Thomas G. Chastain

The combination of very dry and warm weather in spring and early summer 2015 is a cause for concern for growers of grass and forage legume seed crops in the Willamette Valley. Moreover, these conditions have accelerated the timing of the harvest of seed crops in the region. One question that has arisen is how will these conditions affect seed yield?

Seed Field
Aerial view of windrow-harvested seed field in the Willamette Valley.
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Here’s a new article from our seed production research and extension team on trinexapac-ethyl plant growth regulator (PGR) and its effects on seed yield and yield components in red clover (Trifolium pratense L.) seed crops.  The field trials were conducted in the Canterbury region of New Zealand and in seed fields in the Willamette Valley.

Red clover leaf (TG Chastain photo)
Red clover leaf (TG Chastain photo)

This article will appear in an upcoming issue of Agronomy Journal and is a part of our series on PGR tools for use in legume and grass seed production.  The product 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.

Key findings of the article:

  • Trinexapac-ethyl was responsible for seed yield increases in red clover ranging from 9 to 15% in New Zealand and Oregon’s Willamette Valley.
  • One contributing factor for the increased seed yield with trinexapac-ethyl was that the PGR increased the number of heads formed in the red clover crop.  Moreover, the PGR reduced the height of the crop canopy and increased penetration of light into the canopy, possibly leading to the increased head production.
  • Timing of trinexapac-ethyl applications to coincide with early stem elongation gave the best seed yields although split applications at stem elongation and bud emergence produced yield increases in Oregon.
  • Seed weight was generally inversely related to yield; trinexapac-ethyl treatments that produced the highest yield also had the lowest seed weight.

The article can be found at the link below:

Anderson, N.P., D.P. Monks, T.G. Chastain, M.P. Rolston, C.J. Garbacik, Chun-hui Ma, and C.W. Bell. 2015. Trinexapac-ethyl effects on red clover seed crops in diverse production environments. Agron. J. 107:951-956.