Thomas G. Chastain

This spring has seen alternating very dry and warm periods and cool, wet periods in the Willamette Valley.  While the effect of these varying conditions on seed yield remains to be determined, grass seed harvest will soon be under way.  To maximize harvest efficiency, identifying the best timing for harvest is essential.  Seed moisture content has been found to be the most reliable indicator of seed maturity and harvest timing in grass seed crops.

Range of maturity in perennial ryegrass spikes taken from one field (Tom Silberstein photo)
Range of maturity in perennial ryegrass spikes taken from one field (Tom Silberstein photo)

Since pollination and seed maturation are not uniform processes in grass seed crops, a range of seed maturity can be found in a single field.  Harvesting within the correct range of seed moisture contents will maximize seed yield and minimize losses of seed during harvest. Seed moisture content is also an important factor in the storage of harvested seed.  High seed moisture content reduces longevity of seed in storage and reduces seed quality.

To optimize the timing to swath grass seed crops and to maximize the quantity of seed harvested, seed growers must balance cutting late-maturing seeds too early with cutting early-maturing seeds too late.  Cutting too early at high seed moisture content shortens the seed fill period leading to immature seed and reduced seed size or weight.  Cutting too late at low seed moisture content can reduce yield as a result of seed shattering losses.

Illustrated instructions on how to conduct a seed moisture test in grass seed crops and guidelines for seed moisture contents for best harvest efficiency can be found in OSU’s publication EM 9012.  Here’s a link to the publication:

Using Seed Moisture as a Harvest Management Tool

A video showing step by step instructions on collecting seed and several methods to test the moisture content of seed was also developed. Here’s a link to the video:

Seed Moisture Video

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