1. Open Space Grass Management for North Mesa Stables
Dan W McCarn1
and Carlos Valdez2
October 16, 2014
1
Dan W McCarn, Stable Owner at Lot 129, North Mesa Stables
2
Carlos Valdez, Los Alamos County Agricultural Extension Agent, NMSU
12/16/2014 1 &Test Plot Text, final B
Abstract
A 60 x 15 foot test plot on the south side of Lot 129, North Mesa Stables, Los Alamos, New
Mexico was set aside to evaluate methods of grass management on the tract of land known
informally as the gallop track. Located on the south side of North Mesa Stables, the track is in the
shape of a dogleg, about 70 feet wide by 700 feet long. The test plot is on the north side of the
track about 200 feet from the east end. Initially, the grass was allowed to grow to head from early
spring up to 12-18 inches and then sampled to determine the types of introduced and native
grasses in mid-July. Following sampling, the test plot was mown 3 times using a modified power
mower to a 6-inch height from July 15 through September 10, 2014. The grasses were neither
watered nor fertilized, nor were any seeds used to develop the grasses. A dense, lush grass cover
was grown consisting of both native and introduced grass species with minor amounts of
perennial weeds. The grasses are highly palatable for horses and include both cool and warm
season grasses. One perennial noxious weed, Curly Dock, was also identified. The principle
objective was to demonstrate the effect of two types of mowing on the development of the grass.
To this end, the Los Alamos County used a flail mower, cutting the grass from 1/2- to 1-inch in
height. The Test Plot was cut with a rotary mower set at a 6-inch height. The results of the
comparative methods are presented here.
Grass Species Identified
The findings of the identified grass species are presented in Appendix A. These grasses include
both cool and warm season grasses. They include, in order of abundance, Slender Wheatgrass
(Agropyron trachycaulum), Texas Timothy or Common Wolftail (Lycurus phleoides), Mountain
Muhly (Muhlenbergia montana), Spike Muhly (Muhlenbergia wrightii), Muttongrass (Poa
fendleriana), Kentucky Bluegrass (Poa pratensis) and Native Ryegrass (Sp. Unidentified). All are
highly palatable to horses. All of the grasses identified are bunch grasses with the exception of the
introduced, sod-forming Kentucky Bluegrass.
Perennial Noxious Weed Identified
One plant, presented in Appendix A, is the perennial Curly Dock (Rumex crispus) which covered
about 5% of the Test Plot. Curly Dock is toxic to horses and contains high concentrations of
oxalic acid which interferes with calcium & magnesium metabolism causing muscle tremors,
weakness, depression, and recumbency potentially leading to death. Curly Dock is usually not
preferred by horses; however, some horses develop a "taste" for the plant and are at a higher risk.
In dry years, Curly Dock may be one of the few forage plants available due to the deep root
structure.
Implements
The 60-inch flail mower used by LA County is a PTO (Power Take Off) driven tractor implement
designed to cut grass from 1/2 to 1-inch in height. The Test Plot mower is a modified 190 cc
rotary 21-inch power mower with oversized wheels allowing for a cut of 4-6 inches.
Discussion
The Colorado Forage Guide (1) offers important advice about management of clump grasses
common to the High Plains. Overgrazing or cutting too short creates a number of problems

2. Stable Test Plot Results
12/16/2014 2 &Test Plot Text, final B
including 1) damage / death of grass; 2) poor root system; 3) poor grass recovery; 4) erosion from
lack of cover; and 5) greater rainfall-runoff.
Allowing grasses to be maintained at more optimum heights significantly improves 1) The
drought resistance of the grass; 2) Enhanced root system and increased depth of roots; 3) Rapid
grass recovery after moving or grazing; 4) Far better erosion resistance; and 5) Far better rainfall
infiltration and significantly reduced runoff.
