Grazing Intensity Research in the Missouri Coteau of North Dakota

B. Patton, P. Nyren, B. Kreft, and A. Nyren,

 



Contents


Introduction

Livestock Response

Forage Production and Utilization Treatment Effects

Soil Water and Forage Production

Forage Quality

Plant Community Dynamics

Recommendations

Future Research




Introduction


A grazing intensity research project was initiated at the CGREC in 1989. The objectives are to determine the effect of grazing intensity on livestock performance and profitability and its effect on the sustainability of forage production. Five treatments are included: no grazing, light, moderate, heavy and extreme grazing. Each treatment is replicated three times in pastures of about 30 acres each except that the no grazing treatment consists of six 0.3-acre exclosures, placed on both overflow and silty range sites. Livestock are not rotated between pastures and each pasture receives the same treatment each year. We try to stock the pastures each year so that when the cattle are removed in the fall, 65%, 50%, 35% and 20% of the forage produced in an average year is remaining on the light, moderate, heavy and extreme treatments respectively. For these pastures that means 2,063 lbs/ac., 1,623 lbs/ac., 942 lbs/ac. and 484 lbs/ac. of forage remaining on the light, moderate, heavy and extreme pastures respectively. Table 1 presents the stocking history of the study and figure1 shows how much forage was remaining at the end of the grazing season each year. Adjustments in stocking pressure are made each year based on information from previous years to better match our desired grazing intensities. Changes in the vegetation are determined by monitoring permanent plots located on silty and overflow range sites in each pasture and the six exclosures. Table 2 gives the average production on these range sites during each year of the study and the total precipitation for the year.



Table 1. Stocking history of the grazing intensity trial.

Year

Class of Animal

Date

Stocked

Date

Removed

Length of

Season

(days)

1989

Steers

May 22

August 22

92

1990

Bred Heifers

May 30

November 27

181

1991

Bred Heifers

May 29

September 25

119

1992

Bred Heifers

June 1

August 25

  85

1993

Bred Heifers

May 29

September 26

120

1994

Open Heifers & Steers

May 17

November 10

177

1995

Open Heifers

May 18

October 30

165

1996

Open Heifers

May 20

September 23

126

1997

Open Heifers

May 27

November 5

(August 27, extreme)1

162

(92, extreme)

1998

Open Heifers

May 16

October 28

165

1999

Open Heifers

May 27

November 4

161

2000

Open Heifers

May 18

September 25

130

2001

Open Heifers

May 21

September 11

113

2002

Open Heifers

May 23

July 17

55

1Livestock were removed early on the extreme treatment due to a lack of forage.



Table 2. Total crop year precipitation (October 1 to September 30) and peak total above ground biomass production on overflow and silty range sites on the grazing intensity study from 1989 to 2002.

Year

Precipitation

(in)

Above Ground Biomass (lbs/acre)

Overflow

Silty

1989

18.40

3,863

2,089

1990

16.10

3,847

2,962

1991

12.89

3,142

2,629

1992

15.25

2,758

2,065

1993

26.59

3,999

3,446

1994

16.86

4,201

2,803

1995

22.60

4,773

3,134

1996

20.55

3,837

2,645

1997

18.63

3,351

2,376

1998

18.91

3,334

2,855

1999

26.91

4,338

3,152

2000

15.60

3,950

2,846

2001

18.44

3,569

2,678

2002

16.69

1,850

1,175

14-Year Average

18.89

3,629

2,633



Livestock Response


        Table 3 shows the average daily gain, gain per acre and body condition scores from the different grazing intensities for the last five years, average gains by treatment from 1991 to 2002 and average body condition from 1994 to 2002. Grazing pressure was too light on the heavy and extreme treatments in the first two years of the study so there are no significant differences in average daily gains in 1989 and 1990. Following that year average daily gain and animal body condition scores decrease with increasing grazing intensity. The rate at which average daily gain decreases with an increase in stocking rate varies greatly from year to year. The differences between years may be due to variation in forage quality or quantity, the effect of weather on the animals, their initial weight, or their potential to gain.


