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George E. Boyhan, Reid L. Torrance, Jeff Cook, Cliff Riner, and C. Randell Hill

–280 g per 20 plants). These plants were then transplanted to their final spacing with an experimental unit consisting of 5 ft of planted bed with a 5-ft within-row alley between plots. Seedstems (flowers) were counted for each plot on 25 Apr. 2003 and

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George E. Boyhan, David B. Langston, Albert C. Purvis, and C. Randell Hill

Five different statistical methods were used to estimate optimum plot size and three different methods were used to estimate optimum number of replications with short-day onions (Allium cepa L.) for yield, seedstem formation (bolting), purple blotch and/or Stemphylium (PB/S), botrytis leaf blight (BLB), and bulb doubling with a basic plot size unit of 1.5 × 1.8 m (length × width). Methods included Bartlett's test for homogeneity of variance, computed lsd values, maximum curvature of coefficient of variation plotted against plot size, Hatheway's method for a true mean difference, and Cochran and Cox's method for detecting a percent mean difference. Bartlett's chi-square was better at determining optimum plot size with transformed count and percent data compared with yield data in these experiments. Optimum plot size for yield of five basic units (7.5 m length) and four replications is indicated using computed lsd values where the lsd is <5% of the average for that plot size, which was the case in both years of this study. Based on all the methods used for yield, a plot size of four to five basic units and three to five replications is appropriate. For seedstems using computed lsd values, an optimum plot size of four basic units (6 m length) and two replications is indicated. For PB/S two basic units (3 m length) plot size with four replications is indicated by computed lsd values. For BLB a plot size of four basic units (6 m length) and three replications is optimum based on computed lsd values. Optimum plot size and number of replications for estimating bulb doubling was four basic units (6 m length) and two replications with `Southern Belle', a cultivar with a high incidence of doubling using computed lsd values. With `Sweet Vidalia', a cultivar with low incidence of bulb doubling, a plot size of four basic units (6 m length) and five replications is recommended by computed lsd values. Visualizing maximum curvature between coefficient of variation and plot size suggests plot sizes of seven to eight basic units (10.5 to 12 m length) for yield, 10 basic units (15 m length) for seedstems, five basic units (7.5 m length) for PB/S and BLB, five basic units (7.5 m length) for `Southern Belle' doubling, and 10 basic units (15 m length) for `Sweet Vidalia' doubling. A number of plot size-replication combinations were optimum for the parameters tested with Hatheway's and Cochran and Cox's methods. Cochran and Cox's method generally indicated a smaller plot size and number of replications compared to Hatheway's method regardless of the parameter under consideration. Overall, both Hatheway's method and computed lsd values appear to give reasonable results regardless of data (i.e., yield, seedstems, diseases etc.) Finally, it should be noted that the size of the initial basic unit will have a strong influence on the appropriate plot size.

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George E. Boyhan, Reid L. Torrance, Jeff Cook, Cliff Riner, and C. Randell Hill

(version 10.0; StataCorp, College Station, TX). Count data (seedstems and doubles) were transformed with square root (x) before analyses and reported values were back-transformed to their original units. In the 2003–04 season, ‘Sweet Vidalia’ (Nunhems, USA

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George E. Boyhan, Juan Carlos Diaz-Perez, Chris Hopkins, Reid L. Torrance, and C. Randy Hill

seedstems regardless of sowing date. Transplant age and days after transplanting have been investigated for their effect on yield. In Nasik, Maharashtra, India, ‘Agrifound Light Red’ was found to have the greatest yield from 8-week-old transplants harvested

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George E. Boyhan, Albert C. Purvis, William M. Randle, Reid L. Torrance, M. Jefferson Cook IV, Greg Hardison, Ronald H. Blackley, Heath Paradice, C. Randy Hill, and J. Thad Paulk

