Janice Reed and Donn Thill University of Idaho

1. Chemical and Mechanical Suppression of Kentucky Bluegrass Stands In An Alternate Year Production System Janice Reed and Donn Thill University of Idaho

2. Introduction Need to develop alternative residue management systems Maintain stand longevity Economically sustainable Suppression with herbicides in alternate year production Year 1: Suppression, regrowth Year 2: Seed production, mechanical residue removal (mow, harrow)

3. Herbicide Suppression of Bluegrass and Alternate Year Seed Production • Increase yield • Stand thinning • Moisture retention • Residue decomposition

4. Objective • Roundup Timing Studies • Herbicide Comparison Study • Determine the optimum herbicide and herbicide application time to predictably suppress Kentucky bluegrass stands

5. Roundup Timing Studies • Jacklin Seed research site Nezperce, ID • Palouse – early Newport – intermediate Nublue – late • 2001-2002 and 2002-2003 • 10 by 30 ft, RCB, 4 reps • Plots burned prior to trial establishment

6. Roundup Timing Studies • Roundup Ultra at 1qt/A + AMS 8.5 lb/100 gal March 20, 27, April 5, 12, and 19, 2001 March 29, April 4, 11, 19, and 25, 2002 Untreated check • Visual evaluation of suppression and regrowth • Untreated checks harvested and burned year 1 • All plots fertilized fall of year 1

7. 2002/2003 Roundup Timing Study 2003 Cover a a a a a ab ab b b a a ab c bc c

8. Nublue May 2003 4/11/02 4/4/02 3/29/02 4/19/02 4/25/02 Untreated Palouse May 2003 4/11/02 4/4/02 3/29/02 Untreated 4/19/02 4/25/02

9. 2002/2003 Roundup Timing Study 2003 Seed Yield a a ab a ab ab ab a ab b bc bc ab ab ab c b b

10. 2002/2003 Roundup Timing Study Summary • Suppression is cultivar specific • Stand suppression with Roundup is variable • Recovery from Roundup suppression was best with a later-maturing variety • Recovery from suppression and yield generally were best when Roundup was applied earlier

11. Herbicide Suppression Study 2002/2003 • Mosman farm near Craigmont, ID • Residue was not removed; plots mowed and harrowed prior to plot establishment • 8 by 30 ft, split-plot, 4 reps, untreated check • 6 herbicides, 3 timings at 2-week intervals • Roundup Ultra 1.6 pt/A • Gramoxone Extra 1.6 pt/A • Plateau 0.5 pt/A • Liberty 2 pt/A • Maverick 0.66 oz/A • Assure II 0.5 pt/A * All herbicides applied with the recommended spray additives

12. Herbicide Suppression Study Methods • Quantum Leap: 1 yr old stand Short , aggressive, long floral induction April 4, 19, and May 1, 2002 • Newport: 10 yr old stand Tall, less aggressive, short floral induction April 19, May 1, and 16, 2002 • Visual evaluation of suppression and regrowth • Untreated checks harvested and burned in 2002 • All plots fertilized fall 2002

13. Herbicide Suppression Study Newport Yield 2003 a a a a a a a a b a ab a ab b a a b b b b

14. Herbicide Suppression Study Quantum Leap Yield 2003

15. Quantum Leap May 2002 4/4 Roundup 4/19 Gramoxone 5/1 Untreated Gramoxone 4/19 Untreated Assure II 4/19 Assure II 4/4 Quantum Leap May 2003 4/4 Roundup 4/19 Gramoxone 5/1 Untreated Gramoxone 4/19 Untreated Assure II 4/19 Assure II 4/4

16. Herbicide Suppression Study 2003/2004 • Greencreek- Rambo, Worley- Cenex 22 • Residue not removed; plots mowed and harrowed prior to plot establishment • 8 by 30 ft, split-plot, 4 reps, untreated check • 5 herbicides at 3 times • Roundup Ultra 1.6 pt/A • Gramoxone Extra 1.6 pt/A • Plateau 0.5 pt/A • Liberty 2 pt/A • Assure II 0.5 pt/A • Mow at 3 times • Vegatative, heading, early flower

17. Herbicide Suppression Study Rambo Cover 2003 a a a a a a a a a a b b

18. Herbicide Suppression Study Cenex 22 Cover 2003 a a a b b b a a b b b c

19. Herbicide Suppression Study Summary • Bluegrass suppression with herbicides varies with cultivar and application time • Yield from plots treated with Gramoxone, Liberty, and Assure II was equal to or greater than the untreated