2011 University of Delaware Watermelon Pollenizer Trial Gordon Johnson & Emmalea Ernest University of Delaware Elbert N. & Ann V. Carvel Research and Education Center 16483 County Seat Highway Georgetown, DE 19947 (302) 856-7303 [email protected] [email protected] Introduction The purpose of the 2011 Watermelon Pollenizer Trial was to evaluate both special pollenizer varieties and regular diploid watermelon varieties in an in-row planting arrangement with standard seedless watermelons. Ten special pollenizer varieties, and five Allsweet type diploid varieties were tested. As a control, a treatment in which no pollenizer was planted was also included. Variety/Treatment Name Source Company Pollenizer Type Summer Flavor 800 Abbot & Cobb Allsweet Type Tropical Harris Moran Allsweet Type Encore Hollar Seeds/Seedway Allsweet Type Sangria Rogers-Syngenta Allsweet Type Stargazer Seminis Allsweet Type POL - 10319 Abbot & Cobb Special Pollenizer POL - 4290 Abbot & Cobb Special Pollenizer POL - 4370 Abbot & Cobb Special Pollenizer POL - 4400 Abbot & Cobb Special Pollenizer Accomplice Harris Moran Special Pollenizer Sidekick Harris Moran Special Pollenizer Polimax Nunhems Special Pollenizer sp-4 Syngenta Special Pollenizer sp-5 Syngenta Special Pollenizer PollenPro Zeraim Gedera/Siegers Special Pollenizer No Pollenizer Materials and Methods Plot Set-Up The trial was set up in a randomized complete block design with four replications. Black plastic mulch beds were laid on 7’ centers. A total of 32 rows of mulch were laid with a 30’ drive row between every 8 beds. Each of the four sections of eight rows was treated as one block. The third and seventh row out of each 8-row section was a treatment row. The remaining rows were planted in triploid watermelons without pollenizers and served as border rows. The Abbot & Cobb variety SS 9651, which has a solid medium-green rind, was used in the first, second and eighth row of each section, to make it easy to distinguish the melons from the border rows from those of the treatment plots. The fourth, fifth and sixth rows of each section were planted in Liberty, as a part of another study. Each treatment row contained eight plots. Plots were 27’ long and contained ten triploid plants spaced at 3’ and four pollenizer plants which were planted between the regularly spaced triploid plants as shown below. Note that the control treatment did not have pollenizers. The Crimson Sweet-type triploid varieties used in the trial were Melody and SS 7187. Five plants of each variety were planted in each plot. Plots were separated from one another within the row by 15’. The space between each plot and the next was planted with five plants of SS 9651. Plots were separated from one another between rows by three rows of triploid plants with no pollenizers and at least 28’. Layout of a Part of One Eight-Row Section Border Row: SS 9651 spaced at 3 ft Border rows continue S S 9 6 5 1 Border Row: SS 9651 spaced at 3 ft S S 9 6 5 1 Treatment Row 6 more plots B B B B B P S S S P S S M P M M M P M B B B B B P S S S P S S M P M M M P M B B Border Row: Liberty spaced at 3 ft L i b e r t y Border Row: Liberty spaced at 3 ft L i b e r t y Border Row: Liberty spaced at 3 ft L i b e r t y Treatment Row 6 more plots B B B B B P S S S P S S M P M M M P M B B B B B P S S S P S S M P M M M P M B B Border Row: SS 9651 spaced at 3 ft S S 9 6 5 1 B=border plant of SS 9651, P=pollenizer plant, S=SS 7187 plant, M=Melody plant Location Field 1 at the University of Delaware Research and Education Center Farm, Georgetown, DE. Cultural Practices Field was fertilized according to soil test results. On April 21, 2011, 50 lbs/A of nitrogen (30% UAN)+Sinbar 2 oz/A+Prefar 6 qt/A+Profine 75 0.5 oz/A was applied after the beds had been shaped and before black plastic mulch and trickle irrigation were laid on 7’ centers. Plants were seeded in the greenhouse on April 13, 2011. The triploid plants were transplanted to the field on May 17, 2011, and the pollenizers were transplanted on May 18. An application of Gramoxone 1.5 qt/A +Sandea 0.5 oz/A +Crop Oil Concentrate at 1% v/v was made to the row middles on June 3 with a hooded sprayer. Vines were turned before this application as they had just started to run off of the plastic. Tapout 16 oz/A was applied