Short-day onion (Allium cepa) variety trials were conducted in southeastern Georgia from 2000–03. Data collected and evaluated included total yield, graded yield, harvest date, number of seedstems, number of doubles, number of onion centers, bulb shape, disease incidence, bulb pungency, and storability in controlled atmosphere (CA) storage. Fifty-eight varieties were evaluated in the trials with 10 varieties appearing in all 4 years. Twenty-nine varieties appeared only once in the trials. Eight varieties had jumbo yields (≥3-inch diameter) that were not significantly different from the greatest jumbo yielding variety in 2 of the 4 years of testing and included `Century', `EX 19013', `Georgia Boy', `Mr. Buck', `Sapelo Sweet', `Savannah Sweet', `Sweet Vidalia', and `WI-609'. Early season varieties were strongly daylength dependent with foliar lodging occuring early and uniformly. Late season varieties were more prone to bacterial infection particularly if postharvest heat curing was employed. Although significant differences between varieties for seedstems (flower formation) and bulb doubling occurred almost every year, environmental conditions were an important part of their development. Five varieties had seedstems in 2 of the 3 years seedstems were prevalent that did not differ from the greatest number of seedstems for that year and included `Cyclops', `Georgia Boy', `Mr. Buck', `Pegasus', and `SSC 6372 F1'. `Sapelo Sweet' and `Sweet Advantage' had more than 5% bulb doubling in 3 years of the trials. Pungency as measured by pyruvate analysis ranged from 1.1 to 5.4 μmol·g–1 fresh weight (FW) over the 4 years of trials. There were nine varieties that were, for 2 years or more, among the greatest in percent marketable onions after 4.5 months of CA storage: `Georgia Boy', `Granex 1035', `Granex 33', `Ohoopee Sweet', `Sapelo Sweet', `Savannah Sweet', `Sweet Melissa', `Sweet Melody', and `SRO 1000'.

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George E. Boyhan, Juan Carlos Diaz-Perez, Reid L. Torrance, Ronald H. Blackley Jr., and C. Randell Hill

The majority of Vidalia onions are produced as a transplanted crop. Seeding in high density plantings in September is followed 8 to 10 weeks later by transplanting to final spacing. This practice is labor intensive and expensive. Direct seeding would save on labor, cost, and time. Traditionally, transplanting has been done because of better winter survival, more uniform stands, and better irrigation management during seedling emergence. Beginning 5 years ago, we began evaluating direct seeding onions. Initially, seedstems (bolting) and lack of uniform stand establishment were the main problems. Sowing in September resulted in almost 100% seedstems and using a belt planter with raw seed resulted in poor singulation for uniform stand establishment. Mid-October ultimately proved to be the best time for sowing Vidalia onion seed. Earlier sowing resulted in more seedstems and later planting did not give the plants sufficient time to grow resulting in later stand loss during cold winter temperatures. Using polymer coated seed and a precision vacuum planter resulted in uniform, even stand establishment. Fertilizer requirements are almost half with direct seeded onions compared to transplanted onions with a reduction in the need for fungicides and herbicides. We have established direct seeded onions both with drip irrigation and overhead irrigation. There was concern that center-pivot irrigation would not be able to sufficiently irrigate fields during seedling establishment with the frequent hot fall days we experience. Since this work was initiated several growers have successfully produced direct seeded onions under center-pivot systems. Direct seeding Vidalia onions requires attention to detail because there is only one opportunity to get it right. Timing is also critical particularly with planting date and herbicide application.

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George E. Boyhan

.R. 2003 Optimum plot size and number of replications with short-day onions for yield, seedstem formation, number of doubles, and incidence of foliar diseases J. Amer. Soc. Hort. Sci. 128 409 424 Gomez, K.A. Gomez, A.A. 1984 Statistical procedures for

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Susan C. Miyasaka, Charles E. McCulloch, Graham E. Fogg, and James R. Hollyer

plants should be surrounded by border rows. Literature Cited Boyhan, G.E. Langston, D.B. Purvis, A.C. Hill, C.R. 2003 Optimum plot size and number of replications with short-day onions for yield, seedstem formation, number of doubles, and incidence of