ONION DEMONSTRATION PROJECTS EVALUATING FURROW AND DRIP IRRIGATION IN THE UNCOMPAHGRE VALLEY

John Murray, A. Wayne Cooley, Dr. Curtis E. Swift, and Fred Miller
Range Conservationist, NRCS, Montrose, CO; Area Director and Extension Agent (Soil & Crop Science), CSU Extension, Tri River Area; Area Extension Agent (Horticulture), CSU Extension, Tri River Area; Water Management Specialist, Shavano Conservation District, Montrose, CO.

The Natural Resource Conservation Service (NRCS), Montrose, CO, Shavano Conservation District, Montrose, CO, CSU Extension, Tri River Area, producers, and others collaborated to evaluate the effectiveness of drip irrigation for onions when compared to the common practice of furrow irrigation.

The drip tape was injected into the soil approximately 3.5 inches deep and the drip irrigation side was flat rolled again to eliminate the ridge left when the tape was injected into the center of the 30 inch bed.

The initial demonstration was initiated in 2003 on Tuxedo Farms, Olathe, CO. There was 5 acres of onions under drip irrigation and 10 acres of furrow irrigated in a side by side comparison. A white onion (variety Cometa) was planted on April 7 and 8, 2003 at a population of 195,000 seed per acre (4 rows per 30 inch bed) for the drip irrigated onions and 135,000 seed per acre (2 rows per 30 inch bed) for the furrow irrigated onions.

Total seasonal water use was measured for both the drip and furrow irrigated onions. Yield and quality were measured for both the drip and furrow irrigated onions.

The drip irrigated onions used less water (2.57 acre feet) than the conventional furrow irrigated onions (3.98 acre feet). The field weights for the drip irrigated onions resulted in 84,096 lbs per acre as compared to 51,264 lbs per acre for the furrow irrigated onions. This is a 64 percent yield increase for the drip irrigated over the furrow irrigated onions. After grading the onions, the drip irrigated onions had a larger percent of jumbo's and less culls than the conventional furrow irrigated onions.

As a result of the 2003 demonstration trial, Tuxedo Farms installed a drip system for 18 acres of onions in 2004. There was another drip irrigated demonstration site initiated in 2004 on 10 acres of onions at the Homewood Farm involving a variety of white, red, and yellow onions. The field yield weights for the white onion Cometa, were similar to the drip irrigated onions in 2003. There was not a side by side comparison with furrow irrigated onions in 2004 but the drip irrigated onions yielded from 11 to 35 percent more than Duane Homewood's average farm yield for furrow irrigated onions. One reason that our drip irrigated onion yield increases over furrow irrigated were less in 2004 as compared to 2003, Duane Homewood has a higher seeding rate on furrow irrigated onions than other producers (160,000 seed per acre as compared to 135,000).

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