Sorghum halepense (L.) Pers.
Johnson grass (United States, Australia, southern Africa), grama China, maicillo, sorguillo, sorgo de Alepo (Peru), Aleppo grass (southern Africa), Don Carlos (Cuba).
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..
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.
Spring to autumn.
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.
It has good drought tolerance, the rhizomes surviving dry periods and shooting again after rain.
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.
It spreads rapidly from seed and more gradually by rhizomes through the soil or from pieces distributed by machinery. Some is spread by livestock.
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.
100 000-125 000 (Queensland); 286 000 (United States).
The seedling is very vigorous, germinating well and becoming aggressive.
In Texas it yields 17-18 tonnes of hay per hectare under irrigation.
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.
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).
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.
Yields of 300 kg/ha are considered good.
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).
Its perenniality for hay, its palatability.
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.
Tillering increases with temperature up to 27°C in a 12-hour day, and up to 32°C in a 16-hour day; at 32°C, growth is reduced (Ingle & Rogers, 1961).
It is susceptible to frosts but the rhizomes usually survive.
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.
The sorghum midge (Contarinia sorghicola) and sorghum web-worm (Celema sorghiella) affect seed crops.
It is very palatable in the early growing stage.
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 27°C, but at 14 hours day length failed to flower (Ingle & Rogers, 1961).
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).
In moist areas on river banks, in clay soils and wet sandy soils.
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.
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.
The chromosome number is 2n=20, 40. It readily crosses with other sorghum species such as S. sudanense.
Johnson grass seeds heavily and shatters a good deal. It is harvested with combines if necessary.
One of the worst weeds of cultivation in the subtropics throughout the world.
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.
The seed requires after-ripening for a few months.
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.
Marley, 1978; Martin & Leonard, 1959.