Programming production potential and harvest spread through fertilisation in 'Elsanta' trayplants

Using multiple cultivation systems in the pursuit of a year-round production, strawberry growers aim for high production rates and large, high quality fruits. Production potential is established during the plant production phase which takes place on tray fields for the substrate growers in Belgium. 'Elsanta' is the major cultivar used in the different systems throughout the year. In the milder conditions in spring, 'Elsanta' can gradually develop and ripening occurs during longer days towards the summer. Therefore, growers like to use tray plants with a larger production potential, because fruit setting and colouring is not limited by the natural conditions in spring. They also prefer a rather compact harvest, because new plantings for summer or autumn production have to be executed in time. On the other hand, autumn cultivations in glasshouses require plants with a greater harvest spread which will give quantitative and qualitative production later in the year, when market prices are higher. Autumn cultivations have an enforced growth in the early stages because of warmer conditions in summer, therefore flower trusses need to grow out later on and one after the other. The sequential outgrowth also reduces competition between fruit of different flower trusses so that the plant can cope with decreasing day length and temperature during the late harvest period. These desired plant characteristics can be programmed into tray plants by timing and quantifying the fertilisation in the plant production phase. Our trials showed that higher production potential and compact harvest can be achieved with higher fertilisation rates. Plants with great harvest spread need to be stimulated earlier during the vegetative growing period and require a more moderate fertilisation scheme to prevent stretching of the top flower and to maintain low stages of development in the upper leaf buds.