1. Fertility Management
for
Annual Bluegrass
Tom Cook & Brian McDonald
OSU Horticulture Dept.
Oct 30, 2007

2. Putting greens in Oregon range from
80% to almost 100 % annual bluegrass.
Eugene Michelbook
Country Club Country Club
The reality of golf course maintenance in the PNW is that annual bluegrass will eventually
dominate turf on tees, greens, and fairways. The sample on the left is nearly 100% annual
T Cook photo
bluegrass. The sample on the right is 94% annual bluegrass on a shoot count basis.

3. Perennial type Annual type
Virtually all Poa annua biotypes in PNW greens are
perennial types. Annual types are rare.
T Cook photo

4. Compact spreading perennial type
In older greens, it is easy to find 25-30 different phenotypes of annual
bluegrass. The best turf quality comes from compact spreading types.
On greens they often appear tight, dense, and fine textured. Many of these
flower heavily in spring, very little in summer, with a slight burst in fall. Some
don’t flower at all. T Cook photo

5. Erect growing perennial type
Erect growing perennial types tend to be among the early colonizers
and tend to flower during most of the growing season. Most are coarse in
texture and are generally easy to spot in between the distinctive compact
spreading types. T Cook photo

6. Natural occurrence of Poa annua in soils of different P levels
Prevalence
200
150
100
50
0
low med- med med- high
Basically, as P levels in soils low high
Increased the researchers
found more annual bluegrass.
Relative soil P level
From: Kamp 1981

7. Natural occurrence of Poa annua on soils of varying K content
Prevalence
140
120
100
80
60
40
20
0
low med- med med- high
If K was adequate, the annual low high
bluegrass levels were fairly
constant. K had less impact on
annual bluegrass than P. Relative Soil K From: Kamp 1981

8. Natural occurrence of Poa annua at varying soil pH levels
Prevalence
160
140
120
100
80
60
40
20
0
<5 5-5.5 5.5-6 6-6.9 >7
Annual bluegrass occurred over a wide range of
soil pH levels. In the range from 5-7 it was very
common. From: Kamp 1981

9. There has been a modest amount of research on annual bluegrass fertility requirements. The following summaries
detail what we have learned from these studies.
1937
Annual bluegrass and its requirements for growth.
Sprague, H.B. and G.W. Burton. N.J. Ag. Exp. Sta. Bull 630, 24 pp.
General findings:
1. Acid soils (pH 5 or lower) do not favor annual bluegrass.
2. At optimum pH (6.5), balanced nitrate and ammonium
favor annual bluegrass.
3. Liberal phosphate, nitrates, and calcium favor annual bluegrass.
4. In sand cultures, nitrate nitrogen was preferable to ammonium.
Balanced nitrate and ammonium produced best shoot to root ratio.
ex.) 1.8 vs. 2.4 – 3.0.
5. Sulfate of ammonia reduced root and shoot growth.

10. 1969
Nutritional requirements of Poa annua L.
Juska, F.V. & A.A. Hanson. Agron. J. 61: 466-468.
Findings:
1. On loamy sand pH 6.5 produced 2X as much top growth as pH 4.5
2. Added P on loamy sand at pH 4.5, increased top growth.
3. Highest top yields from NPK on loamy sand and silt loam
occurred at pH 6.5.
4. Roots increased with pH in loamy sand but not in silt loam.
5. Seedhead production on loamy sand increased with pH increase.
pH had no effect on flowering on silt loam.
General conclusions:
Annual bluegrass is competitive on acid silt loam soil.
It responds to lime and NPK on poor light textured soils.

11. 1975
The effects of N, P, K, and S on Poa annua L.
in bentgrass putting green turf.
Goss, R.L., S.E. Brauen, & S.P. Orton. J. Sports Turf Res. Inst. 51:74-82.
General Findings:
1. Unbalanced N-P-K reduced annual bluegrass encroachment.
2. Consistent high rates of Sulfur is detrimental to annual bluegrass.
3.5 lbs S/1000 sq ft per year reduced annual bluegrass.
3. Long term application of S lowered pH from 5.6 to 4.6.
3. Increased P levels increased annual bluegrass.
4. Adequate but not excessive S + P tended to increase annual bluegrass.

