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~ Crrcular No. 804

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April 1949 ¢ Washington, D.C.

UNITED STATES DEPARTMENT OF AGRICULTURE

Stocking Northern Great Plains
Sheep Range for Sustained
High Production

By E. J. Woouro.k, forest ecologist, Northern Rocky Mountain Forest and Range
Experiment Station, Forest Service }

CONTENTS

Page Page
TT EROCTIGEIOM Me eee nite. pens oe Se od Le 1 Effects of heavy conservative, and light stock-
How the problem was studied________________ 2 ing—Continued.
Character of northern Great Plains range_____ 5 Effects on number and size of plants________ 24
(The forage and iis utilization. —-.-. _---.2_- ) Effects on height growth of blue grama and
Growth and development of the forage_____ 9 bluestemiwiheatorasss ss eee 26
Relativevsrazine values. 922 =e 2 10 Effects on herbage production_____________- 28
How the forage was utilized___.___________- 12 Effects onthe sole: tees) 2 = ee eee 30
Habits of the yearling ewes_____-_--_« ____.. 14 Biitectsion) the sheepis=: 25 ee eee eee 30
MIN CHO AAC HIV LUeSee ees ee! 2 Sel eel ae hi 14 Degree of forage use recommended for northern
Influence of natural factors_________________ 18 Great Plaims!sheep Trance ssa ee aR.
mflienceyonfences: 222-2 2s 19 Recommended stocking rate for northern Great
Infinence ofpredators=---- = 2. 20 Plains sheep range during average 8- to 9-
Habits indicate desirable management sys- monthiseason se eee ee ee 34
TEST Seer mee ree er eta RSE os a a 20) SAS UMMA sees ey i ie ae ee eee at 35
Effects of heavy, conservative, and light stock- Common and botanical names of species men-
LTT Oggpee ener ed Sap Oe eS is 21 HONE d Seok ae es ee ee E Lar aths Seneca 38
Effects on density of the vegetation_________ Jie Witerature cited =. ka ae ee ee eee 39

INTRODUCTION

The northern Great Plains, which includes approximately the west-
ern half of North and South Dakota, the northeast quarter of Wyo-
ming, and the eastern two-thirds of Montana, constitutes one of the

oO)

largest and most important range-livestock areas in the United States.

The major part produces nutritious native forage, the utilization of
which determines the economic and social pattern of the region. Only
a relatively small proportion is cultivated.

1JIn cooperation with the U. S. Bureau of Animal Industry and the Montana
Agricultural Experiment Station. The author acknowledges the assistance and
cooperation of several members of these agencies and of numerous employees of
the Forest Service who assisted in conducting this experiment. Special acknowl-
edgment is made to Martin J. Doyle, B. A. I. shepherd, who served faithfully and
well throughout the experiment.

821193°—49—-—-1 1

2 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

Much of this range is grazed by cattle and horses, but sheep also
use a considerable part of it. Although wool and feeder lambs are
the chief market products of the local sheep industry, the development
of ewe lambs and yearling ewes into breeding animals by grazing them
for several months to a year on the range is becoming an increasingly
maar ea type of range sheep husbandry in the northern Great

ains.

In this area the low production of supplemental hay and the high
cost of imported feeds, plus generally open winters and the relatively
good forage value of cured range herbage, encourage range grazing
for long periods annually. It is a common practice to graze sheep
on the range continuously for 9to11 months and even year long when
forage is available and weather is not too severe. One of the major
problems which northern Great Plains sheepmen face is how to stock
their ranges to get the greatest possible production year after year
without deterioration of the forage and soil upon which their continued
and successful operation depends. ‘The effect of past grazing use and
the frequent occurrence of severe drought contribute to the wide
variations in stocking which occur in the region.

It has been most difficult to determine the acreage of range per
sheep per month; 1. e., the rate of stocking that will give best results
over a long period. A common but questionable practice has been to
stock heavily during favorable years and then attempt to adjust down-
ward when unfavorable weather and forage conditions occur. This
has led many operators into financial ruin because, unfortunately, a
crisis may develop more rapidly than adjustments can be made during
unfavorable seasons. Furthermore, the range deteriorates severely
under heavy stocking. On the other hand, stocking so light as to
entirely avoid heavy sales of livestock during drought years is not
practical because heavy carrying charges and other expenses make such
a practice unprofitable. The urgent need for information on how to
stock northern Great Plains sheep range for sustained production
led to the study here reported.

HOW THE PROBLEM WAS STUDIED

The Northern Rocky Mountain Forest and Range Experiment
Station in cooperation with the Bureau of Animal Industry and the
Montana Agricultural Experiment Station conducted a study of sheep
grazing from 1936 through 1941 to determine and develop guides to
proper stocking of northern Great Plains range for sustained sheep
production without deterioration of the forage and soil resource. The
study centered on lands of the United States Range Livestock Experi-
ment Station, about 10 miles southwest of Miles City, Mont. This
location is typical of northern Great Plainsrange. Three experimental
pastures (fig. 1) of 332, 476, and 847 acres were established and stocked
with yearling ewes to provide 9.5, 13.6, and 24.2 acres of range per
head in 1936, the first grazing season. During that first season, 1936,
the range pastures received 0.48, 0.34, and 0.19 sheep-months of graz-
ing use per acre, respectively. The smallest pasture was stocked
heavily, the next larger one conservatively, and the largest pasture
lightly throughout the entire test.

Because of favorable weather after late 1937 and substantial re-
covery of the range from the severe droughts of 1934 and 1936, it was
necessary to increase the number of sheep in each pasture to maintain

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE

STOCKED.

CONSERVATIVELY
STOCKED

Custer Flot Wel/

~ HEAVILY
Eckel
se 3
e oS = y LEGEND
Sor !
ag oe \ \ w Reservoir

w j <o Spring

—" Intermittent stream or gully

: s ( ] ys ; -—* Fence

~

re | oe © Well

Figure 1.—The experimental pastures.

3

4 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

these three relative rates of stocking. During the last year, 1941, the
pastures received 2.55, 1.78, and 1.00 sheep-months of grazing use per
acre, respectively, and for the 6-year period stocking averaged 1.35,
0.94, and 0.53 sheep-months per acre under heavy, conservative, and
light stocking. Table 1 shows the grazing season for each year, the
number of yearling ewes that were grazed, and the actual grazing use
for each pasture each year throughout the study.

TaBLE 1.—Actual grazing use by yearling Rambouillet ewes in three
experimental pastures, by grazing season, 1936-41

Stocking (sheep-months)

Num-
ber of 5 ti
vear- | Small pasture iddle-sized
Grazing season, ling (332 acres) pasture Hoe: oe
inclusive dates ewes (476 acres) =
per x
pire P P
ture er er Per
Total Gere Total ae Total BEE
June 16—Oct. 30, 1936___- 35| 159.8) 0.48) 159.8) 0.34; 159.8} 0.19
Apr. 28-Nov. 24, 1937_-- 35|¢ 25087, 2.10; 250) 3) OS ee ae . 30
Mar. 16—Nov. 28, 1938__- AZ 2302. 1) OG s00=d . (4| 352.0 . 42
Mar. 22—Nov. 20, 1939___ 55| 444.6} 1.34 444.6 93) 444. 6 52
Mar. 22—Nov. 16, 1940___ 80} 631.6) 1.90) 6385.8) 1 34) 632.6 75
Mar 18 Nov. 17; 19412 3)5 = 104) 845: 6| 2.55| 845. 7| 1.78) 845: 9) 41.00
otal ose ees 351|2, 684. 4| 8. 09/2, 686. 9} 5. 64/2, 685. 1] 3.17
IAW CYA Gene = jie Ae ee 58.5) 447.4); 1.35) 447.8) .94| 447. 5 . 53

The sheep were quite uniform, well-bred, dry yearling Rambouillet
ewes from the flocks of the United States Sheep Experiment Station at
Dubois, Idaho. <A new group was obtained each spring, grazed in the
pastures, then returned to Dubois at the close of the grazing season.
Except in 1936, when severe drought occurred, and in 1937, the grazing
season extended from about mid-March to late November. Weights
of the individual sheep on each pasture were recorded at the start, at
28-day intervals throvghout, and at the end of each grazing season.

A forage inventory provided the original appraisal of the range
vegetation and the basis for stocking the experimental pastures.
Permanent meter-square chart quadrats were used to study changes
in the range vegetation due to grazing and weather. Herbage produc-
tion as affected by degree of stocking was further studied by harvesting
the herbage from small plots that were ungrazed in 1942. Other
characters of the range, such as number of plants per unit area, size of
plants, and percentage of plants producing seedstalks, were studied by
various sampling techniques and the data compared for the differently
stocked pastures and ungrazed areas. At the end of each grazing
season a survey of utilization was conducted in each pasture.

During the first 3 years of the experiment the surveys consisted of
reconnaissance-type estimates of utilization, but after 1938 the stubble-
height method (3) ? and approved sampling techniques were employed.

? Italic figures in parentheses refer to Literature Cited, p. 39.

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE 3)

The data from these vegetative studies and the weights of the sheep,
plus records of actual grazing use and numerous observations and in-
formal records of plant palatabilities and the grazing habits of yearling
ewes, formed a basis for evaluating the various degrees or intensities
of stocking.

CHARACTER OF NORTHERN GREAT PLAINS RANGE

Northern Great Plains range, sometimes called mixed prairie (1)
and short-grass (9, pp. 460-462) range, supports a cover of native
vegetation in which the “ioe grasses are generally dominant. The
variable soils and topography combine in many ways and each
situation is characterized by certain range plant species or groups of

F-432859

Figure 2.—Blue grama and bluestem wheatgrass and rolling topography char-
acterize a large part of the northern Great Plains range.

species. As might be expected, not all of these situations were
represented on the experimental range. Fortunately, however, four
major situations which are representative of a large part of the
northern Great Plains range composed practically all of the experl-
mental area.

Well-drained soils and rolling topography (fig. 2) characterize vast
areas in the northern Great Plains. These sandy clay loams havea
high water-absorbing capacity and normally remain moderately moist
well into the growing season if conservatively managed. The vegeta-
tion, which on the average covers 25 to 35 percent of the oround sur-
face, is composed largely ‘of grasses and grasslike plants, but numerous
weeds or forbs as well as some cactus, sagebrush, and other shrubs are
also present. The principal species are ‘blue grama, bluestem wheat-

6 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

grass, threadleaf sedge, and needle-and-thread. Several less impor-
tant grasses are also present. F orbs, such as scarlet globemallow,
prairieclover, biscuitroot, several species of Indianwheat, and other
low-value annuals provide some forage during their growing season.
Big sagebrush is rather common, and fringed or pasture sagebrush is
frequently present. Because they produce a great amount and
variety of forage, these rolling grassy areas have the highest grazing
value. They are best adapted to summer and fall grazing owing to
the abundance of late-starting blue grama and the variety of her-
baceous plants which are green and succulent in summer.

