Influence of mineral fertilization on the leaf plastid pigment content and tuber quality of potatoes.

The influence of separate and combined fertilization with nitrogen, phosphorus and potassium, as well as the addition of magnesium to the triple fertilizing combination on the leaf plastid pigments and tuber quality of potatoes under field experimental conditions was studied. The trail was conducted during the vegetation periods of 2013 and 2014. The experiment included the following variants: control (without fertilization), N, P, K, NP, NK, PK, NPK and NPK+Mg. The highest chlorophyll A+B content average for the period of investigation was found in the leaves of variant NP (2,30 mg/g). The fertilization did not influence the carotenoids content in the leaves, which was about 0.70 mg/g in all variants. The highest dry matter content of 23.10% and 22.58% was observed in the tubers of the control variant and variant NРК respectively. In the variant fertilized with nitrogen only (N) the dry matter content was very low – 17.51 %. The fertilization with NPK+Mg had a positive influence on the starch content of the tubers. The content for that variant was 15.42% averagely for the period. The starch content in the tubers of the other variant was lower and varied between 13.01% and 14.90%. The content of reducing sugars did not depend on the fertilization and was about 0.30% in all variants. The quantity of vitamin С was increased in all fertilized variants compared with the control. The highest content of vitamin C was found after the fertilization with NPK+Mg for both years – 11.25 mg/100 g. A positive influence of the separate N fertilization on the content of crude protein in the tubers was observed averagely for the studied period.