Carotenoids and Yield in Hydroponic Tomato As Affected By Nitrogen and Potassium Nutrition.

Effects of N concentration in the nutrient solution (10, 12, 14, and 16 mol_c m^-3) in vegetative stage (45 days after transplanting (dat)) and K concentration (5, 7, 9, 11, and 13 mol_c m^-3) in reproductive stage (46-170 dat) on the yield, lycopene, and β-carotene concentrations of tomato were studied in hydroponics. The evaluation was carried out in the first, third and fifth bunches. A factorial design in split plot-arrangement was used, distributing the N as large plot and K as small plot. Nitrogen affected the concentration of lycopene in fruits of the first bunch; and β -carotene in the first and the third bunches. The interaction N*K differentially affected lycopene and β-carotene concentrations, whereas that of K showed effects on both carotenoids and yield. In the first bunch, increases in the N concentration in the nutrient solution (10 to 16 mol_c m^-3), reduced the lycopene concentration in 18%; the same trend was observed in β-carotene, where the highest concentration of both carotenoids were registered with 10 mol_c N m^-3. Increasing concentrations of K (5 to 13 mol_c m^-3), raised the concentration of both carotenoids. While the best combinations of both factors (N:K, mol_c m^-3 ) were 10:9 and 12:11 for the two carotenoids in the first bunch, in the third and fifth bunches the best performance was observed with the combinations of 14:11 and 10:13, respectively, only for β-carotene. The highest yields of the first, third, and fifth bunches were 1255, 1111 and 960 g plant^-1 respectively, and these yields were obtained with K concentrations of 11 to 13 mol_c m^-3. Increasing N dosage reduced the concentration of lycopene and β-carotene, while K increased them as well as the yield; N*K interaction had differential responses in both carotenoids but no effects on yield.