Figure 2: Sediment on East End ofTrack, 6/14/2013
Figure 4: Vehicular Damage to Track 1/1/2014
Figure 6: Grass Coverage near Test Plot
7/15/2012
Figure 1: Runoff / Erosion on East end near Test
Plot, 6/14/2013
Figure 5: Vehicle Parked on Badly Damaged Soil
20 yards SE of Perimeter Fence 6/3/2013
Figure 3: Runoff / Erosion on West End of Track,
6/14/2013

3. Stable Test Plot Results
12/16/2014 3 &Test Plot Text, final B
Erosion has become a significant problem on the gallop track as shown in the following Figures 1
through 3 taken on 6/14/2013 following a cloudburst looking west from the future site of the Test
Plot. Erosional stripping has denuded a significant portion of the soil by 2013 as shown in Figures
1-3 resulting in significant accumulation of sediment at the base of the gallop track. Damage by
vehicular traffic can be seen in Figure 4 dated 1/1/2013. Figure 5 shows vegetation badly
damaged by use of a flail mower adjacent to North Mesa Stables. Though not complete, grasses
had 75% coverage in the lower half of the track in the summer of 2012 which would have limited
runoff and erosion in 2013. Figure 6 shows the grass coverage on the gallop track on 7/15/2012.
The upper portion of the gallop track developed significant erosional rills which were typically 6-
inches wide by 8 inches deep and up to 10 feet long. These rills posed a threat to horse & rider
because a fall could occur if a horse stepped in one of these rills. They also created a condition in
which significant erosion could occur during a cloudburst. Placing the above Figures 1-5 in
context, the condition of the gallop track was significantly better prior to use of a flail mower in
2012. Figure 6 was taken on 7/15/2012. Management of the grass prior to this photo involved
repeated cuts using a rotary mower set to 4 inches. LA Parks took over management of the grass
during the late summer of 2012.
The present status of the gallop track at large is similar to the conditions of 2013 except that a
large number of annual weeds took advantage of the heavy summer rainfall and monsoon. The
Test Plot faired far better with very few, if any, annual weeds taking root. The Test Plot, as shown
in Appendix A, Figures 1-8 dated from July 2 through September 10, 2014, shows continuous and
significant improvement in the types and quality of grasses present. Figure 7 shows the present
condition of the Test Plot and the cumulative differences caused by mowing method.
Figure 7: Cumulative Effects of Mowing Methods, September 10, 2014

4. Stable Test Plot Results
12/16/2014 4 &Test Plot Text, final B
Figure 8: From CSU Small Acreage Management
Figure 7 in Appendix A demonstrates the effect of rotary mowing and grass development in 2012,
prior to use of the flail mower. Figure 6 above and Figure 10, Appendix A shows the development
of a grassy field 200 yards SE of the Test Plot on Open Space land not subjected to cutting.
Figure 8 represents the development of
roots based on post-grazing stubble. As can
be seen from this Colorado State
University, Small Acreage Management
diagram, root systems are optimized by
proper management.
In the case of the gallop track, cutting the
grass has destroyed all native and
introduced grass species where they were
systematically cut by the flail mower. This
has allowed a great number of annual weeds
to develop. As can be seen in the Test Plot,
the grass effectively limited the
development of weeds.
The vadose zone is that aerated portion of the soil & rock column above the water table which
does not have saturated water. Above the water table is a capillary fringe zone with the relatively
dry soil zone above. Water moves upward via capillary action towards the soil surface.
Root systems of plants interact with this capillary fringe zone by depressing the zone providing
moisture for the plant. With sufficient moisture and when there is no vegetative cover on the soil,
the capillary fringe zone may extend upward into that part of the soil heated by the sun and the
moisture begins to evaporate rapidly. This process, called evaporative pumping, wastes moisture
and concentrates dissolved solids at or near the soil surface in desert climates. This process can
cause the formation of hardpans of silica or
calcite endurating and cementing the soils
depending on the chemistry of the ground
water and increases the sodium hazard for
vegetation, making re-establishment of
grasses more difficult in damaged soils. North
Mesa frequently has perched water on top of
the less permeable volcanic tuff following
rainstorm events and is subject to evaporative
pumping.
