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OSU Extension

College of Food, Agricultural, and Environmental Sciences

June 4, 2018 - 4:21pm -- Anonymous

Did our rainy spring weather prevent the planned renovation of a pasture or hay field?  Warm season annual grasses offer an alternative to provide some high quality, good yielding forage in those fields.  June is a good time to plant summer annuals.  The most common summer annuals used for grazing and stored forage harvest include sudangrass, sorghum-sudangrass hybrids, and pearl millet.  Forage sorghum is a summer annual grass grown as a one-cut silage or green chop crop.  Teff is a summer annual grass native to Ethiopia that works best for hay and silage and will produce several cuttings before shutting down in cooler weather.  Teff does not work as well in a grazing situation because grazing animals can pull the plants out of the ground.

Unlike our common cool season forages, these warm season annual grasses thrive during hot summer temperatures.  Warm season annual grasses have the potential to produce yields of up to three tons of dry matter (DM) per acre within 45 to 50 days of germination.  Good germination and rapid emergence requires soil temperatures of at least 65 degrees F.  As I write this article, the two-inch soil temperature is 75 degrees according to the Wooster OARDC weather station.  Plant seeds into a firm, moist seedbed at a one-half to one inch depth.  Teff is an exception due to its small seed size.  Plant teff no deeper than one-eighth to one-quarter inch.  The Ohio Agronomy Guide recommends seeding rates of 23 to 25 pounds/acre for sudangrass and sorghum-sudangrass.  Plant pearl millet at 20 pounds/acre.  Many seed companies recommend seeding rates of 30 to 35 pounds per acre for sudangrass and sorghum-sudangrass varieties and those higher seeding rates can result in small diameter plant stems that may be an advantage from a forage quality perspective.  Best establishment and yields generally result when soil pH is above 6.0, soil phosphorus is at 15 ppm Bray P1 (28 ppm Mehlich 3), soil potassium at 100 to 120 ppm and when supplemental nitrogen is provided.  When planted into a grass sod as the previous crop, the Ohio Agronomy Guide recommendation is to provide 60 pounds of nitrogen/acre for a 3-4 ton/acre DM yield goal.

Sorghum-sudangrass hybrids, sudangrass, and pearl millet all work well in a grazing operation.  Sheep and goat producers in particular may want to consider these warm season annuals if animal productivity has been limited by a combination of forage quality and parasite infections during the summer months.  Putting some warm season annuals into the grazing mix can provide a “safe” pasture paddock for these animals, especially when preparing the seedbed with tillage before planting because this breaks the lifecycle of the parasite.  In addition, warm season annuals, when managed correctly provide a higher level of nutrition than cool season forages during the summer months.  Better nutrition equals improved resilience to parasite infections.

Warm season annuals grow fast and require good grazing management to take advantage of the quality forage they can provide.  Grazing must begin before plants get too tall and overly mature.  The Ohio Agronomy Guide recommends a starting grazing height of 24 to 30 inches and a post grazing height of 6 to 8 inches.  The use of brown mid-rib (BMR) varieties increases forage quality and digestibility.  Based on some forage sampling I have done on BMR sudangrass harvested at 24-30 inches in height, it is possible to have crude protein levels (CP) of 15-18 % and TDN values of 68-72%.  However, quality drops off quickly as the plant matures and if plant height gets above 48 inches or seed heads begin to emerge, expect single digit CP values coupled with 50% TDN levels.  Good grazing management will allow another grazing pass in about three weeks with adequate soil moisture. 

Warm season forages also work well for harvest as stored forages, as either silage, baleage or dry hay.  According to the Ohio Agronomy Guide, when harvesting for silage or baleage, cut sudangrass between 18 and 40 inches of growth, sorghum-sudangrass hybrids at 30 to 40 inches, pearl millet in the late-boot to early bloom stage of growth and teff in the pre-boot to early boot growth stage.  If the goal is to get another harvest, mowing/chopping to leave a 6 to 8 inch stubble provides the quickest regrowth.  Dry hay production is definitely a challenge for sudangrass, sorghum-sudangrass hybrids and pearl millet because they require prolonged drying time compared to our cool season forage hay crops.  Mow at the boot stage, before heading, or if the plant reaches 3 to 4 feet in height.  Teff, on the other hand, dries down faster and works well in a dry hay production system.

 For more information about warm season annuals and their use within a forage production system, contact the Wayne County Extension office at 330-264-8722.