Influence of varied potassium fertilization on eggplant yield and fruit quality in plastic tunnel

Studies upon the ‛Epic F₁’ eggplant were carried out in 2004 − 2005 in an unheated plastic tunnel. The eggplant was cultivated in cylinders made of rigid foil of 10 dm³ capacity each filled with horticultural peat in 0.6 × 0.5 m spacing. The experiment consisted of two factors in a complete randomized design. The influence of the following factors was examined: 1 - potassium fertilizer kind (KCl, K₂SO₄, KNO₃); 2 - potassium dose (8, 16, 24 g K per plant). Fruit samples were harvested for laboratory analyses in the middle of August in the middle of the fruiting period. Fruits were harvested every 7-10 days at the stage of utilization maturity. Total and commercial yields as well as the number of fruits per 1 m² were evaluated. Fresh fruits were subjected to the following analyses: dry matter - drying method, vitamin C - Tillmans’ method, and sugars - Schoorl-Rogenbogen’s method. The obtained results were subjected to analysis of variance. Different potassium fertilizers did not significantly influence yield size and structure as well as eggplant fruit number. The highest fruit yield was obtained from plants fertilized with potassium in the form of KCl at the largest dose of 24 g K per plant. No effects of potassium doses in a form of K₂SO₄ and KNO₃ on eggplant yield were observed. Instead, significant influence of varied potassium fertilization on the fruits’ biological value was found. Potassium added in a form of KNO₃ at a dose of 8 g K per plant resulted in the highest dry matter and vitamin C content in eggplant.