Cool-season grass hay fields may not be producing the usual yields this year, so summer annual forage crops may be a reasonable alternative for some producers. Summer annuals can be effectively used for grazing or conserved as hay or haylage and can be an important forage source if abused pastures or hay fields are going to be re-seeded to cool-season grasses this fall. General production information below is taken from MU Guide G4661.
The first group of summer annuals are sudangrasses and sorghum-sudangrass hybrids. These can be seeded as late as June 30, but earlier seeding dates are preferred. Drilled seeding rates are 20 to 25 pounds per acre. Allow 45 to 60 days between seeding and first grazing. Grazing can begin when forage height reaches 24 inches. Haying should be delayed until height is 30 to 36 inches. Allow a 10-inch stubble after harvest. Apply 60 to 90 pounds of N at establishment and 40 to 60 pounds after each cutting or grazing. Phosphorus and potassium should be applied to soil test. Nitrates and prussic acid can be issues, but management and rainfall dictate if or when these will be of concern. In general, plants will accumulate nitrates during dry or drought conditions. Normal rainfall patterns should help reduce this concern. Prussic acid is present in new growth, so following the recommended harvest heights should avoid this problem. Quality can be very good if harvested before the plants get excessively tall and stemmy.
Pearlmillet is a second summer annual forage option for hay or grazing. It is typically drilled at 15 pounds per acre and can be planted through the middle of June. Pearlmillet is tolerant of acidic soils and drought. Grazing can begin when it reaches 18 to 30 inches tall. Haying can be done when it reaches 36 inches tall. Leave 8 to 12 inches of stubble after harvest. Pearlmillet does not contain prussic acid but can accumulate nitrates. Days from seeding to first grazing and nitrogen fertilization recommendations are the same as mentioned above for the sorghums.
Harvest management is similar for sorghum-sudangrass and pearlmillet. Hay curing can be difficult with these forages, so mower-conditioners should be used to harvest these crops. Use more roller pressure than used on other hay crops for these forages. It is almost impossible to overcrush the stems.
A couple of years ago, a producer shared with me some harvest results for pearl millet. He harvested the crop for hay and left 4” to 5” inches of stubble height on part of the field. He added shoes and spacers to the mower/conditioner and raised the cutting height on the rest of the field to 10”. Approximately 10 days after hay harvest, the 4”-5” stubble had 6” to 8” of regrowth. The 10” stubble height had over 2 feet of regrowth. Cutting and grazing heights matter!
Additional management information is provided in the publication G4661 available online at https://extension.missouri.edu/publications/g4661 or by contacting your local MU Extension Center and asking for the publication. I can be contacted at firstname.lastname@example.org or by phone at (660) 827-0591 if additional information is required.