        The past two years were unusual. In 2001 precipitation was well above average in June and July and well below average in August and September. This reduced the quantity of forage produced but in these situations the forage often cures at a higher quality. 2002 was very dry in May and June and forage production was the least of any year (table 2). The lack of forage forced us to remove the cattle on September 11, 2001 and on July 17, 2002, the earliest they had come off since 1992 (see table 1). The theory that forage quality was higher than average is supported by the fact that there was no significant difference in animal body condition scores between treatments, the first time this has occurred since 1995 (condition scores for cattle on the extreme treatment were not available in 1997). It was also observed that the quality of animals stocked on the study in 2001 was better than usual. They were not as wild and they fed better. The cattle probably gain well on all treatments at the beginning of the grazing season and reduce their rate of gain on the heavy treatments as forage quantity becomes limiting. In years when the grazing season ends early as in 2000 to 2002 there is less chance for the differences in rate of gain between the light and extreme treatments to become significant. If all years are pooled together the relationship between rate of gain and stocking rate has an R2 of 0.40, which means that stocking rate explains 40% of the variation in average daily gain between pastures. When only one year is considered at a time the R2 varies between 0.45 and 0.98, with the 0.45 coming from 2001. The next lowest was 2002 with an R2 of 0.48, and third was 1993 with an R2 of 0.59. Therefore ignoring 2001 and 2002, between 59% and 98% of variation in average daily gain is a result of the difference in stocking rate. The relationships between stocking rate and average daily gain are illustrated in figure 2. Reference lines indicate the average stocking rates for each of the four grazing treatments.



Table 3. Average daily gains, gains per acre, and condition scores from different stocking intensities.

 

Desired

Grazing

Intensity

Average Daily Gains (lbs/head/day)

1998 1999 2000 2001 2002 Average

1991-2002

Light 1.53a1 1.40a 1.12 1.44 1.34 1.39a
Moderate 1.31ab 1.30a 0.967 1.29 1.47 1.27a
Heavy 0.963b 1.19ab 0.97 1.23 0.960 1.11b
Extreme 0.60c 0.96b 0.82 1.14 0.78 0.77c
LSD(0.05) 0.38 0.25 NS2 NS NS 0.16
             
  Average Gain (lbs/acre)
Desired

Grazing

Intensity

1998 1999 2000 2001 2002 Average

1991-2002

Light 28.29c   36.50b 33.03c  43.18c 20.06 24.39c
Moderate 62.25b   59.73b 42.39bc  59.88bc 37.90 48.51b
Heavy 97.86a   93.93a 58.24ab  67.15b 33.57 77.13a
Extreme 67.98b 108.49a 74.44a 108.27a 38.96 81.35a
LSD(0.05) 29.59   24.31 17.52  23.74 NS 12.73
             
  Condition Score
Desired

Grazing

Intensity

1998 1999 2000 2001 2002 Average

1994-2002

Light 5.81a 5.72a 5.18a 5.78 5.22 5.39a
Moderate 5.71ab 5.65ab 5.20a 5.52 5.18 5.29ab
Heavy 5.21b 5.54bc 5.01a 5.43 5.18 5.13b
Extreme 4.65c 5.41c 4.61b 5.24 5.05 4.78c
LSD(0.05) 0.53 0.18 0.31 NS NS 0.21
             
1Means in the same column followed by the same letter are not significantly different at p=0.05.

2Means not significantly different.


Initially gain/acre increases as the stocking rate increases but there comes a point when further increases in stocking rates result in reduced gain/acre (see figure 3). What happens at stocking rates beyond the extreme stocking rate reference line is mainly hypothetical because we have very few observations on which to base our regression lines. However all but 2001 had at least one observation from a stocking rate higher than the projected rate which would provide maximum gain/acre for the year. Table 4 shows the stocking rate that would have resulted in the maximum gain/acre in each year. Since we can’t predict ahead of time what stocking rate would give the maximum gain/acre in a particular year it would be impossible to stock each year for maximum gain/acre. In retrospect, if we were to pick one stocking rate that would have resulted in the maximum gain/acre over this 12-year period it would have been 2.14 AUM/acre. This is the point labeled optimum in figure 3.

