Soilless cultivation offers new opportunities for growing blueberries. Cultivation in containers leads to improvements in fruit size and firmness.
Cost price reductions can also be achieved through increased yields, shorter plant establishment periods and more efficient use of the available ground surface. This is expected to lead to faster recovery of investment, allowing growers to respond more quickly to changing markets. At the same time, the use of older bushes with poorer quality fruit and higher sensitivity to diseases can be avoided. The pollution caused by fertilisers and herbicides will be strongly reduced.
Research on suitable cultivars, substrates and watering strategies
Since 2009, a consortium of Dutch growers, nurseries and suppliers and Wageningen University & Research has been conducting research on suitable cultivars, substrates and watering strategies on the property of a fruit grower.
Since 2012, the cultivar Aurora is being used in round, black, 20-litre containers lined with an anti-root membrane. The substrate is based on Legro brand potting soil and contains a mix of Legro turf 33 (coarse, hard) and Legro coconut husk mixture. Perlite has been mixed into the bottom half. A layer of fine bark is spread on top of the soil. The oldest plants started producing in 2012. The research is focusing on varying the supply of nitrogen and water to achieve optimum production while keeping nitrogen leaching to a minimum (maximum 25 kg N/ha/year). To this end, the concept of ‘dry cultivation’ is used, whereby the drainage percentage during the nitrogen fertigation phase is kept between 5 and 10% (instead of the 25-35% that is standard in soilless cultivation).
The results to date reveal that the establishment period can be reduced by 40% or 2 years with the dry cultivation system. During the fifth year of production, 17 to 19 tonnes per hectare were harvested during two separate harvests. This is an excellent yield for the Aurora cultivar.
Heavy frosts do not form an insurmountable problem for blueberry cultivation in containers, as was revealed after the heavy frosts of the winter of 2011/2012. There will be little frost damage if growers ensure they select winter-hardy cultivars and time the growth stage correctly.
The drainage measurements revealed that nitrogen leaching can be reduced to maximum 25 kg N/ha/year.