Annual Forages for Integrated Crop and Livestock Systems
The objectives for this project include:
1) Develop a two-year database on production and quality characteristics of fall- and spring-seeded cereal forages, summer annual forages and annual legumes, and
2) Determine the protein degradability of these forages in the rumen for use in the new National Research Council metabolizable protein system for beef cattle.
Annual forages sometimes are used as an emergency feed source or as insurance against reduced grazing or feed resources associated with weather problems. However, more producers are using annuals as an important forage component of grazing or feeding systems while also benefitting from reduced soil erosion, improved weed control and intensified crop rotations. Information is lacking on comparisons of currently available annual forage varieties.
A dryland plot of cereal forages was planted at the High Plains Ag Lab near Sidney, Nebraska, on April 1, 1998 in an area where proso millet had been grown in the previous year and grain sorghum the year before that. Eight cultivars were planted and replicated four times. There were two varieties of triticale, two of barley, three of oats and one combination of oats and field peas. The plot was not fertilized and was harvested for forage on July 6. Plot areas of 4 feet by 15 feet were swathed and weighed. The top yielding variety was a triticale (2700 from Resource Seeds) at 2 tons of dry matter per acre. Crude protein contents for all of these forages were lower than expected, which suggests low nitrogen fertility and maturity were factors. However, available energy contents were good, as indicate by in-vitro dry matter digestibilities and by estimates of TDN and Net Energy.
An irrigated plot of summer annual forages was planted at the Panhandle Research and Extension Center at the Scottsbluff on June 19 and harvested on September 9 and 10. A dryland plot was replanted at the High Plains Ag Lab on July 8 and harvested on September 23 and 25 after a planter problem resulted in missing rows from a planting on June 22. Forage crops included forage sorghum, sorghum x sudangrass, sudangrass, pearl millet and foxtail millet. Iron treatments were included to check for color, quality and yield effects. Nitrogen and phosphorus were applied at 120 and 80 pounds per acre on the irrigated plot and at 60 and 40 pounds per acre on the dryland plot.
The top yielding entry in the irrigated trial was a sorghum x sudangrass hybrid names Super Sweet ST 15 from the Triumph Seed Co., in Ralls, Texas. The second highest yield in this trial and the highest in the dryland yield was obtained with a sorghum x sudangrass hybrid named Att-A-Graze, which was obtained locally from Jirdon Agri-Chem in Morill but produced by Attaberry Grain Company in Happy, Texas. Forage quality tests were complete by the NIRS method at UNL. Crude protein, digestibility and estimates of TDN and Net Energy were higher in the dryland trial, and probably closer to levels that might be expected in two cuttings under irrigation for those varieties that have good regrowth potential. However, results showed that nitrate levels can be a concern for toxicity to animals with some of the varieties grown under high nitrogen fertility. This can be managed by limited initial access or by combining such feeds with other feeds low in nitrate.
For 1999, the irrigated trial was planted in the small plot area of the Panhandle Center on June 14 and subsequently irrigated with a lateral move system. The foxtail millets were harvested on August 18 after a 66-day growing period and remaining summer annual forages were harvested with a plot swather and a field chopper with a pick-up attachment on September 10 after an 88-day growing period.
The dryland trial was planted on June 18 at the High Plains Ag Lab in an area that had been in wheat the previous year. On June 26, a severe hail storm and a pounding rain resulted in crusting that caused stand problems, especially in the foxtail and pearl millets. We were able to harvest an outside row of the foxtail millets on August 18 (61 days) because the stands were good where the rear tires of the planter tractor had gone over the outside rows. The remaining summer annual forages were harvested with a plot swather and a field chopper with a pickup attachment on September 1 (75 days), but we did not harvest any plots with less than 45 percent estimated stand.
Dry matter yields under irrigation were slightly higher in 1999, as the summer annuals responded to the water, fertilizer and warm temperatures. Dry matter yields under dryland conditions were slightly lower in 1999 than in 1998 and were likely due to drier weather and poorer stands.
These trials were essentially repeated for two years in a single cut harvest system. When water from irrigation or rainfall is adequate, the preferred management systems for cultivars with good regrowth capability would be to graze or harvest twice in this climate to obtain feed higher in protein and available energy while reducing chances for lodging. Quality data from lab tests will be provided for 1999 cultivars, including nitrate levels which can be a concern with some cultivars, depending on plant maturity, soil fertility and growing conditions. Another concern for sorghum or sorghum x sudan hybrids would be prussic acid content, but that is usually managed by deferring grazing until plants reach 18 to 24 inches in height. However, pearly millets do not have this problem.