12. 1978
The effects of nutrient supply on flowering and seed
production in annual bluegrass.
Ong. C. K., C. Marshall, & G.R. Sagar. J. Br. Grassland Society. 33:117-121.
General Findings:
1. Seed production increased 30X as nutrient supply increased.
2. High nutrient levels increased flowers at the expense of roots.

13. 1981
Influence of N & P fertilization on the growth and
development of Poa annua L.
Dest, W.M. & D.W. Allison. In Proc. of 4th Int. Turfgrass Res. Conf. pp. 325-335
General Findings:
1. On low P soil, annual bluegrass maintained adequate tissue P
without added fertilizer P.
2. Leaf tissue P levels increased only slightly with added P
No P = .42 % dry wt.
High P = .56 % dry wt.

14. Synthesis of historical research 1937-1981
1. Annual bluegrass tolerates a wide range of soil pH’s.
Optimum is probably 5.5 – 6.5.
2. Annual bluegrass tolerates low soil P but responds
to high P fertilization.
3. Flowering and seed set increases on fertile soils with
adequate N & P.
4. Balanced nitrate & ammonium sources produce healthy
annual bluegrass and optimum shoot/root ratios.
5. Excessive S on mineral soils is deleterious to annual bluegrass
6. Annual bluegrass responds vigorously to fertilizer on sandy soils.

15. What’s the catch?
>All historical studies were trying to figure out
why annual bluegrass invaded other grasses.
>The goal was to learn to manipulate fertility
to discourage Poa annua .
>None were directed at growing healthy
annual bluegrass.

16. Best Guess optimum N-P-K-S ratios
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
N P2O5 K2O S
Based on historical research trial results

17. OSU Poa annua fertility trial
Questions:
1. How does N level affect turf ?
2. How do Ca and S affect turf?
3. Does fertility affect disease incidence?
ex.) Microdochium patch
Anthracnose

18. Sand based Poa annua green at OSU L.B. Farm, Corvallis, OR.
Constructed in spring 2004:
90/10 greens mix donated by Walrath Sand Products, Tacoma,WA.
Established from aerifier cores from Corvallis Country Club.
Basic maintenance:
Mow 5X/week at .110” Toro Flex in summer, .140” in winter
Topdress every two weeks
Core and heavy topdress 2X per year
Groom as needed
Irrigate as needed
T Cook photo

19. Basic N, P2O5, K2O: Andersons 28-5-18 soluble with
.02% B, .07% Cu, .10% Fe,.05% Mn,.05% Mg,
.0005% Mo, .05% Zn
N sources include KNO3 and Urea
Applied 2X per month at .125 lb N or .25 lb N.
S: Elemental Sulfur
Applied 1X per month as per treatment plan
Ca, Silica & Humates:
Calcium Carbonate (35% Ca)
Huma Ca (Ca from gypsum 18%, SO4 from gypsum 5%, Humates 35%)
Huma Phos (P2O5 5% , Ca from gypsum 20%, SO4 from gypsum 5%,
SiO2 10%, Humates 14%)
Applied 2X per year after coring in spring and fall

20. Low N trial annual nutrient target values in lbs/1000 sq ft
trt # N P2O5 K2O S Ca SiO2 Humates
1 3.25 0.58 2.1 0 0 0 0
2 3.25 0.58 2.1 0 8.75 0 0
3 3.25 0.58 2.1 1.25 4.5 0 8.75
4 3.25 1.83 2.1 1.25 5 2.5 3.5
5 3.25 0.58 2.1 1.5 0 0 0
6 3.25 0.58 2.1 2.75 8.75 0 0
7 3.25 0.58 2.1 2.75 4.5 0 8.75
8 3.25 1.83 2.1 2.75 5 2.5 3.5
9 3.25 0.58 2.1 3 0 0 0
10 3.25 0.58 2.1 4.25 8.75 0 0
11 3.25 0.58 2.1 4.25 4.5 0 8.75
12 3.25 1.83 2.1 4.25 5 2.5 3.5

