Description

Family

  • Grass — summer annual.
  • Refers to a wide range of grasses related to sorghum and sudangrass.
  • Usually a cross between a forage or grain sorghum and sudangrass.
Sorghum and sudangrass are warm season grass cover crops that can provide good weed suppression, grazing and forge supply, in addition to the soil structure improvements that can be expected from grasses.
Figure 1. Sorghum and sudangrass are warm season grass cover crops that can provide good weed suppression, grazing and forge supply, in addition to the soil structure improvements that can be expected from grasses.

Cover crop use

  • after early harvested crops
  • as an emergency forage
  • to add biomass to soil
  • suppress nematodes (variety specific)

Growth habits

Germination

  • Requires warm soil for germination — above 12°C.

Top growth

  • Rapidly growing summer annual grass.
  • Wide cultivar variation — height ranges between 45 cm to over 5 m.
  • Has lower leaf area than corn.

Root system

  • Has more secondary roots than corn.
  • Roots can reach depth of greater than 124 cm.
Root mass late in fall may be reduced
Figure 2. Root mass late in fall may be reduced.

Overwintering

  • Easily killed by frost.

Site suitability

  • Extreme drought tolerance.
  • Prefers neutral pH but can tolerate 5.0 to 9.0.
  • Tolerant of salinity.

Sensitivity to herbicides: Weed control

  • There are no herbicides registered for weed control in sorghum sudan grasses. Use narrow rows and appropriate agronomic practices to establish a vigorous crop canopy as soon as possible.

Benefits and concerns

Nutrient management

  • Heavy feeder due to crop biomass.
  • May need additional nitrogen to aid in decomposition.
Longer term growth of a cover crop like sorghum shades and moderates soil temperatures; encouraging more earthworms.
Figure 3. Longer term growth of a cover crop like sorghum shades and moderates soil temperatures; encouraging more earthworms.

Pest management

  • Nematode suppression — selected varieties only.
  • Weed suppression from competition for light, water and nutrients.

Organic matter

  • Can produce massive amounts of dry matter (4,000 to 5,000 lbs/acre).
  • Chop plant down when it reaches 1–1.2 m to encourage tillering and deeper root growth.
  • Manage the crop with chopping to avoid maturity as stalks gets fibrous and woody with age and slow to break down.

Erosion control

  • Reasonable, soil conservation alternative to summer fallowing.

As feed

  • Can be used as forage.
  • Wait until mature to avoid problems with prussic acid.
  • Do not feed if plants have been stressed or frozen.

Getting started

Establishment

  • Plant in warm soils — no sooner than 2 weeks following corn.

Cost and availability

  • There is a wide variation in cultivars available and some confusion with sorghum.
  • Cost is moderate depending on the variety.
  • Some varieties have nematode suppressing properties.
  • Buyer Beware: Make you sure know what you're buying when getting seed.

Managing the cover crops

  • chop of mow plant when it reaches 1–1.2 m to encourage tillering and deeper root growth.
  • manage the crop with chopping to avoid maturity as stalks get fibrous and woody with age and slow to break down.
  • will set seed if not mowed.
Sorghum and sudan grass hybrids will to to seed if not mowed, creating a potential weed problem.
Figure 4. Sorghum and sudan grass hybrids will to to seed if not mowed, creating a potential weed problem.