Journal of the NACAA
ISSN 2158-9429
Volume 3, Issue 1 - July, 2010
MONITORING UTILIZATION OF PASTURE AND RANGELAND FORAGE TO ASSIST GRAZING MANAGEMENT DECISIONS: A CENTRAL TEXAS COUNTY CASE STUDY
- Scasta, J.D., County Extension Agent, Agriculture and Natural Resources, Texas AgriLife Extension Service, Texas A&M University
ABSTRACT
The goal of this project was to implement a user friendly forage utilization monitoring program on a central Texas ranch to serve as a county demonstration model. This project will seek to assist landowners with improper forage utilization which is a critical issue affecting profits, cattle performance and natural resources. The program required two days annually and minimal labor. Short and long term grazing exclosures were established in two pastures. Measurements of plant height and biomass were taken in the late fall, inside and outside of exclosures. Percent utilization figures were calculated. Vegetation transect surveys and photo points were established for long term monitoring. The ranch utilized a two herd, two pasture grazing system. Thirty-four Hereford crossbred cows and two bulls grazed the South Pasture and 24 replacement crossbred heifers grazed the North Pasture. Forage utilization in the South Pasture was high (average 80.9%) and evenly distributed (standard deviation 11.4%) while utilization in the North Pasture was low to moderate (average 42.5%) and unevenly distributed (standard deviation 26.4%). Subsequently, mature cows were identified for culling in the South Pasture herd and alternate supplemental feeding locations used in the North Pasture. This demonstration will be used to instruct other ranch managers on how to apply a forage utilization monitoring program. This will assist them in making critical grazing management decisions based on ranch specific data acquired with minimal time and labor.INTRODUCTION
Improper forage utilization (such as overgrazing or uneven distribution) is a costly mistake for beef cattle producers and the environment. Impacts include increased supplemental feed costs, reduced cattle performance, increased soil erosion, changes in plant community and decreased pasture and range condition. Monitoring utilization has been defined as estimating the amount removed or the degree of use (Drake, 1998). There are many methods of forage monitoring but the easiest and most effective are measuring residual forage stubble heights and utilizing grazing exclosures (Mousel and Smart, 2007). Monitoring rangeland and pastures is important because it improves the landowner or ranch manager’s ability to make proper grazing management decisions. It is critical to observe forage utilization of the current year (short term) by measuring only at the end of the growing season. This information should be compared with long term range trends in order to make management decisions (Laycock, 1997).
This demonstration used monitoring techniques to assess both short term and long term effects of grazing management on rangeland and improved pastureland. It provided production data for forage budgeting and will provide long term trend information as it relates to grazing management on the county demonstration ranch. The method is designed to take only two days annually to acquire practical and relevant data. Once the impacts are quantified and observed, adjustments in management (i.e., adjusting stocking rate, changing supplemental feeding locations, cross fencing, etc.) can be confidently made. It is important to note that monitoring is a tool that should be used to achieve a land management objective (Laycock, 1997). Thus, before monitoring begins, ranch specific management objectives must be established (Reynolds, 1998).
OBJECTIVES
1) Quantify forage production to assist in forage budgeting and setting appropriate stocking rates.
2) Evaluate short term (annual) forage utilization to assist in yearly management decisions.
3) Evaluate long term impacts of grazing management on plant communities and identify range trends.
4) Assist ranchers in making confident grazing management decisions based on timely, ranch specific data with minimal labor.
MATERIALS AND METHODS
This project was established on a Navarro County ranch in early 2009. The South Pasture (180 acres) had 34 Hereford crossbred cows and 2 bulls. This pasture consists of both improved pasture and rangeland dominated by bermudagrass (Cynodon dactylon) and annual threeawn (Aristida purpurea) with brush and forbs encroaching. The North Pasture (185 acres) had 24 yearling commercial crossbred beef heifers grazing year round. It is primarily rangeland with mesquite (Prosopis glandulosa) and eastern red cedar (Juniperus virginiana) brush and a high diversity of grasses and forbs (13 and 5 species identified respectively). Soil is an acidic sandy loam.
Short Term Monitoring
Eight (32” x 32”) short term grazing exclosures were established at the beginning of 2009 with four per pasture. These were used to monitor forage utilization of the current year’s growth by measuring, clipping and moving annually
Long Term Monitoring
- Two permanent photo points were established and photographs taken annually during the spring and fall at permanent photo points (T-Post) and grazing exclosures
- Vegetation transect surveys were conducted annually during the fall sampling date to assess species composition; from photo point to North. The step-point transect was used and is a simple way to collect vegetation data such as diversity and frequency of plant species (Hanselka et al., 2009).
- Two (4’ x 4’) permanent grazing exclosures were established with one per pasture to monitor the long term effects of the grazing management and vegetation changes
Measuring Forage Height
Measurements of the residual stubble heights of forage inside and outside of grazing exclosures were taken. Measurements were then used to calculate the percentage of forage utilized.
Clipping Forage Plots
Twenty inch by twenty inch quadrats (2.777 square feet) were used to clip forage plots at ground level inside and outside of grazing exclosures. Samples were dried, reweighed and values adjusted to pounds per acre of forage and percent utilization calculated.