F—415250

FicurE 3.—The hilly areas, where coarse grasses are abundant, are most valuable
for early spring or winter grazing.

The high proportion of perennial grasses which cure well on the
eround make these areas suitable also for late fall and winter grazing.
However, little protection from storms is provided by the gently
rolling topography, and the low-growing blue grama and threadleaf
sedge are likely to be unavailable because of snow.

Sandy to gravelly loam soils and moderately steep topography
combine to characterize other parts of the northern Great Plains
range (fig. 3). These soils have a high water-absorbing capacity with
consequent low runoff but dry out rather rapidly. The vegetation
normally covers about a fifth to a quarter of the soil surface and
consists principally of coarse perennial grasses and grasslike plants.
Forbs are not conspicuous but one or more browse species may be
rather abundant. Some of the most abundant grasses are bearded
bluebunch wheatgrass, side-oats grama, needle-and-thread, bluestem
wheatgrass, stonyhills muhly, and blue grama. Scarlet globemallow,
lupine, and licorice, as well as skunkbush sumac and small soapweed,

—_— OO eee FT

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE 7%

are characteristic. These hilly grass areas are most valuable either
as early spring or winter range, when old forage from the previous
year’s crop is acceptable to sheep. Some protection from the weather
is afforded livestock by the hills during early spring storms and the
forage is seldom made unavailable by snow. The first green forage
in the spring appears in these hilly areas.

F-432723

Figure 4.—The level or very gently sloping bottom lands are most productive
and constitute an important part of the northern Great Plains range.

The flood plains of the major streams constitute another important
variation of the northern Great Plains range (fig. 4). These areas
are characterized by generally heavy, frequently alkaline, clay soils,
and level or very gently sloping topography. The heavy soils absorb
water very slowly but remain moist longer than lighter soils. Pud-
dling of the surface layer caused by trampling of the wet soil or by
intense rainfall may retard water absorption and make runoff exces-
sive. About a third to a half of the soil surface is normally covered
with vegetation, largely perennial grasses, the most important of
which is bluestem wheatgrass. Nearly pure stands of bluestem are
common on these bottom areas, especially on those portions which
are sometimes flooded by runoff from adjacent slopes following heavy
rains. Buffalograss, green needlegrass, and Sandberg bluegr: ass are
also important on these bottom lands, and some blue erama may be
found on the drier edges. Herbaceous forbs compose a very small
and unimportant part of the vegetation. Silver sagebrush is fre-
quently present on these heavy soils. Forage produc tion per unit
area is higher on these flood plains than on any other part of the
northern Great Plains range. This is undoubtedly due to the deep
soils and the greater amount of flood water received.

8S CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

Because stock water is often available and the vegetation remains
green longer than on other areas, these bottoms are best suited to
summer grazing. Early spring use, particularly when the soil is
wet, may cause damage through trampling.

The rough parts of the northern Great Plains, sometimes called
badlands, comprise another important part of the range (fig. 5). The

61547B

Ficure 5.—The rough parts of the northern Great Plains are sparsely vegetated
and are chiefly valuable as winter range.

topography is rough and broken with precipitous slopes and sharply
cut canyons. The soil is heavy, often alkaline, and locally may be
rather rocky. It is often referred to as ‘“‘gumbo”’ and extensive areas
may be called gumbo ranges. Because of the tightness of the soils
and the steepness of slopes, water absorption is slow and runoff is
very rapid. On some sites, moisture seldom penetrates deeper than
a few inches. The very sparse vegetation consists chiefly of perennial
grasses, but browse is often sufficiently abundant to convey the aspect
of a browse range. Bluestem and bearded bluebunch wheatgrass,
along with blue grama and alkali sacaton, are the most important
grasses on these rough areas. Forbs such as scarlet globemallow,
dwarf phlox, and evening-primrose make up a small percentage of the
vegetation. The remainder is composed of big sagebrush, black
ereasewood, greenplume rabbitbrush, common winterfat, and shad-
scale saltbush.

These browse species, particularly winterfat and saltbush, have an
unusually high protein content (2) during the winter, when many
grasses and other species are low in protein and generally high in
lignin content. Because of this and the protection that the hills
provide against storms, such areas have a particular value for late
fall or winter grazing. Scarcity of stock water usually prevents
extensive use of these rough portions of the range in summer, and
steep topography, plus the sticky gumbo soil, makes them oenerally
unsuitable for extensive early spring use.

:
4
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:

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE 9

THE FORAGE AND ITS UTILIZATION

Of the many plant species which compose the northern Great Plains
range, nearly all provide forage for sheep at some time during the
year. Their forage values are unequal and palatability varies with
many factors. The bulk of the forage is provided by about 25
species. Still a smaller number, mostly perennial grasses, normally
provide forage yearlong. These, blue grama, bluestem wheatgrass,
needle-and-thread, and threadleaf sedge, are considered key species.
Good range management aims to maintain and improve the density
and vigor of key species on the range. Certain weed and browse
species are also of high importance, particularly for the variety they
furnish, but these will ordinarily not be grazed too heavily when
stocking is conservative and is regulated by the estimated allowable
use of the important key grasses or grasslike plants.

GROWTH AND DEVELOPMENT OF THE FORAGE

Spring growth of the range forage begins generally in late March
or early April and ends during late July or occasionally early August.
Some additional growth may occur following fall rains in August or
early September. Either inadequate soil moisture or too low tem-
perature may limit growth at the start of the season but of the two
factors, lack of soil moisture is perhaps the more influential. It is
not uncommon to find green forage present as soon as the snow melts,
provided the snow has melted slowly and the soil has absorbed some
moisture. If snow removal is rapid and runoff excessive, soil moisture
is likely to be low and the start of growth somewhat retarded unless
spring rains follow soon after. Forage growth is closely correlated
with April to September precipitation, which is about 70 percent of
the 13.06-inch annual long-time average for Miles City (fig. 6). Most
of the forage is produced during May and June, which are normally
the 2 months of greatest rainfall.

Sandberg bluegrass and threadleaf sedge start growth earliest in
spring (table 2). The production of forage by these early starting
species is extremely important because it materially lengthens the
grazing season. These species complete their growth cycles early in
the season and frequently produce fair amounts of forage in years

PRECIPITATION (INCHES)

YEAR
WA Growing season (April - September) Ee] Remainder of year

Figure 6.—Annual and growing-season precipitation, Miles City, Mont., 1935-42-

821183°—49 2

10 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

when summer drought greatly reduces the production of late-growing
forage plants. Because herbage growth is normally slow in early
spring, the experimental ewes were forced to subsist largely on the
previous season’s growth for the first few days of the grazing season.
They were observed to search for cured herbage but after the new
growth of Sandberg bluegrass and threadleaf sedge reached sufficient
height to be available, the old growth was seldom grazed.

TABLE 2.—Stages of development of five important forage species on
northern Great Plains range *

: Spring growth Spring srowth
Species starts— in eete completed
Sandberg bluegrass___| Middle of March___| Late April_____ Mid-May to late
June.?
Threadleaf sedge_____ Middle to late | Early to mid- | Late May.
March. April.
Bluestem wheatgrass__| Late March to | Harly June____| Late July.
early April.
Bivieserama 2222 e252 Middle to late April_| Middle to late Do.
June.
Buitalograss 22-2942 atevAprilas2=) ees June 22 awe Do.

1 Dates given are average.
2 Karly stage of seed-head production.
3 Varies widely, depending on spring rainfall.

Bluestem wheatgrass, needle-and-thread, and certain other grasses
start growth soon after Sandberg bluegrass and threadleaf sedge.

As the days lengthen and become warmer, blue grama, buffalo-
grass, and the summer forbs such as scarlet globemallow and prairie-
clover begin growth. The length of the growing period of these forbs
and the variety of such species which appear are closely related to
the amount and distribution of rainfall received. Blue grama and
buffalograss, like most of the perennial grass species, flower and com-
plete their growth by midsummer. Seed ripens and is disseminated
during late summer and early fall.

The late summer and early fall periods are characterized by the
flowering of composite forbs such as hairy goldaster and prairie sun-
flower and most of the browse species. These plants produce seed
before the first frost but dispersal frequently occurs during the follow-
ing winter. :

RELATIVE GRAZING VALUES

Preferences of the sheep for the many forage species varied with
weather, condition and abundance of forage, and many other factors.
In general, practically every species that occurred in the pastures was
utilized to some extent at some time during the grazing season. Even
pricklypear was grazed to a limited extent in early summer before the
spines on the new joints became rigid. Observations of grazing on the
species which provide the bulk of the forage are summarized in table 3.
The principal grasses and grasslike plants are very palatable and
provide forage from early spring until late fall. These species also
provide winter grazing unless unavailable because of snow. <A few
other less abundant grasses supply some additional forage. The forbs,

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE

1]

Tasie 3.—Use by sheep and relative abundance of important forage

plants on experimental pastures, northern Great Plains range, by
species
PRINCIPAL SPECIES
Rela-
: Part of plant Season of Relative | "ve
Species grazed most greatest use abundance pala
ity }
Grasses and grasslike
plants:
Bluegrass, Sandberg_| Leaves_...-.-_- Spring, early | Common___| VG
summer, and
fall.
Boiraloenrass: 222 | 2. Lae Aen ae SUMMER aes wees ee dow VG
Dropseed, sand__-_-_|_---- COE sie BR oe ote Ot 3 eS ek dows. G
Cramas blue: 3} ee MQu t=): = eye: Summerand fall_| Abundant__|’ VG
Needle-and-thread _|____- does = Early summer |_-_--__ doves G
and fall.
Sedge, threadleaf__|__--- dote ae Spree early |= oe dose VG
summer, and
fall.
Wheatgrass, bluestem Deve: and seed | Summer and fall_|_____ dosta2= G
eads.
SECONDARY SPECIES
Grasses:
Grama, side-oats__| Leaves_____._-_- Early summer__-_| Occasional__| G
Muhly, stonyhills__|_____ 5 (0 eae. SA SOS Summer and fall_|_____ dot.*=_= F
Wheatgrass, _| Leaves and old | Spring_._----~-|_---- doses G
bearded blue- growth.
bunch.
Forbs:
Agoseris, pale__-_-- Flowers and | Summer______-_- Common___| VG
leaves.
Biscuitroot: 7. 2. Flowers, leaves, | Early summer_-_-_|___-- dos VG
and fruit.
Gaura, scarlet_____ Plow ers ai Gs] shimmers = 4 sae dos VG
leaves.
Globemallow, sear- |_____ 6 Kasse: Oe En 2 (3 (a RNa a nee! bY ew doses. G
let.
GColdasterhairy= _|- 2 s- doesn esa Late;summer = 2222 - dosses G
Indian wheat, woolly_| Leaves and seed_|_____ G9 eee ee eee ME Gov: ta... G
Onion, textile____-_ Flowers and | Early summer___|____- dovas/ VG
leaves.
Prairieclover, pur- |_---- dol st SLMNTe TG es Saw oh dol G
ple.
Prairieclover, slen- |____- (6 (0 Rae ee lt 6 | @ ees SRI Ea dos. G
der white.
enOliy atm! et HiOWersse ss Spring and early |_____ joo G
summer.
Sunflower, prairie.__| Flowers and | Late summer-__--_|_-_-_-_- dos. 222 G
Browse: leaves.
Rose; Fendler® —_=_}-=.-- dO eee SUmmer 2: ose. 5 Common___| F
Sagebrush, big____- Leaves*e oles: ER ra oh Pe Abundant__| F
Sagebrush, fringed _|- --_- COs Dees Ce Ade eee Common__-_} F
Sagebrush, silver___| Leaves andtwigs_| Summer and fall_|_____ (6 (ere G
Saltbush, Gardner__} Leaves_________|___-- (5 6 lea aaa ee vie Occasional__| G
Saltbush, shad- | Leaves and seed_|__-_-_- dG a ee ee! dg cee G
scale.
Sumac, skunkbush_} Fruit_-__------_- Summer 2s. _ - Common_.- F
. Winterfat,common-_| Leaves and | Summer and fall_|____- ote see G
twigs.

ous.