 

Table 4. Comparison of gain in lbs per acre from selected stocking rates.

 

A

B

C

 

Stocking rate that would result in the maximum gain/acre in each year.

Stocking rate that if held constant would result in the maximum gain/acre over the 12-year period.

Gain/acre over the 12-year period if stocking rate were held constant at 0.96 AUMs/acre, the average of the moderate treatment over this period.

Year

AUMs

/acre

gain

/acre

AUMs

/acre

gain

/acre

AUMs

/acre

gain

/acre

1991

2.26

62.5

2.14

62.4

0.96

41.3

1992

2.68

134.8

2.14

129.2

0.96

77.6

1993

3.41

175.8

2.14

148.9

0.96

74.9

1994

2.27

58.1

2.14

57.9

0.96

38.2

1995

3.08

84.7

2.14

76.5

0.96

42.5

1996

2.04

57.0

2.14

56.8

0.96

38.9

1997

1.92

92.4

2.14

90.96

0.96

65.6

1998

2.08

91.2

2.14

91.1

0.96

60.1

1999

3.18

111.4

2.14

98.4

0.96

51.76

2000

2.81

76.6

2.14

72.2

0.96

42.7

2001

 

*

2.14

99.9

0.96

50.8

2002

0.94

41.5

2.14

-44.6

 

41.5

12-year Avg.

2.42

89.6

2.14

78.3

0.96

52.2

* The regression for 2001 was not suitable to project the peak in gain/acre.

 

Table 4B shows what the gain/acre would have been each year if we had stocked at that rate. We predict that if we had stocked at 2.14 AUM/acre each year gain per acre would have ranged from a loss of 44.6 lbs/acre in 2002 to a gain of 148.9 lbs/acre in 1993 but would have averaged 78.3 lbs/acre. Because so little forage was produced in 2002 the grazing season was cut short and none of the pastures were actually stocked that heavily. The stocking rate on the extreme treatment averaged 1.18 AUM/acre for 2002 and, although gains were not good, only 11 out of the 189 animals in the trial had actually lost weight during the 55 days of grazing. Table 4C shows what the gain/acre would have been each year if the stocking rate were held constant at 0.96 AUM/acre, the average of the moderate treatment over this period.


Figure 4 shows the relationship between stocking rate and economic return. Cost for land, labor and management are not included because they vary greatly from one operation to another. If cattle prices were constant then return/acre would peak at a stocking rate somewhere below maximum gain/acre with the exact point depending on carrying costs (interest, death loss, salt and mineral, vet cost, transportation, labor and land). However, when cattle are worth more per hundred weight in the spring then they are in the fall it causes the point of maximum return/acre to occur at a lower stocking rate and when they are worth more in the fall it causes the maximum return to occur at a higher stocking rate. Again returns for stocking rates beyond the extreme stocking rate reference line are hypothetical and again all but 2001 had at least one observation from a stocking rate higher than the rate which would provide maximum return to land, labor and management for the year. Table 5A shows what the return/acre would have been if we had stocked each year at the stocking rate which would result in the maximum return for that year. These values correspond to the peaks of the curves in figure 4. Obviously we can’t know ahead of time what the optimum stocking rate for a particular year is going to be. If we were going to pick one constant stocking rate that would have provided the maximum return/acre over this last 12-year period it would have been 1.76 AUM/acre. This is the point labeled optimum in figure 4. Table 5B shows what the returns/acre would have been each year if we had stocked at this rate. Table 5C shows what returns/acre would have been each year if stocking rates were held constant at 0.96 AUM/acre, the average of the moderate treatment over this period. Although the average return per acre is higher under the optimum rate there were four years with negative returns while only one year had a negative return under the moderate stocking rate. (Costs for land, labor and management have not been subtracted). Comparing tables 4 and 5 it can be seen that in all but three years (1992, 1996 and 1999) the stocking rate with the greatest economic return was less than the rate with the greatest gain per acre.


Table 5. Comparison of return to land, labor and management from selected stocking rates.