21. High N trial annual nutrient target values in lbs/1000 sq ft
trt # N P2O5 K2O S Ca SiO2 Humates
1 6.5 1.16 4.2 0 0 0 0
2 6.5 1.16 4.2 0 8.75 0 0
3 6.5 1.16 4.2 1.25 4.5 0 8.75
4 6.5 2.41 4.2 1.25 5 2.5 3.5
5 6.5 1.16 4.2 1.5 0 0 0
6 6.5 1.16 4.2 2.75 8.75 0 0
7 6.5 1.16 4.2 2.75 4.5 0 8.75
8 6.5 2.41 4.2 2.75 5 2.5 3.5
9 6.5 1.16 4.2 3 0 0 0
10 6.5 1.16 4.2 4.25 8.75 0 0
11 6.5 1.16 4.2 4.25 4.5 0 8.75
12 6.5 2.41 4.2 4.25 5 2.5 3.5

22. Trial Timeline:
2004: Establish green with aerifier cores
2005: Initiate fertilizer treatments
Plots treated all year but no data taken.
2006: Fertilizer treatments are modified to improve basic quality of
low N plots. Temporarily increased N rates to 4+ lbs N
per 1000 sq ft per year. High N plots receive 2X the low N plots.
Data collected include soil tests, turf quality, and Microdochium patch
activity.
Fungicides applied three times through winter to manage disease.
2007: Fertilizer treatments adjusted back closer to design rates.
All plots receive Primo applications through summer.
Data collected include soil tests, turf quality, and Microdochium patch.
Fungicides applied after disease ratings as needed to avoid
turf damage.

23. Results:
Soil test values from Low Nitrogen Trial
2006 2007
CaCO3 S
Ca
Trt. lb/1000 lb/1000 ppm pH Ca ppm pH
1 0 0 589 5.3 366 6.2
2 25 0 741 5.8 755 7.1
6 25 2.75 597 5.9 760 6.6
10 25 4.25 739 5.7 630 6.6
12 0 4.25 551 5.5 504 5.9
Calcium alone or with sulfur has raised the pH notably and sulfur alone appears to be lowering pH slightly
compared to no sulfur and no calcium.

24. Results:
Soil test values from High Nitrogen Trial
2006 2007
CaCO3 S
Trt. lb/1000 lb/1000 Ca ppm pH Ca ppm pH
1 0 0 669 5.5 602 5.9
2 25 0 770 5.8 787 6.7
6 25 2.75 636 5.7 786 6.7
10 25 4.25 595 5.8 695 6.5
12 0 4.25 593 5.2 507 6
With calcium alone or calcium plus sulfur, soil pH has gone up. Where no calcium has been applied, the pH has stayed
constant so far.

25. Low N Trial: Turf quality ratings
Trt Fert. S Ca Jul-06 Aug-06 Sep-06 Dec-06 Feb-07 Apr-07 May-07 Ave.
1 NPK 0.0 0.0 5.2 5.6 5.2 5.1 4.3 6.3 6.2 5.4
2 NPK 0.0 8.8 5.3 6.7 5.9 4.8 3.7 5.8 5.3 5.4
3 NPK 1.3 4.5 4.9 5.4 5.0 5.5 4.1 6.2 6.0 5.3
4 NPK 1.3 5.0 4.7 6.0 6.0 5.2 4.1 6.2 5.9 5.4
5 NPK 1.5 0.0 5.2 6.2 5.2 5.8 4.4 6.3 6.3 5.6
6 NPK 2.8 8.8 4.9 6.5 5.1 5.3 3.3 5.9 4.9 5.1
7 NPK 2.8 4.5 5.2 6.1 5.7 5.7 4.1 6.4 6.3 5.6
8 NPK 2.8 5.0 4.5 5.2 5.1 5.6 4.4 6.4 6.3 5.4
9 NPK 3.0 0.0 5.0 5.6 5.3 5.4 4.3 6.6 6.7 5.6
10 NPK 4.3 8.8 5.1 6.4 5.6 5.4 3.7 6.2 5.9 5.5
11 NPK 4.3 4.5 4.7 5.8 5.1 5.8 4.2 6.3 6.1 5.4
12 NPK 4.3 5.0 4.7 5.3 4.7 5.4 4.4 6.4 6.0 5.3
LSD @ 05 0.7 1.0 0.5 0.5 0.5 0.5 0.5
Target quality ratings = 6+ . Under low N, none of the plots had high over all quality ratings.

