The grain of grain sorghum is utilized for human consumption, animal feed, and ethanol manufacturing. It is commonly grown in tropical and subtropical countries, originating in Africa. The grain is used to make liquor, animal feed, and bio-based ethanol, among other things.
I. Appearance and Characteristics
Sorghum bicolor, commonly called sorghum and also known as great millet, broomcorn, guinea corn, durra, imphee, jowar, or milo, is a species in the grass genus Sorghum cultivated for its grain. Sorghum originated in Africa, and is now cultivated widely in tropical and subtropical regions.
Sorghum is a large stout grass that grows up to 2.4 metres (7.9 ft) tall. It has large bushy flowerheads or panicles that provide an edible starchy grain with up to 3,000 seeds in each flowerhead. It grows in warm climates worldwide for food and forage. Sorghum is native to Africa with many cultivated forms. Most production uses annual cultivars, but some wild species of Sorghum are perennial; the Land Institute is developing a perennial cultivar that would enable farmers to “produce repeated, sufficient grain harvests without resowing.”
Sorghum grows in a wide range of temperatures. It can tolerate high altitude and toxic soils, and can recover growth after some drought. Optimum growth temperature range is 12–34 °C (54–93 °F), and the growing season lasts for ~ 115-140 days. It can grow on a wide range of soils, such as heavy clay to sandy soils with the pH tolerance ranging from 5.0 to 8.5. It requires an arable field that has been left fallow for at least two years or where crop rotation with legumes has taken place in the previous year. Diversified 2- or 4-year crop rotation can improve sorghum yield, additionally making it more resilient to inconsistent growth conditions. In terms of nutrient requirements, sorghum is comparable to other cereal grain crops with nitrogen, phosphorus, and potassium required for growth.
II. How to Grow and Care
Sunlight and Temperature
Sun and heat are two of the most important aspects of growing sorghum. Aim for a location in full sun, with 12-14 hours of sunlight at the peak of summer. While sorghum can be grown in USDA zones 2-11, it has higher grain yields when grown in temperatures of at least 80°F, with 90°F being even better. Sorghum can survive light frosts but will die once the main stalk is frozen. Sorghum germinates best with a soil temperature at or above 60°F. When soil temperature starts to fall below 60°F, sorghum will have difficulty germinating consistently.
Water and Humidity
Sorghum prefers soil that is consistently moist but not soaked. Aim for 3”–4” of water roughly every 10 days. Watering sorghum in the morning helps protect it from the heat of the day. Sorghum will tolerate both drought and overwatering but has a lower grain yield when pushed to either extreme. Watering at the base of the plants works best, using something like a soaker hose or drip irrigation, which avoids the leaves and seed head of the plant getting too wet.
Soil
Sorghum prefers a well-draining, slightly acidic soil of 5.5-6.5 pH. Sorghum is relatively tolerant of poor soil, but it needs a high amount of nitrogen, so be sure to amend the soil with compost and a nitrogen-heavy fertilizer. Be wary of weed seeds in the soil and practice good weed control measures, as sorghum doesn’t like to compete for nutrients, especially early in its life cycle.
Fertilizing
Being a type of grass, sorghum relies on large amounts of nitrogen to grow quickly. A fertilizer with high nitrogen content like a blood meal or feather meal works well. Even with a healthy topping of compost, aim to fertilize your sorghum with a nitrogen-heavy fertilizer every 6 weeks throughout the growing season. Phosphate and potassium are less important for sorghum growth and the required nutrients should be provided by any healthy soil.
Pruning
Other than the harvesting period, sorghum does not require any specific pruning or training. After harvesting the grain sorghum produces, the plants will occasionally produce a second crop under the right conditions, but most gardeners prune the stalks back and use them in the compost bin.
Propagation
Sorghum is propagated only by seed. Refer to the planting section above for information on planting! If left on the stalk, sorghum seeds will readily self-seed.
Pests and Diseases
- Growing Problems
The most common growing problems that affect sorghum stem from improper planting conditions. Too little sun and low temperatures will produce a lower crop yield. While sorghum is quite drought-tolerant, too much or too little water will also stunt growth.
- Common Pests
Luckily, most pests that affect sorghum are fairly easy to deal with. Two major pests are rodents and birds; they both enjoy snacking on the tasty seed heads. Dealing with these comes down to timing and cover. Once the seed heads start to form, consider covering your crop with a floating row cover or bird netting. Time your harvest so the dry seeds aren’t left out in the garden for too long.
