Seasonal Productivity and Nutrient Uptake Comparisons Among Cool-Season Annual Forage Grasses.

Extending the seasonal forage production of annual ryegrass (Lolium multiflorum Lam.), rye (Secale cereale L.), triticale (X Triticosecale Wittmack) and oat (Avena sativa L.) will benefit livestock grazing and dairies utilizing cool-season forages for silage and nutrient remediation.  Annual cool season forage grasses in the southern U.S. tend to be mid- to late-season producers. Strategies for extending the period of forage growth includes an understanding of production peaks among forage species and cultivars, as well as their nutrient demand and removal from soil.  A two-year, nonirrigated, cool-season forage trial comparing several genotypes within each species was conducted at Marianna, FL, U.S.A.  Forage yield, quality and nutrient uptake via 4 wk clippings were taken during winter/spring of 2007 and 2008.  Seed was sown in October of each year. Oven-dried tissue was analyzed for plant essential elements over time. In many cases, cumulative nutrient uptake, such as nitrogen, correlated with yield.  However, there were some nutrients, such as phosphorus, where content varied between and within species.  Triticale tissue contained some of the highest tissue phosphorus concentrations (over 5.0 g per kg) but some ryegrass cultivars accumulated the greatest total phosphorus.  Tissue nutrient content among forage species also varied during the growing season.  This was especially true for oat cultivars in regard to sulfur (S) and iron (Fe).  Oat forage content typically decreased from approximately 2.5 to 1.7 g S per kg and from approximately 150 to 50 mg Fe per kg, during the season.  These results illustrate how forage selections may impact nutrient management in systems as diverse as low-input ranching to the mitigation of nutrient impacted soils.