We conducted thirteen trials at five commercial farms (map) in multiple locations and seasons (fall, winter and spring) during the 2006-2007 seasons (Table 1). Together the cooperating farms represented 16,000 acres (80%) of staked tomato production in southern and eastern Florida. Soils in the area have a sandy surface layer that is prone to leaching mostly Immokalee and EauGallie fine sand. Growing seasons are defined as fall with planting dates from August to 15 Oct., winter from 15 Oct. to 15 Dec. and spring from 15 Dec. to 1 Feb. These seasons differ in rainfall patterns, temperatures and day length. For example, fall may bring hurricanes, leaching rains, and wide-ranging temperatures; winter brings cool temperatures and unpredictable freezes accompanying cold fronts; spring is typically dry with temperatures cool at the start and warm or hot at the end. Typical growing season lengths are 18, 20, and 16 weeks for fall winter and spring, respectively. Therefore eight trials were done with seepage, two with drip and three a combination seepage/drip irrigation. One trial was conducted in the fall 2006, nine in the winter (2006-07) and four in the spring 2007. Treatments consisted of N fertilizer rates ranging from 200 to 330 lb/acre N applied to seepage-irrigated tomatoes in a (Table 1), except the multiple N rate study with eight N rates from 20 to 420 lb/acre at 60 lb/acre increment in a completely randomized block experimental design with four replications (Table 2). In drip-irrigated fields, there were two individual zones representing IFAS and growers N rates. At the seepage-irrigated fields, the UF-IFAS rates were achieved by changing the rate or composition of the hot mix and by applying custom-made blends to keep P, K micronutrients rates constant. Hot-mix N and K fertilizer sources were water soluble nutrients, except trials 7 and 8 with a 25% slow release fertilizer. The trials represented diverse growing conditions found in Southwest and East Florida, and also included different varieties (mostly ‘Florida 47’ and ‘Sebring’), plant densities (in-row spacing of 18 to 26 inches between plants; 5 or 6 ft bed centers), soil types (described above), and farm sizes (700 to 5,000 acres). Cooperators prepared beds, fumigated the soil, applied bottom and hot mixes and installed polyethylene mulch, transplanted, pruned, staked, irrigated and provided pest and disease control.
Data collection: The water table depth was recorded bi-weekly throughout the growing season. Beginning at first flower buds and continuing until third harvest, fresh petiole sap NO3-N and K concentrations were measured bi-weekly using ion-specific meters (Cardi, Spectrum Technologies, Inc., Plainfield, IL) (Olson et al., 2005). Harvested plots were 15 to 22-ft long row segments of 10 plants. They were clearly marked to prevent unscheduled harvest by commercial crews. Marketable green and color tomatoes were graded in the field according to USDA specifications of number and weight of extra-large (5x6), large (6x6), and medium (6x7) fruit (USDA, 1997) of green and color. Yield data were subjected to analysis of variance (ANOVA) mean separation using Duncan’s Multiple Range Test at the 5% level of significance as well as non-parametric analysis tests like binomial distribution and probability
