|Wilkinson, S - USDA ARS RETIRED|
Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 3, 2004
Publication Date: September 15, 2004
Citation: Franzluebbers, A.J., Wilkinson, S.R., Stuedemann, J.A. 2004. Bermudagrass management in the southern piedmont USA. X. coastal productivity and persistence in response to fertilization and defoliation reqimes. Agronomy Journal. 96:1400-1411. Interpretive Summary: How pastures are managed is likely to have a large impact on long-term productivity, economic return, and environmental quality. Integrative studies to address these issues are needed by producers, educators, and environmental organizations. Scientists at the USDA-Agricultural Research Service in Watkinsville Georgia conducted a 5-year study with conventional and alternative nitrogen inputs for fertilizer to coastal bermudagrass that was managed either by haying, grazing with cattle at low and high intensities, or unharvested to simulate conservation reserve land. Using broiler litter as fertilizer was as effective for producing high-quality forage, but not quite as effective for producing the quantity of forage as with commercial fertilizer. Cattle stocked at a lower density allowed greater persistence of coastal bermudagrass and higher forage productivity, but lower opportunity for short-term economic return than from high grazing pressure. Grazed pastures became more productive with time compared with ungrazed forage systems, suggesting that further long-term research is needed to evaluate the changing balance among agronomic, economic, and environmental consequences of pasture management systems.
Technical Abstract: Productivity, quality, and persistence of Coastal bermudagrass pastures are likely to be affected by fertilization, but their responses to different harvest strategies remain unclear. We evaluated fertilization with equivalent N rates (inorganic, crimson clover cover crop+inorganic, and broiler litter) and harvest strategy (unharvested, low and high grazing pressure, and hayed) on forage dry matter, C-to-N ratio, and botanical composition of pastures on a Typic Kanhapludult in Georgia during 5 yr. Forage productivity averaged 1.6 Mg/ha/yr lower (16%) with grazed than ungrazed systems during the first two years, but averaged 2.6 Mg/ha/yr higher (45%) during the last two years. Forage C-to-N ratio at the end of the growing season was lowest under high grazing pressure (22)and highest under unharvested management (35). Botanical composition of Coastal bermudagrass in pastures declined by 5%/yr with unharvested and high grazing pressures. Pastures with low cattle density were more productive than with high cattle density from a forage perspective, primarily by avoiding the encroachment of undesirable plant species.