) Witte ie, epee

1 During season of greatest use: VG—Very good; G—Good; F—Fair.
2 Includes several species in three genera, Cogswellia, Musineon, and Cymopter-

19 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

although very palatable, were available largely in summer and there-
fore supplied forage only temporarily. The most important browse
species furnished only a small amount of forage in summer and fall.
These species are of greater importance for winter grazing.

The very palatable Sandberg bluegrass and threadleaf sedge were
readily eaten by the sheep in spring and early summer and again in
the fall when new growth appeared. At these seasons but particularly
in early spring, these two species supply a high percentage of the forage
for sheep. Bluestem was relished when it was fresh and green in early
summer and again in the fall, when rain or snow softened the cured
leaves. The ripe seed heads were particularly well liked at that time.
The new growth of needle-and-thread was well liked, but the sheep
did not graze this species after the plants produced heads unless new
fall growth was produced following August or September rains. Blue
erama and buffalograss were grazed throughout the summer and to
some extent in the fall, depending upon weather and snow conditions.
A greater variety of succulent vegetation was available in early sum-
mer than at any other season. The flowers of weeds were particularly
attractive to the sheep.

Besides the grasses and forbs, several browse species regularly made
up a substantial part of the forage. The various species of sagebrush
and saltbush were frequently browsed, and winterfat and rose were
also readily taken. The sheep also ate the fruit of skunkbush sumac
and black chokecherry. Many of the late-blooming forbs were palat-
able to the sheep, and their appetites for these species and the various
browse plants increased as the grasses cured with the advancing season.

How THE ForAaGE Was UTILizED

Obtaining a reliable appraisal of grazing use on a range involves
observations of large numbers of individual plants of the most impor-
tant forage species. The measurement of grazed stubbles and a tally
of numbers of key plants grazed along transects drawn as chords of
concentric circles around the central well provided a basis for apprais-
ing herbage utilization on the experimental sheep ranges. Previously
recorded ungrazed plant heights and height-weight tables for each
species made possible the conversion of stubble heights and percent-
ages of total numbers of plants grazed to percentage of herbage,
figured to ground level, removed by grazing.

The important forage plants were grazed to a low stubble height
(table 4) in all pastures even though more range acreage and forage
were available for each sheep under conservative and light stocking
than under heavy stocking. Variations in utilization between pas-
tures stocked at different intensities resulted more often from differ-
ences 1n the percentage of the total number of plants that were grazed.
This percentage varied with degree of stocking, height growth of the
individual plants, succulence of the herbage, weather, and other
factors. Height growth was an important factor affecting utilization
from year to year even though grazed stubbles and percentage of the
number of plants taken remained fairly constant. Regrowth after
early fall rains complicated appraisal of utilization, particularly in
threadleaf sedge. In this species it could not be distinguished from
spring growth and its occurrence lengthened grazed stubble height
and reduced percentage utilization.

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:
;

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE 13

important forage species under various rates
of stocking, by species and season, 1939-41

: Conservativel | .
Heavily stocked apn alec y Lightly stocked
Species and graz- |
ing season _Aver- Aver- | Aver-
age | Plants} Utili- | age Plants) Utili- _ age | Plants) Utili-

stub-| grazed) zation | stub- grazed zation | stub- grazed zation
b

Blue grama Cm. | cent | cent | Cm.| cent | cent | Cm.| cent | cent
LCE Ce aie | 126 56 39 | 1.6 51 29 | 1.6 Ze 16
ROAG So Foe er 59 AE 18 42 29 |S 42 | 31
LS eS, Soe ee 1 60 46 | 1.4 4] 29 | 1.5 23 | 15

Average___| 1.3 58 44 | 1.6 45 29 oS 31 | 21

Bluestem wheat- |

grass: !
[C2 ce ae 5. 5 60 41/61 29 Ue es lise 37 26
220) Sei Sais | 4.8 65 48 | 6.9 4] D2 |" deal 28 17
Average___| 5. 2 63 45 | 6.5 35 20 | 6.1 33 22

Threadleaf sedge:

CBN Bee eae 2. 2 56 28 | 2.3 46 Pelee. 6 34 12
eS 2 1.9 58 43 | 2.4 36 PAS ad Neyer 6 23 15
EPP Saree! ota} 2. 2 49 ap | 9 18 14 | 2.3 Bh 8

Average___| 2. 1 54 35 | 2.2 33 Oe) 226 23 12

1 Grazing use in 1939 too light to be estimated.

Blue grama received greater use every year in the heavily stocked
pastures than in the others. Stubbles varied only slightly but a
higher percentage of plant numbers were grazed under heavy stocking.

Grazing use of bluestem in all situations was so light in 1939 that
it could not be precisely estimated by available techniques. During
the last 2 years of grazing, the comparative use as between pastures
followed about the same trend described for blue grama. Without
exception, however, bluestem grazing was most prevalent in the fall
and if the season had extended beyond November, heavier use of this
species would undoubtedly have resulted in all pastures. Stubbles on
erazed plants showed more height variation than did those of blue
erama, but this was greatly overshadowed by the wider spread in
percentage of plant numbers grazed.

Threadleaf sedge, like other species, was grazed most in the heavily
stocked pasture. Stubbles were low in all pastures but over 50 per-
cent more individual plants were grazed on the heavy ily stocked pasture
than in the conservatively stoc ked pasture.

In general, all species were most relished by the yearling ewes when
the plants were young, green, and tender. Green forage was grazed
when available, regardless of the amount and kind of cured forage
present. In spring the sheep traveled excessively in search of the
first green plants although a large amount of cured forage was avail-
able. A few species, mostly perennial grasses that started erowth in

14 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

early spring and greened up again in the fall, were grazed considerably
both spring and fall but largely disregarded during the remainder of
the grazing season. 3

The sheep seldom grazed one species to the exclusion of others
but usually mixed the species sufficiently to provide a wide variety.
They grazed the pastures irregularly and often returned to closely
grazed areas for any new growth that might have appeared since
the last visit.

HABITS OF THE YEARLING EWES

Knowledge of the natural habits of range sheep is important both
in the management of the range and in the proper handling of the
animals themselves. Study and observation of the yearling ewes,
their responses to weather conditions and topographic features, and
their preferences for different forage species through the season
provided some knowledge of their habits.

In this experiment the sheep were not herded but were free to
move and graze as they wished. However, each group was located
and counted twice daily and periodically was driven to the corral
for weighing by the attendant, who spent full time looking after them.
No effort was made to direct their movements over the range. Under
these conditions all the vagaries of sheep nature were allowed full
freedom except as restricted by weather, available water and forage,
and the pasture fences. Some concentration and unnecessary
trampling occurred under this system of handling, and distribution
of grazing was uneven and irregular. The Rambouillet yearlings
were gregarious for the most part, but occasionally a group would
divide into two or more small bunches following a predator attack or
other disturbance.

PRriNcipAL ACTIVITIES

GRAZING

The yearling ewes grazed largely during the daylight hours, partic-
ularly in the spring, early summer, and fall, when days were not
too hot. In midsummer, however, when insects were bothersome
and the days long and hot, they frequently grazed at night.

Various grazing formations were observed, depending upon the
forage, the weather, and other factors. A wide are formation, three
or four sheep deep, was frequently observed on rolling blue grama
areas when the sheep were very hungry in early morning or following
confinement in the corral at weighing time. In this formation they
were well spread out and moved very slowly, obtaining the maximum
amount of forage for the time involved and area covered. At other
times the ewes moved rapidly in a close, compact formation, grazing
only the most desirable or easily accessible plants. This habit was
frequently observed in late evening immediately before bedding,
when hunger was not very evident. Apparently only choice forage
was sought during this period. An unusual formation was often
seen around skunkbush sumac or chokecherry thickets when the
ewes would crowd inclosely and browse until nearly every ripe fruit
within reach was taken (fig. 3, p. 6). Sometimes they reached the
higher ones by standing with front feet in a bush or on another sheep.

There was a tendency toward spotty, irregular grazing in all the
pastures. The ewes would return repeatedly to closely grazed areas

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE 15

for any small bit of new forage and would leave adjacent spots
with apparently choice but older and more mature forage almost
entirely ungrazed. Except in early spring, they seemed reluctant to
graze areas which supported old forage froma previous crop even
though large quantities of green forage were intermixed. In the
fall the sheep were less active and consequently the area covered in
a day was much less than in a day of summer grazing. Range
sheep naturally graze very irregularly and are likely to damage the
range locally by heavy grazing and trampling unless their movements
are controlled by fencing or good herding.

BEDDING

The ewes usually bedded down at night, particularly during the
cool seasons and when predators were not active. In late evening
an hour or more after sunset they would lie down in a compact group
where a fence or other obstruction provided some real or fancied
protection from enemies, and would be up grazing again at the first
hint of dawn. There was no indication of a desire to return each
night to an established bed ground. Instead, the sheep bedded
near a fence or any other obstruction which happened to be close
at hand whenever night overtook them. Jardine observed this
tendency in his early studies of pastural sheep grazing (7). Evidently
therefore, the one-night bedding-out system encouraged on national-
forest ranges fits a natural habit of range sheep and is adapted for
more widespread use on northern Great Plains range. It is advan-
tageous to the sheep as well as to the welfare of the range. The
advantages of the one-night versus the multiple-night bedding system
in maintaining the range, increasing lamb and wool production,
and reducing losses from poisonous plants on mountain summer
ranges have been well emphasized by Doran and Cassady (5).

