Improving Silage Yield and Seasonal Distribution of Ryegrass (Lolium multiflorum L.) in the Southeastern USA Ann Blount1, Cheryl Mackowiak1 and Gordon Prine2 1University of Florida – NFREC-Marianna and Quincy, Florida 2University of Florida, Gainesville, FL Results and Discussion Early 4x is an experimental line developed for early-season forage production, crown rust and gray leaf spot resistance. Total seasonal yield from Early 4x was nearly twice the yield of Marshall. Early 4x produced 15.0 Mg ha-1 dry matter compared with 11.2 Mg ha-1 for Jumbo and 8.3 Mg ha-1 for Marshall (Fig. 1). There were no significant differences between the March and May yields. Gray leaf spot disease ratings were similarly low among cultivars in March but the average Marshall rating increased from 2 to nearly 8 by the May harvest (Fig. 2). Early 4x and Jumbo disease ratings remained similarly low. Forage quality as measured by in vitro organic matter digestibility (IVOMD) was over 77% for all cultivars at the March harvest (Fig. 3). Forage quality declined below 65% by the May harvest, with Early 4x having the lowest average value at 58%. An added benefit of using higher yielding forages may be their ability to remove more nutrients from systems receiving effluents or other wastes. The Early 4x removed a total of 63 kg P ha-1 (144 kg ha-1 P2O5), whereas Marshall removed only 36 kg P ha-1 (82 kg ha-1 P2O5). Tissue content was nearly 0.5% in many cases for Early 4x and Jumbo. Introduction Extending the seasonal forage production of annual ryegrass (Lolium multiflorum L.) utilized as silage will directly benefit southern dairy operations. Annual ryegrass cultivars in the southern USA tend to be mid- to late-season forage producers. Early season forage production will accelerate greenchop or silage harvests for dairies. Additionally, environmental impacts of nutrients on water quality in this region makes annual ryegrass an attractive choice for processing lagoon effluent. A north Florida dairy utilizes annual ryegrass as a significant part of their livestock diet for much of the calendar year using a sprayfield production system. It was previously shown that disease resistant cultivars were more productive under their high management dairy silage system. However, production was too late in the season to allow for double-cropping corn. Objectives Evaluate silage production of improved ryegrass cultivars under a sprayfield production system. Assess nutrient removal based on biomass harvested from the field. Materials and Methods First year study: Winter, 2006 Fertilizer: Lagoon effluent via pivot irrigation Seeding rate: 56 kg ha-1 Cultivars: Marshall, Jumbo and experimental Early 4X Tissue P analysis of oven-dried, digested forage was by ICAP. Fig. 3. Forage quality (IVOMD) comparisons found lower IVOMD at the May harvest. Bars with letters represent differences among cultivars at P = 0.05. There were no forage quality differences among cultivars at the May harvest. Fig. 4. Forage removal of soil P, based on the P analysis of the harvested forage and forage dry matter at each harvest. Bars with letters represent differences among cultivars at P = 0.05. Conclusions These data support that forage yield and the distribution of that yield may be improved through breeding and selection for cultivars that fit the desired time-frame for greenchop and silage production on southern US dairies. Selection through plant breeding for earlier growth and high tonnage is providing new cultivars, such as Early 4x, for high nutrient input forage systems. Acknowledgements: We would like to thank the owners and staff at the Shenandoah Dairy for their assistance with this project. Funding was provided in-part by a grant from the Florida Department of Agriculture and Consumer Services. Fig. 1. Dry matter yield in the spring of 2006 from 3 annual ryegrass cultivars. There was no differences between the March and May harvest. Bars with letters represent differences among cultivars at P = 0.05. Fig. 2. Incidence of gray leaf spot disease using a rating scale of 1 to 9, where 1 = no symptoms and 9 = leaf death. Bars with letters represent differences among cultivars at P = 0.05. There were no disease rating differences among cultivars at the May harvest.