2009 Grazing Management and Forage Demand
Grazing management for each pasture was documented and forage demand for each herd was calculated using the following constants (Lyons and Machen, 2001).
1 AU = Animal Unit = 1,000 lbs cow with calf at her side
AUE = Animal Unit Equivalent = conversion factor to determine actual AU’s
Daily Forage Requirement for 1 AU = 26 lbs of air dry forage (or 2.6% of body weight)
HUE = Harvest Use Efficiency (25%) loss due to trampling, insects, desiccation and wildlife
RESULTS AND DISCUSSION
The vegetation inventory quantifies the vegetational composition of each pasture. The South Pasture is 69% grass, 28% forbs and 3% brush while the North Pasture is 64% grass, 23% forbs and 13% brush. Future inventories will allow for a comparison to assess if vegetational composition is changing over time as a function of grazing management. Annual monitoring in subsequent years is critical in determining if past decisions are producing the expected results (McGinty and White, 1998).
SOUTH PASTURE RESULTS
South Pasture Herd – Grazing Management and Forage Demand
34 cows w/ calves and 2 bulls grazing for 365 days
Average cow weight = 1,000 lbs; Average bull weight = 1,600 lbs
1.0 AU x 34 head of cows = 34 AU
1.6 AUE (bulls) x 2 bulls = 3.2 AU
34 AU(cows) + 3.2 AU (bulls) = 37.2 Total AU
37.2 AU x 26 lbs forage/cow/day = 967.2 lbs forage for herd/day
967.2 x 365 days = 353,028 lbs forage to feed herd for 1 year
180 acres @ 3,906.7 lbs of air dry forage/acre annually = 703,206 lbs/acre
Stocking Rate = 4.8 ac/AU
Supply = 703,206 lbs/acre
Demand
Cow Demand = 353,028 lbs annually
HUE (25%) = 175,801.5 lbs annually
TOTAL DEMAND = 528,829.5 lbs/acre
Potential Utilization (528,829.5 / 703,206) * 100 = 75.2%
Table 1: South Pasture Utilization Data
| FORAGE HEIGHT DATA |
FORAGE CLIPPING DATA | |||||
| Exclosure |
In. Ht. |
Out Ht. |
% Use |
Lbs/Acre |
Lbs/Acre Dry Forage Outside |
% Use |
| a | 10.0 | 3.0 | 70.0 | 4217.8 | 829.7 | 80.3 |
| b | 12.0 | 1.8 | 85.4 | 3941.2 | 138.3 | 96.5 |
| c | 7.0 | 2.0 | 71.4 | 4148.7 | 138.3 | 96.7 |
| d | 6.0 | 1.5 | 75.0 | 3318.9 | 138.3 | 95.8 |
| Average Utiilzation = 75.5% | Average Utilization = 92.0% | |||||
Average Forage Production for the South Pasture = 3,906.7 lbs of forage/acre
NORTH PASTURE RESULTS
North Pasture Herd – Grazing Management and Forage Demand
24 replacement heifers grazing for 365 days
Average heifer weight = 600 lbs
1 AU x 0.6 AUE = 0.6 AU
0.6 AU x 24 head = 14.4 AU
14.4 AU x 26 lbs forage/cow/day = 374.4 lbs forage for herd/day
374.4 x 365 days = 136,656 lbs forage to feed herd for 1 year
185 acres @ 4,753.77 lbs of air dry forage/acre annually = 879,434.5 lbs/acre
Stocking Rate = 12.8 ac/AU
Supply = 879,434.5 lbs/acre
Demand
Cow Demand = 136,656 lbs annually
HUE (25%) = 219,858.6 lbs annually
TOTAL DEMAND = 356,514.6 lbs/acre
Potential Utilization (356,514.6 / 879,434.5) * 100 = 40.5%
Table 2: North Pasture Utilization Data
| FORAGE HEIGHT DATA |
FORAGE CLIPPING DATA | |||||
| Exclosure |
In. Ht. |
Out Ht. |
% Use |
Lbs/Acre |
Lbs/Acre Dry Forage Outside |
% Use |
| a | 9 | 1.75 | 80.6 | 2350.9 | 276.6 | 88.2 |
| b | 16 | 8 | 50.0 | 7882.5 | 4771.0 | 39.5 |
| c | 11 | 7 | 36.4 | 2904.1 | 1382.9 | 52.4 |
| d | 10 | 9 | 10.0 | 5877.3 | 4425.3 | 24.7 |
| Average Utiilzation = 44.2% | Average Utilization = 42.9% | |||||
Average Forage Production for the North Pasture = 4,753.7 lbs of forage/acre
Figure 1: Comparison of Percent Utilization Figures: Plant Height Versus Plant Biomass
1Standard Deviation of All South Pasture Percent Utilization Measurements = 11.4%
2Standard Deviation of All North Pasture Percent Utilization Measurements = 26.4%
Table 3: Comparison of Average Percent Utilization Figures
| South Pasture |
North Pasture |
|
|---|---|---|
| Measuring Forage Heightw | 75.5% | 44.2% |
| Clipping Forage Plotsx | *92.0% | 42.9% |
| Calculating Forage Demandy | 75.2% | 40.5% |
| Percent Utilization Averagez | 80.9% | 42.5% |
* Variation attributed to difficulty in clipping extremely overgrazed forage plots
wCalculating Percent Utilization using Residual Plant Height measurements inside and outside grazing exclosures
wCalculating Percent Utilization using Residual Plant Height measurements inside and outside grazing exclosures
xCalculating Percent Utilization using clipping methods inside and outside grazing exclosures
yCalculating Percent Utilization based on forage production figures from forage clipping and animal demand
zAverage Percent Utilization calculated from three methods applied
CONCLUSION
The rangeland grazing management rule of thumb, ‘take half, leave half’ targets 50% utilization (of which 25% is accounted for in the HUE for trampling, decay, insects, etc.) (Lyons and Machen, 2001). Forage utilization in the South Pasture was high (average 80.9%) and evenly distributed (standard deviation 11.4%) (Table 1, Figure 1) while utilization in the North Pasture was low to moderate (average 42.5%) and unevenly distributed (standard deviation 26.4%) (Table 2, Figure 1). This indicates that it may be prudent to reduce stocking rate of mature cows in the South Pasture and that grazing distribution might be better manipulated in the North Pasture by using alternate supplemental feeding locations.