Well developed root systems create a well-
aerated soil condition, allowing earthworms
to further bioturbate the soil making it more
permeable. Vegetated soils allow far more
moisture to penetrate downward following
rainstorm events than soil barren of
vegetation with far less permeability.
Figure 9 is a photograph taken in the South
Paddock of Lot 129 on August 4, 2014
Figure 9: Shovel Section in South Paddock, 8/4/2014

5. Stable Test Plot Results
12/16/2014 5 &Test Plot Text, final B
showing the lack of permeability. In the paddock, the composition is tight clay, probably the
result of soil loss for the top 10-20 cm. The upper 2-5 cm is disturbed by horse activity below
which tight, compacted clay is present. Because the source rock is volcanic, a good assumption is
that the clay weathered from the underlying tuff is a swelling clay or montmorillinite - bentonitic
clay which seals off water. In the photograph, the upper 2.5 cm is saturated & disturbed with the
underlying clay being damp but not wet. So, in spite of significant rainfall, water percolation
though the soil of the paddock is minimal resulting in large runoff.
Fire Adaptation and Fire Management Issues
Fire adaptation is a characteristic feature of prairie clump grasses. The identified grass species are
resilient to fire when they have a good root structure and can easily re-grow following a fire. All
grasses identified in the test plot have good adaptation and no identified species are prone to
cause significant fire risk. Managed grass areas can also serve as fire breaks. The summer of 2014
also showed that without proper management, the area is particularly vulnerable to encroachment
of thick, dense annual weeds, which when they die and dry, can provide significant fuel for a
ladder fire. The test plot showed that with proper development of grasses, annual weeds were not
evident at all.
Grass Management for LA County Open Space Areas
As must be understood by LA County employees implementing any program, proper management
of Open Space areas does not mean that grass should be cut as if it were a golf course or "to be
neat". The types of grasses used for yards and golf courses are sod-forming grasses which can be
cut to 2 inches; prairie clump grasses require a different management and may not be cut shorter
than 4 to 6 inches without significant damage to the grass and subsequent damage to the
environment.
The major advantages of developing an effective grass management plan is that
1) The grass will hold soil in dry and wet periods;
2) The grass absorbs a significant amount of rainfall, preventing excessive run-off and
trapping sediment and organic debris during downpours; and
3) The deeper roots allow for far better drought resistance.
Effective fire management & protection involving grasslands must also be addressed. Proper
management of grass resources can provide healthy grasslands with deeper roots allowing for
more drought resistance, good fire adaptation and consequently, fewer fire risks.
Recommendations include allowing the grass to come to full height early in the season followed
by mowing 2-3 times, but never shorter than 6 inches.
Undesirable Grass Species
1) Cheatgrass - Fire issues, problems with dogs (seeds).
2) Tall Fescue - Toxic to mares in foal. Fescue Toxicosis is an important issue in a horse
park where pregnant mares may encounter tall fescue grasses. It is almost impossible to
distinguish fescues from other grasses, especially when cut. Fescue Toxicosis causes
abortion of foals.

6. Stable Test Plot Results
12/16/2014 6 &Test Plot Text, final B
Recommendations & Conclusions
Well established grasses, properly managed, reduce runoff, significantly reduce sediments and
organic debris from damaging watersheds and prevent the degrading of water quality in
drainages. The EPA has already sanctioned the Race Track in Albuquerque for not managing
animal-related discharges into the Rio Grande (2). Measures taken at the North Mesa Stables to
reduce effluent runoff during storms should not be limited to retention ponds as they are now
proposed. A very effective measure in achieving these objectives is to encourage the growth of
native and selected introduced grasses on at North Mesa Stables.
Based on grass species and the Table I from the Colorado Forage Guide (3), the recommended
minimum cutting height for the grasses present on the test plot is 6 inches.
