GRAZING EFFECTS ON THE STRUCTURES AND DYNAMICS
OF GRASSLAND ECOSYSTEMS

Project No. 1786

Complementary Rotation Grazing System in Western North Dakota

L.L. Manske, M.E. Biondini, J. E. Struble, D.O. Erickson,
P.J. Sjursen, T.J. Conlon, J.L. Nelson and D.G. Landblom

Introduction

Complementary grazing system used domesticated grass, legume, or annual crop pastures to add to or complement native range pastures. Rotation grazing moves livestock through a successive series of pastures in a preplanned sequence. Management of native range and domesticated grass pastures must be based on sound ecological principles that consider the growth and development of the dominant species and physiological needs, weaknesses and strengths of the plants to maintain productive stands. The nutritional needs of the livestock must be included in management considerations. Sound management recommendations can only be based on reliable scientific research.

Procedures

This project compares nongrazed, seasonlong grazing and rotation grazing on three native range sites to evaluate species composition, herbage production, and animal performance and the use of domesticated grass pastures in a complimentary rotation grazing system. The present complementary rotation grazing system has been in place at the ranch headquarters of the Dickinson Research Center since 1983. It consists of two crested wheatgrass (Agropyron desertorum) pastures of 13 acres for spring grazing from early May to 1 June and two altai wildrye (Elymus angustus) pastures of 30 acres for fall and early winter grazing from 15 October to 15 December. Native range has been grazed as two sets of three pastures during the summer from 1 June to 15 October and managed as a twice over rotation system. Two pastures were 80 acres and one pasture was 75 acres. Twenty-three cow-calf pairs were used on each replication of the rotation grazing treatment. The seasonlong pasture treatments were established in 1986 and grazed from mid June to late October and consisted of 3 replicates of 80 acres of native range. Ten cow-calf pairs were used on each replication of the seasonlong grazing treatment. The two native range nongrazed treatments were established in 1987 and have not been grazed for more than 30 years.

The intended purpose of the trial is to maximize herbage and livestock production for a cow-calf operation, lengthen the grazing season in the spring and fall, improve range condition of native range, and reduce total acreage required to carry a cow and calf. The intention is to accomplish these goals with a low number of pastures with few rotation times and be flexible enough to be adapted by a wide range of livestock operations. This type of grazing system should improve operation efficiency, reduce costs and decrease labor per unit of production, and increase saleable production per acre.

Plant data collected on the treatments in this study were above ground herbage production, plant species composition, and leaf height measurements and phenological phases of eight major graminoid species. Animal weight performance for the commercial crossbred cattle used in this trial was collected only while livestock were on pasture at 15 or 30 day intervals.

Results and Discussion

The 1990 grazing season experienced drought conditions. A total of only 12.07 inches of precipitation fell for the entire year. The long term mean was 15.89 inches. Only 11.14 inches of precipitation occurred during the growing season, April to October.

The length of the grazing periods on the complementary rotation grazing system and seasonlong grazing treatments were reduced because of the drought conditions. The crested wheatgrass pastures were grazed from 21 May to 4 June for 14 days. Generally these pastures were grazed for 21 days. The native range was grazed from 4 June to 17 September for 105 days. The native range was previously grazed from 1 June to 15 October for 136 days. The altai wildrye pastures were grazed from 17 September to 17 October later for 30 days. Generally these pastures were grazed from 15 October to 15 December or later for 60 plus days. The native range seasonlong pastures were grazed from 20 June to 10 September for 82 days. Generally these pastures were grazed from mid June to late October 129 days.

The total plant basal cover (Table 1) decreased on the nongrazed treatments on the sandy, shallow and silty range sites. The seasonlong grazed treatments on the sandy, shallow and silty range sites increased in basal cover compared to 1989 data. The rotation grazing treatments increased in total plant basal cover on the sandy, and shallow range sites but decreased slightly on the silty range sites. Generally the native range sites on the seasonlong and rotation grazing treatments showed a slight improvement in plant basal cover compared to 1989 data despite the prevailing drought conditions in 1990. The range sites on the nongrazed treatments did not show this improvement in plant basal cover.

The total above ground herbage production (Table 2) decreased on the rotation grazing treatments by 29%, 15%, and 14% on the sandy, shallow, and silty range sites, respectively, compared to 1989 data. The herbage production (Table 2) on the seasonlong grazing treatments decreased by 18% and 9% on the sandy and silty range sites and increased 9% on the shallow range sites. The herbage production (Table 2) on the nongrazed treatments increased by 33%, 49%, and 15% on the sandy, shallow, and silty range sites, respectively, compared to 1989 data.

The cow and calf average daily gain (Table 4) was decreased in 1990 compared to 1989 on the seasonlong treatments. The calf average daily gain (Table 4) was increased on the crested wheatgrass, native range, and decreased on the altai wildrye pastures of the complementary rotation treatments in 1990 compared to 1989. The cow average daily gain (Table 4) for the rotation was decreased on the crested wheatgrass, native range and altai wildrye pastures in 1990 compared to 1989. The cow and calf performance in 1990 was generally reduced compared to 1989 because of the continuation of drought conditions from August 1986.

