Cover Crops: Sorghum Sudan

Table of Contents

  1. Description: Family
  2. Cover Crop Use
  3. Growth Habits
  4. Sensitivity to Herbicides: Weed Control
  5. Benefits and Concerns
  6. Getting Started
  7. Managing the Cover Crops
  8. Related Links

Description

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.

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.

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

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

Figure 2. 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

Figure 3. Longer term growth of a cover crop like sorghum shades and moderates soil temperatures; encouraing more earthworms.

Figure 3. Longer term growth of a cover crop like sorghum shades and moderates soil temperatures; encouraing 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 & 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

Figure 4. 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.


Related Links


For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca
Author: Anne Verhallen - Soil Management Specialist (Hort Crops)/OMAFRA; Adam Hayes - Soil Management Specialist (Field Crops)/OMAFRA; Ted Taylor - Technical Coordinater, BMP Program/OMAFRA
Creation Date: June 2001
Last Reviewed: 25 August 2003