Development of a Nitrogen Fertigation Program for Grape Tomato

ABSTRACT

Grape tomatoes (Solanum lycopersicon L. var. cerasiform) have recently gained in popularity among consumers because they can be eaten without being cut, they are deep red in color, and their flavor is intense and pleasant. Current nitrogen (N) fertilization recommendations were developed for determinate tomato varieties that have a 3-month long growing season, whereas that of the indeterminate grape cultivars may be up to six months. ‘Tami G’ grape tomatoes were grown on a Lakeland fine sand at the North Florida Research and Education Center—Suwannee Valley, near Live Oak, FL in Springs 2005 and 2006 using standard plasticulture practices under 0%, 33%, 66%, 100%, 133%, and 166% of the current recommended N rate for round tomato (224 kg/ha). Due to a longer growing season in 2006, plants received an additional three weekly injections of 22 kg/ha of N each in the 100% rate, that were also proportionally applied to the other treatments. Tomatoes were transplanted March 24, 2005 and April 4, 2006 and harvested, weighed and graded five (2005) and seven (2006) times. Season marketable yield (SMY) responses to N rates were quadratic (both years P < 0.01) and highest SMY (40,340 and 36,873 kg/ha) occurred with 314 and 280 kg/ha of N in 2005 and 2006, respectively. Fruit soluble solids concentrations ranged from 6.25 to 7.5, and 7.0 to 8.3° Brix in 2005 and 2006, respectively, and were not significantly affected by N rate. These results suggest that N fertilization for grape tomato grown in Spring with plasticulture could be done by incorporating 56 kg/ha of N in the bed, followed by daily rates ranging from 0.5 to 3.5 kg/ha/day. Because the length of the growing season for grape tomato may vary, emphasis should be placed on daily N rates and irrigation management, rather than on seasonal N rate.

Keywords:

• Solanum lycopersicon L. var. cerasiform
• best management practices
• BMP
• nutrient management
• plasticulture

Notes

^zEach year, other treatments represented 0%, 33%, 66%, 133% and 166% of the N amount injected; WAT = weeks after transplanting; 1 kg/ha = 1.12 lbs/A; WAT = weeks after transplanting

^yTotal N rate = preplant N rate + cumulative injected N rate.

^xIn 2005, fertilizer injections were made on 5, 6, 7, 8, 9, 10, 11, and 12 WAT and harvests were made on 11, 12, 13, 15, and 16 WAT.

^wIn 2006, fertilizer injections were made on 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, and 15 WAT, and harvests were made on 9, 10, 11, 12, 13, 14, and 15 WAT.

^zSee table 1 for actual N rates applied until each sampling date. Round/Roma tomato sufficiency ranges are 600–800, 300–400, and 200–400 mg/L of NO₃-N, and 3500–4000, 2500–3000, and 2000–2500 mg/L of K in petiole sap at first open flowers, first harvest, and second harvest, respectively (Olson et al., 2006).