In summer, when insects were most active, short bedding periods
were alternated with intervals of grazing at mght. These night
activities were determined by actual observations and by retracing
the courses traveled during the night. In the fall, particularly after
snow came, the yearling ewes remained longer on the bed ground,
frequently until midforenoon, and were more inclined to seek a
sheltered spot for bedding than during the milder seasons.

RESTING

The daylight hours at any season in the northern Great Plains
provide ample time for sheep to eat their fill of range forage, provided
it is abundant and the animals are unmolested. In the experimental
pastures, particularly the conservatively and lightly stocked ones,
the yearling ewes frequently alternated between grazing and resting
during the day. To rest they would stand or lie singly or in small
eroups and chew their cuds. The rest periods were usually of short
duration but were frequently repeated during a day. In summer,
except during the periods of greatest insect activity, the sheep com-
monly left the bed ground at dawn, grazed for an hour or two, then
rested perhaps as long as an hour. Afterwards grazing was resumed
and frequently continued well into the forenoon. These rest periods
were distinctly different both in nature and purpose from those
periods spent bedded down at night or ‘‘shaded up” for protection

16 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

from insects during the day. When the sheep rested they apparently
felt well-fed and content to remain quiet and ruminate. This was
conducive to better weight gains and improved welfare, and was
considered as indicative of satisfactory management.

FIGHTING INSECTS

Range sheep that are herded have the well-known habit of congre-
gating on summer days, frequently near watering places. This
practice is commonly known as shading up. It is usually attributed
to hot weather and has become so entrenched in the daily routine that
herders sometimes appear to encourage the practice by keeping their
sheep congregated, often near water, for a considerable part of the
day even though natural conditions may not prompt the sheep to
congregate. Such concentration from midmorning until late afternoon
causes damage to the range.

F-415243

Figure 7.—Sheep congregated, or shaded up, under a high bank near a developed
spring.

In the experimental pastures the yearling ewes frequently congre-
gated during the day, but observations indicated that it was primarily
for protection from insects. They frequently grazed for short periods
during the hottest part of the day if insects were inactive, then con-
eregated at other times when temperatures were lower but insects
obviously more troublesome. Barren, dusty places or steep, browse-
covered slopes sometimes near water ‘(fig. 7) were very often selected,
but actual shade was not a requirement. Little, if any, rest was
gamed when the ewes congregated under these conditions because a
substantial part of a group was constantly in motion as individuals
lay down, got up, kicked, or moved about to dislodge annoying insects.

Unnecessary congregating should not be encouraged by poor
herding or other questionable practices. There can be little doubt

Pe Se ee ee

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE 7

that excessive trampling is one of the major causes of damage on
sheep range. Countless steps by the narrow, sharp hoofs of the sheep
cut the crowns of forage plants and loosen the soil around them. The
loose soil is then moved by wind, and the shallow roots become
exposed, dry out, and frequently die.

WATERING AND SALTING

The experimental yearling ewes did not water regularly even though
watering places were plentiful and well distributed. It was not un-
usual for a group to drink three or four times in a single day but at
other times and for no apparent reason the same group would go to
water only every other day. even in the hottest part of summer, the
sheep would occasionally go 2 days without a drink. Puddles formed
by melting snow in early spring, and small ponds formed during
showers in summer, served tempor arily as watering places. In the

F-415234

Figure 8.—A small spring which was developed and the water piped into troughs
to improve distribution in the pastures.

fall, water was taken less frequently than in summer. When snow
covered the range, water was seldom taken.

A number of small springs and seeps were developed in the pastures
to provide additional w atering places. This resulted in noteworthy
improvement in distribution as compared to watering at one central
location. Such weak springs (fig. 8) are quite common on many
dry ranges where shale formations outcrop. These developments
Geiteizated that small springs have a definite value in a range sheep

821193°—49——_3

18 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

operation when the cost is moderate and storage troughs are provided
to collect the slight flow. A spring which yields only one-fourth to
one-half gallon per minute will water a band of 700 to 1,200 ewes
every other day on the average if adequate storage facilities are
supplied.

Salting away from water in an attempt to improve distribution and
lighten the use near the watering places was unsuccessful. The
yearling ewes did not graze the pastures uniformly and, therefore,
seldom returned to the salt again, even though driven to it once, when
it was placed a great distance from water. This indicates that the
established practice on the national forests (7) of salting range sheep
at night on the bed ground is preferable to salting away from water
and that little use can be made of salt as an aid to distribution of
sheep on these ranges.

INFLUENCE OF NATURAL Facrors

WIND

Of all the climatic factors which affected the movement of the ewes,
wind was the most influential. Between April 1 and November 13,
1941, the manner in which 3 groups grazed with respect to wind direc-
tion was observed and recorded 522 times. Based on these observa-
tions, the sheep grazed into the wind 44 percent of the time, with the
wind 30 percent, and sidewise to the wind 26 percent of the time.
Even before this record was made, the tendency for sheep to graze
into the wind was noticed and used to advantage in locating the various
groups. A gentle to moderate wind from any direction would fre-
quently attract the sheep to the corresponding corner of the pasture,
and knowledge of this fact often saved time and miles of travel in
inspecting the flocks in the various pastures. This knowledge of the
reaction of range sheep to wind is useful in formulating handling
systems. Under the 1-night bedding system, alternate routes of
travel can be planned ahead to take advantage of anticipated wind
movement.

TEMPERATURE

High summer temperatures frequently restrict the movements and
erazing habits of range sheep. In the experiment, the effects of hot
weather were apparently complicated by insect activity. The groups
of yearling ewes were frequently observed grazing at midday under a
scorching sun and at other times when insects were particularly
troublesome they would shade up throughout most of the daylight
hours even though it was not particularly hot. Only at night was
much grazing done under such conditions. In the absence of insects,
however, the sheep pursued their normal activities with little regard
for temperature even on the hottest days. In their early studies of
sheep grazing Jardine and Anderson (8) recognized this tendency and
recommended that range sheep should not be restricted by close
herding if both the sheep and the range were to be maintained in the
best possible condition.

Low temperatures restricted the movements of the sheep. A
group would frequently remain for 2 or 3 days during a cold period in
a small rough drainage where forage and some protection from the

ee

OF tes

. ae ee eee es eee pee POE ee TF

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE 19

weather were available. This habit was evident particularly if there
was snow on the ground. A combination of low temperature and
high wind sometimes caused the sheep to drift down wind. These
observations suggest that rough ranges which provide protection
from storms and cold winds should be reserved for winter erazing.

INFLUENCE OF FENCES

The fences obstructed to some extent the natural movements of the
sheep and served as barriers along which grazing use was frequently
so concentrated as to do considerable damage to the range (fig. 9).
As a result, the pattern of grazing use in each pasture resembled a
series of irregular concentric bands ranging from very heavy along
the boundary fences to somewhat lighter in the interior of the pas-
tures. The Rambouillet sheep instinctively sought the shelter of
some sort of barrier for shading up or resting and the fences were
selected most frequently. Some of the effects of these instinctive
habits on both the ewes and the range could undoubtedly have been
avoided if greater care had been used in locating the pasture fences.
These experiences indicate that fences complicate the natural move-
ment of sheep over the range. Unnecessary or poorly located fences
are an obstacle in the proper use and management of typical northern
Great Plains range.

F-373152

Ficure 9.—The sheep repeatedly rested or shaded up along pasture fences, often
causing severe damage to the range vegetation.

20 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

INFLUENCE OF PREDATORS

The experimental ewes were frequently attacked by coyotes, bob-
cats, and renegade dogs. Death losses due to these predators were
high each year and additional unmeasured losses also undoubtedly
occurred in the form of reduced weight gains due to disrupted acti-
vities. The combined efforts of a Government hunter and the shep-
herd, who tended the sheep and who had considerable experience and
skill in trapping, failed to control the predators or prevent heavy
losses. Prior to the start of the experiment, losses were light on this
same area when the sheep were herded. Predator attacks increased
the nervousness of the sheep and made them more easily disturbed.

Several motives for attack by the predators were apparent. Some,
probably the renegade dogs and immature coyotes, killed for fun and
caused the heaviest losses. Their attacks were infrequent but some-
times involved the groups in every pasture with the loss of a dozen or
more sheep in one night. Transient coyotes occasionally killed to
satisfy hunger and a female coyote or bobcat with young sometimes
killed one sheep each night until the den and the young were located
and destroyed. These females with young caused heavy losses and
their attacks were most frequent through late June and July when
the young were being taught to provide for themselves. Many of the
ewes lost as a result of predator attacks died from injuries received
while fleeing at night in rough, broken country. Attacks were most
numerous at night but were also recorded in daylight hours. Direct
observations of daylight attacks indicated that the coyotes first
frightened the sheep, and then killed the individuals that left the
eroup. A frightened, running sheep was at their mercy.

An electrically charged wire spaced 6 inches from the ground and
the same distance below the next higher wire of the boundary fence
served temporarily to reduce the number of predators that entered
the pastures. Coyotes soon became ‘‘educated,’’ however, and were
observed searching for depressions under the fence through which
they could crawl without contacting the charged wire. Maintenance
of a charged wire so close to the ground was expensive and would
probably not be practical on a ranch. These experiences indicate
that predator losses are likely to be too high in the northern Great
Plains to justify large-scale, free pasture grazing by Rambouillet
sheep. However, in northwestern South Dakota, where predators
are few and are closely controlled during lambing, when sheep are
constantly observed and extra care is provided, pasture grazing has
been practiced successfully. The practice may have advantages
elsewhere in the northern Great Plains.

Hasrts INDICATE DEsIRABLE MANAGEMENT SYSTEMS

Because range sheep tend to return repeatedly to favored grazing
areas until heavy use and range damage occur, and because predators
are usually numerous and not closely controlled in the northern Great
Plains, it is inadvisable to turn sheep loose to freely graze large fenced
areas of range. The foregoing observations and experiences indicate
how knowledge of the natural habits of range sheep may be used in
devising handling systems that will aid in obtaining good range and
livestock management on northern Great Plains range. Slow, quict
handling with some latitude for choosing the direction of movement

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE PA |

with reference to the wind and freedom to graze and rest alternately
for short periods is beneficial to the sheep and the range. Frequent
changes of bed grounds and overnight camps make for better dis-
tribution over the range and uniform use of the forage. Many well-
distributed water developments will also aid in more uniform grazing
use. Predator losses can be decreased through the presence of a
vigilant herder. All of these factors, coupled with conservative

stocking, help to improve the welfare of range sheep and safeguard
the range.