Aphids, caterpillars, and sorghum midge are more difficult to tackle. Aphids can be removed easily with hard sprays of water from a hose or by planting trap crops like nasturtium or marigolds nearby. Caterpillars and sorghum midge can quickly destroy crops and should be aggressively treated. Neem oil sprays work well for many gardeners, but if you have a heavy infestation (especially with sorghum midge) consider pulling out stronger insecticides. Repeat the application of neem oil or insecticidal spray every 3 to 5 days after initial treatment until the issue is relieved. Bacillus thuringiensis spray can also aid in the control of many caterpillar species.
- Common Diseases
Sorghum leaf blight, bacterial leaf spot, head smut, downy mildew, and anthracnose are all caused by varieties of fungi. They primarily affect the leaves and can result in stunted growth or death. In this case, the best defense is preventative care. Selecting disease-resistant cultivars and planting in well-draining soil with plenty of sun helps keep fungi levels low. If that doesn’t work, a fungicide like organic copper fungicide or neem oil should be applied.
Sorghum ergot is also caused by fungal buildup, but can not be easily treated by the methods mentioned above. Ergot primarily affects the pollinating florets of the plants and is difficult to control. There are currently no available varieties of sorghum that are resistant to ergot and treatment involves heavy applications of strong fungicides, which are usually only available to farmers in large scale quantities.
Maize dwarf mosaic virus (MDMV) and Sugarcane mosaic virus (SMV) are both viruses carried by aphids. Genetic resistance and control of aphid populations is the best way to prevent these diseases. Once afflicted with the virus, it’s best to destroy the plant.
As with most crops, crop rotation can play an important role in avoiding these pest issues. Fungal spores and disease-carrying pests often overwinter in the ground, so rotating crops can be one of the best ways to prevent pest issues in the first place.
III. Uses and Benefits
- Culinary uses
Sorghum is widely used for food and animal fodder. It is also used to make alcoholic beverages, and biofuels such as ethanol. It can be made into couscous, porridge, or flatbreads such as Indian Jōḷada roṭṭi or tortillas; and it can be burst in hot oil to make a popcorn, smaller than that of maize. Since it does not contain gluten, it can be used in gluten-free diets.
In Nigeria, the pulverized red leaf-sheaths of sorghum have been used to dye leather, while in Algeria, sorghum has been used to dye wool.
In South Africa, characteristically sour Kaffir beer is made from sorghum or millet. The process involves souring the mashed grain with lactic acid bacteria, followed by fermenting by the wild yeasts that were on the grain.
In India, the panicle stalks are used as bristles for brooms.
In countries including the US, the stalks of sweet sorghum varieties are crushed in a cane juicer to extract the sweet molasses-like juice. The juice is sold as syrup, and used as a feedstock to make biofuel.
- In human culture
In Australia, sorghum is personified as a spirit among the Dagoman people of Northern Territory, as well as being used for food; the local species are S. intrans and S. plumosum.
In Korea, the origin tale “Brother and sister who became the Sun and Moon” is also called “The reason sorghum is red”. In the tale, a tiger who is chasing a brother and sister follows them up a rotten rope as they climb into the sky, and become the sun and moon. The rope breaks, and the tiger falls to its death, impaling itself on a sorghum stalk, which becomes red with its blood.
In Northeastern Italy in the early modern period, sticks of sorghum were used by Benandanti visionaries of the Friuli district to fight off witches who were thought to threaten crops and people.
IV. Harvesting and Storage
Harvesting sorghum is straightforward and simple but the techniques differ based on whether you’re growing sweet sorghum (aka cane sorghum), grain sorghum, or broom sorghum.
Harvesting
If you’re growing sweet sorghum to produce sorghum syrup, cut the stalks down at the base about two weeks after the “milk” stage. Like corn (and other grains) the milk stage refers to the time when the seeds will produce a milky substance when pressing a fingernail into them. Next, strip the leaves off the stalks and press the canes, which will produce a light green juice that can be cooked down into sorghum syrup.
If you’re growing grain sorghum, the crop needs to be left until the seeds are fully developed. Once the seeds are hard and glossy, they are ready to be harvested. Cut off the top portions of the stalk with the seed heads still attached and leave them in a warm place to dry for at least a week. Once dry, roll the seed heads over a section of hardware cloth or wide sieve to free the seeds.
For broom sorghum, the dried stalks and seed heads can be cut and used to make traditional brooms, floral arrangements, or other crafts.
Storing
Processed, dry grain sorghum can be eaten immediately or stored in a cool, dark location inside a tightly sealed container like a jar. Stored this way, it can last several years. If you choose to ground your harvest into flour, it should be stored similarly to other flours; in a closed container out of direct light or heat.
Sorghum syrup can be stored like honey, in a closed container within a cupboard. Try to avoid any temperature extremes and it will last for many months. If the syrup crystallizes, gently heat the jar in a pot of warm water.