Grazing Intensity Research in the Missouri Coteau of North Dakota


Introduction

A grazing intensity research project was initiated 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 the pastures we are dealing with that means 2,148 lbs./ac., 1,693 lbs./ac., 982 lbs./ac. and 516 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 try and 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

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 2000.
Treatment
Year Light Moderate Heavy Extreme
1989
1990
1991
1992
1993
1994
1995
1996
1997
1998
1999
2000
Ideal Remaining
2,078
2,634
2,385
1,915
2,924
2,017
2,772
2,552
2,550
2,674
2,269
2,387
2,148
2,074
2,383
1,494
1,353
2,256
1,728
1,906
1,975
1,711
1,848
2,108
2,246
1,693
2,035
2,023
833
574
1,290
1,393
1,583
1,064
689
686
806
1,130
982
1,701
1,985
641
406
608
901
504
513
560
522
609
718
516


 

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 2000.


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
12-Year Average 19.11 3,783 2,750

 
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