 

 

A

B

C

 

Stocking rate that would result in the maximum return/acre to land, labor and management in each year.

Stocking rate that if held constant would result in the maximum return to land, labor and management over the 12-year period.

Returns/acre to land, labor and management over the 12-year period if stocking rate were held constant at 0.96 AUMs/acre, the average of the moderate treatment over this period.


Year

AUMs

/acre

returns

/acre

gain

/acre

AUMs

/acre

returns

/acre

gain

/acre

AUMs

/acre

returns

/acre

gain

/acre

1991

0.88

$4.10

38.8

1.76

-$1.60

59.4

0.96

$4.06

41.3

1992

3.12

$97.11

130.9

1.76

$77.87

118.4

0.96

$48.67

77.6

1993

2.39

$105.11

158.3

1.76

$97.64

130.1

0.96

$66.39

74.9

1994

0.67

$1.99

28.5

1.76

-$4.76

55.1

0.96

$1.52

38.2

1995

1.44

$2.05

59.5

1.76

$1.36

68.4

0.96

$0.49

42.5

1996

2.06

$31.763

56.9

1.76

$30.967

55.8

0.96

$21.60

38.9

1997

1.11

$13.35

73.5

1.76

$8.32

91.7

0.96

$13.06

65.6

1998

0.961

$2.11

63.1

1.76

$-3.46

88.7

0.96

$2.08

60.1

1999

3.24

$56.58

111.3

1.76

$43.46

87.0

0.96

$25.41

51.76

2000

2.19

$18.05

72.8

1.76

$17.22

65.7

0.96

$11.21

42.7

2001

 

*

 

1.76

$42.01

85.0

0.96

$25.59

50.8

2002

0.31

-$1.49

17.8

1.76

-$29.56

1.6

0.96

-$7.14

41.5

12 yr. avg.

1.67

$30.07

73.8

1.76

$23.30

75.6

0.96

$17.74

52.2

* The regression for 2001 was not suitable to project the peak in returns to land, labor and management.



Forage Production and Utilization Treatment Effects


The first year in which the amount of forage produced under the various grazing treatments was significantly different was 1992 on silty range sites and 1993 on overflow range sites. Table 6 gives the average forage production by treatment on silty range sites at the beginning of the grazing season, mid-season, peak of the season and end of the season for the period from 1992 to 2002. Table 7 gives the same information for overflow range sites averaged over the period from 1993 to 2002. For both range sites the extreme grazing treatment produces the least forage. However the ungrazed treatment is not the most productive, although it is only slightly less productive than the light treatment on the silty range site at the beginning of the grazing season. The light treatment is the most productive on silty range sites. There is little difference between light, moderate and heavy treatments on overflow range sites but moderate tends to be the most productive. There is no year X treatment interaction between treatments on overflow range sites. That means the effect of grazing intensity on forage production is consistent across all of these years. However there is year X treatment interaction on silty range sites at the beginning and end of the grazing season.



Table 6. Average above ground biomass production by grazing treatment on silty range sites from 1992 to 2002.

 

Above ground biomass (lbs/acre)

Treatment

Beginning

of season

Middle of

season

Total

yield

End of

season

Ungrazed

1,336 a1

2,488 b

2,729 b

 2,530 bc

Light

 1,410 a

 2,813 a

3,196 a

  3,034 a

Moderate

1,238 b

  2,491 b

2,891 b

2,756 b

Heavy

  895 c

 2,123 c

2,376 c

  2,271 cd

Extreme

  722 d

  1,702 d

2,070 d

2,048 d

LSD(0.05)

96

190

246

261

1Means in the same column followed by the same letter are not significantly different at P=0.05.




Table 7. Average above ground biomass production by grazing treatment on overflow range sites from 1993 to 2002.

 

Above ground biomass (lbs/acre)

Treatment

Beginning

of season

Middle of

season

Total

yield

End of

season

Ungrazed

1,061 b1

3,243 b

3,303 b

2,735 b

Light

1,155 ab

3,915 a

4,148 a

3,824 a

Moderate

1,263 a

3,846 a

4,322 a

4,142 a

Heavy

1,260 a

3,782 a

4,106 a

4,069 a

Extreme

   857 c

2,270 c

2,721 c

2,652 b

LSD(0.05)

117

353

365

387

1Means in the same column followed by the same letter are not significantly different at P=0.05.



