Thomas G. Chastain

The big concern in the region continues to be the persistent drought and high temperatures that have prevailed throughout May and June.  These months are very important for grass seed yields because two important processes take place during the period: pollination and seed filling.

Drought and heat both can adversely affect pollination and subsequent seed filling.  The lack of water as a result of drought means that the movement of sugars into the seed is impeded, and thus, are not available for filling of the seed’s endosperm tissues with starch.  Heat can have direct effects on enzymes that are involved in seed filling.  Consequently, seed yield can be reduced by both reduction in seed weight (light seed) and seed number (aborted seed).

Average temperatures for June (+4.5°F above the long-term average) at Corvallis were the 2nd warmest since 1948 with 1992 having the warmest June in that period.  May was 2.2°F above the average.  Rainfall in May and June was also very low with the combined rainfall the 3rd lowest since the mid 1970s.  The lowest combined May and June rainfall was recorded on 1992.  This year’s drought and heat bears a strong resemblance to 1992.

Seed yields of perennial ryegrass were reduced by 11% in 1992 and tall fescue experienced a 14.5% loss in yield in that year.  By contrast, a large number of seed growers are reporting greater losses in seed yield of these crops this year even though the drought and heat have not been as severe in 2015 as they were in 1992.

For more information on this still developing story, see the following article in the Capital Press:

Grass seed suffers from drought, heat

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