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.  But will that be the case in spring 2013?

The winter months of January through March 2013 have been the 2nd driest winter period on record at Corvallis with only 6.28 inches recorded.  Can we expect more of the same dry weather during spring?  No one can say for sure, but an examination of weather records for the past 124 years reveals that when precipitation is very low (50% or less of the 16.02 inch normal) in January through March, the following April through June period averages 5.78 inches or near normal rainfall (normal is 5.83 inches). 

Despite the very dry weather that has been recorded to date, there may still be enough rainfall present in coming months to make lodging a problem for local seed growers.

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

Lodging during flowering restricts pollination and reduces fertilization of the crop (Fig. 2). Grass seed crop yield is reduced as a result of lodging in two ways: seed filling is reduced due to self-shading of the lodged crop and the number of seed produced is reduced by lodging.

Figure 2. Lodged tiller. (Illustration by T.G. Chastain)

Elongation of the tiller in spring in grass seed crops results from activity of the intercalary meristem found above each node (Fig. 3). Each internode in the tiller elongates independently and this growth is promoted by the plant hormone gibberellic acid (GA).

Figure 3. Elongation of grass tillers and development of the inflorescence in spring. (Illustration by T.G. Chastain)

There are two lodging control agents (plant growth regulators) available for grass seed producers in Oregon. Palisade (trinexapac-ethyl) and Apogee (prohexadione-calcium) plant growth regulators (PGRs) are acylcyclohexanedione inhibitors of the 3-β hydroxylation of GA. In other words, the tiller does not elongate to the same extent when treated at the proper time with these PGRs. The PGRs are structurally similar to 2-oxoglutaric acid, a cofactor in the hydroxylation reaction. Palisade is registered for use in perennial ryegrass, tall fescue, and fine-leaf fescues. Apogee is registered for all grass seed crops grown for seed.

One interesting observations is that the seed yield enhancing benefit of these PGRs is not realized without the application of spring nitrogen on the grass seed crops. PGR-induced seed yield increases are most pronounced in the first year of the stand, but economic seed yield increases are common throughout the life of the stand. The best application timing begins after stem elongation has begun (BBCH scale 30-32) in the spring.

A final observation regarding spring weather conditions and PGR use in grass seed crops, our research has shown that seed yield is increased in perennial ryegrass even in low rainfall springs with the reduced lodging that accompanies these periods.

The study shows that camelina seed yield ranged widely across the four study sites in the Pacific Northwest due to differences in annual precipitation and soil available N.  Applied N increased the seed yield of camelina at all sites except the very low rainfall Lind Washington site.  The study was the first to show that oil content in the seed of camelina was not influenced by applied N and to report nitrogen use efficiency values for the crop.  Seed yield was also not affected by applied sulfur.

Click on the citation below to go to the article:

Wysocki, D.J., T.G. Chastain, W.F. Schillinger, S.O. Guy, and R.S. Karow.  2013.  Camelina: seed yield response to applied nitrogen and sulfur.  Field Crops Research 145:60-66.

Here is a summary of the findings from Dr. Young:

In brief, the combined value for all grass and legume seed crops in the 2011-12 crop year ($406,251,000) increased almost 21% over the value of production in 2010-11. Oregon growers harvested 408,000 acres of grass seed crops in 2012, an increase of 34,705 acres (+9.3%) over last year. However, the estimated value of all grass seed species increased by 24.1% due to the combination of more acres and improved prices received by growers.  Legume seed crop acreage declined by almost 5% (2,118 acres) from the 2010-11 crop year, and the estimated value of this year’s production dropped by 6.6% to $35,656,000 when compared to last year’s record $36,532,000 crop.

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

2012 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.

Krista Heuttig

The study reports several important findings and was the first study to demonstrate that spring irrigation increases seed yield in tall fescue.  Tall fescue seed yield responses to spring irrigation varied among the cultivars tested.  Increased number of seed in tall fescue was most responsible for the seed yield improvement observed with spring irrigation.   Strategic timing of spring irrigation to support seed filling was more important for increasing seed yield than season-long irrigation.

Click on the citation below to go to the article:

Huettig, K.D., T.G. Chastain, C. J. Garbacik, W.C. Young III, and D.J. Wysocki.  2013.  Spring irrigation of tall fescue for seed production.  Field Crops Research  144:297-304.

This article has been ranked as one of the top-10 most-read or most-downloaded articles in 2012 according to the Journal’s website.  This distinction was not just accorded for articles published in 2012, but for all articles downloaded over the entire history of the journal.

Here’s a link to the article:

Hampton, J.G., B. Boelt, M.P. Rolston, and T.G. Chastain.  2013.  Effects of elevated temperature and CO₂ on seed quality.  J Agric Sci (Cambridge) 151:154-162. doi: 10.1017/S0021859612000263, Published online by Cambridge University Press 30 March 2012.

You can read my review of this book that was published last month in the Quarterly Review of Biology at this link:

Review of Crop Ecology