Lecture 18

SORGHUM
Sorghum bicolor

TOPIC
Sorghum is a crop that originated in Ethiopia.  Sorghum has greater heat and drought tolerance than corn and provides mankind with the same basic necessities that corn does in wetter environment.
LEARNING OBJECTIVES
    1. Understand how the center of origin of sorghum helps to explain the crop characteristics of sorghum.
    2. Learn the climatic and edaphic requirements of sorghum and how this influences sorghums distribution
    3. Understand the advantages sorghum has over corn in hot/dry climates and which plant structures give sorghum this advantage.
    4. Learn both the positive and negative characteristics of sorghum and how this affects sorghum production
OVERVIEW
Sorghum is a C-4, short day plant like corn.  Sorghum produces food for people, feed for animals, and is even used as a building material.  Sorghum fits in the same social/economic niche as corn, but is found in hotter and drier places.

The reason sorghum has the advantage over corn in hot/dry places has to do with origins. Corn comes from the humid tropics, sorghum the semi-arid tropics.  To adjust to the drier climate, sorghum has 2 times the roots of corn, can go dormant in a drought, and has better water use efficiency than corn.  Sorghum is best adapted to 17-25 inches of rainfall where corn prefers 20-40 inches.  Sorghum can also continue to respire and photosynthesize to 95º F, where corn shuts down at 87º F.

When planted head to head in corn-adapted land, sorghum will not compete with corn.  But in environments where corn is not well adapted, sorghum out produces corn.  Sorghum is the world's 5th cereal in acreage, after wheat, rice, corn, and barley.

ORIGINS, DOMESTICATION
1.  Center of diversity - Ethiopia

2.  Progenitor - Sorghum verticilliflorum

  • African tropical forest grass
  • Great variation
  • Readily crosses with S. bicolor
  • Found in areas where sorghum cultivated
  • Yields well
  • CONCEPT
    Modern sorghum, S. Bicolor, developed
    from the wild species S. Verticilliflorum.
    Geographic spread - history

    1.  From Ethiopia where domesticated in 3000 BC.  Spread to Arabia 1000-800 BC

    2.  Later went to India (First century AD) and by track routes to China (3rd century AD)

    3.  From India to Italy 60-70 AD

    4.  To America by slaves

    5.  Cultivation after introduction of varieties 1853-1857

    6.  Widespread growth - Oklahoma, Texas, of milos 1880s.

    7.  800,000 Acres of sorghum (1919-21)

    8.  Dwarf sorghum - combine height

    9.  Mid 1950's - commercial hybrids - derived from milo-kafir cytoplasmic male steriles

      CONCEPT
    Sorghum moved east from its center of origin,
    following the trade, to India.  It only
    moved west during the Roman Empire.
    Adaptation

    1.  Temperature

  • Best mean growth 37º C - min 15º C.
  • Less cold tolerance but stands heat better
  • CONCEPT
    Sorghum's lack of cold tolerance limits
    sorghum distribution in colder climates.
    2.  Environments
  • Short day plant
  • Widely adapted -growing season 90-140 days
  • 3.  Water relations
  • Extensive fibrous root system
  • Well adapted to 17-25 in rain/year
  • Under extreme drought - goes dormant
  • Bolliform cells near midrib - folds like butterfly
  • Better water use efficiency
  • Crop 
    kg H2O/kg dry matter
    Sorghum 
     322 
    Corn 
    368 
    Barley 
    434 
    Wheat 
    514 
  • H2O requirement increases with growth - peaks during flowering, declines
  • Can stand wet feet
  • 4.  Fertilizer
  • Some lines very responsive, some unresponsive to N fertilizers
  • CONCEPT
    Many indigenous sorghum species are not
    responsive to fertility - so improvement in
    genetics is essential.
    World Importance


    1.  Yield potential of rice, wheat, maize

    2.  Highest field yields 11,000 kg/ha, 246 Bu/A

    3.  Worldwide - 3-4,000 kg/ha in better conditions; 300-1,000 kg/ha when moisture limiting

      CONCEPT
    Sorghum has high yield potential in favorable soils
    and climate, but is not competitive with other
    grains under those conditions.
    4.  Low average yield due to hot/dry climates where grown

    5.  Area increasing

    6.  Among major cereals - 5th in area sown

    7.  Production in some locations (Latin America) increasing dramatically

    8.  Leading producers: U. S., India, Nigeria, Argentina, Mexico, Sudan

    9.  Grown in all countries except cool N. W. Europe

    10.  World utilization:

      • Human food
      • Animal feed
      • Building material
      • Fuel
      • Molasses
      • Brooms
      • Popcorn
      • Wine, beer
      • "Ear roast"
     CONCEPT


    Where sorghum is the major cereal it does it all.
    Similar to the role of corn (maize) in cultures where
    corn is the precominant crop.
     

    Crop 
    Average Yield (World)kg/ha
    Crop
    Average Yield (World)kg/ha
    Maize
    2829
    Wheat
    1774
    Rice 
    2428 
    Rye
    1683
    Barley
    2030
    Sorghum
    1179
    Oats
    1666
    Millets
    707


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