23
Wetland Meadow Forage Management
R. L. Dovel and J. Rainey
INTRODUCTION
Wetland meadows occupy over 95,000 acres in Klamath County and
provide summer grazing for over 100,000 cattle each year. The major
native species encountered in such sites include tufted hairgrass
(Deschampsia caespitosa), Kentucky blue grass (Poa pratensis), meadow
foxtail (Alopecurus pratensis), Nebraska sedge (Carex nebraskensis),
Carex nigricans, and Lieburg bluegrass (Poa lieburgi). Many of these
species are found throughout Oregon and the entire Northern United
States in wetland meadows; however, little information on the productivity, quality, or management of many of these species is available.
Virtually all beef ranchers grazing wetland meadows in Southern
Oregon practice set stock grazing. The species composition of many
wetland meadows has been altered due to heavy continuous grazing. Less
palatable species such as, various rushes and sedges, meadow barley, mat
mutely, and foxtail barley, have increased under heavy grazing pressure.
This shift in species composition can adversely affect both forage
production and forage quality. Forage produced in a sedge-dominated
wetland meadow had protein levels of 13 percent on May 19; yet, by midJune forage protein content had dropped to 8.7 percent, which is below
the nutrient requirements for steers and lactating cows. By September,
forage protein content from the same pasture dropped to 6.9 percent
which is only marginally adequate for dry cows.
Animal performance on these meadows is also hampered by extreme
variability in forage production with season and declining forage
quality with age. Dry-matter production on these meadows reaches a
peak in early July then declines rapidly through August and September.
If meadows are stocked at rates high enough to efficiently harvest the
vigorous early season growth and not allow rank dead vegetation to
accumate, then slow late-season forage production results in overgrazing and poor animal performance. Animal production and the condition of
desirable native meadow species both suffer under such a system.
Improved grazing management to prevent the accumulation of low-quality
forage and to maintain desirable species in the sward could greatly
increase the productivity of these wetland meadows and provide a more
ecologically sound management alternative.
1/ Assistant Professor, Biological Sciences Research Technician,
respectively, Klamath Experiment Station.
Acknowledgments: Land and irrigation management were provided by
the Rock Creek Ranch.
24
Intensive grazing management has improved overall productivity,
efficiency, and profitability in New Zealand. The use of intensive
grazing management has also allowed the maintenance of high-quality,
highly palatable species in the sward, even with heavy utilization.
One requirement for intensive grazing management is a knowledge of
forage growth rates. Knowledge of growth rates in the spring and the
time of onset of growth for different forage species is critical in
strategic planning to reduce hay feeding.
Regrowth following clipping or grazing is dependent on various
environmental and management parameters. The amount of forage left
after grazing or clipping greatly affects regrowth. Residual dry matter
(RDM) is not easily measured by the producer; however, height is closely
related to RDM and is easily measured by cattlemen and ranchers.
A clipping study was initiated to determine the productivity and
quality of the major forage species in three wetland meadow plant
associations.
PROCEDURES
Plots were set up along a moisture gradient. The bluegrass/clover
association occupied the driest location and plants experienced moisture
stress before the other associations. The mixed grass/sedge association
was in an alternating flooded/dry situation which allowed growth of the
grass species to continue when the bluegrass/clover associations were
too dry to support active growth. The sedge association was almost
continually flooded or very moist allowing growth to continue even when
the grass/sedge association had ceased growth due to moisture stress.
Thus, yields reflect not only the relative yield potential of the
species present, but also the effects of the moisture regime in which
they are growing.
Plots were established within a livestock exclosure. Three cutting
heights (2, 4 and 6 inch) were imposed. The RDM left by each cutting
height was determined by clipping a 1-m 2 quadrate to ground level. Plots
were harvested and forage weighed monthly throughout the growing season.
Forage quality was assessed by determining crude protein (CD) content
and acid detergent fiber (ADF) content of the forage.
The relative forage production and quality of continuously grazed
versus simulated rotationally grazed swards (clipped) was evaluated
using exclusion cages. Accumulated forage mass was determined prior
to protecting a section of continuously grazed sward with a 1-m 2 cage.
After one week the cage was removed and the forage mass determined.
This allowed an estimate of the pasture growth rate for that week. The
cage was then moved to a previously unprotected site and the process
repeated.
25
RESULTS AND DISCUSSION
The mixed grass/sedge association was the highest yielding association in the trial. This is probably due to having a more favorable
location for growth (less prone to moisture stress) than the bluegrass/
clover association and having a greater yield potential than the sedge
species in this study. It may also be that the flooded conditions often
present in the sedge association locations impeded growth due to anoxia.
The bluegrass/clover and sedge associations produced similar yields
at the two and four inch cutting heights. However, yields of the sedge
association fell significantly below that of the bluegrass/clover association when cut at a height of six inches (Table 1).
Cutting height significantly affected yields of all three associations in this study. Yields of all three associations decreased as
cutting height was raised (Table 1). Raising the cutting height from
two to six inches cut total forage yields in half in the sedge and mixed
grass/sedge association. Reduction in total forage produced by the
Bluegrass/clover association was not as drastic.
