Thomas G. Chastain

The late summer and early fall period has long been thought to be critical for regrowth of the perennial ryegrass and tall fescue 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 improves the appearance of the stand (number of tillers and stand cover) going into the winter.  But what about the impact of fall irrigation on seed yield in perennial ryegrass and tall fescue?

Our studies conducted at Hyslop Farm over an extended period suggest that there is no seed yield benefit of post-harvest fall irrigation applications from mid-August until the end of September in perennial ryegrass and tall fescue.  In our work, fall irrigation was applied in five years in perennial ryegrass and for two years in tall fescue.  Three cultivars of perennial ryegrass and one cultivar of tall fescue was evaluated in the experiments. Weather conditions ranged from very dry to very wet in fall in the study years.

Seed yield in perennial ryegrass and tall fescue was not improved with fall irrigation in any of the years (See table below).

These 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.