Dry conditions are normal for the Willamette Valley in July and August. This is an important period for flowering and seed development in red clover seed crops. While much of the region’s red clover seed crop is not irrigated, would the crop benefit from additional water during this dry period? That is one of the questions that the seed production research and extension team has addressed.
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.
The media is reporting that 2013 was a very dry year unlike any in the recent past. The graphic below shows the long-term annual precipitation for Corvallis since the late 1880s. Also on the graph is the long-term average (dashed line), a 5-year running mean, and the individual orange triangle symbols show the yearly annual precipitation. The precipitation for 2013 is indicated by the round black symbol.
The graphic shows that while 2013 was very dry, there have been other years that have also been similarly dry or drier than the present. Examination of the trends in the 5-year running mean show that there are cyclical wet and dry periods that are evident in the precipitation record over time with the driest period in the 1930s. The region is currently in a dry period that began in the early 2000s.
What does this mean for the region’s seed crops? It is too early to know at this point but we do know this, seed yield is rarely affected by annual precipitation. Seasonal precipitation such as in spring is much more important for high seed yields in crops such as grass seed crops than annual precipitation. Even though the year might be dry overall, yields still can be good if spring rainfall is near normal.
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.
An international team of scientists led by Dr. John Hampton of New Zealand is developing a series of articles on the effects of elevated temperature and CO2 on seed quality and seed production. I’m a member of this team and the first installment of our series was published last year in the Journal of Agricultural Science.
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.
The Willamette Valley has experienced very dry late summer and early fall conditions to date and long-range projections are for more of the same coming in the middle and late parts of fall. How dry has it been? Rainfall for the July through September period has been 0.87 inches at Hyslop Farm or 37% of the normal 2.35 inches for the period. Only 10 years in the past 123 years have been this dry or drier in the Willamette Valley. In these dry years, rainfall in October has averaged 2.11 inches or 66% of normal. When it gets this dry in July through September, dry Octobers typically follow. Thus, no relief from the dry conditions in the near term can be expected given either the forecasts or the historical records observed in past drought periods. Continue reading →
For more information
Thomas G. Chastain, Ph.D.
Department of Crop and Soil Science
351C Crop Science Building
Oregon State University
Corvallis, Oregon 97331-3002