Most sorghum is grown where the climate is too hot and dry for CORN
The largest acreages are in ASIA and AFRICA, but the greatest production is the the USA (p 4-2, GCM)
Very little sorghum is grown in EUROPE and RUSSIA because their climates are too cool for sorghum
Generally grown from the tropics to latitudes as high as 45^o North and South

During the past 25 years, the sorghum acreage in the US has ranged from 15 to 18 million acres/year. This means that the sorghum acreage in the US is somewhat greater than the acreages of oats and barley, but considerably less than acreages of CORN, WHEAT, and SOYBEANS.

In the US, sorghum is grown primarily in the SOUTHERN GREAT PLAINS

LEADING STATES:

TEXAS KANSAS 2-4 million acres/yr
NEBRASKA MISSOURI OKLAHOMA SOUTH DAKOTA 1/2 to 1 million acres/year

ADAPTIVE FEATURES

Like corn, sorghum is a C₄ species and is a high dry matter producer

Sorghum's most outstanding characteristics are HEAT and DROUGHT tolerance

Requires warm days and nights for high yields
In the Southern Great Plains, highest yields are usually obtained when the mean temperature for July is in the 80-85^oF range.
If the average July temp is below 75^oF, yields won't be high

Sorghum is slightly more tolerant of both acid and alkaline soils than corn pH 5.5 - 8.5

Like corn, sorghum is a short-day plant. Most hybrids are photoperiod sensitive, but some daylength-insensitive hybrids are being developed

Sorghum is resistant to both CORN ROOTWORMS and CORN BORERS.

USE of Sorghum (grain)

Worldwide, sorghum is a FOOD GRAIN About 3/4 of the world's production is used as food for humans Sorghum is a principal food source in parts of Africa, India, and China 4

In the US, sorghum is used primarily as a FEED GRAIN

In the SOUTHERN GREAT PLAINS, sorghum is an excellent crop for meeting both GRAIN and ROUGHAGE requirements for livestock.

Sorghum is very close to corn in FEED EFFICIENCY for most types of livestock.

CLASSIFICATION of Sorghums

GRAIN SORGHUMS

While there are seven grain sorghum groups, most current sorghum hybrids have been developed by crossing MILO with KAFIR
Most sorghum hybrids have either 2 or 3 dwarfing genes in them, are 3 to 4 ft in height, and are easy to combine
Prior to 1940's, most sorghums (grain) were 5 to 7 ft in height, which created harvesting problems

SWEET SORGHUMS and GRASS SORGHUMS are grown for hay, silage, or pasture

BROOMS are made from BROOM CORN, which is another type of sorghum BROOM CORN grows 8 to 10 ft in height

BOTANY OF SORGHUM

Vegetative CHARACTERISTICS

Sorghum is an annual that is similar to CORN
Sorghum stalks have more sugar than corn stalks
Sorghum tillers more than corn

Root characteristics

Sorghum has a fibrous root system that is similar to corn:
Seminal roots
Crown roots
Brace roots
However, there are differences between sorghum and corn
- Sorghum roots are MORE FINELY BRANCHED than corn roots
- Sorghum has about twice as much root branching as corn.
- Therefore, sorghum's root system is considered to be twice as efficient as corn in absorbing moisture from a given volume of soil.
- Sorghum roots usually don't penetrate as deeply into the soil as corn roots
- SORGHUM 3-4' CORN 5-6'

INFLORESCENCE

The sorghum head is a PANICLE
Spikelets occur in pairs (same as tassel and ear of corn)
- One member is SESSILE, while the other is PEDICELLATE
- The SESSILE spikelet is fertile and the PEDICELLATE spikelet is sterile
Grain sorghum is free-threshing (lemma and palea are removed during combining)
Some types of sorghum are not free-threshing - Broom corn - Grass sorghums
Many sweet sorghums
Seed color is variable.

The Grain Standards book classes sorghum seeds as:

Yellow
White
Brown: high in tannins, which lower palatability
Mixed

Percentages of sorghum seed components (endosperm, embryo, and pericarp) are very similar to corn

POLLINATION

Sorghum flowers begin to open and pollinate soon after the panicle has completely emerged from the boot Pollination begins at the top of the panicle and progresses downward for 6-9 days
Pollination normally occurs between 2 and 8 A.M., but is delayed by cool temp's
Early pollination is one of the reasons why sorghum has excellent heat and drouth tolerance
Fertilization takes place 6-12 hrs after pollination
Sorghums are normally self-fertilized, but they can outcross very easily

GROWTH AND DEVELOPMENT

Growth and development of sorghum is similar to corn, with several exceptions

Sorghum seedlings are proportionately smaller than corn seedlings-due to small seed size
Sorghum has a lower concentration of LEAF juices than corn, but the STALK, CROWN, and ROOT juices are higher in SORGHUM than in corn
Sorghum leaves wilt more slowly than corn leaves because sorghum has a thicker wax coating (cuticle) covering the epidermis
As a result, sorghum has a LOWER TRANSPIRATION rate and a slower drying rate than CORN.
This permits sorghum to withstand DROUGHT longer than corn
Sorghum plants suffering from drought can become dormant and then resume growth when moisture becomes available. Not so with corn
Sorghum can branch from its upper stalk nodes. If drought and heat ruin the main panicle, branches can bear panicles that ripen and produce grain

CULTURE AND MANAGEMENT

Sorghum in crop rotations

Sorghum readily follows other crops in rotations, but crops following sorghum may have problems, especially if a winter grain is planted shortly after sorghum is harvested in the fall
Dryland sorghum depletes soil moisture more than other crops
Irrigated sorghum depletes soil N extensively
When sorghum stalks are plowed under, soil N can be tied up for a period of time
Sorghum stalks are high in sugar (C). Microbes feed on the sugars, and the stimulation of microbial activity increases the amount of N required by the microbes. Until the C:N balance is restored to normal, microbes will compete with growing plants for available N.

Response to irrigation:

Sorghum responds to irrigation, but usually not as well as corn. In areas where both corn and sorghum are grown, sorghum yields more grain than corn if moisture is limiting, but not if moisture supplies are good throughout the season

Response to fertilizer

In irrigated conditions sorghum responds very well to fertilizer (especially N), but in dryland conditions sorghum may not respond very well if moisture is more limiting than soil fertility

PLANTING TIME

Sorghum requires a warmer seedbed than corn
soil should be at least 60^oF at 2" depth
In areas where both corn and sorghum are grown, sorghum is usually planted 1 to 2 weeks after corn is planted
Sorghum usually is planted in rows with corn planting equipment. Plant population decisions are affected by tillering capacity of the sorghum hybrid

HARVEST

Drydown is usually not a problem in the SOUTHERN GREAT PLAINS, but can be a serious problem in northern states such as Wisconsin
Sorghum is usually harvested when kernel moisture ranges from 18 to 25%

PRUSSIC ACID POISONING

Young sorghum plants, particularly the leaves, contain a substance called DHURRIN, which breaks down to form PRUSSIC ACID (= Hydrocyanic acid = HCN)
Prussic acid is poisonous to RUMINANT livestock (cattle, sheep, goats)
Losses from grazing occur in the SOUTHERN GREAT PLAINS each year Prussic acid content decreases as the plant matures.