Location: Forage and Range Research
2011 Annual Report
Objective 2. Optimum grass-legume mixtures will be determined by evaluating tall fescue, meadow brome, orchardgrass, alfalfa, birdsfoot trefoil, and cicer milkvetch in grass/legume binary mixtures. Legume plant densities of 0 (with N fertilizer), 0 (without N fertilizer), 25, 50, 75, and 100 percent will be tested with each grass for a total of 48 treatments. Grazing pressure will be applied to the entire experiment for 7 days on a 28-day rotational interval. Immediately prior to each grazing period, one-half of each plot will be harvested with a forage plot harvester. Forage production and forage quality parameters including crude protein, neutral detergent fiber, acid detergent fiber, acid detergent lignin, and in vitro true digestibility will be evaluated.
Objective 3. The effects of tannins on nutrient cycling will be evaluated for the plant, soil, and soil water phases. Plant samples will be collected before and after each grazing event and herbage dry matter and total nitrogen (N) will be analyzed to determine the nutrients removed in the forage. Soil samples will be collected in the spring, prior to grazing, and in the fall after the growing season to a depth of 1.5 meters. Four soil cores will be taken in each plot and divided into three subsamples: 0-30 cm, 30-60 cm, 60-152 cm. Composite soil subsamples for each depth will be analyzed for available nitrogen (ammonia and nitrate) and for total Nitrogen. Soil water (leachate) nitrogen will be monitored by means of zero-tension lysimeters that were previously installed to a 120 cm depth. Leachate will be collected from the lysimeter collection basin every two weeks during the growing season and winter months. Samples will be analyzed for nitrate-nitrite. A mass balance approach comparing total nitrogen outputs against total nitrogen inputs for each treatment will be utilized to estimate losses due to volatilization.
During FY-2011: The work outlined in the SOW was initiated. It was discovered that legumes had died out of previously established pastures. These tall fescue-legume (alfalfa and birdsfoot trefoil) pastures were re-established in 2011. However, the graduate student on this project used the existing pastures to collect a second year’s data on livestock intake and gains, fatty acid profiles, ruminal pH and ammonia, and forage production and quality comparing tall fescue with and without N-fertilizer and feedlot treatments. Preliminary results were presented at the Annual Meeting of Western Section, American Society of Animal Science in June 2011 and at the Joint Annual Meeting of ADSA-ASAS in July 2011, and indicated that applying N fertilizer to tall fescue did not influence growth performance or carcass characteristics.
Additional research initiated during FY2011 included installation of lysimeters during the re-establishment of the tall fescue-legume pastures, which were used to determine the initial nitrogen in the leachate. These pastures will be grazed next year. The small plots of binary mixtures of five grasses (orchardgrass, tall fescue, meadow brome, timothy, and perennial ryegrass) and three legumes (alfalfa, birdsfoot trefoil, and cicer milkvetch) were established and data collection was begun. Ratios in the mixtures included 0, 25, 50, and 75% legume composition. Samples from these plots were used to initiate development of an NIRS equation that can determine composition of legume in mixture plots.