Category Archives: Grass Seed Crops

Post-harvest Irrigation and Grass Seed Yield

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Thomas G. Chastain

The efficacy of post-harvest fall irrigation (mid-August until the end of September) in perennial ryegrass and tall fescue is an important question for Willamette Valley seed producers. We conducted research to determine whether irrigation in this period is beneficial for these seed crops.

Sprinkler on linear irrigation system (TG Chastain photo)
Sprinkler on linear irrigation system (TG Chastain photo)

Some of the perennial ryegrass work was done in the very dry years of the early 1990s. Those years were as dry as our current three-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.

The late summer and early fall period has long been thought to be critical for regrowth of the grass seed crops after harvest and for the following year’s seed yield. Extremely dry conditions during this period in the Willamette Valley can reduce stands and crop regrowth in both seed crops. There is good evidence from our research that irrigation does improve the appearance of the stand (number of tillers and stand cover) going into the winter.

In a second set of trials, post-harvest irrigation was applied (5 inches) in three years in perennial ryegrass and in tall fescue from 2010 through 2012. This was compared with no irrigation. Weather conditions ranged from very dry to very wet in fall in the study years. Our results clearly indicate that there was no effect of this irrigation on seed yield in perennial ryegrass and tall fescue.

Our investigations suggest that while early fall irrigation increases tiller production and may enhance stand persistence under Willamette Valley conditions, there were no beneficial effects of fall irrigation on seed yield in perennial ryegrass and tall fescue even under dry conditions. The soil at our Hyslop Farm research site is a medium textured soil (Woodburn silt loam) that is typical of many places in the valley where tall fescue and perennial ryegrass seed crops are grown. This soil is deep and has good water holding capacity.

So what about other soils? If tall fescue or perennial ryegrass is grown on a light textured soil with poorer water holding capacity and high drainage such as soils that have high sand content and low clay content, then we cannot rule out the possibility that irrigation might be beneficial for stand persistence especially in areas that have gravel bars. But it is not known whether irrigation in these soils is beneficial for seed yield.

Residue management for grass seed production

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Thomas G. Chastain

The stubble and straw remaining in grass seed fields after harvesting seed is known as residue.  Post-harvest residue burning has been justified on the basis of pest control and stimulation of seed yield.  Public concern over air quality and the potential for adverse health impacts on the region’s residents has necessitated the identification of alternative residue management practices.  Oregon legislation (SB 528) has, in effect, ended the practice of field burning in the western part of the state for most species except for fine fescue seed crops.

Residue management in tall fescue - full straw load (left), clean non-thermal (right). TG Chastain photo.
Residue management in tall fescue – full straw load (left), clean non-thermal (right). TG Chastain photo.

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High temperature and drought affects Willamette Valley seed crops

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Thomas G. Chastain

The big concern in the region continues to be the persistent drought and high temperatures that have prevailed throughout May and June.  These months are very important for grass seed yields because two important processes take place during the period: pollination and seed filling.

Drought and heat both can adversely affect pollination and subsequent seed filling.  The lack of water as a result of drought means that the movement of sugars into the seed is impeded, and thus, are not available for filling of the seed’s endosperm tissues with starch.  Heat can have direct effects on enzymes that are involved in seed filling.  Consequently, seed yield can be reduced by both reduction in seed weight (light seed) and seed number (aborted seed).

Average temperatures for June (+4.5°F above the long-term average) at Corvallis were the 2nd warmest since 1948 with 1992 having the warmest June in that period.  May was 2.2°F above the average.  Rainfall in May and June was also very low with the combined rainfall the 3rd lowest since the mid 1970s.  The lowest combined May and June rainfall was recorded on 1992.  This year’s drought and heat bears a strong resemblance to 1992.

Seed yields of perennial ryegrass were reduced by 11% in 1992 and tall fescue experienced a 14.5% loss in yield in that year.  By contrast, a large number of seed growers are reporting greater losses in seed yield of these crops this year even though the drought and heat have not been as severe in 2015 as they were in 1992.

For more information on this still developing story, see the following article in the Capital Press:

Grass seed suffers from drought, heat

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Irrigation Management in Perennial Ryegrass Seed Crops

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Here’s a new article from our seed production research and extension team on frequency and seasonal timing of irrigation and its effects on seed yield and yield components in perennial ryegrass (Lolium perenne L.) seed crops.  Field trials were conducted in the Willamette Valley over a 5-year period at OSU’s Hyslop Farm.

Irrigation system (TG Chastain photo)
Irrigation system (TG Chastain photo)

This article will appear in an upcoming issue of Field Crops Research.

Key findings of the article:

• Spring irrigation increased seed yield of perennial ryegrass but fall irrigation did not.
• Most perennial ryegrass cultivars tested responded to spring irrigation with increased seed yield.
• Seed yield increases attributable to spring irrigation resulted from increased seed number and seed weight.
• Seed yield was not substantially affected by the expression of other seed yield components.

The article can be found at the link below:

Chastain, T.G., C.M. King, W.C. Young III, C.J. Garbacik, and D.J. Wysocki. 2015. Irrigation frequency and seasonal timing effects on perennial ryegrass (Lolium perenne) seed production. Field Crops Research 180:126-134.

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Concerns for the seed harvest include drought and heat

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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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Grass and Forage Legume Seed Production Estimates for 2014

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Bill Young, OSU professor emeritus and extension agronomist in seed production, has recently updated Oregon’s grass and forage legume seed crop production estimates for the 2014 crop year.  This information was gathered by OSU Extension crops agents working in Oregon’s seed production regions and Nicole Anderson, an OSU Extension Field Crops Agronomist, played a key role in coordinating this effort.

This report provides a wealth of useful information about quantity of seed produced, crop yields, and economic value of seed crops in Oregon.

Here is a summary of key findings in Dr. Young’s report:

In brief, the combined value for all grass and legume seed crops in the 2013-14 crop year ($510,880,000) increased by 10.6% over the value of production in 2012-13 ($461,693,000) to mark a new record high over the $505,309,000 value set back in the 2007-08 crop year. The value of grass seed sales increased 7.5% ($31,392,000) over last year, and legume seed crops forged ahead 40.4% over last year’s record sales of $44,067,000 to a new high of $61,862,000. Acres of grass seed crops increases only 0.6% (2,634 acres) while total poundage surged by 10.8% (71,287,000 pounds). Legume seed crop acreage increased by 7.8% (3,142 acres) while total production jumped 16.4% (4,601,000 pounds).

Here is a link to the report on OSU’s Seed Crops page:

2014 Grass and Legume Seed Crop Estimates

You can follow the links on the Seed Crops page to find information about this past year’s seed crops and comparisons to previous crop years. Historical reports are also archived at this page.

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