Long-Term Ecological Grazing Intensity Research in the Missouri Coteau of North Dakota

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 2046, 1641, 942, and 493 lbs/ac. of forage remaining on the light, moderate, heavy and extreme pastures, respectively. Table 1 presents the stocking history of the study and Figure 1 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 attain the 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

2003

Open Heifers

May 23

September 19

119

2004

Open Heifers

May 19

September 9

113

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



Above ground biomass remaining (lbs/acre) on each treatment at the end of the grazing season from 1989 to 2004.

 

Treatment

Year

Light

Moderate

Heavy

Extreme

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

2,078

2,634

2,385

1,915

2,924

2,017

2,772

2,552

2,550

2,674

2,269

2,387

1,933

1,225

2,434

1,801

2,074

2,383

1,494

1,353

2,256

1,728

1,906

1,975

1,711

1,848

2,108

2,246

1,883

1,132

2,128

1,775

2,035

2,023

833

574

1,290

1,393

1,583

1,064

689

686

806

1,130

1,197

701

1,205

1,284

1,701

1,985

641

406

608

901

504

513

560

522

609

718

617

329

678

518

Ideal Remaining

2,046

1,641

942

493



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 2004.

Year

Precipitation

(in)

Above Ground Biomass (lbs/acre)

Overflow

Silty

1989

1990

1991

1992

1993

1994

1995

1996

1997

1998

1999

2000

2001

2002

2003

2004

18.40

16.10

12.89

15.25

26.59

16.86

22.60

20.55

18.63

18.91

26.91

15.60

18.44

16.69

15.39

21.95

3,863

3,847

3,142

2,758

3,999

4,201

4,773

3,837

3,351

3,334

4,338

3,950

3,569

1,850

3,128

3,676

2,089

2,962

2,629

2,065

3,446

2,803

3,134

2,645

2,376

2,855

3,152

2,846

2,678

1,175

2,730

2,814

16-Year Average

18.86

3,601

2,650


 

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