Summary

The management of this complementary rotation grazing system has been based on ecological principles that consider the physiological needs, weaknesses, and strengths of the dominant plant species. Consideration of the nutritional needs of the livestock have been incorporated. Season of use of each pasture type was limited to periods of grazing when the detrimental effects of grazing were minimized and the potential for improvement in animal weight performance was maximized near potential. Effort has been made to limit the number of pastures and rotation times to be the minimum. One pasture of crested wheatgrass was used for spring grazing. A second pasture may be necessary to move the starting date earlier. The native range was managed with three pastures, each grazed two times during the grazing season. One pasture of altai wildrye was used in this system for fall and early winter grazing. The grazing season has been lengthened from the traditional 6 months to 7.1 months. This system has the potential to lengthen the grazing season to 8.0 months with additional research. The acreage required to carry a cow and calf was reduced from 24.4 acres for 6 months to 11.6 acres for 7.1 months.

By using a complementary rotation grazing system similar to the one at the Dickinson Research Center, livestock producers have the potential to: lengthen the grazing season, reduce the acreage required to feed a cow and calf, and increase the amount of saleable beef produced from each livestock unit.

Table 1. Mean percent basal cover for native range treatments, Dickinson Research Center, July, 1990.

Range Site
Treatment

Grass

Sedge

Forb

Shrub

Other
plant

Total
plant

Litter

Soil

Sandy

Ungrazed

Nongrazed

12.2

6.3

1.7

0.3

0.0

20.5

78.9

0.7

Seasonlong

—

---

---

—

—

—

—

—

Rotation

11.5

6.3

5.6

0.6

0.0

23.9

74.2

2.0

Grazed

Seasonlong

13.0

13.8

8.8

0.5

0.0

36.0

61.0

3.0

Rotation

10.0

8.7

5.5

0.4

0.0

24.6

72.5

2.9

Shallow

Ungrazed

Nongrazed

6.8

9.4

3.8

0.0

0.0

19.9

76.8

3.3

Seasonlong

---

---

---

---

---

---

---

---

Rotation

12.4

7.9

4.5

0.5

0.4

25.6

70.9

3.5

Grazed

Seasonlong

13.3

11.5

6.0

0.1

0.1

31.0

60.4

8.5

Rotation

13.2

7.2

3.3

0.3

0.1

24.1

68.7

7.3

Silty

Ungrazed

Nongrazed

9.1

5.2

4.3

2.0

0.1

20.7

79.3

0.1

Seasonlong

16.8

5.8

11.0

0.0

0.3

33.8

65.0

1.2

Rotation

14.3

5.7

6.1

0.0

0.1

26.3

71.1

2.7

Grazed

Seasonlong

18.5

4.3

9.9

0.0

0.0

32.6

64.9

2.4

Rotation

13.8

4.2

4.5

0.0

0.0

22.5

72.6

5.0

 

Table 2. Mean herbage in pounds per acre, Dickinson Research Center, July, 1990.

Range site
Treatment

Cool
season

Warm
season

Sedge

Forb

Shrub

Total
live

Standing
dead

Total above ground herbage

Litter

Sandy

Ungrazed

Nongrazed

269

785

234

16

0

1305

832

2137

4275

Seasonlong

253

232

458

241

0

1184

179

1363

2730

Rotation

218

194

304

143

0

858

143

1001

1588

Grazed

Seasonlong

60

212

371

108

0

750

104

854

2475

Rotation

93

116

287

95

0

591

45

636

1292

Shallow

Ungrazed

Nongrazed

210

38

623

102

0

974

325

1299

2640

Seasonlong

163

114

337

170

0

783

96

879

1217

Rotation

240

118

236

107

0

701

105

806

543

Grazed

Seasonlong

110

89

376

85

0

660

37

697

1737

Rotation

86

123

200

59

0

468

32

500

680

Silty

Ungrazed

Nongrazed

241

247

478

182

0

1147

356

1503

2439

Seasonlong

396

289

108

307

0

1100

207

1307

2324

Rotation

339

222

200

174

0

934

157

1091

887

Grazed

Seasonlong

139

214

133

82

0

567

72

639

1845

Rotation

148

201

100

82

0

531

67

598

898

 

Table 3. Mean cow and calf periodic weight in pounds, Dickinson Research Center, 1990.

Treatment

1
May

 

15
May

 

1
Jun

 

15
Jun

 

1
Jul

 

15
Jul

 

1
Aug

 

15
Aug

Seasonlong

             

Native

Rotation

 

Altai

Crested

         

Native

   

Cow

Seasonlong

             

1335

       

1356

   

Rotation

 

1190

 

1203

 

1232

 

1264

 

1271

 

1286

 

1297

 

Calf

Seasonlong

             

285

       

372

   

Rotation

 

200

 

235

 

266

 

307

 

335

 

378

 

435

 

 

Table 3. Mean cow and calf periodic weight in pounds, Dickinson Research Center, 1990 cont’d.

Treatment

1

Sep

 

15

Sep

 

1

Oct

 

15

Oct

 

30

Oct

 

15

Dec

Seasonlong

Native

                 

Rotation

   

Altai

           

Cow

Seasonlong

 

1331

                 

Rotation

1258

 

1246

     

1156

       

Calf

Seasonlong

 

494

                 

Rotation

484

 

539

     

568

       

 

Table 4. Mean cow and calf average daily gain and gain per acre in pounds, Dickinson Research Center, 1990.

 

Crested

wheatgrass

Native

range

Altai

wildrye

Total

system

Average Daily Gain (ADG)

Cow

Seasonlong

—

-0.25

---

-0.25

Rotation

2.18

0.14

-2.09

-0.21

Calf

Seasonlong

---

2.54

---

2.54

Rotation

2.30

2.60

0.96

2.26

Gain/Acre (G/A)

Cow

Seasonlong

---

-0.42

---

-0.42

Rotation

54.00

1.45

-59.22

-2.78

Calf

Seasonlong

---

25.42

---

25.42

Rotation

57.00

26.72

47.50

30.44