Water Quality: The Rangeland Component
R-1028, February 1992
Kevin Sedivec, Rangeland Management Specialist
Introduction
Proper Grazing Management
Range Improvement Practices
Summary
Rangelands can be a major component in
many watersheds, and proper grazing management is essential in minimizing runoff into the
watershed. Lowering the runoff potential from rangelands will improve the water quality of
the watershed.
The Bowman-Haley watershed in North Dakota is an example of a watershed that contains a
high percentage of rangeland. This watershed consists of 316,800 acres of land situated in
southwestern North Dakota. Over 175,000 acres (55.3 percent) are native rangeland with
another 46,000 acres (14.5 percent) tamegrass pasture and hayland. Improving grazing
management techniques must be emphasized if water quality is to be improved in this or any
other watershed in North Dakota.
Many acres of the rangeland is currently overgrazed and over-utilized, which has
promoted a deterioration in range condition. Researchers studying rangeland hydrology show
that as range condition decreases, rainwater and snowmelt infiltration decreases and
runoff increases. High runoff causes a shortage of moisture needed for plant development,
increases soil erosion and moves sediment into water resources. Plant growth must be
increased to slow down runoff and increase infiltration by improving the soil structure.
Sediment in water has been recognized as a pollutant in the same content as industrial
waste, sewage effluents, and other forms of pollution. Range management that controls
erosion and sediment movement will help us reach water quality goals.
Researchers have found that achieving ground cover of 60 percent or greater is
recommended to keep surface runoff less than 5 percent, if rainfall was 2.5 inches for one
hour. Ground cover of 35 to 40 percent will allow about 15 percent runoff at the same
rainfall rate. A minimum of 30 percent ground cover at all times is recommended. With
proper grazing this goal is attainable.
Research shows that proper grazing (50 to 60 percent utilization of aboveground
biomass) will allow sufficient plant growth for adequate ground cover. Many researchers
have shown that stocking rate seems to be a consistently more important influence on
infiltration rate and bulk density than the type of grazing system. Well managed grazing,
stocked at proper rates, resulted in little to no increase in erosion compared to no
grazing. However, a marked increase in erosion will occur under heavy grazing.
There are several natural and introduced factors, including grazing, that influence
erosion. Observed changes in erosion (variance) between different locations can help
determine which factors affect erosion the most. Those factors that create the greatest
variance are the most important.
Grazing and its attendant effects on depletion of plant cover and litter and trampling
of the soil was the most important factor contributing to erosion and sediment build-up
(Table 1). Plant cover can be restored by implementing range and livestock management
improvements, especially on areas highly susceptible to erosion. All practices designed to
control erosion will potentially reduce sedimentation.
Table 1. Variance in erosion
associated with the following seven
factors expressed in percent
(Renner, 1936. USDA Tech. Bull. 528:32).
---------------------------------------
Gradient 2.9
Rodent infestation 4.9
Plant density 6.8
Aspect 10.6
Soil condition 12.8
Plant type 13.4
Past grazing as expressed
by accessibility of range
to livestock 15.3
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Proper Grazing Management
Utilization
A common rule for proper grazing use is "take half - leave half" or 50
percent utilization. Proper grazing is defined as the degree of use that will maintain or
improve range condition.
Before a grazing management system can be designed to improve range health, range
condition must be assessed. Range condition is determined through careful observation and
some special techniques. Cages that prevent grazing are often used to compare grazed and
un-grazed range to determine levels of use. Small cages (18 inches by 36 inches) are
adequate to allow visual comparisons between grazed and ungrazed range.
Degree of use can then be estimated (Figure 1, 2, 3, 4, and 5).
Taylor and Lacey (Monitoring Montana Rangelands, Ext. Bull. 369, 1987) developed these
five figures and indicate in Figure 1 an illustration of a 25 percent use (by weight) for
a bunchgrass. Figures 2-5 illustrate percentage weights of various grass species as
utilized at different stubble heights. Remember, proper use is 50 percent (take half -
leave half).
Timing of Grazing
One of the most important techniques in range management is proper timing of grazing.
Native rangeland in North Dakota should be grazed no earlier than June 1, with the
exception of the southeastern region where about May 20 is recommended. April and May are
critical growth months for the cool-season grasses, late May and June critical periods for
warm-season grasses. Plants are most sensitive to grazing during this time period. Most
plant species defoliated or grazed in April and May rely on stored nutrients from the
roots to provide regrowth. Nutrient reserves are then depleted and cannot be replenished
adequately due to loss of leaf area needed to perform photosynthesis. Forage production is
reduced (Table 2).
Table 2. Percent of potential forage production
compared by start of grazing date on seasonlong
treatments (Rogler et al., 1962, ND Agri. Exp.
