EFFECTS OF INCREASED CONDUCTIVITY OF THE NUTRIENT SOLUTIONS AND OF THE ADDITION OF POTASSIUM SILICATE AGAINST ALTERNARIA JAPONICA ON ROCKET ERUCA VESICARIA IN SOILLESS CULTIVATION
E.E. Cogliati, G. Gilardi, A. Garibaldi, M.L. Gullino
The objective of this study was to evaluate the effects of potassium silicate and of the electrical conductivity of nutrient solutions in three experiments against Alternaria japonica attacks to rocket (Eruca vesicaria) grown in a closed soilless system. Potassium silicate was added at 100 mg l-1 of nutrient solution at three different levels of electrical conductivity (EC): 1.5-1.6 mS cm-1 (EC-1), 3-3.2 mS cm-1 (EC-2, 0.70 g l-1 NaCl) and 4-4.2 mS cm-1 (EC- 3, 0.95 g l-1 NaCl). Rocket plants were inoculated with A. japonica conidia 18-38 days after sowing or transplant. Electrical conductivity values were negatively correlated with the incidence and severity of the disease, the highest conductivity solution giving the best results. The addition of potassium silicate to the different nutrient solutions resulted in a significant reduction of disease incidence and severity compared with a solution without silicate. The best results were given by the addition of silicate with the highest electrical conductivity (EC- 3) in all the trials carried out. The suitability and benefits of applying silicon amendments in practice are discussed.