Balanced fertigation and improved sustainability of June bearing strawberry cultivated three years in open polytunnel.

OBJECT: Improved precision fertilization by introducing sensors and remote control to secure fruit yield and reduce nutrient leaching in soil culture. MATERIAL AND METHODS: We broadcasted before bedding and mulching 50 g m(-2) of a multi-mineral fertilizer. Beds had two plant rows 20 cm apart, with plant distance of 25 cm. Experimental design was split plot with three replications and three treatments. Treatments: fertigation in large plots, cultivar in small plots and year. RESULTS: Plant development in the establishing year had no benefit of fertigation in addition to fertilizer given before bedding. When the yield is 3 kg m(-2) a nutrient solution of 6 g N m(-2) gave highest yield, using 4 g m(-2) from two weeks before harvest and during harvest. 'Florence' and 'Sonata' developed well; however, 'Florence' had mildew on fruits in the last cropping year. 'Korona' presented well the first cropping year, but grew small fruits heavily infested by mildew in the last cropping year. CONCLUSION: Fertilization had effect on fruit yield. It is discussed how a fertilization schedule for the establishment year and cropping years can be adapted to plant development stages. Mildew infestation on fruits was dependent of cultivar and fertilization. Introducing sensors for recording of growth factors and in situ ion-levels of soil water nutrients, proved valuable.