Influence of different doses of mineral fertilizer and the controlled water deficit on the antioxidants parameters in tomatoes (Solanum lycopersicum L.) irrigated with a drip irrigation system

Antoniya Stoyanova, Petya Veleva, Elica Valkova and Mitko Georgiev

Abstract: The main objective of this study is to analyze the mutual influence of different irrigation schemes and fertilization rates on the greenhouse tomato yield, and the irrigation water usage efficiency for a period of three years (2016-2018). Different irrigation schemes have been examined, achieved by reducing the irrigation depth at different levels. Fertilization plays an important role in the technological process with different rates. This experiment was focused on the effect of both factors (the fertilization rate and the irrigation regim) on the main quality parameters of the greenhouse tomatoes. Multivariate data analysis was applied to process the data, including Scheffe and Dunnett’s tests (depending on the Levene's test of equality of variances) were used to find the significant differences (P < 0.05) between the control variant and all other irrigation and fertilization schemes based on the investigated quality parameters (Dry matter, %; Ascorbic acid, mg%; Titrable organic acids, %; General dyes, mg%; Lycopene, mg% and β - carotene, mg%) in greenhouse-grown tomatoes. The analysis showed a medium to a high correlation (R2 = 0.988, 0.990, and 0.062 for the three investigated years) between Dry matter content and the two investigated factors (the fertilization rate and the irrigation depth) and a very strong correlation (R2 = 0.999, and 1.000) between Ascorbic acids and both factors of influ-ence for the first two years and a weak correlation (R2 = 0.287) for the third experimental year. A weak to moderate cor-relation between Titrable organic acids (R2 = 0.414, 0.669, and 0.079), β – carotene (R2 = 0.252, 0.673, and 0.471), and both influencing factors were found, and a moderate correlation between General dyes (R2 = 0.532, 0.815, and 0.590), Lycopene (R2 = 0.685, 0.796 and 0.643), and the variants of irrigation and fertilization for the three experimental years.

Keywords: antioxidants; fertilization; greenhouse tomato; irrigation regime

Date published: 2020-12-14