Wednesday, November 7, 2007
270-5

Grazing Intensity and Frequency Effects on Herbage Accumulation and Nutritive Value of Tifton 85 Bermudagrass.

Kesi Liu1, Lynn Sollenberger2, Sindy Interrante1, and Renee White1. (1) University of Florida, P.O. Box 110500, Gainesville, FL 32611, (2) PO Box 110300, University of Florida, Agronomy Dept., 2185 McCarty Hall, Gainesville, FL 32611-0300

‘Tifton 85’ is one of the most productive bermudagrass cultivars and is widely grown in the southern USA and other warm-climate regions. Assessing the impact of grazing management on pasture productivity and nutritive value is important to making most efficient use of this pasture resource. Herbage accumulation (HA), crude protein (CP), and in vitro digestible organic matter (IVDOM) responses of Tifton 85 to grazing management were studied in 2006 on a loamy, siliceous, hyperthermic Grossarenic Paleudult soil in northern Florida. Treatments were the factorial combinations of three post-graze stubble heights (SH) (8, 16, and 24 cm) and three grazing cycle (GC) lengths (14, 21, and 28 d). All treatments were replicated two times in a randomized complete block design. Plots were 400 m2 in area, and grazing periods were from 1 to 10 h. There was interaction for total-season HA because increasing GC resulted in greater HA when SH was 8 cm (11.6 to 15.3 Mg/ha for GC of 14 and 28 d), but when SH was 24 cm HA decreased with increasing GC (14.1 to 11.9 Mg/ha for GC of 14 and 28 d). Herbage CP concentration ranged from 108 to 149 g/kg and was affected primarily by GC, decreasing an average of 23 g/kg as GC increased from 14 to 28 d. The effect of SH was not consistent across levels of GC. Herbage IVDOM decreased linearly from 630 to 601 g/kg as GC increased from 14 to 28 d. First-year results suggest that high HA of Tifton 85 can be achieved by grazing less frequently (28 d) to an 8-cm SH or more frequently (14 d) to a 24-cm stubble. Grazing to approximately 24 cm every 14 d provided the best combination of herbage accumulation and nutritive value.

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