Silvopastures integrate trees, forages, and livestock. Tall fescue, the dominant forage in much of the U.S., harbors an endophyte that produces toxic ergot alkaloids. Diluting the sward with other forages can reduce ergot alkaloid concentrations, but it is unknown how shade impacts alkaloid production and productivity of different forage mixtures. This study tested the effects of increasing shade and mixture complexity on sward yield, botanical composition, nutritive characteristics and ergot alkaloid concentrations. Slatted shade structures created 30, 50, and 70% shade compared to full sun. Three forage mixtures were evaluated (SIMPLE = tall fescue and white clover; INTERMEDIATE = SIMPLE + orchardgrass and red clover; and COMPLEX = INTERMEDIATE + Kentucky bluegrass, birdsfoot trefoil, and alfalfa).
Fifty and 70% shade reduced yield while red clover and orchardgrass dominated shaded swards. Birdsfoot trefoil, Kentucky bluegrass, and white clover did not perform well in any treatment. Nutritive value declined beneath shade in spring and fall. Sward ergot alkaloid concentration increased beneath shade in simple mixtures because of greater proportions of tall fescue. In the intermediate and complex mixtures, ergot alkaloids were diluted by other forage species and was not affected by shade. This illustrates the importance of incorporating multiple species into the sward. Low light levels may not have been sufficient to meet the forages' high energetic demands in the spring. Even though total forage production or nutritive value may be sacrificed during part of the year, this may be compensated for by diverse swards diluting ergot alkaloid concentrations. / Master of Science / Silvopastures are an integrated land use practice that incorporate trees into pasture systems. Well-managed silvopastures have the potential to improve tree, forage, and/or livestock production, but local climate, individual system components, and management result in a wide range of conditions that can variably influence each element’s production. Therefore, we designed a study to evaluate a range of shade levels and forage mixtures in order to gain a better understanding of how each factor influences forage production in silvopastures. Shade levels ranged from 0 to 70% shade while forage mixtures contained 2 to 7 species. Responses of interest were yield and quality of shaded forage mixtures as compared to mixtures grown in full sun. Forage yields were reduced at moderate and heavy shade levels, and red clover and orchardgrass were dominant species in shaded mixtures, while white clover, Kentucky bluegrass and birdsfoot trefoil scarcely contributed to pasture yield. Forage quality somewhat declined in spring and fall, but negative factors such as toxicity were reduced when more diverse mixtures were planted. This research illustrates the importance of using site-adapted, shade tolerant forages in silvopasture systems, while also demonstrating that tree canopy management is necessary in order to maintain adequate yields.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/77424 |
| Date | 18 April 2017 |
| Creators | Mercier, Kelly Marie |
| Contributors | Crop and Soil Environmental Sciences, Fike, John H., Teutsch, Christopher D., Munsell, John F., Tracy, Benjamin F., Strahm, Brian D. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
Page generated in 0.0161 seconds