Howard F. Schwartz, Colorado State University, Bugwood.org
These crops will perform well in dry conditions but have the potential to really produce high quality forage under optimum growing conditions too. For forage producers who anticipate short forage supplies, these crops may help to stretch forage supplies. Early June is an ideal time to establish these forage crops for both dry and normal growing conditions.
The following is a brief review of agronomic production issues related to Sorghum sudangrass production. First, select for high forage quality characteristics. Digestibility of hybrids with brown midrib genetics is important for highest forage quality levels. Plant anytime after soil temperatures are above 60 degrees for rapid seedling development. Seed at 65 to 70 pounds of seed per acre and plant at a depth of ½ to ¾ inch. Do not plant too deep! Successful establishment of stands from seedings up to July 4 is possible.
If you are no-tilling into an old alfalfa or grass sod a burndown treatment with glyphosate will be needed. Rarely will weeds out-compete the development of sorghum sudangrass hybrids after seeding. Because of multiple harvesting, weeds are rarely problems thus no herbicides are needed after establishment. High fertility levels are necessary for optimum yields. Phosphorous and potassium requirements are similar for these forages as for corn silage. Sorghum-sudangrass hybrids are also significant users of nitrogen. One hundred pounds of nitrogen is recommended at planting and a second application of 100 pounds of nitrogen following first cutting is recommended for high yield potential. Base this second application on moisture levels and yield potential.
Manure can be used as a nitrogen source but is not recommended. Growth response to manure applications is slow and will not keep up with the high demand for N by rapidly growing plants. In addition traveling on stubble after first cutting with a manure spreader will damage too many crowns and result in injury and poor regrowth.
Harvest stands early and frequently. Begin considering harvest when plants are 30 inches tall. Do not delay cutting. These plants will grow rapidly to 3 feet and if not managed on time can quickly attain 4 feet or more. Do not let these stands get ahead of your planned cutting height. Under optimum growing conditions second cutting may be ready for harvest in as little as 25 days. Mow at a cutting height of 3 to 4 inches to encourage rapid regrowth. Do not harvest stands less than 2 feet in height.
This crop contains high levels of moisture and will require wide windrow management to ensure rapid dry down. The shorter the period from mowing to harvest, the better the quality of the forage. This crop should be planned for haylage or baleage production.