EFFECTS OF HEAVY, CONSERVATIVE, AND LIGHT
STOCKING

For several years prior to 1936, the first year of the sheep-grazing
experiment, the experimental range was grazed conservatively each
summer by a band of herded sheep and a few horses. This conservative
use preceding the experiment permitted the range to maintain high
vigor and productivity until severe drought struck in 1934. Nearly
normal rainfall occurred in 1935, but the range failed to recover from
the effects of the previous drought year. Severe drought occurred
again in 1936, accompanied by ‘erasshopper infestations, and vege-
tation density and herbage production were reduced even below the
low levels reached in 1934. On adjacent similar ranges grazed con-
servatively by cattle, total vegetative density was reduced by these
two drought years to 9 percent of its 1933 level (6).

Recovery of short-grass range from the effects of severe drought was
slower on the pasture heavily stocked for 6 years than on the pastures
conservatively and lhghtly stocked. This was manifest in the thinner
vegetative cover, smaller sized plants, shorter plant heights, and
reduced herbage production per unit area on the heavily stocked
pasture. Low- “value annual species were more abundant at the end
of the grazing experiment on the heavily stocked pasture than on the
others and in 1942 their herbage made up a high proportion of the
weight of the vegetation harvested from a series of plots. To the
stockman these effects of hee avy stocking mean less forage, a shorter
grazing season, greater drought and winter risks, and higher produc-
tion costs.

EFFECTS ON DENSITY OF THE VEGETATION

In 1938, the third season of grazing, when effects of the 1934 and
1936 droughts were still evident, meter-square chart quadrats, here-
after referred to as plots, in all stocking intensities and in areas fenced
that year had rather low total densities; 765 square centimeters on
the heavy, about the same on the light, and 809 and 850, respectively,
on the conservatively grazed and on plots recently fence ed (table 5).

Practically no recovery from this low level was shown in 1939.
The decline in little bluegrass just about offset the increase in blue
erama and other dependable perennial grasses on the lightly stocked
and ungrazed plots. Under heavy and conservative “stocking, an
actual decline in total density occurred.

After 1939 the total density improved on all plots regardless of
erazing use. By 1941 total density of perennial species under heavy
stocking had increased 326 square centimeters per plot, while the

22 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

conservative, light, and ungrazed plots increased 297, 370, and 508
square centimeters, réspectively, on the average.

Without any grazing in 1942 and following the favorable rainfall
of 1941, the perennial vegetation made remarkable recovery in density
on all plots. For the 5 years 1938-42, total perennial vegetative
density increased 749, 849, 1,143, and 1,172 square centimeters,
respectively, on the heavily, conservatively, and lightly grazed and
ungrazed plots.

TABLE 5.—Average density of important range vegetation on meter-
square experimental plots, by stocking rate and year, 1938-42

Other
Sencline rate Bie Bluestem) Little |perennial) Peren- ‘Total, all
ad eae ama | Wheat- | blue- |grass and| nial | Browse |perennial
ea Qe See grass | grass | grasslike! forbs | species
plants
|
Heavy: | Cm.2 Cm2 | Cm? Cm Cm.? Cm? > Cm
POS Ba tisie oe eae 158 Cie Broke’ ie 0 0 765
OS Oa ree nes | 300 14 | 290 PE) 3 1 | 635
OAS aes See | 545 205 Sos 60 | 5 4 798
LOANS a 765 30° | 55 90 | 6 15 961
19426 ao? 267. 38 36 139 || 4 30 1, 514
Conservative | |
LOSSee a ere 96 18 683 12 | 0 0 809
L939 = s 2G. 23 418 18 | 2 (1) 678
ROA Q ee 8 eee 357 32 247 40 3 4 683
OAc eae 737 55) 99 Sie leowas 28 975
ROADS Sees 1, 427 50 35 104 | 4 38 1, 658
Light: |
LOSS oe eee 100 29 630 4 0 | 0 776
NOS Ore: Sea 221 48 > 484 28 | 5 | 0 785
TOA OE ee PRS 44] 51} 382 AS 25 9 951
OAM Tne eee | 856 SS elSS 46 | 23 | 17 ASG
NQAD ok eo 1, 612 13 {> 107 93 225) 12 1, 919
Ungrazed:? | | | |
LOSSe= Sates 135 17 667 ol | 0 (1) 850
193 Oe eee 273 31 495 58 | 2 (1) 859
BGA see | 570 38 295 101 4 (1) 1, 008
OA eae eae | 949 CE 140 178 5 18 jo ele
19422 c2 tse = [Sale oe Den 73 62 345 4 26 2, 022

|
|

1 Less than 1 Cm
? These areas were fenced in 1938 and thereafter entirely protected from sheep
grazing.

BLUE GRAMA

In 1938, blue grama covered 1 to 2 percent of the ground surface
on the average and composed 12 to 20 percent of the total perennial
vegetative cover. There was a greater density of blue grama on plots
in the heavily stocked pasture at that time than in any of the other
pastures or the ungrazed areas. During the 4 years of grazing, 1938—
41, blue grama density increased through the establishment of new
plants and the enlargement of old ones ‘by 814, 756, and 641 square
centimeters per plot on the ungrazed, lightly, and conservatively
stocked pastures, respectively, but under heavy stocking the increase
was only 607 square centimeters per plot. In the relatively good
rainfall year of 1942, when none of the pastures was grazed, blue grama
made striking density increases on all plots; 502, 690, 756, and 563

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE 23

square centimeters on the average on the heavily, conservatively, and
lightly grazed, and ungrazed plots, respectively.

For the 5 years 1938-42 , the greatest increase, 1,512 square centime-
ters, occurred on the plots under hght stocking. These plots also had
the highest final grama density. The total increase under conservative
stocking was slightly smaller as was final density. On the protected
plots, blue grama density increased 1,377 square centimeters per plot
and the 1942 density was intermediate between the lightly and con-
servatively stocked levels for that year. Under heavy stocking the
increase in blue grama density between 1938 and 1942 was only 1,109
square centimeters per plot. In 1942, when none of the pastures was
grazed, plots on range that had previously been heavily stocked had
the lowest density of all situations.

BLUESTEM WHEATGRASS

The density of bluestem increased each year from 1938 through
1941 under all intensities of stocking and under protection. The
greatest increase over the 4 years, 60 square centimeters per plot,
occurred on the ungrazed areas. Under heavy stocking, the increase
was 23 square centimeters compared with 37 and 52 per plot under
conservative and light stocking. Thus, recovery of this valuable
forage species was directly related to the rate of stocking; least where
erazing use was heaviest, and progressively more through conservative
and light erazing to protection.

In 1942, when rainfall was relatively good, bluestem density actu-
ally decreased on the plots that were conservatively and lightly stocked
even though grazing was not permitted that year. At the same
time, it continued to recover from past grazing use and drought on the
plots that were heavily grazed.

For the 5 years 1938-42, the greatest total increase in bluestem
density occurred on the plots protected from sheep grazing since 1938.
The fact that bluestem density continued to increase on the heavily
erazed plots after grazing ceased but actually declined on areas pre-
viously grazed lighter and protected, illustrates how much heavy
erazing delayed the natural tendency of this range to reach a balance
following a major drought disturbance.

By 1942 the lightly grazed and ungrazed plots had equal densities
of bluestem. Plots on the conservatively erazed area had only two-
thirds as much bluestem density and the heavily grazed plots only
about half as much as those protected and lightly grazed.

LITTLE BLUEGRASS

Largely because of its ability to grow early in spring when moisture
is available and then lie dormant during the dry summer, little blue-
grass increased during and immediately after the drought when later
starting species were losing density. By 1938 it composed 75 to 85
percent of the vegetative cover exclusive of cactus and browse on
plots in the sheep pastures. From 1938 through 1942 it declined
steadily under all three intensities of grazing and even with protection
from sheep grazing. This steady decline just about offset the increase
in density of other perennial species in 1939 under light grazing and
protection and caused a decline in total density under conservative
. and heavy stocking. Under heavy stocking the loss in little bluegrass
density in the 4 years 1938-41 was 91 percent as compared with 86

24. CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

percent on the conservatively grazed pasture, and only 79 percent
with light stocking and protection. By 1942 little bluegrass made up
only 2 to 6 percent of the vegetative cover on the plots.

OTHER PERENNIAL GRASSES AND GRASSLIKE PLANTS

The group of other perennial grasses and grasslike plants, composed
of species such as sand dropseed, needle-and-thread, and threadleaf
sedge, recovered very slowly under all degrees of stocking. Greater

competition from the principal perennial species which were recover-_

ing rapidly under conservative and light stocking retarded recovery
of this group more than did heavy grazing and somewhat less competi-
tion in the small pasture.

By late 1942, the density of this group had just about doubled as
compared with the 1941 level on plots in the areas previously stocked
conservatively and lightly. On the heavily grazed plots the increase
after grazing was slightly more than 50 percent above the 1941 level.
The trend under protection was comparable with that on the conserva-
tively and lightly stocked plots.

PERENNIAL FORBS AND BROWSE

Browse species and perennial forbs, although common on the ex-
perimental range, were very sparse or entirely absent from all plots
in 1938. They increased slowly under all situations throughout the
study but none became important constituents of the plots.

EFFECTS ON NUMBER AND SIZE OF PLANTS

Under average weather and with good grazing management, the
principal clump-forming forage species in the northern Great Plains
are vigorous and well-spaced, but they seldom form a complete cover.
Severe drought in 1934 and 1936 greatly reduced the stand of perennial
forage plants in the northern Great Plains (6) and it is evident from

TABLE 6.—Average number of plants, by species, on 2 by 5 decimeter
plots randomly located in 1942, after 6 years of sheep grazing at various
stocking rates

Con-
, Heavily | serva- | Lightly Un-
Species stocked | tively stocked grazed
stocked
Clump-forming: Number | Number | Number | Number
IB UND Key on zy 00k: Weemmneeth Catia are tAwe) ES 8 i als} 0. 75 0. 81 0. 47
ihreadleatisedse ss. 02 eas as eee 2. 66 Us, US 5. 20 1. 02
bittlesbluegrasss «= ae a= = yee el . 43 aro 1. 19
Needle-and-thread ____=__-.---2-=- . 16 68 . 41 gal.
PROG AVES 2 pel es 2 RPS say ae eae ee 4, 71 9. 59 6. 79 2. 80
Single stem:
Blwestemawheaterass == eee 8. 73 8. 19 13. 82 21. 36
Dhireadleat sed gess 23 3a 20. a een . 87 . 40 . 24 2. 93
A ter ae Bes yoo nee tee, See 9. 60 8. 59 14. 06 24. 29
AUT UAC SHE CLES ee eee eee ee en 64, 74 13. 65 34. 17 67. 53

“pln tae eee a ee

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE 25

the vegetative-density record in table 5 that the stand was still at a
low level in 1938.

