Location: Forage and Range Research
2013 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.
A related study is now evaluating cattle performance when grazing grass-legume mixtures. During FY2013, the first year of this study was completed evaluating beef steers grazing tall fescue (TF) pastures with or without low- and high-tannin legumes and the resulting effects on growth performance, ruminal fermentation, and carcass characteristics. In response to grass-legume mixtures, the preliminary (1-yr) average daily gains (ADG) were 1.7, 1.4, 1.4, and 0.8 pounds per day for TF+Birdsfoot trefoil, TF+Alfalfa, TF+Nitrogren Fertilizer, and TF-Nitrogren Fertilizer, respectively, with the TF no fertilizer being statistically lower than the other treatments. Forage yields followed a similar pattern with the TF+ fertilizer yield being the highest (4950 lbs/acre) but not significantly different than mixtures with alfalfa and birdsfoot trefoil, and all three being higher than TF with no fertilizer (3591 lbs/acre). Carcass quality and forage yield and quality data are being analyzed. This study will be repeated for a second year. This research is being conducted in partial completion of a M.S. thesis and results were presented by the graduate student at the Western Society of Crop Science meetings in Pendleton, OR.
A small-plot of binary mixtures of five grasses [orchardgrass (OG), tall fescue (TF), meadow brome (MB), timothy, and perennial ryegrass (PR)] and three legumes [alfalfa (AF), birdsfoot trefoil (BF), and cicer milkvetch (CM)] were established previously. Ratios in the mixtures included 0, 25, 50, and 75% legume composition. Results revealed that tall fescue, OG, and MB grass-legume mixes averaged 6.0, 5.0, and 14.0% higher forage production than their respective grass monocultures. The highest seasonal forage production of TF combinations was 1.62 Mg/ha TF:AF (50:50), 1.63 Mg/ha TF:BF (75:25), and 1.64 Mg/ha TF:CM (75:25). Highest forage production of OG combinations was 1.10 Mg/ha OG:AF (50:50), 1.09 Mg/ha OG:BF (75:25), and 0.99 Mg/ha OG:CM (75:25). Highest seasonal forage production of MB combinations was 1.23 Mg/ha MB:AF (50:50), 1.25 Mg/ha MB:BF (75:25), and 1.11 Mg/ha MB:CM (75:25). These results suggest that grass-legume mixtures can be an effective strategy to improve pasture productivity. Mixtures with cicer milkvetch and birdsfoot trefoil were most productive when they constituted 25% of the mix, whereas, mixtures with alfalfa were most productive when it comprised 50% of the mix. This research was conducted in partial completion of a M.S. thesis, and was presented at two professional meetings.
Nutrient cycling data were collected in FY2013. Soil subsamples are analyzed for available nitrogen (ammonia and nitrate) and for total N by combustion. Leachate samples were collected every two weeks during the growing season. Samples will be analyzed for nitrate-nitrite. Plant samples, collected before and after each grazing event, are used to determine the nutrients removed in the forage. A mass balance approach comparing total nitrogen outputs against total nitrogen inputs for each treatment will be utilized to estimate losses due to volatilization. The effect of tannins on nitrogen cycling will be examined.