Sorghum halepense (L.) Pers.

Home

Graminae

Common names

Johnson grass (United States, Australia, southern Africa), grama China, maicillo, sorguillo, sorgo de Alepo (Peru), Aleppo grass (southern Africa), Don Carlos (Cuba).

Description

A strongly rhizomatous perennial, moderately stout, 50-200 cm tall. Culms arise from a stout, extensively creeping, scaly rhizome which is well rooted at the nodes; prop roots arise from the lower above-ground nodes (Tothill & Hacker, 1973). Leaf-blades have midrib preeminently white. Spikelets in pairs, one sessile, the other pedicellate, both dorsally flattened; at maturity, falling entire, together with the subtending joint and pedicellate spikelet. The sessile spikelet is 4.5-5.5 mm long and smaller than that of S. sudanense and S. verticilliflorum..

Distribution

Believed to be of Mediterranean origin (Meredith, 1955), but introduced very early to India (Bor, 1960); now widespread through the subtropics. Called "Johnson grass" after Colonel Johnson who first grew it in Alabama, United States.

Season of growth

Spring to autumn.

Rainfall requirements

It prefers semi-arid to subhumid areas, but does not do well in wet tropical places. A rainfall of 500-750 mm with a summer dominance is best.

Drought tolerance

It has good drought tolerance, the rhizomes surviving dry periods and shooting again after rain.

Soil requirements

It is essentially a crop for rich soils, and does not produce well on poor soils. It usually invades first-class alluvial soils and is enhanced by irrigation; it thrives in ditches.

Ability to spread naturally

It spreads rapidly from seed and more gradually by rhizomes through the soil or from pieces distributed by machinery. Some is spread by livestock.

Sowing methods

It is usually rolled into a well-prepared seed-bed, at 11-22 kg seed/ha. Rhizomes can be cut up by disc cultivation and spread by harrows.

Number of seeds per kg.

100 000-125 000 (Queensland); 286 000 (United States).

Seedling vigour

The seedling is very vigorous, germinating well and becoming aggressive.

Dry-matter and green-matter yields

In Texas it yields 17-18 tonnes of hay per hectare under irrigation.

Suitability for hay and silage

In the southern United States it provides a good deal of hay. It is cut in the boot stage, and before the seed matures, two or three times a year. The coarse material dries slowly and thorough curing is necessary.

Value as a standover or deferred feed

Frosted Johnson grass in which rough pea has been planted is used as winter feed in Alabama, Mississippi and Texas, United States. The peas provide green forage (Bennett, 1973).

Toxicity

In common with other Sorghum species it is toxic at times due to its HCN content. A yield of 0.029 percent HCN was recorded at the Darling Downs, Queensland, in September, 1958, and this would increase as growth accelerated in summer (Everist, 1974). For symptoms and treatment of the poisoning refer to Sorghum almum.

Seed yield

Yields of 300 kg/ha are considered good.

Diseases

It is subject to leaf diseases similar to those that affect Sudan grass, i.e. leaf spot (Cercospora sorghi); zonate leaf spot (Gloecercospora sorghi) and anthracnose (Colletotrichum graminicola).

Main attributes

Its perenniality for hay, its palatability.

Main deficiencies

Its problem as a weed overshadows its value for hay and pasture, and it is not now sown. Eradication is the best aim, if possible and economical.

Optimum temperature for growth

Tillering increases with temperature up to 27C in a 12-hour day, and up to 32C in a 16-hour day; at 32C, growth is reduced (Ingle & Rogers, 1961).

Frost tolerance

It is susceptible to frosts but the rhizomes usually survive.

Ability to compete with weeds

It competes very successfully with weeds because of its shade effects and vigorous root-stock. It often becomes a weed in such crops as Sudan grass or even oats.

Pests

The sorghum midge (Contarinia sorghicola) and sorghum web-worm (Celema sorghiella) affect seed crops.

Palatability

It is very palatable in the early growing stage.

Response to photoperiod

Flowering is accelerated by short days of 12 hours or less (Evans, Wardlaw & Williams, 1964). Plants at eight to 12 hours day length flowered at 27C, but at 14 hours day length failed to flower (Ingle & Rogers, 1961).

Chemical analysis and digestibility

Fertilized Johnson grass (cut at the boot stage) averaged 13.5 percent crude protein and 65.8 percent digestibility, compared to unfertilized grass at 7.2 percent crude protein and 47.5 percent digestibility (Bennett, 1973).

Natural habitat

In moist areas on river banks, in clay soils and wet sandy soils.

Fertilizer requirements

Johnson grass gives linear yield increases up to 1 075 kg N/ha, but economical increases amounting to 9 tonnes per hectare are obtained with 538 kg N/ha (Bennett, 1973). A fertilizer mixture in the ratio of 6N:0.SP:0.8K is recommended. Nitrogen should be applied in split applications.

Compatibility with other grasses and legumes

Johnson grass will initially grow in association with grasses such as Paspalum dilatatum, Chloris gayana and Cynodon dactylon, but will gradually dominate them. It can become sod-bound, which reduces its productivity. It will grow in alfalfa (Medicago sativa) crops and can be controlled a little when the alfalfa is mown periodically for hay.

Genetics and reproduction

The chromosome number is 2n=20, 40. It readily crosses with other sorghum species such as S. sudanense.

Seed production and harvesting

Johnson grass seeds heavily and shatters a good deal. It is harvested with combines if necessary.

Economics

One of the worst weeds of cultivation in the subtropics throughout the world.

Animal production

Johnson grass is used for grazing where a decision is made to live with it rather than attempt eradication. It is cut for coarse hay over large areas of the southern United States.

Dormancy

The seed requires after-ripening for a few months.

Value for erosion control

Johnson grass will quickly vegetate suitable areas and act as an effective cover against wind and water erosion. However, its aggressive, weedy nature makes it less useful than other species which are available for this purpose.

Links:

Links for the genus:

Further reading

Marley, 1978; Martin & Leonard, 1959.