This indicates that the weather for the year, or the previous year may affect which grazing treatment produces the most forage. At the beginning of the grazing season the most productive site varied between the ungrazed, light and moderate treatments with the extreme or heavy always being least productive. At the end of the season the light or moderate was most productive and the extreme or heavy was least productive although ungrazed produced the least in 1994. Although there were no significant differences in biomass production in 1991 the fact that there were differences at the beginning of the 1992 grazing season indicates that grazing must have reduced the amount of carbohydrate reserves that the plants were able to carry over to the next season. Part of the variability in production on the ungrazed treatment may be the result of litter buildup that can prevent rainfall and sunlight from reaching the ground. In 1992 and 1993 the ungrazed treatment produced the most forage on silty range sites and production decreased as grazing intensity increased. Annual rainfall in 1993 was the second highest of any year during this study and the greatest forage production on silty range sites occurred during that year (see table 2). The buildup of litter in that year may have been the factor that caused the ungrazed treatment to be the least productive treatment in 1994.



Soil Water and Forage Production


Soil water has been sampled bi-monthly throughout the growing season on each of the vegetation monitoring sites and differences in available water have developed between the different grazing treatments. On overflow range sites, lightly grazed pastures have more available water than heavily grazed pastures. The differences in available water occur during both soil water recharge and discharge. This indicates that on heavily grazed sites more water runs off during a rain and sunlight evaporates more water from the soil surface. On silty range sites, moderately grazed pastures have more available water than ungrazed or heavily grazed pastures. The ungrazed treatment has less available water because the plants on that treatment have more leaf area than the grazed plants, and more water is removed from the soil by transpiration.



Forage Quality


The nutritional quality of the forage was sampled at the middle of the grazing season each year for the first 10 years of the study. On silty range sites the grasses have higher crude protein and digestibility and lower fiber components at the higher grazing intensities. On the heavily grazed treatments the grass that is available for grazing is mostly regrowth that is of higher quality. However on overflow sites both grasses and forbs are highest in fiber components on the heavy grazing treatment. Perhaps on these sites cattle are selecting species of higher quality and leaving those that are higher in fiber. On silty sites forbs are highest in neutral detergent fiber on the ungrazed and extreme grazing treatments. As the ungrazed forage matures on the ungrazed treatment it becomes higher in fiber. On the heavily grazed treatments only forbs of lower quality would remain ungrazed. These differences in nutritional quality have occurred gradually over the course of the study.



Plant Community Dynamics


Changes in the plant community are monitored by sampling the frequency of occurrence, density per unit area and percent basal cover of all plant species as well as sampling the weight of herbage produced. Frequency data was collected each year of the study. Density was collected on forbs and shrubs in 1988 and 1990 to 2002 and on cespitose (bunchgrasses) from 1992 to 2002. Basal cover was sampled on plant species in 1988, 1990, 1992, 1993, 1996, 1999, and 2002 and basal cover of litter and bare ground was sampled in 1996, 1999 and 2002. The change in abundance of species between years was determined for each site. The arcsine transformation was applied to frequency and basal cover data to convert it from a binomial distribution to a nearly normal distribution. Analysis of variance was performed to determine if there was a change in species abundance across all sites, which might indicate a response to weather, or if there was a change in response to the different grazing treatments. All tests were performed at the P=0.05 level. Table 8 lists plant species that appear to be favored by no grazing or light grazing. Table 9 lists species that appear to be favored by moderate grazing and table 10 lists species that appear to be favored by heavy grazing. An asterisk marks species in Table 10 which appear to be invasive. These are species that have not been found or are extremely rare on the ungrazed or lightly grazed treatments. On overflow sites, total forb density and total plant density (includes forbs, bunchgrasses and shrubs but not rhizomatous grasses) have become greatest on the extreme and heavy treatments and least abundant on the ungrazed treatment and total plant basal cover has increased on the extreme treatment. On silty sites, total forb density and total plant density increase as the grazing intensity increases. Also on silty range sites total plant basal cover has decreased on the ungrazed and lightly grazed treatments between 1992 and 1999 and increased on the extreme and heavy treatments between 1996 and 1999. In addition to the changes listed for plant species, litter has decreased and bare ground has increased on both silty and overflow range sites under heavy grazing.


