Growing degree days (GDD) are commonly used to schedule the beginning of spring nitrogen fertilizer applications in grass seed crops. Typically, 200 GDD (base 0 C) from January 1st is used as the opening date of spring nitrogen fertilizer applications.  This number of GDD marks the beginning of the period that the average daily temperature reaches 5 C (41 F) and as a result, grass seed crops resume growth after winter quiescence.

The current (February 13th) GDD  is 197 GDD at Hyslop Farm near Corvallis.  At the current rate of GDD accumulation, 200 GDD should be attained on the 14th.  The long-term average date for attaining 200 GDD is February 14th.

Thomas G. Chastain

Here’s an article just published by our seed production team on nitrogen’s effect on seed yield and other seed production characteristics in yellow mustard.  Trials were conducted on this crop over a 3-year period at OSU’s Hyslop Farm by Alyssa DuVal, a former graduate student and current instructor in the department.  Yellow mustard is a potential seed crop for the high rainfall areas of western Oregon and unlike many other Brassica family crops, there is no threat of crossing of yellow mustard with the region’s vegetable seed crops.

Yellow mustard crop pods prior to harvest. (Photo by T.G. Chastain)

This article was published in Agronomy Journal and can be found at the link below:

Duval, A.S., T.G. Chastain, C.J. Garbacik, and D.J. Wysocki.  2017.  Nitrogen affects seed production characteristics in yellow mustard (Sinapis alba L.).  Agron. J. 109:995-1004.

Key findings of the article:

  • Applied N increased seed and oil yield in yellow mustard in a high rainfall environment.
  • Seeds m–2 was the most influential factor in determining seed yield in yellow mustard.
  • Applied N increased height, biomass, tissue N content, leaf area index, and crop growth rate.

OSU is presenting three seed production field days in May where the public can visit research farms and learn more about research activities. The field days provide a convenient choice for those located in either the western or eastern parts of the state.

May 18 – Native Wildflower Seed Production – Seed production of native plants in eastern Oregon. Starts at 9 AM and ends at noon.

Located at Malheur Experiment Station, 595 Onion Avenue, Ontario, OR.  Phone 541-889-2174.

May 25 – Grass Seed Field Day – Various topics focused on grass seed production practices and pests and more. Starts at 8:00 AM and ends at noon.

Located at OSU’s Hermiston Agricultural Research and Extension Center, 2121 S. First Street, Hermiston, OR 97838. Phone (541) 567-6337.

May 24 – Hyslop Farm Field Day – Plant growth regulators and nutrient management in grass seed crops, weed management in grass seed crops, cereals, and more. Starts at 8 AM and ends with lunch provided by the OSU Crops Club.

Located at Hyslop Crop Science Field Research Laboratory just off Highway 20 between Corvallis and Albany at 3455 NE Granger Corvallis, OR 97330. Phone (541) 737-6067. Hyslop Farm location


Thomas G. Chastain

An often asked question is whether there is a benefit to application of irrigation in late summer or early fall (mid-August until the end of September) in grass seed crops such as perennial ryegrass and tall fescue in the Willamette Valley.  Our  research and extension team in seed crops conducted studies over a broad range of years to determine whether irrigation in this period is helpful for these seed crops.

Big gun
Big gun style irrigation system in grass seed field (TG Chastain photo)

Some of our perennial ryegrass work was done in the very dry years of the early 1990s. Those years were as dry as our recent multi-year drought in western Oregon. What we found was that in two cultivars of perennial ryegrass, there was no effect of 2 inches of irrigation water in August and September on seed yield over a three-year period.

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