There has been limited research to determine the amount of nitrogen to apply to sorghum-sudangrass grown as a forage crop. A recent study conducted in New York suggests optimum nitrogen rates of 112 to 130 pounds per acre per cutting when grown without further nitrogen inputs. For sites that follow sod plow-down or recent manure application, nitrogen rates should not exceed 36 to 54 pounds per acre per cutting.

Brown midrib forage sorghum-sudangrass was grown in a two-cut management system with a split application of nitrogen. The forage was cut when 36 to 43 inches tall, leaving a stubble height of 3 to 3.5 inches.

The study consisted of six field trials in 2003 and 2004 with soil type ranging from silt loam to fine sand to gravelly loam. Planting date varied from June 2 to June 9.

At the sites with no additional nitrogen, dry matter yields ranged from 3.5 to 4.3 tons per acre. At the sites with prior nitrogen inputs, yields were higher (4.6 to 6.2 tons of dry matter per acre).

The study was reported in the September-October 2007 issue of Agronomy Journal.