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 irrigation and trinexapac-ethyl PGR effects on seed yield and yield components in red clover seed crops. Field trials were conducted in the Willamette Valley over a 3-year period at OSU’s Hyslop Farm. Trinexapac-ethyl 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.
This article appears in the current issue of Agronomy Journal and can be found at the link below:
Field trials conducted in the Willamette Valley showed that crop water use from April 1st through seed harvest in perennial ryegrass seed crops was 10.5 inches on a medium textured soil (silt loam). Crop water use in tall fescue during the same period was 10.1 inches on the same soil type. A perennial ryegrass or tall fescue seed field will need a combination of water stored in the profile over winter and irrigation to meet this water use for best seed yields especially if rainfall is short of this 10.1 to 10.5 inch total.
Spring rainfall at Corvallis averages 5.8 inches, but the crop water use need exceeds 10 inches on a medium textured soil. Our results indicate that a single irrigation (over a few days) of 3.7 inches timed at early flowering (BBCH 60) resulted in a seed yield increase of 16% in perennial ryegrass. However, the highest perennial ryegrass seed yield increase of 25% was made possible with multiple irrigations (total irrigation water = 6.5 inches) timed between spike emergence (BBCH 50) and peak flowering (BBCH 65). Continue reading →
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.
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.
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.