In 1942, the first season after grazing was terminated in the pastures,
and following the good growing season of 1941, there were fewer plants
of the 4 major clump-forming species per unit of area on the heavily
stocked range than on the other grazed areas (table 6). Collectively,
blue grama, threadleaf sedge, little bluegrass, and needle-and-thread
averaged about 10 and 7 plants per plot on the conservatively and
lightly stocked pastures but only about 5 plants on the area heavily
stocked. Also, the average size of plants of these 4 clump-forming
species was less per plot under heavy stocking than under conservative
or light (table 7). On plots ungrazed after early 1938, the plants of
these 4 species combined were the fewest in number and the smallest
in size of those in all situations.

TABLE 7.—Average area of plants, by species, on 2 by 5 decimeter plots
randomly located in 1942, after 6 years of sheep grazing at various
stocking rates

Con-
: Heavily | serva- | Lightly Un-
Species stocked | tively | stocked | grazed
| stocked

Cm2 Cm.2 Cm.2 Cm.2

LEAS (Giera tit poe ae Sa eS eee ee en 11. 97 12. 30 12. 47 on
iiTReAeaTeNCOU Rs. 2 aS ee ee 2. 21 1. 62 ie yea 2a
LLTES {lel Of Cover ea hSTS TR Sean hg ane ae ama ee 1. 53 1. 33 1. 66 1. 89
Meedic-and-thread—_ =) See ee Bgl 5. 16 7. 30 6. 56

LOGUE ak Bae Fo ad a ee ee 18. 82 20. 41 23. 14 18. 09

BLUE GRAMA

Individual plants of blue grama were more numerous in 1942 on
heavily stocked range than on conservatively and lightly stocked
range by 57 and 46 percent, respectively (table 6). The areas pro-
tected from sheep grazing from 1938 to the end of the experiment had
fewer blue grama plants than any of the grazed pastures. Although
most numerous on plots heavily grazed, the plants were slightly
smaller than those on lighter grazed plots (table 7). The closer
erazing and more severe trampling associated with heavy stocking
prevented small blue grama mats from merging into compact clumps.
Heavy stocking also apparently retarded the enlargement of indi-
vidual established clumps of blue grama. On protected areas both
numbers and size of blue grama plants were restricted by competition
with other species for soil moisture and nutrients.

THREADLEAF SEDGE

In 1942 the pasture heavily stocked previously had less than three
plants or clumps of threadleaf sedge per plot in comparison with
nearly eight for the conservatively stocked and five for the lightly
stocked (table 6). Even though the plants were slightly larger on the
area heavily stocked than elsewhere (table 7), this difference was
sufficient to account in part for the 1942 plot densities summarized in
table 5. Since threadleaf sedge plants were less numerous but slightly

26 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

larger on the heavily stocked pasture than elsewhere in 1942, after 6
years of sheep grazing, heavy stocking evidently had such effects as
killing the small plants that survived the drought or preventing the
establishment of new plants following the drought. The important
point is that threadleaf sedge was only about half as abundant on the
small pasture after 6 years of heavy stocking as on other pastures
stocked more lightly. On the area protected after early 1938, the
plants were intermediate in size between those on heavily and con-
servatively stocked range but were very sparse.

NEEDLE-AND-THREAD

Needle-and-thread grass, another important clump-forming species
and one of the most sensitive to grazing, was by 1942 very sparse in
the heavily stocked pasture. Plants on the sample plots averaged
only about one-fourth and one-half as numerous, respectively, as on
the conservatively and lightly stocked pastures (table 6). Besides
being much less numerous, needle-and-thread clumps were less than
half as large on the heavily stocked pasture as in the lightly stocked
and unstocked areas (table 7). The plants were somewhat smaller
on the conservatively stocked than on the protected and lightly
grazed areas but still considerably larger than under heavy stocking.
Heavy grazing and trampling retarded the recovery from drought
of surviving needle-and-thread plants and limited the establishment
of new plants from seed. These findings strengthen the plot-den-
sity data and help explain the sparser stand of vegetation on the
heavily stocked pasture.

. BLUESTEM WHEATGRASS

In 1942 there was nearly twice as many stems of bluestem per plot
on the lightly stocked range and more than twice as many on areas
protected since 1938 as on the heavily stocked. There was little differ-
ence in the stand of bluestem on conservatively and heavily stocked
areas. Because of its single-stemmed growth habit, bluestem does
not form a sod but by means of underground rootstocks increases
rapidly in the stand when relieved from grazing. The large number of
stems per plot on the lightly stocked and protected areas undoubtedly
helps to account for the greater total density on these areas in 1942.

ALL ANNUAL SPECIES

Low-value annual species such as woolly Indianwheat and sixweeks
fescue were five and two times more abundant in the heavily stocked
pasture by 1942 than in the other two grazed pastures, respectively
(table 6). By retarding the recovery of palatable perennial species,
heavy stocking permitted an increase in annual species (fig. 10) which
at best are only temporary and provide a limited amount of forage.

EFFECTS ON HEIGHT GROWTH OF BLUE GRAMA AND BLUESTEM
WHEATGRASS

Height growth of blue grama leaves and seedstalks was greater in
1942 on the conservatively stocked pasture by 22 and 3 percent,
respectively, than on the heavily stocked pasture (table 8). On the
protected areas the leaves and seedstalks were 55 and 10 percent taller
than on areas stocked heavily during 6 previous years. The propor-

eee ee ee ee

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE 27

F-415227

FicurE 10.—Six years of heavy sheep grazing and trampling changed the vege-
tative composition of typical northern Great Plains range to a dense stand of
low-value annual plants mostly woolly Indianwheat except in the protection
of pricklypear clumps.

tion of plants producing seedstalks was very similar in the ungrazed
areas and the conservatively stocked pasture. In the heavily stocked
pasture, however, about 10 percent more of the plants produced seed
stalks than in the conservatively stocked pasture and 5 percent more
than in the ungrazed areas. Although heavy stocking retarded
height growth, it stimulated the production of seedstalks in blue

TABLE 8.—Average maximum length of leaves and height of seedstalks,
and proportion of plants that produced seedstalks, by rate of stocking
and species, 1942

: Plants
. . Length | Height of a
Stocking rate and species ‘ ane with
of leaves | seedstalks seadsuallea
Heavy: Cm. Cm. Percent
Peers Ora iy Staeen. 0 8 Ee 9 30 91
Piueastem wheaterass. 2. 2 -=-L 2. 28 56 17
Conservative:
BRreeeNa ee: Mal. Net ie ns NEOs i Lt 31 83
imestem-wheaterass_ ..-_..-.-=22-.2- 30 60 13
Ungrazed:
Pere EDITED = sen eee ek Ce 14 33 87
iwestem. wheatgrass... <__--...----..- 35 61 15

28 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

erama. It is not inferred that greater seedstalk production as a
result of heavy stocking means greater production of viable seed.
Although data are not available, heavy grazing may have actually
reduced the quantity of good seed produced even though more seed-
stalks appeared on the heavily than on lighter stocked areas.

Leaves of bluestem grew tailer on the conservatively stocked pas-
ture and the ungrazed areas in 1942 by 7 and 25 percent, respectively,
than on the heavily stocked pasture, and seedstalks were 7 and 9
percent taller (table 8). However, the plants on the heavily stocked
pasture produced more seedstalks that year by 31 and 13 percent
than plants on the conservatively stocked and ungrazed areas. Thus,
as with blue grama, heavy stocking retarded the height growth but
stimulated seedstalk production. Again, however, the effect on pro-
duction of viable seed is not known, but heavy stocking may well
have caused the production to decline.

EFrFrects ON HERBAGE PRODUCTION

Where intensive use of range vegetation retards its recovery from
drought, the result is less herbage production, less usable forage, and
lower grazing capacity.

Taste 9.—Production of air-dry herbage per acre and estimated usable
forage per acre* under various stocking rates, by species, 1942

}
|

: Conserva- .
Heavily Lightly
$ tively 2S Ungrazed
stocked stocked stocked
Species = rs "8 “=
© =a 2) a © = 2 © aes
= = 6 OQ |-60 = = 6 2 |-=6
® ‘ws @= ea eso a S ass
oy ea cr is) a0 SS ry je)
Perennial grasses: | Lbs. | Lbs. | Lbs. | Lbs. | Lbs. | Lbs. | Lbs. | Lbs.
Blucwrama os 1232s | 149 66 250 @ | 279 |--59 |: Sts) is
Bluestem wheatgrass_| 110 50 245 49°| 445. | 98-)" i5acbeetcee
Threadleaf sedge_____| 124 | 43 | 365 | 69| 204 | 24) 39 7
Other perennial |
STASSESt eee | = “875| 52) 1983-419 109 65 108 65
opie eee cS Cee | 470 | 211 |1, 058 | 310 |1, 037 |'246 [1,315 | 352
Perennial forbs" — 2-2 < 143 29 94 | 19 93 19 40 8
STO WSe Sees Ae ee (2) =|) 50e=5 te] 2@). le S45 2 33 2
Potash es 613 | 240 |1, 153 | 329 |1, 175 | 267 |1,388 | 362
PRTERTU AIS 28 Oo we Set 815 | 163 79 16 306 | 61) 437) 87

Total, all species_________ 1,428 | 403 |1, 232 | 345 1, 481 | 328 |1,825 | 449

'

1 Estimates of usable forage for blue grama, bluestem, and threadleaf sedge
derived by applying utilization figures in table 4 to pounds of air-dry herbage per
acre. For other species the following factors were used for all stocking intensities:
other perennial grasses, 60 percent; perennial forbs, 20 percent; browse, 5 percent;
annuals, 20 percent.

2 Less than 1 pound.

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE 29

Not all herbage, even of the most palatable species, can be con-
sidered as usable for age. Of the many factors involved, the necessity
of leaving considerable herbage to protect the soil and insure regr owth
of the range vegetation is most important. Since grazing capacity is
based only on herbage that should properly be used instead of total
herbage produced, a conversion is necessary. To make this conver-
sion, total pounds of air-dry herbage for each key species were weighted
by the aver age percentage grazing use obtained during 3 years (table 4,
p. 13) in the sheep pastures under each intensity of stocking. For

other species or groups of species for which average use per centages
were not available, weighting was done by applying estimated factors
for all areas regardless of degree of stocking. These data (table 9)
indicate the proportionate part of total herbage that was considered
to be usable forage on the differently stocked areas.

In 1942, when the pastures were not grazed, the pasture that had
been heavily stocked for 6 years pr oduced less perennial-type herbage
per acre, based on samples hand-clipped to a 1-centimeter stubble,
than either of the other pastures (table 9). Even when the yields of
blue grama, bluestem, and threadleaf sedge were mathematically
converted into usable forage, the advantage was still with the con-
servative and light stocking rates. With the addition of annual-type
herbage, however, the area that was heavily stocked showed greater
production in total herbage than the conservative and in usable forage
than all but the ungrazed area. The fact that the annual type forage
is nutritious only when lush and green and that it dries and weathers
away quickly, offsets any advantage the greater quantity might
appear to have. Year-long sheep operations in the northern Great

F-415238

Figure 11.—Six years of conservative sheep grazing did not materially change
this typical northern Great Plains range. Palatable perennial grasses are
abundant but low-value annuals very inconspicuous.