Sta. Bull. 439 and Campbell, 1952, J. Range
Manage. 5:252-258)
-------------------------------------------------------
Starting date of May May June June July July Aug
grazing season 1 15 1 15 1 15 1
-------------------------------------------------------
Mandan, N.D.
Percent of
Max. Total 24 43 57 67 92 100 87
Percent Lost 76 57 43 33 8 0 -13
Canada
Percent of
Max. Total 55 88 93 100 82
Percent Lost 45 12 7 0 -18
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Crested Wheatgrass - Smooth Bromegrass and Timing
Pastures or range dominated by crested wheatgrass or smooth bromegrass should be grazed
separately. Crested wheatgrass and smooth bromegrass are introduced cool-season grasses
that begin growth earlier than the native grass species. Early grazing, beginning the end
of April to early May, is recommended. These introduced grasses can maintain a heavier
stocking rate than native rangeland, about 1.0 animal units/acre/month (ex. one cow/calf
pair per acre or five sheep per acre) in southwestern North Dakota to around 2.5 animal
units/acre/month in eastern North Dakota if fertilized annually. Mature crested wheatgrass
becomes extremely rank and is seldom grazed after July 1. Mature crested wheatgrass is
best harvested for hay to eliminate old plants from inhibiting grazing the following
spring.
Carrying Capacity and Stocking Rates
Determinating carrying capacity of the rangeland and current stocking rate is necessary
for proper grazing management. Carrying capacity can be calculated using the Soil
Conservation Service (1984) technical guidelines.
Recommended carrying capacity or stocking rate is equivalent to the forage demand on a
unit of land over time. A change in one or both of two factors, 1) amount of land grazed
and 2) time of grazing season, will change the carrying capacity of the range resource.
The stocking rate of the present livestock herd can be determined by multiplying the
number of animals times their animal unit equivalent (AUE) (Table 3). Then multiply the
number of AUEs times the number of months desired for grazing. The resulting number is the
animal unit months (AUMs) of forage needed to support the herd. Refer back to the carrying
capacity (AUMs of forage produced on your range resource), determined earlier from the SCS
Technical Guidelines. The stocking rate should be close to the carrying capacity for the
most efficient use of the resource.
Table 3. Animal unit equivalents*
--------------------------------------------------
AU
Animal Equivalent
--------------------------------------------------
Cattle
Mature 1,000 lb cow with or without calf 1.00
Mature 1,100 lb cow with or without calf 1.07
Mature 1,200 lb cow with or without calf 1.13
Mature 1,300 lb cow with or without calf 1.19
Steers and heifers (2 yrs and over) 1.00
Calves (over 3 months) 0.30
Weaned calves to yearling 0.60
Yearling cattle 0.75
Dairy cattle 1.30
Mature bulls 1.30
Sheep
Mature ewes with or without lambs 0.20
Weaned lambs to yearling 0.12
Mature rams 0.25
Goats
Mature does with or without kids 0.17
Weaned kid to yearling 0.10
Mature bucks 0.22
Wether 0.16
Others
Deer 0.17
Mature buffalo 1.00
Mature horses 1.50
-------------------------------------------------
*1.0 animal unit is based on 26 lbs/day
consumption of dry matter.
Range Improvement Practices
Range improvements are special treatments, developments, and structures used to improve
forage production and resource, or to facilitate use by grazing animals. Water
developments, fencing, burning, mowing, and salt and mineral placement can be used to
control livestock distribution. More uniform distribution of livestock will improve forage
efficiency and reduce damage from overgrazing on areas of livestock concentration.
Planning is the key to successful range improvement practices. The planning process
should include a range situation map showing the producer's fences, water, natural
barriers, range sites, and range condition. Based on the map, problems and solution can be
assessed. An overall plan can then be developed that includes possible range improvements
and changes in live-stock management.
Grazing Systems
A grazing system is a management plan intended to provide a more uniform and proper use
of forage resource. Maintenance or improvement of the rangelands to provide a high level
of animal production is the major objective.
In North Dakota, native and tamegrass pastures are grazed under several different
grazing treatments (Table 4). Grazing systems must be adapted for individual farms or
ranches. Systems are developed to suit each particular set of circumstances. Consideration
must be given to availability of water in each pasture, the type of livestock operation,
kind and type of forage available for grazing, number, size and/or carrying capacity of
different pasture units available, and relative location of pastures for easy movement of
livestock between pastures.
Table 4. Grazing treatments used in
NorthDakota based on grassland or
forage type.
