An often asked question is whether there is a benefit to application of irrigation in late summer or early fall (mid-August until the end of September) in grass seed crops such as perennial ryegrass and tall fescue in the Willamette Valley. Our research and extension team in seed crops conducted studies over a broad range of years to determine whether irrigation in this period is helpful for these seed crops.
Some of our perennial ryegrass work was done in the very dry years of the early 1990s. Those years were as dry as our recent multi-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.
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.
• 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 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?