Species
(In Order of Abundance)
Type Minimum
Stubble Height
Slender Wheatgrass Cool-season, perennial, bunch grass 4-6 inches
Texas Timothy Warm-season, perennial, bunch grass 6 inches
Mountain Muhly Warm-season, perennial, bunch grass 6 inches
Spike Mukhly Warm-season, perennial, bunch grass 6 inches
Muttongrass Cool-season, perennial, bunch grass 4 inches
Kentucky Bluegrass Cool-season, perennial, sod grass 2 inches
Native Ryegrass Cool-season, perennial, bunch grass 4 inches
As can be seen in Appendix C, Examples of Grass Mowing Guidelines, grass management must
include date ranges as well as stubble heights in accordance with the type of grass. Care must be
taken to never cut lower than the recommended height. Table 1 from the Colorado Forage Guide
(1) recommends a minimum stubble height of 4-6 inches for most clump grass species. For the
gallop track based on the test plot results, it is recommended that grass should not be cut before it
comes to full head, approximately July, and then managed by cutting when required to a stubble
height of not less than 6 inches.
Management of noxious plants such as the perennial Curly Dock can be managed in two ways:
1) Appropriately timed mowing, never allowing the plant to mature thus eliminating seeds;
and
2) Cutting the tap root below grade with a pick-axe, immediately applying Roundup to the
root, and covering with soil.
Limitations for vehicle access to the gallop track are strongly recommended, limiting the access to
Lot Owners on the South side for maintenance & hay delivery and county vehicles as required -
but restricting all access in wet conditions. Consideration should be given to ripping, disking &
leveling the most heavily compacted soils, in use as an ad hoc road, on the site prior to seeding
with an appropriate seed mix.
Vehicular traffic causes severe surface damage to vegetation as well as soil compaction in wet or
damp soils and should be avoided. Soil compaction prevents most grasses to develop and provides
a location in which cloudburst-mediated erosion can rapidly occur. Restrictions for parking except
in designated areas would assist in protecting the grass resources of LA County Open Space
Areas. Access when the ground is frozen or during dry spells is not so problematic.

7. Stable Test Plot Results
12/16/2014 7 &Test Plot Text, final B
As required, a grey water line exists alongside of the gallop track which could be used to initially
establish grasses and to support grasses during dry years.
A PTO-driven rotary mower, 60-84 inch in width depending on the tractor horsepower with a 3-
point suspension is recommended for all LA County Open Space grassed areas including the
stable area. Cutting height should range from 2 to 9 inches. Cost for new units range from $2,000-
$3,500 depending on available horsepower and width of mower.
Summary
The Stable Test Plot on the south side of Lot 129, North Mesa Stables has demonstrated that
native and introduced grass species can grow and be effectively managed. Annual weeds are
minimized and noxious perennial plants such as Curly Dock can be moderated at low cost. All
appropriate areas of the North Mesa Stables including the gallop track, the round pen area, grass
borders on individual lots and the grass around the indoor and outdoor arenas should be managed
to encourage improved grass cover. These actions will reduce the amount of rainfall-runoff from
the stable area and minimize erosion.
References
(1) Jennifer L. Cook, Joe E. Brummer, Paul J. Meiman & Thaddeus Gourd, 1997, Colorado Forage Guide, Adapted
from the Forage Guide for the Northern Colorado Front Range, by Ron Jepson, Colorado State University,
Cooperative Extension, 1997.
(2) EPA Orders Albuquerque Racetrack to Stop Discharges to Protect Rio Grande, Release Date: 01/25/2012, Contact
Information: Dave Bary or Jennah Durant at 214-665-2200 or r6press@epa.gov
(3) Jennifer L. Cook, Joe E. Brummer, Paul J. Meiman & Thaddeus Gourd (2012), Colorado Forage Guide, Colorado
State University Extension, December 2012, Adapted from the Forage Guide for the Northern Colorado Front Range,
by Ron Jepson, Colorado State University Cooperative Extension, 1997.
http://www.ext.colostate.edu/sam/forage-guide.pdf
Attachments
Appendix A - Plant Species Indentified at Stable Test Plot (July, 2014)
Appendix B - Figures: Stable Test Plot
Appendix C - Examples of Grass Mowing Guidelines by Various Departments of Transportation