EFFECTS OF CATION COMPOSITION OF THE NUTRIENT SOLUTION ON TIPBURN INCIDENCE IN STRAWBERRY (FRAGARIA x ANANASSA DUCH.) SOILLESS CULTIVATION

Six nutrient solutions were used to fertigate strawberry plants (cv ‘Camarosa’) in coconut peat grown under a glasshouse. Different proportions of K+, Ca2+ and Mg2+ in the nutrient solutions were adjusted following a {3,2} simplex lattice design to maintain the cation composition of the nutrient solutions at 30 meq l- 1. Concentrations of each cation varied between 2.25 and 12 meq l-1 (K and Ca) and between 0.75 and 10.5 meq l-1 (Mg). The yield and quality of the production, leaf area, petiole length and tipburn incidence were measured. The response was modelled fitting a second degree canonical polynomial equation (cation proportions) to the results. Yield and quality parameters were greater with nutrient solutions containing high levels of Ca2+ despite K+ or Mg2+ concentrations, but tipburn incidence was greater with high levels of K+, medium to low levels of Mg2+ and low levels of Ca. Leaf area per plant and petiole length were also greater with high levels of K+, medium to low levels of Mg2+ and low levels of Ca, which suggests a possible relation of luxury growth with tipburn incidence in strawberry.