Effect of Potassium Foliar Nutrition on Changes in the Content of Carotenoid Pigments and on Some Parameters of the Nutritional Value of Tomato Fruit

The aim of the study was to investigate the effect of potassium foliar nutrition on changes in the content of carotenoid pigments and on some parameters of the nutritional value of tomato fruit. The experiments were conducted on three tomato cultivars: Faustine F₁, Atut F₁ and Magnus F₁. All trial plots with plants were additionally fertilized with 0.3% Final K and 0.3% Kalisol whilst in the control plots no foliar nutrition with potassium was applied. The chemical composition of tomato fruit depended on two factors: tomato cultivar and fertilization method and differed from year to year of investigation. In 2005 neither the cultivar nor the foliar fertilization affected the level of β-carotene while the fertilization with Final K resulted in the increase of lycopene content compared with the control. In 2006 and 2007 the fruits from treatments fertilized with Kalisol had significantly higher content of β-carotene and lycopene in compareson with those treated with Final K. The obtained results do not clearly show the effect of potassium foliar fertilization on the increase of dry matter, sugars or acids contant in tomatoes. Foliar fertilization with Kalisol increased the content of L-ascorbic acid in tomatoes in 2005 and 2007. In 2006 the content of this acid in fruit treated with Kalisol was at the same level as untreated plants but higher in plants treated with Final K. The effect of foliar nutrition with potassium had a variable influence on the level of the investigated macroelements (K, P, Ca, Mg). The content of β-carotene was positively correlated with the content of phosphorus and negatively correlated with the acidity of fruit.