Effects of nitrogen rates on chemical composition of yellow grape tomato grown in a subtropical climate.

摘要

Grape tomatoes (Lycopersicon esculentum Mill.) are gaining popularity among consumers because of their flavor, sweetness, potential health benefits, and ease of consumption. Most grape tomatoes are indeterminate varieties. Hence, current production practices (including fertilization rates) may need to be adjusted to larger plants, longer growing seasons, and harvests over several months of the indeterminate varieties. The responses of physical (color and moisture content) and chemical [vitamin C, pH, total titratable acidity (TTA), carotenoids, and soluble solid content (SSC)] parameters for 'Honey Bunch' yellow grape tomato to nitrogen (N) rates were evaluated. In Spring 2005, tomatoes were grown on a Lakeland fine sand in North Florida using plasticulture and N rates of 0, 78, 157, 235, 314, and 392 kg/ha. Tomatoes were harvested fully ripen on 81 and 105 d after transplanting (DAT=0 on March 24th), and uniform 20-fruit samples were carefully selected. Increasing N rate significantly reduced vitamin C concentration from 44 to 35 mg/100 g and TTA from 0.47% to 0.38% citric acid, but did not significantly affect lutein (mean=0.26 micro-g/g) and beta -carotene (mean=0.82 micro-g/g) concentrations or color. Response of pulp pH to N rate was significant but within the narrow 4.5 to 4.7 range. Soluble solid contents decreased as N rate decreased for the first harvest (8.1 to 5.6 for 0 to 392 kg/ha of N), but increased for the second harvest (6.9 to 10.1 for 0 to 314 kg/ha of N). Overall, N rate did not have a marked effect on selected quality parameters, suggesting that variety and/or other environmental factors may be more important than N rate in determining chemical composition of grape tomato..