To provide Western Colorado onion producers with variety data appropriate for the growing conditions in Western Colorado. The onion variety trial held in the summer of 2000 was based on grower requests.

Duane Homewood, Montrose. Cultivation, fertilization, irrigation and weed control was provided by the grower.

Seed company representatives were contacted by George Novotny, Schall Chemical, Delta and Curtis Swift, Area Extension Agent (Horticulture) for seed. Each variety was planted four times in a randomized complete block design. Each plot was 25 feet long and one bed (30") wide. Two lines of seed were planted on each bed. Plots were planted on 11 April.

Onions were harvested and graded on 20 September. MSTAT-C, The Michigan State MicroProcessor Statistical Program, was used to evaluate statistical differences among cultivars. Total marketable yield and total yield of colossal, jumbo and medium onion bulbs differed significantly. The probability of accuracy of this trail was quite high. We can expect to get the same results 99 times out of 100 times we plant this trial as long as all other factors are equal.

The yield difference between onion varieties is indicated by the letter(s) which follow the CWT/A yield figures. For example, there is no significant difference in the yield of Red Beauty and Eagle as indicated by the `d' following the yield data of each of these varieties even though the CJM yield of Red Beauty was 767.3 cwt/A while the CJM yield of Eagle was 860.8 cwt/A. The yields of Gallatin (' 693.3 f') and Vision ('923.0 ab'), however , are significantly different from the yields of Red Beauty and Eagle as indicated by the different letters following the yield data.

The difference in percent of colossal, jumbo, medium and prepack onion bulbs for each variety provides guidance on which of the 18 cultivars to plant based on the size onion bulb desired by the grower. Growers wanting a high yield of jumbos should consider planting Eagle (82.85% jumbo), Vison (81.89% jumbo), Teton (86.78% jumbo) and Spinnaker (83.82% jumbo). If a high percentage of medium size onion bulbs is desired, growers should consider Arsenal (57.93% medium), Frontier (53.87% medium), Expression (40.24% medium), and BGS 156 (68.75% medium). Caballero was the only variety producing a relatively high percentage of collosals (10.83%).

The assistance of Avelino Hernandez, and members of the CSU Master Gardener program is greatly appreciated.

* Values followed by the same letter are not significantly different. P=0.01, Least Significant Difference Test.

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