------------------------------------------
Grassland or forage type
------------------------------------------
Grazing Native
Treatments Native Tame & Tame
------------------------------------------
Continuous grazing x x
Rest-rotation x
Deferred-rotation x
Switchback-rotation x
Twice-over rotation x
Short-duration x
Complementary x
------------------------------------------
Continuous grazing is the most common grazing method used in North Dakota. It consists of
unrestricted livestock access to any part of the range during the entire graz-ing season.
Livestock utilize the most desirable forage first with seasonlong grazing. Livestock
distribution is very poor, especially in larger pastures. Severe overgrazing occurs where
cattle congregate, leaving other areas under-utilized. Maintenance of long-term
productivity can only be maintained by moderate levels of stocking under continuous
grazing.
Rotation grazing systems are usually designed to give most attention to certain key
plant species. A proper system allows range plants to recover from the shock of close
cropping by livestock. Time is required for plants to regain their vigor through build-up
of carbohydrate reserves. Rest after intense grazing is provided by moving live-stock
among two or more pastures on a scheduled basis. A pasture may be alternately grazed and
rested several times during a grazing season.
However, longer rotations may be on a basis of rotating the deferred pasture or the
rested pasture among months, or even years.
Specialized grazing management plans, once in operation, often permit increased
stocking rates, thus increasing livestock production per acre. Depending on the degree of
intensification of grazing management, observations indicate stocking rate increases of 15
to 25 percent are possible when compared to normal stocking for properly managed
continuous grazing on native rangelands. If stocking rates are excessive before
implementing a grazing system plan, a reduction in animal numbers should be made until
forage production and plant vigor are improved.
The range should be stocked to get full use of the total available herbage in grazed
units during the grazing season under a good rotation system. This means 50 to 60 percent
utilization would be desired. Heavier grazing (60 percent utilization) can be tolerated
under a good grazing system, because it is not sustained for long periods.
Any amount of rotation is better than none at all. When designing a rotation system,
start with water development and availability, then construct the fencing design. The
simplest grazing system is two pasture switchback grazing. It involves rotating
livestock back and forth between two pastures every two to three weeks.
Rest-rotation grazing systems in North Dakota are designed to include four
pastures. Three are grazed, leaving one idle each year. The first pasture is grazed in the
spring, second in the summer, and third in the fall. The starting pasture is alternated
every year.
Deferred rotation grazing allows discontinuation of grazing on different parts
of the range in succeeding years. This allows each grazed part to rest during the
succeeding growing season. Traditionally, deferred rotation grazing generally implies no
grazing until seed is mature on one unit during the first growing season, or on another
unit during the second year, and so on in rotation. A pasture grazed early in the growing
season but left ungrazed during rapid growth and flowering of key plant species would not
be a deferred pasture.
The twice-over rotation grazing system is a variation of deferred-rotation
grazing. This system rotates the livestock faster, resulting in more acceptable forage for
livestock throughout the grazing season. During the first grazing cycle, cool-season
grasses and sedges are utilized before they become too mature and unpalatable. High
quality vegetative regrowth forage is available during the second grazing cycle. Three to
five pastures are commonly used in this system.
Twice-over rotation grazing allows for a long period of rest between rotations. Only
one pasture is grazed during the critical period in plant development, when carbohydrate
root reserves are being used for spring growth. The grazing sequence will alternate from
year to year.
Short-duration grazing, also known as rapid-rotation and time- controlled
grazing, is a rotation system using multiple pastures and usually one livestock herd. It
involves a large herd combined with many small pastures, resulting in a high stocking
density (animals/area). The system is usually designed with eight or more cells. Grazing
period is short, usually seven days or less, to eliminate grazing of new plant regrowth.
The rest period, generally 30 days or more, allows regrowth to recover for grazing prior
to maturity.
Number of grazing cycles obtained during the grazing season depends on stocking rate
and forage regrowth potential. Four to five cycles should be obtained if properly stocked.
This grazing method should not be implemented unless grass and herd management practices
are at a high skill level.
Complementary grazing uses domesticated grass, legumes, and annual crop pastures
to add to or "complement" native range pastures. Crested wheatgrass and smooth
bromegrass are often used for spring grazing, and altai wildrye and Russian wildrye can be
used for fall and early winter grazing. Crested wheatgrass and smooth bromegrass have the
following advantages:
- they begin growth earlier in the spring;
- they produce more early season forage;
- they can be grazed earlier; and
- fewer acres are required per animal unit compared to native grasslands.
Seeded grasses used in spring can provide excellent grazing for 45 days or longer.
Water Development
Water development may allow increased stocking rates by lengthening the season of use,
spreading moisture usage more evenly over the range, or opening up more range to grazing.
Stocking rates must also be evaluated in terms of adequate drinking water for livestock.
