Monday, November 13, 2006 - 3:15 PM

Micronutrient Concentrations of Stockpiled Tall Fescue Treated with Phosphorus.

Will Mcclain, "University of Missouri, Columbia", 1-31 Ag Bldg, 1-31 Ag Bldg, Columbia, MO 65211, United States of America and Dale Blevins, "Agronomy Dep., 1-87 Agric.Bldg", University of Missouri, University of Missouri, Columbia, MO 65211, United States of America.

In the Midwest, beef producers utilize stockpiled tall fescue (Festuca arundinacea) to extend the grazing season and reduce winter feeding costs. While this cool season forage provides an important resource for beef production, very little is known about the micronutrient concentrations of leaves during the stockpiling season. Essential micronutrients are necessary for the health of grazing livestock and, as in plants, these micronutrient are only required in trace amounts and deficiencies can lead to considerable losses in animal productivity. For Missouri, many soils used for tall fescue pasture are characterized by low pH, low plant available phosphorus (P), and high levels of soluble aluminum (Al). The nutrient status of these soils can impact not only forage production but also the micronutrient concentrations available to grazing livestock. 

The objective of this study was to determine the effects of P fertilization on the micronutrient concentrations of stockpiled tall fescue during fall, winter and spring. Results of micronutrient analyses of stockpiled tall fescue showed that P fertilization increased the leaf concentrations of manganese (Mn), iron (Fe), zinc (Zn) and Al compared to untreated controls. Phosphorus fertilization had no effect on copper (Cu) concentration of tall fescue leaves. However, there was a 3-fold increase in Cu concentrations from winter to early spring. Tissue concentrations of Mn, Fe, and Al, peaked in February and declined into early spring. Requirements for most micronutrients are not well defined, and producers often provide supplementation to grazing beef cows throughout the year. Results from this research showed that most micronutrients were below the toxic levels for grazing beef cows. However, most micronutrient concentrations showed changes over time which might lead to over-supplementation and negatively impact animal performance and health.