Differences in Percent Utilization figures can occur depending upon the method utilized (Laycock, 1997) and that became apparent when the different methods are observed together (Table 3, Figure 1). Potential causes for the variation in South Pasture figures may be attributed to the difficulty in trying to clip extremely overgrazed areas (thus exaggerating utilization). Nonetheless, trends can be observed with both methods. It is important to note that measuring forage height is less labor intensive than clipping forage plots. However, by clipping forage plots actual production figures are developed. This makes it critical to use methods properly and in context of a total management scheme (Krueger, 1997).
In addition to monitoring forage utilization, survey data was also acquired to evaluate sustainable stocking rates currently applied in this area (not factoring in plant species). This baseline stocking rate data for Navarro County was collected in 2009 by surveying 28 ranchers. Average ranch size and cattle herd was 253 acres and 39.4 head respectively. Average stocking rate was 7.5 acres per animal unit (ac/AU). The range of stocking rates went from 1.8 ac/AU to 26.7 ac/AU with two ranches completely deferring grazing at the time of evaluation. Stocking rates on the ranch monitored in this study were 4.8 ac/AU in the North Pasture and 12.8 ac/AU in the South Pasture, prior to the implementation of management decisions based on this study (See Results and Discussion).
The data generated in this report only took two days during the year. Once grazing exclosures are in place the amount of labor annually is greatly diminished. As a result of this demonstration, the ranch owner has made the following management decisions and considerations:
1) The South Pasture herd was reduced to 21 cows and one bull (to reduce demand on forage resources) for a new stocking rate of 8.0 ac/AU (4.8 ac/AU prior).
2) In the North Pasture, a bull was put in with the now 800 lbs heifers (8 heifers were sold, leaving 16 heifers) to maintain a stocking rate of 12.8 ac/AU.
3) Alternative feeding locations have been used to improve grazing distribution in the North Pasture.
4) Brush management, water developments and cross fencing are being considered to further enhance forage production and grazing distribution.
5) Monitoring will be continued annually to identify range trends and forage production to ensure the sustainability of the ranching operation.
ACKNOWLEDGEMENTS
Appreciation is extended to the ranch owner, Mr. Paul Curington and to Dr. Charlie Hart, Extension Range Specialist.
LITERATURE CITED
Drake, D.J. 1998. How to Monitor Rangeland Resources: Level II Advanced Monitoring Methods, Utilization of Forage. University of California Cooperative Extension. http://animalscience.ucdavis.edu/extension/FactSheets/ (Confirmed March 5, 2010).
Hanselka, C.W., Hart, C.R., and McGinty, A. 2009. Texas Rangeland Monitoring: Level II. Texas AgriLife Extension Service Publication L-5454.
Krueger, W.C. 1997. Integrating Utilization Measurements into Monitoring Programs. 50th Society for Range Management Annual Meeting. Rapid City, SD.
Laycock, W.A. 1997. Variation in Utilization Estimates Caused by Differences Among Methods, Years and Observers. 50th Society for Range Management Annual Meeting. Rapid City, SD.
Lyons, R.K., and Machen, R.V. 2001. Stocking Rate: The Key Grazing Management Decision. Texas AgriLife Extension Service Publication L-5400.
McGinty, A., and White, L.D. 1998. Range Monitoring with Photo Points. Texas AgriLife Extension Service Publication L-5216.
Mousel, E.M., and Smart, A.J. 2007. Monitoring Rangelands and Pastures: A Rancher’s Approach. South Dakota State University Cooperative Extension Service Publication FS 940.
Reynolds, D.A. 1998. Wyoming Rangeland Monitoring Manual. University of Wyoming Cooperative Extension Service Publication B-1065.