Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: February 2, 1998
Publication Date: N/A
Interpretive Summary: Excessive seed shattering of commonly used forage grasses often results in major economic losses to seed producers that can total over 50% of the seed crop. In this study, heat units expressed as growing degree-days after seed pollination were related to seed development in four cool-season forage grasses -- Russian wildrye, crested wheatgrass, intermediate wheatgrass, and western wheatgrass. Seed germination and vigor were assessed at different stages of development to establish guidelines for an appropriate time to windrow a seed crop of these grasses. Plots sampled at the stiff-dough stage had a seed water concentration of about 35% (dry weight basis), and the seed was at or near its maximum weight. Seed quality would not be seriously compromised if the crop were windrowed 2 days before maximum seed weight is attained. This practice would prevent much of the seed losses from shattering.
Technical Abstract: Excessive seed shattering of perennial grasses in the Triticeae tribe results in major economic losses to seed producers. In this study, heat units expressed as growing degree-days (GDD) after anthesis were related to seed development in tetraploid crested wheatgrass [Agropyron desertorum (Fisch. ex Link) Schultes], Russian wildrye [Psathyrostachys juncea (Fisch.) Nevski], intermediate wheatgrass [Thinopyrum intermedium (Host) Barkw. & Dewey], and western wheatgrass [Pascopyrum smithii (Rydb.) A. Love]. Seed quality at different stages of development was assessed by germination percentage and emergence of seedlings from a 5.0-cm planting depth in a Parshall fine sandy loam soil (coarse-loamy, mixed Pachic Haploborolls). Water concentration of the seed at maximum seed mass (dry weight basis) ranged from 303 g kg-1 for intermediate wheatgrass to 376 g kg-1 for western wheatgrass. Seed mass was closely associated with seed quality in all four grass species as evidenced by correlation coefficients between seed mass and seedling emergence of 0.88** for crested wheatgrass, 0.93** for Russian wildrye, 0.92** for intermediate wheatgrass, and 0.77** for western wheatgrass. Plots sampled at the stiff-dough stage had a water concentration of approximately 350 g kg-1 (dry weight basis), and the seed sample was at or near maximum seed mass. Seed mass and germination would not be seriously compromised and seed yield losses from shattering would be reduced if windrowing were completed about 40 GDD or 2 calendar days before maximum seed mass were attained.