2 single row beddings with a slender crown (system 1: 2.70×2.00 m; system 2: 1.75×2.9 m) and a hedgerow ((2.4×2.0 m)×1.5 m). Half of the trees were grown without cover as control. The pruning of the beddings was made by hand and that of the hedgerow mechanically. The harvest date was advanced by 7-19 days; yield was 7-12 t ha^‑1 in system 1 (1027 trees ha^‑1), 8-12 t ha^‑1 in system 2 (706 trees ha^‑1) and 13-18 t ha^‑1 in the hedgerow (2000 trees ha^‑1). In consequence, the small planting density enables a proper yield on small areas. The use of mechanical thinning signified a substantial time and workload savings.