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

Annual ryegrass [Lolium perenne L. ssp. multiflorum (Lam.) Husnot] seed crops have been produced on some Oregon farms continuously for decades without rotation of crops or farming practices.  The long-term influences of this continuous cropping of annual ryegrass have not been examined nor have any long-term practices been evaluated in annual ryegrass seed production.

Annual ryegrass seed field in Oregon (TG Chastain photo)

Long-term annual ryegrass cropping systems trials were initiated in the 2005-06 crop year in a project led by former OSU Extension Agent, Mark Mellbye.  His vision was for a 9-year project to study the long-term effects of several cropping practices on annual ryegrass seed production.

While there are several long-term cropping systems practices studies in field crops such as wheat at a variety of locations around the world, no long-term studies in grass seed crops and annual ryegrass in particular, have ever been conducted.  The following six cropping systems practices treatments were employed in the study:

  1. Continuous conventional tillage and planting system
  2. Continuous no-till planting system
  3. No-till/conventional tillage rotation (alternate year tillage)
  4. Volunteer/conventional tillage rotation (alternate year tillage)
  5. Burn and no-till/conventional tillage rotation (alternate year tillage)
  6. Volunteer/no-till/conventional tillage rotation (tillage every 3rd year)

The following were the primary findings of the study:

  • Annual ryegrass seed yield varied with tillage and establishment system, and environment.
  • No-till produced the lowest seed yields.
  • Environment x system interaction effects governed seed production characteristics.
  • Increased tillage frequency and residue removal are required to sustain long-term seed yields.
  • Yield differences among systems were attributable to seed number.

This article was published in Field Crops Research and can be found at the link below:

Chastain, T.G., C.J. Garbacik, and W.C. Young III. 2017. Tillage and establishment system effects on annual ryegrass seed crops. Field Crops Res. 209:144-150.



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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