Effect of Timing of Harvest on Onion Yield and Storability Clint Shock Erik Feibert Oregon State University Malheur Experiment Station Ontario, Oregon

Acknowledgements: IEOOC Onion Seed Companies Irrometer Co. Western SARE This project was partially funded by the Western Sustainable Agricultural Research and Education Program, the Idaho- Eastern Oregon Onion Committee, Irrometer Co. cooperating seed companies, and Oregon State University.

In Treasure Valley: Most onions marketed out of storage from October through March

Purpose: To evaluate and document current grower harvest practices Justification: - Few studies in literature - Only study at Malheur Experiment Station was done in 1985

Constraints on harvest timing and field curing ? - Air temperature - Relative humidity - Precipitation

66-year average precipitation at Ontario: August: 0.34 inch September: 0.45 inches

Collapsed onion top used as indicator of time to undercut to initiate field curing At what percentage of tops down should onions be undercut to achieve highest yield and storability?

Planting date: - March 19, 2009 No effect of irrigation treatment on onion response to harvest timing

Onion harvest timing (undercutting) in 2009: August 13 August 20 August 27 September 3 September 10 Last drip irrigation September 5

Sampling procedure: One sample from every plot of each variety Bulbs were topped, placed in burlap bags, left to cure on bare ground for 1 week Percentage of tops down rated at each sampling

Following 1 week of curing: Samples graded, placed in cooler at 34 o F Each month, starting in late October: - samples weighed - decomposed bulbs removed - samples re-weighed - placed back in cooler

Conclusions: Vaquero and Joaquin: - Yield increased as tops went down -Yield increased until the last harvest, one week after last irrigation

Final packout was highest for onions harvested at highest percent tops down (last harvest) Percent tops down at last harvest: Vaquero 90% Joaquin 30%

The 2009 harvest timing trial results are similar to the 2008 harvest timing trial results. In both years, for the drip irrigated onions, yield at harvest and storability increased for Vaquero and Joaquin as tops went down.

Thank you