Thomas G. Chastain

Here’s a new article from our seed production research and extension team on irrigation and trinexapac-ethyl PGR effects on seed yield and yield components in red clover seed crops.  Field trials were conducted in the Willamette Valley over a 3-year period at OSU’s Hyslop Farm.  Trinexapac-ethyl is marketed around the world as Palisade, Moddus, and several generic products for lodging control and seed yield enhancement in cool-season grass seed crops and legume seed crops.

Floret bleaching in red clover, a common effect of TE PGR application (TG Chastain photo)
Floret bleaching in red clover, a common effect of trinexapac-ethyl PGR application (TG Chastain photo)

This article appears in the current issue of Agronomy Journal and can be found at the link below:

Anderson, N.P., T.G. Chastain, and C.J. Garbacik. 2016. Irrigation and trinexapac-ethyl effects on seed yield in first- and second-year red clover stands. Agron. J. 108:1116-1123.

Key findings of the article:

  • Irrigation strategically-timed to coincide with peak flowering consistently increased seed yield in red clover regardless of stand age.
  • Trinexapac-ethyl PGR increased seed yield in second-year red clover stands but not in first-year stands.
  • Irrigation and trinexapac-ethyl independently increase the yield of red clover seed crops but there were no interactions between the two.

Thomas G. Chastain

Field trials conducted in the Willamette Valley showed that crop water use from April 1st through seed harvest in perennial ryegrass seed crops was 10.5 inches on a medium textured soil (silt loam).  Crop water use in tall fescue during the same period was 10.1 inches on the same soil type.  A perennial ryegrass or tall fescue seed field will need a combination of water stored in the profile over winter and irrigation to meet this water use for best seed yields especially if rainfall is short of this 10.1 to 10.5 inch total.

Spring rainfall at Corvallis averages 5.8 inches, but the crop water use need exceeds 10 inches on a medium textured soil. Our results indicate that a single irrigation (over a few days) of 3.7 inches timed at early flowering (BBCH 60) resulted in a seed yield increase of 16% in perennial ryegrass.  However, the highest perennial ryegrass seed yield increase of 25% was made possible with multiple irrigations (total irrigation water = 6.5 inches) timed between spike emergence (BBCH 50) and peak flowering (BBCH 65).
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Thomas G. Chastain

Growth and development of grass seed crops are progressing at a faster rate than is usual for the Willamette Valley as a result of warm winter and spring temperatures in the 2015-16 crop year (Fig. 1).  The same pattern was observed in the 2014-15 crop year.  These crop years were both much warmer than the average temperatures observed for the region and this is reflected in the growing degree days (base temperature = 5°C or 41°F) accumulated during the crop years.

Figure 1. Growing degree days (GDD) for the crop year through April 21 at Corvallis, Oregon.
Figure 1. Growing degree days (GDD) for the crop year through April 21 at Corvallis, Oregon.


These warm temperatures in the past two crop years are the result of strong El Niño conditions that have been prevalent.  The effect of more growing degree days (GDD) accumulated earlier in the crop year drives development of the crop so that stages of crop development are reached at earlier calendar dates.  In other words, the crops are progressing toward maturity at a faster rate than seed growers might otherwise expect.  Certain management practices like PGR applications and others are taking place earlier in the season as a result.

One aspect of the 2015-16 crop year that is different than in 2014-15 is the high precipitation in the current crop year.  While it has been warm, it has also been wet.  Last year was marked by severe drought conditions.  Looking ahead, scientists are projecting that the El Niño conditions have waned and that there is a possibility of cooler weather in the next crop year.

OSU is presenting two 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 25 – Hyslop Farm Field Day – Plant growth regulators and nutrient management in grass seed crops, plant growth regulators and irrigation management in clover seed crops, weed management in grass seed crops, cereals, and more. Starts at 8:15 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

May 26 – 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.

Seed growers are reporting winter cutworm in Willamette Valley seed fields this fall and early winter.  The extent and severity of this pest in fields is unknown at this time as is the potential for future seed yield loss.  A new OSU Extension publication addresses the pest and problems it may cause.  The publication can be found at the link below:

Winter Cutworm: A New Pest Threat in Oregon

EM9139 cover image

There have been a number of questions regarding Oregon seed production statistics and in particular, trends in seed crop acreage and seed yields. To address these questions, a new feature has been added to Seed Production – tables of sortable data for Oregon’s seed crops.

The source of this data is the Oregon State University Extension Service. The tables can be found under the Production Statistics tab near the top of the main page.

Below is the first installment, the Alfalfa Seed Production Statistics Table:

YearAcreage (Acres)Yield (lbs/acre)