Sweet Sorghum Production Basics

Potential for Sweet sorghum as a biofuel.
Sweet Sorghum Production Basics - Articles

Updated: December 5, 2013

Sweet Sorghum Production Basics

It is relatively drought tolerant, has a high forage and ethanol yield per acre, has relatively low cost of production, is adaptable to no-till, has a co-product called bagasse that could be used for animal feed, and the crop itself could be used for silage if needed. It is also a late planted crop that fits well into cover cropping systems. Yields of 25 tons (fresh weight) are possible with juice yields of 2500-3000 gallons per acre possible.

Planting

  • Planting should be delayed until soil temperatures reach 65°F at the 2- to 4-inch depth. This usually occurs in mid to late May.
  • Sorghum is often planted in 30 inch rows but could be planted in 15 or 20 inch rows to maximize production potential.
  • Seeding rates range from about 60,000 to 80,000 seeds per acre. This is about 3-4 seeds per foot of row in 30 inch rows and translates into about 5 pounds of seed per acre.
  • Planting depth is 0.75 to 1.25 inches.
  • Sorghum is well adapted to no-till planting.

Soil Fertility

  • The nitrogen requirement is likely in the range of 100 to 120 pounds per acre. We have recommended higher rates of N for forage sorghum production in the past, similar to corn silage production, but these could result in more lodging and lower sugar levels.
  • P and K requirements are modest and probably depend on whether the bagasse is removed from the site. If that is the case, then The nutrient recommendation for a soil testing in the optimum range for P and K is 120 pounds of N, 65 pounds of P2O5, and 120 pounds of K2O for a crop with a 21-ton per acre yield potential.
  • Soil pH should be near 6.0

Crop Rotation

  • Sorghums are very flexible and can be planted after many crops. They are tolerant of atrazine so following corn is not an issue.
  • The later planting of sorghum makes it possible to harvest a hay or small grain crop prior to planting.

Weed Control

  • Fewer herbicides are available for forage sorghum compared to corn, so control of some problem weeds may be a bit more challenging without tillage.
  • Sorghum seed treated with Concep II seed safened allows the grass herbicide Dual to be applied without injuring the crop.
  • Specific herbicide recommendations are updated annually in the Penn State Agronomy Guide.
  • A good sorghum crop can function as a smother crop-reducing weed pressure in subsequent crops.

Pest Management

  • Sorghum has few insect pests in Pennsylvania. Occassionally fall armyworm damage may be observed.
  • Sorghum is not a host for western corn rootworm, hence corn can follow sorghum with no risk of rootworm.
  • Some foliar diseases can appear on sorghum. Anthractnose is a foliar disease that can appear on leaves and stalks.
  • Sorghum is less preferred by groundhogs and deer than other crops like corn, soybeans, sunflowers or canola.

Harvesting

  • Traditionally sweet sorghum was harvested by hand and fed through a press to extract juice.
  • Mechanized systems are being developed that are similar to silage chopping and hauling the material to plant for processing.
  • Others are considering on site processing to extract and store juice.
  • Harvesting occurs near the soft dough stage often 120 days or so after planting. A Brix meter can be used to assess the sugar content at harvest.
  • Stalks, leaves, and grain left after processing could be used for pelletizing for energy, digested for energy or ensiled into a feedstuff.
  • One issue with sorghum is that the material needs to be processed soon after harvest unlike other graincrops used for biofuel.

Prepared by Greg Roth, Professor of Agronomy, Penn State