Maximum livestock gains can be obtained only when both forage and water needs are met.
Rolling topography contains many draws and ravines with opportunities for water
development. Waterways are often dammed with spillway dams that create small reservoirs.
They function as both water holes and sediment traps. These small reservoirs are either
permanent or temporary.
Dugouts are also commonly developed to hold water for livestock consumption. Dugouts
are developed by digging a large depression in a low-lying area that normally collects
runoff water from adjacent slopes. Low areas that often hold water in spring or have a
water table close to the surface provide good locations for dugout development.
Water development on rangeland may also include techniques in waterspreading.
Waterspreading is a practice of diverting runoff water from stream channels or courses and
distributing it over flood plains or lower lying prairie. The velocity of water is slowed
and the water allowed to infiltrate into the soil, filtering out sediments. Increased
forage production and reduced channel erosion is the result. Water may also be spread via
a single furrow or ditch leading from a channel or complex system at dikes and dams.
Piping is another common water development technique. Piping water from one place to
another is a common practice in western North Dakota. This technique involves developing a
pipeline that begins at a current water supply and ends at a destination where water is
needed.
Other Range Improvement Practices
Range improvement practices that are direct means of developing and improving range
forage resources include:
- control of undesirable range plants;
- applying fertilizer;
- grass interseeding and reseeding; and
- runoff control, i.e contour furrowing.
Runoff control -- Contour furrows and pitting on rangelands are used to control
moderate amounts of runoff and improve infiltration for increased forage production. These
are best used on moderate to nearly level slopes and on fine-textured soils. Pitting
equipment has been used on rangelands to form small pits that can store 1/3 to 2/3 inch of
water. The water is then available for vegetative growth. Deferment from grazing for one
year is recommended.
Control weeds and woody plants -- Gumweed, fringed sage, leafy spurge, thistles,
buckbrush, and sagebrush are moisture and nutrient competitors. They can be controlled by
mowing, burning and applying herbicides. Brush management should take into account the
benefits of brush for late-season forage and wildlife cover.
Reseeding -- Complete tillage and reseeding to native or introduced grasses can
be used to restore previously cultivated lands, areas disturbed by mining, or over-grazed
lands that are irreversibly damaged. Reseeding can eliminate undesirable plants and
improve productivity. Deferment of grazing for two or more growing seasons is recommended
for full establishment of native grass seeded area. Grazing deferment for one or more
growing seasons is recommended when a full establishment of crested wheatgrass and smooth
bromegrass seeded areas are conducted.
Interseeding -- Seeding into an established vegetation cover can improve
rangeland lacking high-producing desirable plants. Decreaser plant species and legumes can
be planted in furrows that are accessible to interseeding by specific drill equipment.
Deferment from grazing for one growing season is recommended.
Fertilizer-- Increased use of fertilizers is part of a trend toward more
intensive management of soil and forage resources. Nitrogen is the most commonly used
fertilizer on native rangelands and introduced perennial domestic (tame) grass pastures
(ex. bromegrass and crested wheatgrass pastures). Increased herbage production and plant
palatabilty have been observed in fertilized pastures. Studies at the Dickinson and
Central Grasslands Research Centers have shown economic benefits from fertilization of
domestic grass pastures even during drought years. However, fertilization of native range
has yet to show economic benefits when warm-season grasses dominate the plant community.
In fact, fertilizing native rangeland in consecutive years causes an unbalanced
combination of warm-and cool-season grasses.
Proper rangeland management is an important step in the improvement of water quality in
rangeland dominated areas. Rangelands that are in good condition and maintaining 50
percent of the aboveground cover by weight will have little to no runoff, protecting water
quality. Maintaining proper use (50 percent utilization) and incorporating a grazing
management plan that maximizes the range resource will provide the most benefit to the
land owner and improved water quality for drinking and aquatic life.
A solid grazing management plan should include the elimination of early grazing of
native rangelands, removing no more than 50 percent of the aboveground herbage by weight,
and improving livestock distribution through the use of a grazing system. Water quality
will be protected and maximizing the use of the forage resource achieved.
Other NDSU Extension Service publications of interest relating to rangeland management
and grazing systems:
R207 . . . Renovation of Rangeland and Grassland Pastures
R750 . . . Range Condition...A Guide to Grazing Management
R580 . . . Range Site Identification
R741 . . . North Dakota Grasses and Sedges
R778 . . . Interseeding Native Pasture
R559 . . . Grazing Systems
R1006 . . . Design and Characteristics of the Twice-over Rotation Grazing System
ES Report No. 1 . . . Implementing and Evaluating Short-duration Grazing Systems
R1028, February 1992
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