‘Allsweet’ and blocky ‘Crimson Sweet’ hybrids are the most commonly grown diploid watermelons in Florida.  Diploid (seeded) watermelons generally weigh from 18 to 35 lb and represent at least half of the commercial crop grown in Florida.  Icebox watermelons weigh 6 to 12 lb each and are grown on a very small acreage.  Triploid (seedless) watermelons usually weigh 15 to 20 lb and are grown in Florida on perhaps 40% of the acreage.  Florida produced 8.6 million cwt of watermelons of all types from 24,000 harvested acres in 2000-2001, which provided an average yield of 310 cwt/acre.  The average price was $5.70/cwt resulting in a crop value of over $42 million which accounted for 2.5% of the gross value of the state=s vegetable crops (Fla. Agr. Stat., 2002).

The purpose of this trial was to evaluate some of the recently introduced commercial hybrids and experimental lines of the blocky >Crimson Sweet= and >Allsweet= types.

 

Materials and Methods

Soil samples from the experimental area obtained before fertilization were analyzed by the University of Florida Extension Soil Testing Laboratory (Hanlon and DeVore, 1989): pH = 7.2 (target pH is 6.0) and Mehlich I extractable P = 105 ppm (very high), K = 12 ppm (very low), Mg = 54 ppm (high), Ca = 552 ppm (adequate), Zn = 9.7 ppm (adequate), Cu = 4.4 ppm (adequate), and Mn = 4.9 ppm (adequate).

The EauGallie fine sand was prepared in late January by incorporation of 0-0.8-0 lb N-P₂O₅-K₂O per 100 linear bed feet (lbf).  Beds were formed and fumigated with methyl bromide:chloropicrin, 67:33 at 2.45 lb/100 lbf.   Banded fertilizer was applied in shallow grooves on bed shoulders at 3.1-0-4.3 lb N-P₂O₅-K₂O/100 lbf after the beds were pressed and before application of the black polyethylene mulch.  Total fertilizer applied was equivalent to 148-40-206 lb N-P₂O₅-K₂O/acre.  The final beds were 32-in. wide and 8-in. high and were spaced on 9-ft centers (4840 lbf), with four beds between seepage irrigation/drainage ditches which were on 41-ft centers.  The diploid watermelons were planted in rows adjacent to the ditches and also served as pollenizers for triploid watermelons that were being evaluated in the two center beds of each land.

Watermelon seeds were planted on 20 February in holes punched in the polyethylene mulch at 3-ft in-row spacing.  Seedlings were thinned at the two true-leaf stage to one per hole.  Twenty-two entries (Table 1) were included in the trial.  The 30-ft long plots had ten plants each and were replicated four times in a randomized complete-block design.  Weed control in row middles was accomplished by cultivation and application of paraquat.  Plant stands recorded just before vines grew together showed no significant difference among plots.  Pesticides were applied as needed for control of gummy stem blight (chlorothalonil, azoxystrobin, and maneb), and lepidopterous larvae (Bacillus thuringiensis and spinosad).

Watermelons were harvested twice during the 17-23 May and 30 May-5 June periods.  Marketable fruit (U.S. No. 1 or better) according to the U.S. Standards for Grades of Watermelons (U.S. Dept. Agr., 1978) were separated from culls and counted and weighed individually.  Fruit 12 lbs and larger were assumed to be marketable.  Soluble solids (a measure of sweetness) determinations were made with a digital, hand-held refractometer on six fruit of each entry at each harvest, polar and equatorial dimensions were obtained and the incidence of hollowheart was recorded for these fruits.   Flesh color was visually estimated. Data were subjected to analysis of variance and mean separation was by Duncan=s multiple range test.

 

Results and Discussion

Maximum temperatures (Table 2) were higher than average in March and April and minimum temperatures were above average in March, April, and May.  This resulted in an earlier than usual crop.  Rainfall was near normal throughout the period.

Total yields (Table 3) varied from 535 cwt/acre for ‘Gold Strike’ to 925 cwt/acre for ‘Rojo Grande’.  Nineteen other entries had yields similar to those of ‘Rojo Grande’.  Average fruit weight over the entire season ranged from 18.2 lbs for ‘Gold Strike’ to 24.8 lbs for ‘Dulce’.  Fruit per plant varied from 1.9 for ‘Gold Strike’ and XWD 98210 to 2.8 for ‘Rojo Grande’.  Soluble solids, a measure of sweetness, concentrations ranged from 11.5% for ‘Festival’ to 13.6% for SWD 403.  Seasonal average soluble solids for all entries exceeded the 10% specified for optional use to designate very good internal quality in the U.S. Standards for Grades of Watermelons (U.S. Dept. Agr., 1978).  The incidence of hollowheart in those fruit sampled varied from none in ten entries to 50% in ‘Dulce’ and ‘Piñata’.  Overall, hollowheart was less of a problem than in recent years.

The proportion of fruit in market weight classes is shown in Table 4.  ‘Mardi Gras’, RWM 8133, ‘Sangria’, and ‘Summer Flavor 790’ produced more than 50% of their fruit in the most desirable 18-24 lb weight class.  At least 80% of the fruit produced by ‘Dulce’, RWM 8134, RWM 8142, ‘Summer Flavor 800’, SWD 7201, amd 98212, exceeded 18 lbs average weight.  SWD 7201 and 98212 also produced uniform large fruit in the 2001 season.

 

Summary

Watermelon variety evaluations have been conducted at this location each spring season since 1991.  The highest yields ranged from 439 cwt/acre in 1996 to 1026 cwt/acre in 1993.  In spring 2002, the highest yield was 925 cwt/ acre which was considerably greater than the 11-year average yield of 777 cwt/acre.

Variety shape and rind patterns, based on observations in this trial, are shown in Table 1.  Varieties producing blocky or elongated/blocky fruit are generally favored in the market.  Distinctively striped melons are more attractive for the U.S. market than those with dark stripes on a very dark green background, or those with a solid dark or medium green rind.  Flesh color was generally good ranging from 3.3 for ‘Dulce’ to 4.8 for HSR 2942, Olé, RWM 8134, and ‘Sangria’.

Based on this and previous trials, the following ‘Allsweet’ and blocky ‘Crimson Sweet’ type varieties are expected to perform well in Florida: ‘Jamboree’, ‘Mardi Gras’, ‘Regency’, ‘Royal Star’, ‘Royal Sweet’, ‘Sentinel’, ‘Starbrite’ ‘Stars-N-Stripes’, and Summer Flavor 790, 800, and 900 series.  ‘Gold Strike’ (for trial) should be evaluated for the niche orange-fleshed, seeded market.  Other varieties may perform equally well on some farms.

 

Note

The information contained in this report is a summary of experimental results.  No discrimination is intended and no endorsement implied where trade names are used.