30 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

Plains are dependent upon adequate range forage at all seasons. The
perennial species, which in 1942 produced more herbage and more
usable forage on areas that had been conservatively and lightly stocked
than on the heavier stocked pasture, are the only ones that can be
depended upon to provide forage at all seasons of the year (fig. 11).

Individual perennial species show in general the same comparisons
as the entire group of perennial plants. The lower production both of
herbage and usable forage for all perennial species on the heavily
stocked area confirms the lower density, smaller size, and shorter
height growth of plants already mentioned as evidence that heavy
stocking retarded recovery.

EFFECTS ON THE SOIL

Heavy stocking removed too much herbage from the range and
reduced the accumulation of litter on the soil surface, thereby exposing’
the soil surface to washing and blowing. Trampling on these barren,
unlittered surfaces lossened the topsoil for easy removal by the wind
and exposed the roots of the plants. On flat or level sites, some of the
most persistent plants survived on pedestals a few inches higher than
the surrounding surfaces.

On slopes in the sandy loam soil type, heavy grazing and trampling
loosened the soil and coarser subsoil materials which were moved down
the slopes by gravity (fig. 12, A). Under conservative and light
stocking there was little evidence of accelerated erosion or soil move-
ment due to grazing even on the steepest slopes (fig. 12, B).

EFFECTS ON THE SHEEP

Heavy stocking affected the grazing habits of yearling ewes by
forcing them to return to areas already too heavily grazed more often
than they naturally would have done. This caused extremely heavy
use on certain areas because there were fewer favored places to return
to in the smaller pasture. Also, with less forage in the heavily stocked
area, the yearling ewes necessarily spent considerably more time
searching for forage than those on conservatively and lightly stocked
range. Seasonal gains in weight averaged 32 and 33 pounds per head
on the conservatively and lightly stocked ranges, and 31 pounds on the
heavily stocked range. These differences were statistically significant
when corrected for age and initial weight of the ewes.

At the start of the grazing season the yearling ewes weighed from
70 to 77 pounds. Carry-over forage, together with a little green
growth, was sufficient in all pastures to permit some gain during the
first few weeks of each season, beginning in late March. This carry-
over was confined to limited areas on the heavily stocked pasture but
was available over most of the conservatively and lightly stocked
pastures. An apparent loss of weight occurred at shearing time,
usually during the third 28-day period, but this was followed by
another period of rapid gain (table 10). By midsummer the choice
forage was usually gone from the heavily stocked range and the
yearling ewes gained less rapidly than earlier. The weight trends for
the sheep grazed at the heavy intensity were similar to the trends for
the others, but the tendency to lag at a somewhat lighter weight after
midseason was noticeable. Weight gains usually continued with

a ——

—

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE 4

F-415231, 41524

FicureE 12.—A, This bank and talus deposit in the head of a small drainage
in the sandy loam soil type resulted from too heavy grazing and trampling.
B, Natural erosion, though evident on this steep heavy clay soil, was not
noticeably accelerated by grazing and trampling under conservative stocking.

some variations until late August or early September. After this
date, a period of leveling off or even of slight decline in weight extended
largely throughout September, but when there was ample green fall
growth after late September or October rains, a noticeable gain
occurred in all lots through late October or early November. Average
final weights ranged from 101 to 109 pounds during the 5 years.

CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

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STOCKING NORTHERN GREAT PLAINS SHEEP RANGE 33

DEGREE OF FORAGE USE RECOMMENDED FOR
NORTHERN GREAT PLAINS SHEEP RANGE

The degree of forage use obtained on a range during a given grazing
period is directly affected by the rate of stoc ‘king. However “forage
use may also be influenced by such factors as weather and poor
distribution of livestock. Estimates of degree of use are valuable as
checks on the rate of stocking and provide a basis for adjusting it along
with other management practices.

The conservatively stocked pasture showed the best balance between
forage utilization and sheep weights. The estimates obtained there-
from for bluestem wheatgrass, blue grama, and threadleaf sedge
(table 4, p. 13) are considered a reliable basis for recommended rates
of forage use.

Because of its fine texture and generally high palatability, blue

erama was grazed to lower stubbles than any other species. A larger
percentage of the herbage of this species was removed under conserva-
tive stocking than of either bluestem or threadleaf sedge. Not more
than 29 percent of the herbage of blue grama should be removed by
erazing on a properly stocked sheep range comparable to the experi-
mental range. Such use results from grazing 45 percent of the total
number of individual plants to an average stubble of 0.6 inch (1.6
centimeters). Costello (4) recommends a 1%-inch stubble for blue
grama on properly grazed cattle ranges in Colorado, where this species
grows taller, is more abundant, and | composes a oreater percentage of
the vegetative composition than in the northern ‘Great Plains.

In accordance with the utilization obtained under conservative
stocking Walle 4), bluestem should not be grazed to an average stubble
shorter than 2) inches, and not more than 35 percent of the plants
should be orazed for proper use on northern Great Plains sheep range.
Such use removes about 20 percent of the herbage produced.

For threadleaf sedge, grazed stubbles should average about 0.8 inch.
The percentage of individual plants grazed should not exceed 33 to 35
percent. This degree of grazing removes 19 to 20 percent of the
herbage.

To insure that all parts of a range similar to the experimental area
are conservatively grazed in accordance with these recommended
euides, a definite seasonal plan of use should be followed. Growth,
development, and seasonal palatability of range forage, and _ the
erazing habits of sheep indicate that each portion of the range, accord-
ing to topography, soil, and composition of the A aga can be
erazed to the best advantage at a certain season of the year. The first
grazing in March or sometimes earlier should be confined a the areas
having moderately steep topography and sandy or gravelly loam soils
where bluebunch wheatgrass and other coarse species provide ample
old forage from the previous year’s crop. Seldom is the carry-over
herbage entirely unavailable because of snow.

With the coming of new growth there is a natural movement of the
sheep to the rolling areas having sandy clay loam soils where a variety
of perennial grasses pr edominate. Less important species contribute
a great deal to the summer forage and plans should provide for
utilizing them to the best possible advantage. Flood plains or bottom
areas along the main drainages are also most useful during summer
Their heavy soils are only slich tly disturbed by trampling during the
dry summer and the bluestem and buffalograss are then green and

34 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

more palatable than they are later. These species, plus the blue
grama and the many forbs of the rolling areas, should carry the burden
of grazing until late fall, when storms encourage movement to the
rough hills for browse and coarse grass forage as well as the protection
such areas afford. Range areas especially adapted to grazing during
critical winter or early spring periods should be reserved throughout
the summer and early fall in order to have them in good condition
when urgently needed. Some variation from this plan of seasonal
use may be necessary to obtain the use of all areas to the best ad-
vantage on individual ranges.

Conservative stocking, frequent utilization checks, and regulated
seasonal grazing will not insure phenomenal success in range sheep
production or wholly eliminate the risks incident to a drought, but
they will stabilize operations over a long period of time and help to
perpetuate the range resources.

RECOMMENDED STOCKING RATE FOR NORTHERN
GREAT PLAINS SHEEP RANGE DURING AVERAGE
8- to 9-MONTH SEASON

Rate of stocking, the relative intensity of animals on a range, is
usually expressed as the number of acres of range allowed for each
animal for a specific period. It may also be expressed in numbers of
livestock per section (643 acres) of range for the period. Range
managers find such numerical expressions useful, but recognize that at
best they are only guides to grazing capacity on comparable ranges.
Such a guide must be checked against results of stocking on a given
range and changes made as required to avoid stocking too heavily
for safety or too lightly for best results in the long run.

During the 6 years of the grazing experiment, 1936-41, the stocking
was increased each year after 1936 (table 1, p. 4, and fig. 13) in all
pastures as the range recovered from drought. This was accom-
plished in 1937 by lengthening the grazing season and in 1938 to 1941
by annual increases in the number of sheep grazed, which brought
corresponding reductions in acreage per head. Precipitation in-
creased materially each year, except 1939, during the period (fig. 13).
With the favorable weather forage production increased also, as
judged by the amount of unused forage left on the ground at the
end of each grazing season.

In 1941, the last year of the test, when the range had recovered
somewhat from drought and weather was quite favorable for growth,
the middle-sized pasture was stocked at the rate of 0.56 surface acre
per month per yearling ewe.

A margin of safety in allotting range forage is essential because dry
or drought years of low forage production often occur. If there is no
such margin or reserve of forage, abnormal expense for supplemental
feed or heavy liquidation may be necessary in order to avoid disastrous
sheep losses. Although no supplemental feeding was done in the
experiment, it would have been required in the heavily grazed pasture
had the sheep been left on the range any longer each season. The
quantity, cost, and availability of supplemental feed reserves to meet
such emergencies on a ranch should be considered in determining the
additional range area needed to assure stability and safety for the
range operator. ‘Twenty percent of additional range is the recom-

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE 35

mended minimum that should be allowed to meet the ever present
risk of unfavorable weather.

On this basis, 0.56 surface acre per yearling ewe per month, the
average allowance under conservative stocking during 1941, plus the
20 percent margin, amounts to 0.67 acre per yearling ewe month.
Thus about 5.4 acres is considered the minimum acreage for a dry
yearling ewe on good northern plains range similar to the experi-
mental range during a relatively favorable season of 8 months begin-
ning in March.

3

Precipitation

ine)

Stocking:
\ Heavy al
a

tae Moderate

STOCKING (SHEEP-MONTHS PER SURFACE ACRE)
ANNUAL PRECIPITATION (INCHES)

O O

1936 1937 1938 1939 1940 1941

Ficure 13.—Total annual precipitation was increasingly favorable each year after
1936, except in 1939, and stocking was increased accordingly in all pastures.

SUMMARY

The northern Great Plains constitute one of the most important
range areas in the United States for the production of wool, feeder
lambs, and replacement breeding ewes. In this region, the major
range problem confronting sheep ranchers is how to stock their range
(1) to get the greatest possible production year after year without
deteriorating the forage and soil and (2) to permit recovery from
drought within a reasonable time.

To obtain guides to proper stocking of northern Great Plains range,
the Northern . Rocky Mountain For est and Range Experiment Station,
in cooperation with the Bureau of Animal Industry and the Montana
State Agricultural Experiment Station conducted a study of sheep
grazing near Miles City, Mont., from 1936 to 1941. Three range
pastures, having areas of 332, 476, and 847 acres, were established and
stocked each year with equal numbers of yearling Rambouillet ewes
to maintain three relative intensities of grazing. Studies of density,
composition, and herbage production of the vegetation, plus surveys

36 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

of utilization, periodic weights of the sheep, and observations of their
grazing habits formed a basis for evaluating the three rates of stocking.