on July 15, 2011 to control grass. Applications for disease and insect control were as follows: Chloronil at 3 pt/A on 6-17, 6-25, 7-1, 7-8, 7-16, 7-23, 7-30, 8-7, 8-20 and 8-25; Pristine at 18.5 oz/A on 7- 1 and 7-30; Previcur Flex at 1.2 pt/A on 8-7; Inspire Super at 20 oz/A on 7-16, 7-23 and 8-20; Presidio at 3 oz/A on 8-25; Oberon at 8.5 oz/A on 7-1 and 8-7; Radiant at 8 oz/A on 7-1; Asana XL at 9.6 oz/A on 7-16; and Warrior II at 1.9 oz/A on 7-30. The trial was fertigated on June 5 with UAN to supply 40 lbs/A N; on June 23 with 8-2-8 to supply 40 lbs/A N, 10 lbs/A P, and 40 lbs/A K; and on August 2 with 8-2-8 to supply 50 lbs/A N, 13 lbs/A P, and 50 lbs/A K. Data Collection The following data were collected on June 10 and 13 and again on June 17 for one SS 7187 plant, one Melody plant, and the Allsweet-type pollenizers from each plot in replications 1 through 3: number of stems, stem length, and female flower location (node number) and stage of development (set, aborted, open, not yet open). Stem number, vine length, and number of open male flowers were recorded for one pollenizer plant from each plot in replications 1 through 3. Leaf surface temperature was measured for one Melody plant, one SS 7187 plant and one pollenizer plant in each plot on June 10 and 13. Melons from the treatment plots were harvested four times: July 27, August 8, August 24 and September 7. All ripe melons were harvested from the SS 7187, Melody and Allsweet-type diploid pollenizer varieties. The weight of each watermelon harvested was recorded individually and each melon was designated as marketable or unmarketable based on fruit shape. On each harvest date up to three melons from each variety (SS 7187, Melody or Allsweet-type diploid) plot were cut and evaluated for presence of hollow heart and soluble solids levels. Obviously unmarketable melons (>7 lbs or misshapen) were not used for hollow heart and soluble solids testing. Soluble solids were measured using a hand-held refractometer and hollow heart cracks were measured at their widest point with a metric ruler. On August 25, we estimated the yield of melons from the border rows that were associated with each pollenizer plot. Melons were counted if they were of marketable size and shape and were located on the soil space on either side of the treatment plot or on top of the mulched bed of the treatment plot. Results Yield of seedless melons was analyzed as a split-plot design with pollenizer treatment, seedless variety, and block as variables (Table 1). Six different measures of yield of seedless melons were analyzed: Total Yield, in terms of number of melons and weight of melons; Marketable Yield I, which excluded misshapen culls and melons less than 7 lbs, in terms of number of melons and weight of melons; and Marketable Yield II, which excluded misshapen culls, melons less than 7 lbs, and melons more than 24 lbs, in terms of number of melons and weight of melons. Pollenizer treatment was a significant source of variation in yield by all measures. The yield effects of the different pollenizer treatments are further analyzed and discussed in the following sections of this report. The interaction between seedless variety and pollenizer treatment did not have a significant effect on yield by any of measures used. This means that although Melody is an earlier maturing variety than SS 7187, pollenizer varieties performed equally well with both seedless varieties in terms of season-long yield. For some measures of yield there was a significant effect for block and the interaction between pollenizer treatment and block. We observed that the block located closest to the bee hives had higher yields and more melons set in the treatment with no pollenizer plants. As with most field experiments, variation in soil conditions are also likely to be partially responsible for the block effects. Seedless variety was a significant source of variation in yield, by all measures, as SS 7187 produced significantly higher yields than Melody. Pollenizer Effects on Season-Long Yield By all measures of yield, the treatment with no pollenizer produced significantly lower yields than any of the treatments with pollenizers (Table 2). The triploid plants in these plots also had excessive vine growth due to low fruit set.