Co-composting as a method to produce nutrient-rich compost from olive mill waste to use as a substitute for growing strawberries in the UK

A compost was produced by co-composting olive mill wastewater (OMW) and chicken manure (CM), with green waste as a bulking agent. Two different variants of OMW compost were used in growth trials during the 2014 season in the UK, one twice composted and one that was composted three times. The composting was on a pilot scale in windrows. During the first composting procedure, these windrows were turned 14 times. For the second composting, CM and OMW were added to the compost from the first stage used as the bulking agent; this was turned eight times. This compost was used as a bulking agent for the third composting, with CM and OMW added. Amounts of this product in ratios of 10, 25 and 50% were combined with substrate to create a soilless medium suitable for the growth of strawberries (Fragaria × ananassa). Fruits were assessed for quality by measuring sugar content and flesh firmness using a refractometer and penetrometer, respectively. The extent of these trials was not enough to get an understanding of any consistent differences in the production of strawberries when grown in different substrates. Trials in 2015 will have greater scope to clarify if this substrate has an impact on marketable crop quality.