Table 8. Plant species that appear to be favored by no grazing or light grazing (P≤ 0.05).

 

Overflow Range Sites

 

Bromus inermis

smooth brome

Helianthus rigidus

stiff sunflower

Rosa arkansana

prairie rose

Solidago mollis

soft goldenrod

Silty Range Sites

 

Artemisia absinthium

wormwood

Helianthus rigidus

stiff sunflower

Medicago sativa

alfalfa

Melilotus officinalis

yellow sweetclover

Poa pratensis

Kentucky bluegrass

Polygonum convolvulus

wild buckwheat

Psoralea esculenta

breadroot scurf-pea

Tragopogon dubius

goat's beard



Table 9. Plant species that appear to be favored by moderate grazing (P≤ 0.05).

 

 

Overflow Range Sites

Ambrosia psilostachya

western ragweed

Anemone cylindrica

candle anemone

Aster simplex

panicled aster

Campanula rotundifolia

harebell

Carex lanuginosa

wooly sedge

Galium boreale

northern bedstraw

Glycyrrhiza lepidota

wild licorice

Juncus balticus

Baltic rush

Poa pratensis

Kentucky bluegrass

Sisyrinchium montanum

blue-eyed grass

Solidago rigida

stiff goldenrod

 

Silty Range Sites

Agropyron repens

quackgrass

Ambrosia psilostachya

western ragweed

Artemisia dracunculus

green sagewort

Artemisia ludoviciana

cudweed sagewort

Bromus inermis

smooth brome

Carex filifolia

thread-leaved sage

Cirsium flodmanii

Flodman’s thistle

Comandra umbellata

comandra

Dichanthelium wilcoxianum

Wilcox dichanthelium

Erysimum inconspicuum

smallflower wallflower

Geum triflorum

prairie smoke

Lactuca oblongifolia

blue lettuce

Orthocarpus luteus

owl clover

Psoralea argophylla

silver-leaf scurf-pea

Ratibida columnifera

prairie coneflower

Rosa arkansana

prairie rose

Sisyrinchium montanum

blue-eyed grass

Solidago missouriensis

Missouri goldenrod

Solidago mollis

soft goldenrod

Solidago rigida

stiff goldenrod



Table 10. Plant species that appear to be favored by heavy grazing (P≤ 0.05).

 

 

Overflow Range Sites

  Achillea millefolium

western yarrow

  Agropyron caninum

slender wheatgrass

  Agropyron smithii

western wheatgrass

  Agrostis hyemalis

ticklegrass

  Androsace occidentalis

western rock jasmine

  Artemisia ludoviciana

cudweed sagewort

  Astragalus agrestis

field milk-vetch

  Aster ericoides

heath aster

  Bouteloua gracilis

blue grama

* Buchloe dactyloides

buffalograss

  Carex heliophila

sun sedge

  Carex obtusata

sedge

  Cerastium arvense

prairie chickweed

  Cirsium flodmanii

Flodman's thistle

  Conyza canadensis

horse–weed

  Draba nemorosa

yellow whitlowort

  Erysimum inconspicuum

smallflower wallflower

  Euphorbia serpyllifolia

thyme-leaved spurge

  Geum triflorum

prairie smoke

  Grindelia squarrosa

curly-cup gumweed

* Lithospermum incisum

yellow puccoon

* Medicago lupulina

black medic

   Oxalis stricta

yellow wood sorrel

   Penstemon gracilis

slender beardtongue

   Polygonum convolvulus

wild buckwheat

* Polygonum ramosissimum

bushy knotweed

   Potentilla norvegica

Norwegian cinquefoil

* Potentilla pensylvanica

Pennsylvania cinquefoil

   Ratibida columnifera

prairie coneflower

   Solidago missouriensis

Missouri goldenrod

  Stipa viridula

green needlegrass

  Taraxacum officinale

common dandelion

* Trifolium repens

white clover

  Vicia americana

American vetch

  Viola pedatifida

larkspur violet

 