Many combinations of soil and topography, each characterized by
certain range plant species, are found in the northern Great Plains.
Only four of the major situations were well represented on the experi-
mental range. The rolling areas of sandy clay loam soils are generally
occupied by blue grama, bluestem wheatgrass, other less important
grasses, a few herbs, and some big sagebrush. Rougher areas having ©
sandy to gravelly loam soils and characterized largely by bunch-
forming grasses make up a considerable part of the range. Bottom
areas are usually level or gently sloping, have heavy clay soils, and
are largely given to bluestem, buffalograss, and silver sagebrush. The
roughest portions are sometimes called badlands. The soil is heavy
and alkaline and the topography rough and broken. A variety of
browse species and a few hardy grasses and forbs compose a scanty
cover on these areas.

Herbage production occurs largely during the main growing season,
April through September, coincident with about 70 percent of the
average annual rainfall. Spring growth begins generally in late
March or early April and is completed on the average by late July
or early August. During favorable years some additional herbage
may be produced in early fall by a few species that resume growth
following August or early September rains.

Although the northern Great Plains range supports a wide variety
of native plants, most of the forage is provided by about 25 of the
most palatable species. The palatability and forage value of these
as well as other species varies with season of the year, stage of develop-
ment, and composition in the stand. On the experimental range all
species were most palatable when the plants were fresh and succulent
early in the growing season. Changes in forage value and palatability
during the grazing season affected its utilization by the sheep.
Greater utilization of the key species, blue grama, bluestem, and
threadleaf sedge, which resulted under heavy stocking as compared
to conservative and light stocking, was due to a higher percentage of
the total number of individual plants grazed rather than to lower
grazed stubble heights.

The principal activities of the yearling ewes were grazing, bedding,
resting, and fighting insects. Grazing was accomplished largely
during daylight hours except in midsummer when insects and high
temperatures induced shading up. Under these conditions the year-
ling ewes frequently fed at night, alternating short periods of grazing
with frequent brief rest periods. During cool seasons and when
insects were not prevalent, the yearling ewes bedded throughout the
night, usually near a fence or other obstruction. Watering habits
were very irregular and salt was regularly used only when placed near
a watering place. When salt was placed away from water in ap_
attempt to aid distribution, the unherded sheep seldom found it.

Natural factors such as wind and temperature affected the yearling
ewes. ‘Their movements showed a strong relation to wind direction.
Both extremely high and low temperatures tended to restrict their
movements. The pasture fences affected the movements of yearling
ewes. This resulted in heavy grazing use near the fences and pro-
eressively lighter use at increasing distances from them. Predators
disrupted their activities and caused many actual losses in addition
to unmeasured losses in weight gain and general welfare.

4
:
4

wer ae

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE oe

Important range plants and the vegetation as a whole were con-
siderably affected by heavy stocking with sheep for 6 years, as com-
pared with conservative and light stocking. Recovery of vegetation
from drought levels was retarded, and there was much less increase in
total vegetation density. Although blue grama plants were more
numerous, they were smaller in size at the close of the experiment.
Both the number and size of needle-and-thread plants were decreased.
Bluestem wheatgrass also became less abundant, and showed reduced
height growth. Low-value annuals, on the other hand, increased
manyfold.

Because of the high proportion of annuals growing in the heavily
stocked pasture in 1942, the total production per acre of range herbage,
clipped to a centimeter stubble, was actually larger than in other
pastures. This was not a real advantage, however, since at best
annual plants are low in palatability and cannot be depended upon
to provide forage for several months each year. The dependable
perennial species, mostly grasses, produced considerably more herbage
on the conservatively and lightly stocked range. Converted to usable
forage by applying the percentage of utilization resulting from con-
servative stocking, production still favored conservative over heavy
stocking. The comparative weights of annual- and perennial-type
herbage plus the greater number of annual plants present at the close
of the experiment indicate that 6 years of heavy stocking with sheep
caused the composition of the range vegetation to shift from a pre-
dominance of perennials to a predominance of low-value annual spe-
cies. Some movement of topsoil, particularly on the slopes, occurred
under heavy stocking.

On heavily stocked range, the yearling ewes gained significantly
less weight during the average grazing season than those on conserva-
tively and lightly stocked range. Average seasonal gains over a
5-year period were 31, 32, and 33 pounds, respectively. Up to mid-
summer, the difference in gain between lots on differently stocked
range was hardly noticeable, but throughout late summer and fall
the ewes on heavily stocked range lagged badly in weight gains.
Starting weights ranged from 70 to 77 pounds and final weights from
101 to 109 pounds on the average.

A minimum of 0.67 surface acre of range, similar to the experi-
mental range, per month or 5.4 acres for an 8-month season begin-
ning in March is recommended for normal development and main-
tenance of a dry yearling ewe. This rate of stocking will also allow
some improvement in the range vegetation and provide for a desirable
carry-over of unused forage at the end of each grazing season. Utiliza-
tion of the range should be gaged by the percentage of plants grazed
and average stubble heights to which certain key species are taken
by sheep. Sheep range similar to that studied should be considered
properly used when the three key species, blue grama, bluestem, and
threadleaf sedge, are grazed rather uniformly over the range in accord-
ance with the utilization guides given in this publication. The
guides include a measure of safety against a low forage crop during
drought and do not take into account possible regrowth of herbage
after grazing.

In addition to conservative stocking and uniform, proper utiliza-
tion of key forage species, use of the range in accordance with a
seasonal plan lends stability to range-liv estock operations and aids
in minimizing the risks due to drought.

38 CIRCULAR 804, U. S. DEPARTMENT OF AGRICULTURE

COMMON AND BOTANICAL NAMES OF SPECIES
| -MENTIONED

GRASSES AND GRASSLIKE PLANTS
Bluegrass, Sandberg (syn. little blue- Poa secunda

grass).
iButtalograssse 2s 22 ete es epee Buchloe dactyloides
Dropseed, sand steed eS ee ae ee Sporobolus cryptandrus
IeScuersixweeks: so = ees Sees Festuca octoflora
Grama blues. === Best ca tae sil Be eee Boutelowa gracilis
Gramariside-oats-4 9 == 62s ae ee B. curtipendula
Muhihy.stomyhillssea 252s eee Muhlenbergia cuspidata
Needle-and-thread_________________ Stipa comata
Needlegrass, green________________-_ S. viridula
Sacaton, alkalines se. Sasa eee Sporobolus atroides
bedge. threadleatiy ss) os ia Carex filifolia
Wihteaterass'sblueste nis = ass ssaete eee Agropyron smithat
Wheatgrass, bearded bluebunch_____ A. spicatum

HERBACEOUS PLANTS
INCOSerISM pales = fie we Les Be Bonne Agoseris glauca
IBISCUICTOOU fee ee ee ee ee Cogswellia sp.
CAMO CERUS pes eee eet ee eee Cymopterus sp.
Gaura scariest 23 Usain ar ees ee Gaura coccinea
GlobemallowAscarlet= 322" aa Sphaeralcea coccinea
Goldasterchainyet == 2 a ee: Chrysopsis villosa
incianwheat. woolly. 992-55 =o oes Plantago purshu
WiCOniCe= Se atk oD ee ae eee ane Glycyrrhiza sp.
DE Ufo 114 @ etn Rt ee ee Lupinus sp.
Wiaripo sas = ois she 2a aun aes Calochortus sp.
IMnISTIA CO Ties 2 al eee Pe eee Musineon sp.
Onion textile. ae ae ew ee ee Allium textile
RhloOx dwarkassee staal See ere Phlox sp.
Prairie clover pUnple zw. = sseea= seas Petalostemum purpureum
Prairieclover, slender white_________ P. oligophyllum
IPTIMMROSE Ke Vie MUS eis eee ea re Oenothera sp.
Sunflower, prainiess: a=) ee ee Helianthus petiolaris
BROWSE PLANTS

Chokecherry- black 3a ssa ee Prunus virginiana melanocar pa
Greasewood! (blacks =a. 2 aa oa Sarcobatus vermiculatus
Prickly pear plains] 26. 8 !se. eso. Opuntia polyacantha
Rabbitbrush, greenplume____—-____-_ Chrysothamnus graveolens
Rose Hendler 22222 oe nee ae ___ Rosa woodsi fendlert (syn. R. fendlerz)
OEVEXE) OP ADIS) ols OYUN awe es ee ee SS Artemisia tridentata
SENS OAS oly MANNE a Be A. frigida
Sagebrush, silver -- __- eS Ye pet ae A. cana
SalitioushiaGarcdineiess =. oe sie Atriplex gardneri
Salitioush shia ds calle epee see) ae eee ee A. confertifolia
Noapweed scmlalileesse ee eee es eae Yucca glauca
Sues keumalkcto ic ines eee ee ee = Rhus trilobata

WanGerfat Common: 2] ssi caue neers Eurotia lanata

(1)

(2)

(8)

(9)

STOCKING NORTHERN GREAT PLAINS SHEEP RANGE 39

LITERATURE CITED

ALLRED, B. W.
1945. SOME CONDITIONS AND INFLUENCES PERTAINING TO THE NATIVE
FORAGE CROP OF THE NORTHERN MIXED PRAIRIE. Amer. Soc.
Agron. Jour. 37: 876-887, illus.
BiIpwe Lt, G. L., anv Wooton, E. O.
1925. SALTBUSHES AND THEIR ALLIES IN THE UNITED STATES. U.S. Dept.
Agr. Bul. 1345, 40 pp., illus.
Couuins, Ropert W., AND Hurtt, Leon C.
1943. A METHOD FOR MEASURING UTILIZATION OF BLUESTEM WHEATGRASS
ON EXPERIMENTAL RANGE PASTURES. Ecology 24: 122-125, illus.
CosTELLo, Davin F.
1942. MAINTAINING SHORT-GRASS RANGES. Colo. Agr. Col. Ext. Bul.
D-—33, 11 pp., illus.
Doran, C. W., anp Cassapy, J. T.
1944. MANAGEMENT OF SHEEP ON RANGE INFESTED WITH ORANGE SNEEZE-
WEED. U.S. Dept. Agr. Cir. 691, 28 pp., illus.
Exuison, LINcoLN, AND WoOoLFOLK, E. J.
1937. EFFECTS OF DROUGHT ON VEGETATION NEAR MILES CITY, MONTANA.
Ecology 18: 329-336, illus.
JARDINE, J. T.
1910. THE PASTURAGE SYSTEM FOR HANDLING RANGE SHEEP. U.S. Dept.
Agr., Forest Serv. Cir. 178, 40 pp., illus.
AND ANDERSON, MARK
1919. RANGE MANAGEMENT ON THE NATIONAL FORESTS. U.S. Dept. Agr.
Bul. 790, 98 pp., illus.
WEAVER, JOHN E., AND CLEMENTS, FREDERICK E.
1938. PLANT EcoLOGY. Ed. 2, 601 pp., illus. New York and London.

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