New Approaches to Organic Blueberry (Vaccinium corymbosum L.) Production in Alkaline Field Soils

Production of Vaccinium corymbosum L. is limited to acidic soils with high organic matter content. This specific soil requirement is limiting the possibilities to cultivate V. corymbosum L. in many regions of Central Europe. The aim of this study was to overcome the limiting production factors occurring under the soil and climate conditions of Switzerland: (1) evaluation of natural growing substrates without peat as required for organic production; (2) adjustment of the optimal pH in the growing substrate; (3) regulation of water issues (water quality and mulching) and (4) development of a suited planting system. Pine sawdust was evaluated to be the best alternative growing substrate compared to peat moss. Optimal pH adjustment in pine sawdust substrate was found to be 3.8 (CaCl2) and 4.2 (H22O). In field cultivation, an amount of 30 g S year-1 plant-1 to lower the pH of the pine sawdust ditches was sufficient for good plant and yield development. This acidification resulted in better growth (+48 %) and higher yield (+55 %) when alkaline ground water (357 mg L-1 CaC03) was used for irrigation. Acidification with citric acid gave poor results. A mulch of pine bark on the sawdust ridge increased growth by 59 % and yield by 25 %. The newly developed flat ditch system with low sawdust ditches buried partly into the ground was as suitable as the standard planting system with deep ditches lined with plastic film. By integration and application of these new findings, a system for commercial organic blueberry production under Swiss conditions and on alkaline soils was developed