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.

Thomas G. Chastain

Several scales have been constructed for use in assigning developmental stages to crop plants.   The BBCH (Biologische Bundesanstalt, Bundessortenamt und Chemische Industrie) scale is used to ascertain the developmental stages of crops and is based on the Zadoks scale for cereals but has been standardized and extended to many other crops including dicots.

The uniform nature of the BBCH scale has encouraged the wide-spread use of this system by agronomists and by agricultural practitioners alike.  One advantage of the BBCH scale is the simplicity of staging of crop plants because only one scale (with minor modification) is needed for multiple species.

Ten principal stages form the basis for the scale in each crop.  Below is a table showing the adaptation of the scale for grass seed crops.

Stage Description – BBCH scale
0-9 Seed germination/bud development
10-19 Leaf development
20-29 Tiller development
30-39 Stem elongation
40-49 Booting
50-59 Inflorescence emergence/development
60-69 Flowering/pollination
70-79 Seed development
80-89 Seed maturation and harvest
90-99 Senescence


A new nutrient management guide for tall fescue seed crops has been published by OSU’s seed production research and extension team.  The 42-page publication (EM 9099) is a product of many years of  field work in tall fescue seed crops by the members of the research and extension team.

Tall fescue cover

The nutrient management guide covers the impacts of application of nutrients on seed yield, seed yield components, crop growth and development, plant growth regulator use, pests, and others.  Extensive use of tables, figures, and appendices supplement this comprehensive guide to tall fescue seed crop nutrient management.

The publication can be accessed at the link below:

Tall Fescue Grown for Seed: A Nutrient Management Guide for Western Oregon, EM 9099

Here’s a new article from our seed production research and extension team on trinexapac-ethyl plant growth regulator (PGR) and field burning effects on the expression of yield components in strong creeping red fescue (Festuca rubra L. subsp. rubra) seed crops.  The field trials were conducted in the Willamette Valley over a 4-year period at Hyslop Farm.

This article will appear in the next issue of Agronomy Journal and is a part of our series on PGR tools for use in grass and legume seed production.  The product is marketed as Palisade, Moddus, and several generic products for lodging control in grass seed crops and legume seed crops.

Strong creeping red fescue in flower (T.G. Chastain photo)
Strong creeping red fescue in flower (T.G. Chastain photo)

Key findings of the article:

  • Fall applications of the PGR had no effect on seed yield components.
  • Culm length was reduced and lodging was lessened by spring applications of PGR in strong creeping red fescue.
  • Spring applications of PGR increased the number of florets produced.
  • A combination of burning and spring PGR applications increased seed number and seed weight, thus contributing to higher seed yields in strong creeping red fescue.

The article can be found at the link below:

Zapiola, M.L., T.G. Chastain, C.J. Garbacik, and W.C. Young III.  2014.  Trinexapac-ethyl and burning effects on seed yield components in strong creeping red fescue.  Agron J. 106:1371-1378.

Thomas G. Chastain

Why is lodging important in grass seed crops?

Under certain conditions, the tiller cannot support the weight of the developing inflorescence and seed. The tiller lodges or falls to the ground, especially when there are high levels of nitrogen fertilizer and soil moisture present (Fig. 1). Both conditions are common in Oregon’s commercial grass seed production fields in the spring.

Figure 1. Lodging in ryegrass. (T.G Chastain photo)

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