2013 Annual Report for LNC11-338
Mob Grazing Increases Efficiency and Profitability of Livestock Production
Summary
We continued the mob grazing study that was initiated in 2012 with 9 cooperating producers scattered throughout South Dakota. In 2013, we resampled soils and vegetation at each site. Two graduate students initiated new projects to evaluate the impact of mob grazing on 1) the function of litter and 2) the impact of pasture weeds. Three Youtube videos were developed as “virtual tours”. In December, an annual meeting was held with all the producers and researchers. We will continue with the research and work on analyzing the soils to determine impact on soil carbon and nitrogen.
Objectives/Performance Targets
1) Collect vegetation and soil monitoring data at each site 1 to 2 times per grazing period
2) Develop videos of “virtual tours” of three producers
3) Hold an annual meeting to go over data collected and plan tours for next year.
Accomplishments/Milestones
1) Vegetation data collection
We continued the mob grazing study across the different ranches in South Dakota (Figure 1). Stocking density ranged from 20,000 to 1,000,000 lbs of beef per acre with cattle rotated once per day up to nine times per day. Stocking densities were greater for most sites in 2013 than 2012, likely because of increased moisture availability across the state (Figure 2). Experimental stocking densities used at two sites (Reliance – 1,000,000 lbs/acre and Volga – 200,000 lbs/acre) did not change from 2012 to 2013.
Pre and post grazing standing vegetation and litter biomass was sampled during the reporting period at 3 sites in South Dakota. Sites were located in Quinn (western SD), Chamberlain (central SD) and Hayti (eastern SD) to look at harvesting efficiency and biomass differences across a climatic gradient. Paired 0.25 m2 quadrats were clipped before and after grazing along 8 transects per site with 10 replicates per transect. Standing vegetation and litter biomass samples were placed in separate bags, dried at 70 C for 72 hours, and weighed. New trampled litter biomass after grazing was measured by placing green litter into a separate bag. Between 80 and 90% of the standing vegetation biomass was utilized (consumption + trampled) during mob grazing at the sampled sites (Figure 3). Chamberlain had 4 to 6 times more trampled new litter and greater pre-grazing forage than the other sites (Figure 4).
Biomass was sampled before and after grazing with 5 experimental stocking densities at Volga, SD in 2012 and 2013 (Figure 5). Increasing stocking density from 50,000 lbs/acre to 200,000 lbs/acre at this site in 2012 resulted in a significant increase in total utilization (i.e. forage harvested and trampled litter). However, no further increase was observed when densities increased to 400 and 800,000 lbs/acre in this year. Between 20 and 40% more forage was utilized in 2013 than 2012 and utilization was highest for the 400 and 800,000 lbs/ac stocking densities. Average rainfall from Apil 1 to Sept 31 was higher in 2013 (14.9 inches) than 2012 (10.7 inches). These results suggest that increasing stocking density does not always equate to greater utilization and producers may want to adjust stocking densities based on moisture conditions to achieve desired utilization rates.
We monitored soil temperature and moisture under different vegetation cover types (intact grassland vegetation, bare ground, and mob grazed vegetation) at 3 different sites across South Dakota (Figures 6-11). Soil temperature was typically higher for bareground treatments than ungrazed or mob grazed treatments irrespective of site. Soil moisture at the 2 inch depth was variable across treatments and sites but ungrazed vegetation often had lower soil water potential (likely from water uptake by intact vegetation). Results suggest that changes in groundcover from mob grazing may impact soil conditions that are important for microbial activity.
At three sites, weedy plants were measured for their canopy volume before and after grazing at three sites in 2013 (Figure 12). Mob grazing reduced buckbrush volume compared to no grazing at Chamberlain. At Selby, mob grazing had a slight reduction in buckbrush volume compared with no change in the rotational grazed pasture. At Hayti, wormwood sage did not reduce in volume in either rotational or mob grazing. When an area was treated with 2,4-D, the cattle consumed the wormwood sage and completely defoliated the plants. It was likely that cattle were attracted to the plants due to the salty flavor of the herbicide treated plants. This may warrant further study.
2) Videos and tours
We collected video footage to document mob or intensive grazing demonstrations performed in Chamberlain, Hayti, and Quinn, SD. Videos range from 6 to 8 minutes in length and they show conditions associated with successful mob grazing operations in South Dakota. Ranchers talk candidly about their experiences with mob grazing and the methods they use to maintain profitability while attempting to improve the quality of their land. These videos are designed to target land managers already practicing mob grazing that are interested in viewing other operations and people interested in potentially implementing intensive grazing practices.
http://youtu.be/fWC9qkYdDNA (Guptill)
http://youtu.be/MJ4tlSkVxAk (Totton)
http://youtu.be/NA9D5eiLHlw (Smith)
We held our annual South Dakota investigator site tour on July 15, 2013 at Quinn and Reliance, SD (Figures 13 and 14). Participants included: Sharon Clay (SDSU), Alexander Smart (SDSU), Michelle Ohrtman (SDSU), Larry Janssen (SDSU), Bronc McMurtry (SDSU), Emily Helms (SDSU), Heidi Myer (SDSU), Justin Hansen (SDSU), Martha Mamo (UNL), Jerry Volesky (UNL), Matt Stockton (UNL), Walt Schacht (UNL), Pat Guptill (Rancher SD), Randy Holmquist (Rancher SD), Judge Jessop (SD Grassland Coalition), and Steve Woodruff (NRCS, East National Technology Support Center).
3) December Annual meeting
On December 18, 2013 in Chamberlain, SD. We shared the 2013 results with the producers. Discussion focused on the soil health aspects of the study, namely soil C, and an economic analysis. We indicated that soil sampling for a long period of time would help understand the change. Producers said that they would continue mob grazing and that SDSU researchers would try to identify grant opportunities to analyze long-term soil carbon changes. The focus in 2014 will be to finish the 2 M.S. projects and work on an economic analysis with anticipated finish of the grant project in December 2015. No major plans were made for a tour. The producers really appreciated the three videos. Some said that they might be interested in a pasture walk. Doug Sieck held a pasture walk at his place in early October. The pasture walks are relatively easy to hold with little expense.
Impacts and Contributions/Outcomes
We have completed two years of the mob grazing study. So far we have gained some insight into the mechanisms governing the trampling effect and adding litter to cover bare ground in relation to stocking density, plant height, and location (influence of local plant-soil-climate factors). Mob grazing did increase the distribution of cattle manure. Producers are getting an increase in harvest efficiency, probably 40-50%, which is almost twice that over season-long continuous grazing at a moderate stocking rate. It remains to be seen how the soil health will change, ultimately affecting plant productivity. The financial and production assessment is incomplete, but we suspect that once we complete the analysis, the increases in grazing efficiencies will likely be profitable compared with less intensive rotations.