26. High N Trial: Turf quality ratings
Trt Fert. S Ca Jul-06 Aug-06 Sep-06 Dec-06 Feb-07 Apr-07 May-07 Ave.
1 NPK 0.0 0.0 6.3 6.7 5.8 5.6 5.9 6.7 7.1 6.3
2 NPK 0.0 8.8 6.1 7.7 5.6 5.4 4.6 6.6 6.8 6.1
3 NPK 1.3 4.5 6.4 7.6 5.6 6.4 5.4 6.7 7.2 6.5
4 NPK 1.3 5.0 5.9 7.3 5.6 6.1 5.5 6.8 7.1 6.3
5 NPK 1.5 0.0 5.7 7.3 5.3 5.9 5.8 7.2 7.2 6.3
6 NPK 2.8 8.8 6.1 7.1 5.3 5.9 5.7 6.4 6.8 6.2
7 NPK 2.8 4.5 6.2 7.6 6.2 5.8 5.9 7.4 7.1 6.6
8 NPK 2.8 5.0 5.8 7.2 5.4 6.5 6.0 7.2 7.1 6.5
9 NPK 3.0 0.0 5.6 6.9 5.3 6.0 6.3 7.7 6.8 6.4
10 NPK 4.3 8.8 6.7 7.5 6.0 6.2 5.7 6.8 7.2 6.6
11 NPK 4.3 4.5 6.4 7.1 5.3 6.3 6.1 7.9 7.2 6.6
12 NPK 4.3 5.0 6.0 6.9 5.7 6.3 6.1 7.9 7.2 6.6
LSD @ 05 0.7 ns 0.5 0.5 0.5 0.5 ns
Target quality ratings = 6+. Turf quality ratings were notably higher at the high N rate.

27. Low N Trial vs High N Trial: Turf quality ratings
Trt Fert. S Ca Low N High N Dif.
1 NPK 0.0 0.0 5.4 6.3 .9
2 NPK 0.0 8.8 5.4 6.1 .7
3 NPK 1.3 4.5 5.3 6.5 1.2
4 NPK 1.3 5.0 5.4 6.3 .9
5 NPK 1.5 0.0 5.6 6.3 .7
6 NPK 2.8 8.8 5.1 6.2 1.1
7 NPK 2.8 4.5 5.6 6.6 1
8 NPK 2.8 5.0 5.4 6.5 1.1
9 NPK 3.0 0.0 5.6 6.4 .8
10 NPK 4.3 8.8 5.5 6.6 1.1
11 NPK 4.3 4.5 5.4 6.6 1.2
12 NPK 4.3 5.0 5.3 6.6 1.3

28. High N plots
General turf quality is acceptable for annual bluegrass putting turf.
There is a balanced mix of bentgrass and annual bluegrass in most
plots. Annual bluegrass is dominant in fall winter and spring and
bentgrass comes on in summer.
T Cook photo

