Location, Year, Maturity, and Alfalfa Competition Effects on Mineral Element Concentrations in Smooth Bromegrass1
- M. D. Casler,
- Michael Collins and
- J. M. Reich2
Many environmental factors influence the level of herbage mineral elements and ratios, often to an extent potentially affecting ruminant performance. This study was conducted to estimate main effects and interaction effects of locations, years, stand types (pure stands vs. binary mixtures with alfalfa, Medicago sativa L.), and growth stages on the concentration of 11 mineral elements and three elemental ratios of smooth bromegrass (Bromus inermis Leyss.) herbage. Nine families of smooth bromegrass were grown in 1.7m2 plots, with and without alfalfa, at Hancock, WI (mixed, mesic, Typic Udipsamment soil) and Lancaster, WI (fine-silty, mixed, mesic Typic Hapludalf soil). Plots were sampled for seven weekly intervals in 1982 and 1983, from the 17- to 22-cm height stage to 7 days post-anthesis. Stand types were whole-plots in four randomized complete blocks; herbage samples were pairwise-composited to provide two replicates. Samples were analyzed for P, K, Ca, Mg, S, Zn, Mn, Fe, and Cu by plasma emission spectroscopy and for N by micro-Kjeldahl. Location, year, or stand type effects were significant for every element or ratio [Ca/P, N/S, and K/(Ca+Mg)]. The direction and magnitude of these effects varied considerably among elements and ratios. All three environmental effects (locations, years, and stand types) interacted strongly for most elements and ratios. All elements and ratios decreased with advancing maturity, except Ca/P, which increased. Relative changes over a 40-day early May to mid-June period were greatest for N (−97% of the overall mean) and smallest for Mn (−8% of the overall mean). Rate of change due to maturation for most elements tended to follow the pattern: 1982 > 1983, Hancock > Lancaster, and pure stands > mixed stands. For the diet of a moderately producing dairy cow (Bos spp.), smooth bromegrass herbage was severely deficient in P, Ca, Mg, S, Zn, Fe, and Cu at advanced stages of maturity, and excessive in K/(Ca+Mg) at all maturity stages. Although some of these deficiencies could be corrected by breeding, most would be more effectively corrected by fertilization or supplementationPlease view the pdf by using the Full Text (PDF) link under 'View' to the left.
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