Bromegrass in Alaska. III. Effects of Planting Dates, and Time of Seeding-Year Harvest, on Seeding-Year Forage Yields and Quality, Winter Survival, and Second-Year Spring

Forage Yield

Leslie J. Klebesadel, Emeritus Professor of Agronomy

Agricultural and Forestry Experiment Station; Palmer, Alaska

Bulletin 96; December 1993 (13 pages)

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Summary

Objectives of this study were to (a) determine yields and quality of forage that could be obtained in the seeding year from smooth bromegrass (Bromus inermis) seeded in spring without a cereal companion crop, and (b) determine whether planting dates and date of the seeding-year harvest influenced subsequent winter survival and forage yield in the following year.

Bromegrass plots were harvested for forage yield once during the seeding year on several dates approximately 10 days apart during August, September, and early October; effects of those harvest dates were measured by comparing yields of all plots harvested on the same date in the second year of growth. Five of the six experiments were conducted at the University of Alaska's Matanuska Research Farm (61.6oN) near Palmer in southcentral Alaska, and the other was at the Research Center in Palmer.

· Yields of 'Manchar' bromegrass forage increased regularly from near 0.6 T/A in early August to about 1.6 T/A in early September; thereafter, yields changed little with later harvests.

· Percent dry matter in herbage increased from about 17% in early August to 26% to 28% by early October.

· Percent crude protein in herbage decreased regularly from about 23% in early August to 12.5% in early October.

· Stored food reserves just prior to onset of winter conditions (mid-October) were highest in plants that had been harvested in early August; levels were lower with progressively later harvests until about 10 September, and then were slightly higher in plants that had been harvested later.

· Where seeding-year harvest had been taken about 10 September, winter survival of Manchar bromegrass was poorest, thinned stands were weediest in the second year, and second-year forage yield was lowest (mean = 0.6 T/A).

·With seeding-year harvest dates progressively earlier or later than 10 September, winter survival and

forage yields of Manchar the following year improved markedly.

· Earliest seeding-year harvest of Manchar (on 10 August) resulted in the highest second-year, first-cut forage yield of about 2.25 T/A. The latest seeding-year harvest about 1 October resulted in a modest second-year, first-cut forage yield of about 1.2 T/A.

· Considering the two least-injurious times for seeding-year harvest of Manchar, the earliest harvest on 10 August resulted in a low seeding-year yield of high-quality forage (as indicated by high percent crude protein and low percent dry matter), while the latest harvest (1 October) resulted in a considerably higher yield but of lower quality (low percent crude protein, high percent dry matter).

· 'Polar' bromegrass planted in mid-May produced uniformly high forage yields (between 1.6 and 1.9 T/A) on six different seeding-year harvest dates from 19 August to 10 October.

· Polar bromegrass planted 1 June produced progressively increased seeding-year yields from about 1 T/A on 19 August to near 2 T/A on 10 October.

· Polar bromegrass planted in mid-June produced much lower seeding-year yields, increasing from a low of about 0.25 T/A on 19 August to about 1 T/A on 1 October.

· Polar bromegrass stands were most winter-injured following seeding-year harvest on 31 August; stands were markedly less injured following seeding-year harvest only 12 days earlier on 19 August, and were increasingly less injured as seeding-year harvest dates were progressively later than the end of August.

· These findings revealed that spring-seeded bromegrass is very sensitive to time-of-harvest in the seeding year. Stands were weakened and predisposed to severe winter injury when harvested at an inappropriate time.

· Conversely, bromegrass stands were favored toward better winter survival by avoiding seeding-year harvest between about 20 August and 20 September.

· For best seeding-year forage yields of high quality, harvested when the stand will not be predisposed to winter injury, a winterhardy bromegrass should be planted no later than mid-May and seeding-year harvest should be no later than about 20 August.

· These findings provide growers with information that should be helpful in choosing among management options in bromegrass establishment. Informed choices can achieve grower goals while avoiding ill-timed operations that could weaken the grass and predispose it to winter injury.

· These results were obtained in experiments with very effective herbicidal control of broadleaf weeds. Similar results in farm practice will require equally effective control of weeds.