Objective:

Tests were initiated with AuxiGro on onions at two locations during the 2002 growing season to determine if onion size could be increased significantly.

Materials and Methods:

A backpack sprayer was utilized to apply AuxiGro to onions at two locations in the Uncompahgre Valley of Colorado. The sprayer delivered 25 gallons per acre with 30 psi pressure at the CO2 tank. The spray boom was fitted with 8002 TeeJet spray tips.

The treatments and plot plan can be found in Table I for both locations. Each treatment at the Duane Homewood location was 2 beds by 30 feet on 30-inch beds, replicated 4 times. Each 30-inch bed contained two rows of onions. The treatments at the Jerry Hines location was 2 beds by 30 feet on 34-inch beds, replicated 4 times. Each 34-inch bed contained two rows of onions.

The environmental conditions on July 22, 2002 at the Duane Homewood location were:

Air temperature - 76 F, Soil temperature - 66 F, Relative humidity - 56%, and wind 0 to 2 mph at 9:10 a.m.
Onion bulb size was 1.25 to 1.5 inches in diameter.

The environmental conditions on July 22, 2002 at the Jerry Hines location were:

Air temperature - 79 F, Soil temperature - 62 F, Relative humidity - 46%, and wind 0 mph at 9:45 a.m.
Onion bulb size was 1.25 to 2.0 inches in diameter.

The environmental conditions on August 14, 2002 at the Duane Homewood location were:

Air temperature - 62 F, Soil temperature - 60 F, Relative humidity - 62%, and wind 0 mph at 8:45 a.m.
Onion bulb size was 1.5 to 2.0 inches in diameter.

The environmental conditions on August 14, 2002 at the Jerry Hines location were:

Air temperature - 65 F, Soil temperature - 57 F, Relative humidity - 52%, and wind 0 mph at 9:20 a.m.
Onion bulb size was 3.0 to 3.5 inches in diameter.

The onion variety at Duane Homewood was Frontier and at Jerry Hines was Vega.

The onions were harvested on September 16, 2002, at the Duane Homewood location, and on September 19, 2002 at the Jerry Hines location.

Results and Discussion:

The harvest results can be found in Table II and Table III for Duane Homewood and Jerry Hines locations, respectively. There were no significant differences between treatments at either location. Although there were no significant differences, the Jerry Hines location did indicate a trend toward more colossals for AuxiGro at 4 oz/A applied twice. Since we didn't see the same trend at the Duane Homewood location, varieties could respond differently to AuxiGro applications.

2002 was an extremely dry year, which could have had an effect on the results. To fully determine the effectiveness of AuxiGro, tests should be initiated again in 2003 in the Uncompahgre Valley.

^1/Treatments 1 and 2 had 6 oz/100 gal of silicone base surfactant added. Treatments replicated 4 times.

^1/Sequential treatment applied on July 22, 2002 and August 14, 2002.
^2/Applied on August 14, 2002.

Table III Onion Results Following AuxiGro Applications at the Jerry Hines Location - 2002

^1/Sequential treatment applied on July 22, 2002 and August 14, 2002.
^2/Applied on August 14, 2002.

Placed on the Internet February 15, 2003

Curtis E. Swift, Ph.D., Area Extension Agent, Horticulture
Colorado State University Extension
2775 US Hwy 50, Grand Junction, CO. 81503
voice: 970-244-1834
fax: 970-244-1700
Comments are appreciated.