Silty Range Sites

   Achillea millefolium

western yarrow

   Agropyron smithii

western wheatgrass

* Agrostis hyemalis

ticklegrass

  Androsace occidentalis

western rock jasmine

  Artemisia frigida

fringed sagewort

  Bouteloua gracilis

blue grama

  Carex eleocharis

needle-leaved sedge

  Carex heliophila

sun sedge

  Carex obtusata

sedge

  Cerastium arvense

prairie chickweed

  Chenopodium desiccatum

narrow-leaved goosefoot

  Draba nemorosa

yellow whitlowort

  Erysimum asperum

western wallflower

  Euphorbia serpyllifolia

thyme-leaved spurge

  Grindelia squarrosa

curly-cup gumweed

  Hedeoma hispidum

rough false pennyroyal

* Juncus interior

inland rush

  Koeleria pyramidata

junegrass

  Lepidium densiflorum

peppergrass

 *Medicago lupulina

black medic

  Oxalis stricta

yellow wood sorrel

  Plantago patagonica

wooly plantain

* Polygonum ramosissimum

bushy knotweed

   Potentilla norvegica

Norwegian cinquefoil

  Potentilla pensylvanica

Pennsylvania cinquefoil

  Symphoricarpos occidentalis

buckbrush

  Taraxacum officinale

common dandelion

  Vicia americana

American vetch

* Invaders, these species have not been found, or are extremely rare, on the ungrazed and lightly grazed treatments.



Recommendations


The objective of this study is to determine what stocking rate would result in the greatest economic return to the livestock producer in the long run. For the past 12 years in this study the stocking rate that would have resulted in the greatest return was 1.76 AUM/acre. However for a number of reasons we feel this stocking rate may be too heavy to recommend. First, the extreme and heavy pastures have been deteriorating in condition through the course of the study and may not be able to support the rates of gain we have seen in the past. Also we have had higher than average precipitation through much of this period. The average annual precipitation for the first 13 years of this study was 19.06 inches/year compared to the 51-year average of 17.99 inches/year. As we move into a period of drier weather, forage production and annual gains are reduced. Both profits and losses are higher at higher stocking rates depending on the difference between spring and fall livestock prices. The producer would experience more years with negative returns at the higher stocking rates.


It appears that the moderate stocking rate may be too conservative if maximizing profit is the objective. In only three out of 12 years returns would have been higher with a stocking rate less than the moderate rate of 0.96 AUM/acre. In all other years a higher stocking rate would have resulted in higher returns. For a stocker operation in this area the optimum stocking rate would fall in the range of 0.96 to 1.76 AUM/acre. As you move to lower rainfall areas farther west in the state these values would be reduced.

 

These stocking recommendations cannot be applied to a cow-calf operation because calf gains are largely dependent on the cows’ milk production. Higher stocking rates could reduce the cows’ condition and conception rates and result in higher over-wintering costs to bring the cows back up to condition to calve in the spring. Season-long grazing is used in this study. We would recommend a rotation grazing system. By concentrating cattle on a smaller area for a shorter period of time more of the grass plants will receive use. Later when the cattle are moved back into the area they can graze regrowth on the plants they grazed on the first rotation. In this way one can take advantage of the higher forage quality found on the extreme grazing treatment and still give plants a rest avoiding the reduced production also found on the extreme grazing treatment.



Future Research


We plan to continue this research for a number of years. Changes in the forage production and the plant species composition of the pastures are still continuing in response to the different grazing treatments and these factors will affect the livestock’s response to the grazing treatments. The pastures in this study are also being used to study the response of pastures with different grazing histories to drought, the movement of water through the soil profile, the movement of water through range plants, fertilization, and the distribution of nongame birds.


Table of contents

  
NDSU Central Grasslands Research Extension Center
Home2002 Annual Report