29. Fertility effects on Microdochium patch
T Cook photos

30. Microdochium (Fusarium) patch activity
High N Trial Fall 2006, Spring 2007
NPK + S Ca SiO2 Humates # Spots Activity
lbs / yr lbs / yr lbs / yr lbs / yr per plot 1–9
9 = worst
10 26 06 4 9 07
N, P, K 0.0 0.0 0.0 0.0 4.0 4.3
N, P, K + CaCO3 0.0 8.8 0.0 0.0 17.0 5.0
N, P, K + Huma Cal 1.3 4.5 0.0 8.8 9.0 4.0
N, P, K + Huma Phos 1.3 5.0 2.5 3.5 6.3 4.3
N, P, K 1.5 0.0 0.0 0.0 3.3 3.3
N, P, K + CaCO3 2.8 8.8 0.0 0.0 6.7 5.0
N, P, K + Huma Cal 2.8 4.5 0.0 8.8 4.7 4.3
N, P, K + Huma Phos 2.8 5.0 2.5 3.5 2.7 4.7
N, P, K 3.0 0.0 0.0 0.0 1.0 1.3
N, P, K + CaCO3 4.3 8.8 0.0 0.0 8.7 4.0
N, P, K + Huma Cal 4.3 4.5 0.0 8.8 1.7 1.3
N, P, K + Huma Phos 4.3 5.0 2.5 3.5 3.3 2.0

31. Disease response:
Based on visual observations we have observed an increase in
Fusarium patch activity when lime is applied to the turf.
This trend is dramatic in the high N trial and less apparent in the low N trial.
The other trend that has emerged so far is that plots receiving higher levels of
sulfur have less Fusarium patch activity than plots receiving lower levels of sulfur.

32. We have utilized image analysis software to help us
distinguish differences in disease activity. The red spots
indicate turf damaged by Microdochium nivale.
Estimating % area affected by disease
via image analysis software.
Software developed by Doug Karcher &
Mike Richardson at U of Arkansas.

33. Software computes area of damaged turf
based on color differences between healthy
and injured turf.

34. Results: Microdochium (Fusarium) patch activity
HIGH N Plots Fall 2006, Fall 2007
NPK + S Ca SiO2 Humates # Spots % plot
lbs / yr lbs / yr lbs / yr lbs / yr per plot area
10 26 06 10 23 07
N, P, K 0.0 0.0 0.0 0.0 4.0 4.9
N, P, K + CaCO3 0.0 8.8 0.0 0.0 17.0 8.5
N, P, K + Huma Cal 1.3 4.5 0.0 8.8 9.0 7.3
N, P, K + Huma Phos 1.3 5.0 2.5 3.5 6.3 3.0
N, P, K 1.5 0.0 0.0 0.0 3.3 4.2
N, P, K + CaCO3 2.8 8.8 0.0 0.0 6.7 3.1
N, P, K + Huma Cal 2.8 4.5 0.0 8.8 4.7 2.2
N, P, K + Huma Phos 2.8 5.0 2.5 3.5 2.7 1.9
N, P, K 3.0 0.0 0.0 0.0 1.0 0.6
N, P, K + CaCO3 4.3 8.8 0.0 0.0 8.7 8.2
N, P, K + Huma Cal 4.3 4.5 0.0 8.8 1.7 0.4
N, P, K + Huma Phos 4.3 5.0 2.5 3.5 3.3 0.2
LSD .05 = 5.6

35. Microdochium patch activity Fall 2007
Low N Trial Sulfur levels lbs./1000/yr.
0-1.3 1.5-2.75 3-4.25
% plot area affected
N,P,K 3.5 2.3 2.4
N,P,K + CaCO3 2.6 3.2 2.3
N,P,K + Huma Cal 3.0 4.7 3.8
N,P,K + Huma Phos 3.3 3.2 1.6
High N Trial Sulfur levels lbs./1000/yr.
0-1.3 1.5-2.75 3-4.25
% plot area affected
N,P,K 4.9 4.2 0.6
N,P,K + CaCO3 8.5 3.1 8.2
N,P,K + Huma Cal 7.3 2.2 0.4
N,P,K + Huma Phos 3.0 1.9 0.2
LSD @ 5% = 5.6

36. General Trends Through Fall 2007 *:
1. Two full years of treatments starting to affect soil pH
High lime plots are showing a slight pH increase
High sulfur plots are showing a slight pH decrease
2. High N plots have higher plot quality
3. Microdochium patch generally worse in High N plots
4. High lime plots tend to have worse disease
5. High N without lime but with high S has less disease
6. No apparent effect from Humates
* Variability in ratings makes interpretations difficult

37. Thanks to:
Western Canada Turfgrass Association
Northwest Turfgrass Association
Walrath Sand Products
For financial and in kind support for this trial