Forage Sorghum – Forage sorghum is an excellent choice when used for silage in a single cut system. Stems and leaves look very similar to corn. Although they can regrow, their second growth is much slower than sorghum x sudangrass or sudangrass.
FSG 114 BMR 6 GW 2120
GW 400 BMR 6
Sorghum sudangrass – These are primarily used for grazing and hay production in a multiple cut system, because of their high regrowth potential. They have faster regrowth than forage sorghum and stronger stalk strength versus sudangrass, however the larger stems makes drying for hay more difficult than for sudangrass. Yield is generally less than forage sorghums, but slightly higher than sudangrass.
Surpass BMR 6 Sugar Graze II
FSG 214 BMR 6 Greengrazer V
GW 300 BMR 6 Sweet Six BMR 6
Sudangrass – Sudangrass is used primarily for grazing and hay production. This species has smaller leaves and finer stems, making drydown more efficient.
Planting rates vary by type, the intended use and whether the crop grown is irrigated or not. It is best to consult your sales representative for specific recommendations. Below are only general suggestions.
Forage Sorghums: Only plant forage sorghum seed once soil temps reach 55-60◦F. Typically one-time cut forage sorghums are planted in 30″ rows (due to facilitate easy cutting with conventional equipment)
- Do NOT overplant. Overplanting reduces stem diameter and raised the odds of lodging.
- On the average, 4-8#/acre for dryland and 6-10#/acre for irrigated.
- Minimum seeding rate for effective light capture is about 3#/acre
Sorghum Sudangrass: Sorghum sudangrass seed is generally seeded at higher rates than forage sorghum seed. For hay production, even higher seeding rates are used. Higher populations reduce stalk diameter allowing faster drying time and improved palatability.
- Generally LOWER seeding rates than with conventional sorghum sudan (>12#/acre). This increases stalk diameter and maximizes yield.
- Rates too low (<12#/acre) will lose tonnage/allow weeds/etc.
- Maximum rates should be no more than 60% of conventional hybrids.
- 25-30#/acre south of I-70.
- 50-60#/acre up north (Wisconsin, etc.)
- 40-80#/acre (lower end for dryland, higher rates for irrigated ground)
Nitrogen: Apply nitrogen (N) at a rate of 1-1¼ lb. of actual N per growing day.
- Start at 80-100# actual N/acre on higher management.
- Add 30-40#/acre after cuttings or grazing, and side-dress 30-50# on grain types.
- Side-dressing N is recommended above ground (as knifing in NH3 or liquid N can prune roots)
- Adding all the nitrogen at planting for sorghum sudangrass leads to lodging and high nitrates on the 1st cut.
- One time cut forage sorghums can have their N applied all at preplant.
Potassium and Phosphorus: Similar/slightly less than corn.
Cutting height – Always leave 1-2 nodes (4-8″). This is critical for light capture and quick regrowth.
Forage sorghums – When used for silage, they are generally harvested around 2 weeks after flowering (soft to mid dough stage)
- 65-70% moisture
- Optimal chop length is about ¾ – 1 ¼” depending on moisture.
Sorghum Sudangrass – Can be chopped, gazed or baled
- Chop – 2 pass system (swath, wilt, chop)
- Graze after 24″ tall. Monitor grazing height for proper regrowth
- Hay harvest at 30-36″ and leave 6-8″. Use conditioner and wide windrows. PATIENCE!
AVOIDING NITRATE AND PRUSSIC ACID POISONING:
Managing for Nitrates
- Nitrates can accumulate when stressed and in soils where ample nitrogen is available
- Best practice is ensiling to reduce nitrate levels (up to 1/2). Dilute high nitrate silage with normal forage and/or grain.
- Dry baling only concentrates nitrates more. Nitrate doesn’t dissipate like prussic acid.
- Do not green chop or feed direct cut forage if high nitrate levels are present
- Cut at a high stubble height. Nitrates tend to accumulate in the lower stalk.
- It is best to test to verify nitrates are at safe levels
Managing for Prussic Acid
- High levels of prussic acid forms when sorghums are injured by frost, resumes growth following drought, high soil N fertility, low P levels in soil, and 2,4-D applications.
- Don’t graze the crop until 18-24″ in height. Young plants and regrowth have higher prussic acid levels.
- Do not graze or green chop after a light frost. Wait 7-10 days before grazing or green chopping. After a killing frost, wait until the plant has completely dried, approximately 7 days.
Most prussic acid is lost during the curing process. Crops cut and allowed to wilt before chopping or ensiling, and field drying will allow for the acid to volatilize from the forage.