Origin
Sorghum bicolor (L.) Moench ssp. arundinaceum (Desv.) de Wet & Harlan, commonly known as sweet sorghum, is a crop plant originally from Africa and Asia. It was first domesticated in Ethiopia about 8,000 years ago and has been cultivated in many parts of the world ever since.
Common Names
Sweet sorghum is also known as sorgo dulce, sorgho sucré, and chimmairiya, among other names in various languages. The name sweet sorghum emphasizes its high sugar content and distinguishes it from other types of sorghum that are used for different purposes.
Uses
Sweet sorghum is valued for its ability to produce a large amount of juice that can be processed to make sugar, syrup, ethanol, and other products. It is also used as animal feed, green manure, and biomass for energy production. In some countries, sweet sorghum is grown as a source of food for humans, either as grain or as a vegetable. Additionally, sweet sorghum has been found to have potential for phytoremediation of contaminated soils and water.
General Appearance
Sweet sorghum is a tall, leafy plant that can reach a height of 3 to 5 meters. Its stems are thick and juicy, with a diameter of about 2 to 4 centimeters. The leaves are long and narrow, up to 60 cm in length and 5 cm in width, and have a bluish-green color. The inflorescence, or seed head, is a compact panicle that can be cylindrical or conical in shape and up to 50 cm long. The seeds are small, round, and yellowish-white in color. Sweet sorghum can thrive in a wide range of soils and climates, but it prefers warm temperatures and moderate rainfall.
hereLight Requirements
Sorghum bicolor ssp. arundinaceum requires full sun exposure for optimal growth and development. It can tolerate partial shade, but prolonged periods without sufficient light can negatively impact plant growth and yield.
Temperature Requirements
This plant is known to be thermophilic, thriving in warm to hot temperatures. The optimal temperature range for growth is between 25°C and 35°C. However, it can tolerate temperatures between 15°C and 45°C, but growth and development may be slower at the lower and upper ends of the range, respectively.
Soil Requirements
Sorghum bicolor ssp. arundinaceum can grow well in a range of soils, including sandy, loamy, and clay soils. However, it prefers well-draining soils with a pH range of 6 to 8. It can also tolerate mildly acidic soils with a pH as low as 5.5. The plant can tolerate soils with low fertility, but it responds well to soils that are rich in nitrogen, phosphorus, and potassium.
Cultivation Methods
Sorghum bicolor ssp. arundinaceum is grown mainly in tropical and subtropical regions, particularly in Africa. The plant grows well in regions with high temperatures and low humidity, making it ideal for dry areas. Sorghum prefers well-drained soils with a pH ranging from 6.0 to 8.5 and can tolerate both acidic and alkaline soils. The best time to plant sorghum is at the beginning of the rainy season when the soil is moist. The recommended planting density is 45,000-60,000 plants per hectare.
Watering Needs
Sorghum bicolor ssp. arundinaceum requires adequate moisture during its growing cycle, particularly in the early stages of growth. The plant is drought-resistant and can tolerate dry conditions, but it requires some irrigation during the dry season for optimal growth. The amount of water required depends on the soil type, the stage of growth, and the climatic conditions. Overwatering should be avoided as it can lead to waterlogging and root rot.
Fertilization
Sorghum bicolor ssp. arundinaceum requires adequate fertilization to produce optimal yields. The plant responds well to nitrogen, phosphorus, and potassium fertilizers. Soil testing is necessary to determine the nutrient status of the soil and the appropriate fertilizer rates. The recommended fertilizer rate is 30-60 kg/ha of nitrogen, 20-30 kg/ha of phosphorus, and 15-30 kg/ha of potassium.
Pruning
Sorghum bicolor ssp. arundinaceum does not require much pruning; however, removal of diseased, broken, or dead stalks is recommended. Pruning can also be done to improve air circulation, which reduces disease incidences and promotes plant growth. Pruning should be done during the early stages of growth to avoid damaging the plant. Pruned material should be disposed of appropriately to prevent the spread of diseases and pests.
Propagation of Sorghum bicolor (L.) Moench ssp. arundinaceum (Desv.) de Wet & Harlan
Sorghum bicolor (L.) Moench ssp. arundinaceum (Desv.) de Wet & Harlan can be propagated by various means including seed, vegetative, and tissue culture methods.
Seed Propagation
Seed propagation is the most common and easiest method of propagating Sorghum bicolor. The seeds should be planted in well-draining soil, with a pH range of 6.0 to 7.5, and should be kept moist until germination. Once germinated, the seedlings should be thinned to prevent overcrowding, which can lead to the development of diseases and pests. The optimal temperature for seed germination is between 20-30°C.
Vegetative Propagation
Vegetative propagation involves the use of plant parts other than seeds, such as stem cuttings or root divisions. This method is more challenging and less common than seed propagation. To propagate Sorghum bicolor vegetatively, a stem cutting should be taken from the plant during its vegetative growth stage and planted in a well-draining soil mix. The cutting should be kept moist and in partial shade until it roots. Root division is also a method of vegetative propagation where a section of an established plant’s root system is divided and replanted in a new location.
Tissue Culture Propagation
Tissue culture propagation is a modern propagation method that involves growing the plant cells in a nutrient-rich medium outside the plant. This method has several advantages, including the creation of a large number of new plants quickly and the production of genetically uniform plants. Tissue culture involves the use of meristem tissue or immature embryos. The process involves growing the plant cells in an agar-based medium with a carefully controlled environment of temperature and light.
Disease Management
Sorghum bicolor (L.) Moench ssp. arundinaceum (Desv.) de Wet & Harlan is susceptible to a number of diseases, including anthracnose, downy mildew, leaf blight, and smut. Anthracnose is caused by the fungus Colletotrichum graminicola and manifests as small, water-soaked spots on leaves and stems. Downy mildew, caused by Peronosclerospora sorghi, produces white, fluffy growth on the leaves and can severely stunt growth. Leaf blight, caused by Exserohilum turcicum, leads to the development of tan, elongated lesions on the leaves. Smut, caused by various species of the fungus Ustilago, forms large, black galls on the stem, leaves, and inflorescence.
To manage these diseases, it is crucial to implement preventative measures such as crop rotation, planting disease-resistant cultivars, and maintaining proper irrigation practices to avoid creating a conducive environment for the pathogens. Additionally, the use of fungicides at the first sign of infection can help to prevent further spread of the disease.
Pest Management
Insects such as aphids, corn leafhoppers, and stem borers can also cause significant damage to Sorghum bicolor (L.) Moench ssp. arundinaceum (Desv.) de Wet & Harlan. Aphids feed on the sap of the plant and excrete a sticky substance that can attract secondary pests such as ants. Corn leafhoppers damage the plant by sucking sap from the leaves, eventually causing them to turn yellow and die. Stem borers tunnel into the stem and can cause significant damage or death to the plant.
To manage these pests, it is recommended to implement preventative measures such as planting in healthy, well-draining soil, using pheromone traps to monitor the presence of pests, and intercropping with plants that have insect-repelling properties. In some cases, insecticides may be necessary to control populations of harmful pests, but it is important to carefully follow label instructions and avoid using toxic chemicals that can harm beneficial insects and other wildlife.
