PSXI-18 - Nitrogen fertilization management of winter pastures for stocker cattle production

Bermudagrass is often over-seeded with a cool-season annual grass for grazing purposes. In the Gulf Coast region, summer perennials will not become dormant until there are low soil and ambient temperatures. Nitrogen fertilizer is an expensive input and its split application for winter pastures is recommended. The objective of this experiment was to evaluate the time of application of N fertilizer or its substitution with red clover as a source of N. Three treatments were evaluated in 3 consecutive years (2 replicates per year) on annual ryegrass (cv. Marshall) no-tilled planted (45 kg/ha) on Tifton-85 bermudagrass: 1) Urea in late November and mid-late January; 2) Red clover planted with annual ryegrass; 3) Urea in January only. Thirty crossbred steers (203±24 kg) were blocked by BW and randomly assigned to 1 of 6 groups. Each group were continuously stocked on 1.34 ha pastures for 90 d. Forage mass, botanical composition, and nutritive value of the pastures were determined from the time of the first N application and every 15 d thereafter. There was treatment x year interaction (P = 0.03) in botanical composition. Greater proportions (P = 0.03) of bermudagrass were present on the 2-application treatment on every sampling date until d 15 of the grazing period in Year 1 and 3. This was a result of N absorbed by bermudagrass which impacted its nutritive value (P = 0.01) although not forage production (P = 0.07). In Year 2, annual ryegrass dominated the swards due to a cold artic front in early November. Steers grazing fertilized treatments had greater gains (P = 0.04), while production per ha was greater (P = 0.03) when N was applied in January than when no N was applied. Hay production (kg DM/ha) was similar (P = 0.06) among treatments. Opportunities for improved economics of production and enhanced sustainability appear to be realistic objectives with changes in fertilization strategy.