Traditional methods of winter hay feeding for beef cattle often entail numerous challenges, including high labor demands, high fuel consumption, soil compaction, limited nutrient dispersion, heightened nutrient runoff risks, low forage yields, and nitrogen loss from manure. Rotational bale grazing (RBG) offers an innovative approach to winter hay feeding by strategically positioning hay bales on pasture prior to the onset of winter feeding, then allowing controlled access to the bales. However, its feasibility in the temperate climate of the Southeastern U.S. remains uncertain.
Therefore, this dissertation, conducted over two years at the Shenandoah Valley Agricultural Research and Extension Center in Raphine, VA, aimed to assess the feasibility of implementing RBG in Virginia. Three pre-established sacrifice paddocks (SP) and three five- paddock rotations for RBG treatments were utilized, with cattle being winter hay-fed for approximately 60 days. The study commenced with soil grid sampling across Novel Endophyte Tall Fescue (Schendonorous arundinaceous) pastures, strategically placing hay bales in areas with the lowest Mehlich 1- phosphorus (P). Changes in Mehlich 1-P, Mehlich 1-potassium (K), water-soluble P (WSP), nitrate (NO3-N), and pH were monitored over a two-year RBG implementation period. The results indicated that bale placement did not significantly alter the spatial distribution of Mehlich 1-P concentrations, but consistently influenced Mehlich 1-K distribution. The WSP concentrations remained consistent with bale placement but decreased without. Bale placement had no significant effect on NO3-N or pH.
Furthermore, this study investigated the effects of RBG on nutrient and sediment runoff in comparison to traditional SP. Artificial rainfall simulations were conducted on a SP, RBG first paddock grazed in the rotation (RBG first), and RBG last paddock grazed in the rotation (RBG last). The most significant differences were observed between the RBG first and last treatments, with forage presence in the RBG first paddock contributing to diminished runoff volume and nutrient load. Notably, the SP treatment showed no significant difference from the RBG treatment, likely due to many years of manure deposition increasing soil organic matter and water infiltration. The findings suggested that an RBG paddock grazed last in the rotation may lead to increased runoff volumes, sedimentation, and nutrient concentrations compared to an RBG paddock grazed first in the rotation.
To understand the impact of RBG on forage biomass recovery, spring forage biomass was measured using ground manual samples and drone imagery. Manual samples and drone flights were conducted three times post-winter hay feeding. While the SP system exhibited the highest biomass recovery in high animal impact areas, RBG showed numerically higher biomass by the third sampling date in low animal impact areas. Drone imagery showcased potential for biomass estimation, but processing of drone images took excessive time and rendered it less feasible compared to manual samples. / Doctor of Philosophy / During the winter months, when forage production becomes limited, beef cattle are typically fed hay. Conventional systems, known as sacrifice paddocks (SP), confine cattle to a single paddock where they are regularly provided hay bales by the producer. However, this method presents several drawbacks, including high labor demands, high fuel costs, soil compaction, limited nutrient dispersion in the soil, heightened runoff risks, low forage yields, and nitrogen losses from manure. Recognizing these challenges, producers in regions like the Northern Great Plains and Canada have turned to rotational bale grazing (RBG) as an alternative approach. Rotational bale grazing involves pre-placing hay bales directly onto pastureland before winter feeding begins, then allowing controlled access to the bales. Yet, the applicability of RBG in regions with different climatic conditions, such as Virginia, remains uncertain.
This dissertation explores the comparison between traditional SP systems and RBG systems, with three replications of each. The initial chapter offers a comprehensive review of previous RBG studies. Subsequently, the study investigated RBG's potential to enhance the spatial distribution of manure nutrients, focusing on Mehlich 1- phosphorus (P) and Mehlich 1- potassium (K). Additionally, environmental aspects of both SP and RBG systems are evaluated, analyzing soil water-soluble phosphorus (WSP), pH, and nitrate-nitrogen (NO3-N) concentrations.
The dissertation's third chapter examined RBG's impact on runoff and nutrient loads through artificial rainfall simulations. Results indicate that RBG paddocks grazed last, with less time for forage recovery, exhibited significantly higher runoff and nutrient loads compared to those grazed first, which had more time for recovery, thus increasing forage biomass. Notably, the SP treatment showed no significant difference from the RBG treatment, likely due to long term manure deposition increasing soil organic matter and water infiltration over time.
Lastly, the study explores RBG's effect on spring forage recovery compared to traditional SP systems. Manual ground samples and drone imagery are utilized across three sampling dates to estimate biomass recovery. While SP treatments showed greater manual biomass in high animal impact areas across all sampling dates, no significant differences were observed in low animal impact areas. However, RBG displayed numerically higher biomass. Drone imagery showcased potential for biomass estimation, but processing of drone images took excessive time and rendered it less feasible compared to manual samples.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/119146 |
| Date | 28 May 2024 |
| Creators | Thomas, Summer Payge |
| Contributors | Crop and Soil Environmental Sciences, Maguire, Rory O., Greiner, Scott P., Shafian, Sanaz, Pent, Gabriel J., Tracy, Benjamin Franklin |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Language | English |
| Detected Language | English |
| Type | Dissertation |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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