The majority of total forage produced for all associations was
harvested in the June cutting (Table 1). Growth rates declined as the
season advanced and yields in the July and August cuttings were less
than half that seen in June. This is due in large part to the onset of
moisture stress as the season advanced. In 1988 drought stress was
delayed until the third cutting in the two wetter association locations,
and yields remained fairly high. Yields dropped sharply at the third
cutting due to moisture stress. In contrast, in 1989 moisture stress
was evident by the second cutting and yields declined dramatically.
Increased irrigation and lower than normal temperatures in August
allowed for some recovery and higher growth rates late in 1989.
Forage quality of plant associations and selected native plant
species was monitored from June to September. Cutting height did not
significantly affect forage quality (ADF or CP content). The bluegrass/
clover association had the lowest ADF content throughout the trial
(Table 1). The sedge association had ADF value significantly higher
than the other two plant associations at each sampling date. However,
ADF levels of the sedge association never exceeded 42 percent. An ADF
content of 40 percent in grasses corresponds to TDN levels in excess of
59 percent. Cows nursing calves only require feed with a TDN content
of 55 percent. Dry cows only require feed with 52 percent TDN to
perform well. Pregnant yearling heifers require feed with 58 percent
TDN to gain 1.8 lbs per day. Yearling cattle require higher energy
levels than that provided by the sedge association to gain over 1 lb per
day; however, the energy requirements of a cow-calf operation can be
met by the sedge association.
26
Baltic rush (Juncus balticus) had the lowest ADF values of the three
species observed. By mid-September no green baltic was left in the
exclosures. Nebraska sedge (Carex Nebraskansis) had higher ADF values
than C. nigricans, the dominant fine-leafed sedge species in this study.
As seen in the sedge association quality samples all three species
maintained ADF values below 42 percent.
The bluegrass/clover association had crude protein contents averaging roughly 3 percentage points higher than the other two plant associations throughout the growing season, due largely to the clover component. The mixed grass/sedge association had significantly higher
crude protein contents than the sedge association; however, the crude
protein content of the sedge association did not drop below 9.0 percent
until the September 15 sampling date. This falls below requirements for
growing finishing steers and heifers. However, crude protein requirements for all animal classes in a cow-calf operation, including pregnant
yearling heifers and lactating cows of average milking ability are below
9.0 percent. Thus, the sedge association could serve as the sole source
in a cow-calf operation without nitrogen supplementation. It is more
realistic to expect the sedge component to make up only a portion of the
diet and higher protein associations would effectively raise the
protein level of the diet to levels significantly higher than minimum
requirements.
27
Table 1. Summary of cutting height effects of total forage yield of
three wetland meadow plant associations, 1988-1989.
Cutting height
--- inches ---
1988
2
4
6
2654
1802
1392
LSD(0.05)
Yield, lbs/acre
1989
Avg.
Bluegrass/Clover
2129
1550
1684
2391
1676
1539
456
498
280
2
4
6
4878
2784
2039
Mixed Grass/Sedge
3861
2419
1976
LSD(0.05)
1186
996
643
2
4
6
3529
2184
1093
Sedge 1550
1030
708
2539
1607
901
104
559
239
LSD(0.05)
4370
2601
2008
Table 2. Summary of forage yield of three wetland meadow plant associations by cutting date, 1988-1989.
Yield, lbs/acre
1989
Avg.
Bluegrass/Clover
1630
71*
86
1787
1584
205
79
1868
1817
1211
206
3234
Mixed Grass/Sedge
1967
178*
608*
2752*
1892
694
407
2993
1293
762
214
2269
Sedge 745*
212*
140
1096*
1019
487
17
1682
Cutting height
--- inches ---
1988
First
Second
Third
Total
1538
339
72
1949
First
Second
Third
Total
First
Second
Third
Total
* Yields in 1989 were significantly different from yields in 1988
28
Table 3. Summary of estimated digestibility (ADF) of wetland meadow
plant associations and species grown in Klamath County, 1988.
Harvest date 8/17
9/2
ADF, % Plant
association
6/20
7/22
Bluegrass/Clover
31.2
33.4
34.7
36.9
37.6
Mixed Grass/Sedge
33.9
36.0
35.6
38.4
40.1
Sedge
36.7
41.2
42.0
42.0
41.5
Juncus balticos
34.7
35.4
36.3
38.3
Carex Nebraskensis
34.7
39.9
40.3
40.3
38.6
Carex nigricans
36.7
39.1
38.0
38.4
37.3
9/15
Species
Table 4. Summary of crude protein content of wetland meadow plant
associations and species grown in Klamath County.
Harvest date
8/17
9/2
Crude protein, X Plant
association
6/20
7/22
Bluegrass/Clover
17.2
16.4
16.1
12.3
15.0
Mixed Grass/Sedge
14.0
13.9
11.2
10.7
11.0
9.6
9.0
9.6
9.7
8.6
Juncus balticos
11.3
7.1
5.6
Carex Nebraskensis
11.1
6.7
7.5
6.7
6.6
9.8
8.9
9.6
8.7
8.6
Sedge
9/15
Species
Carex nigricans