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Sorghum almum Parodi |
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Graminae Columbus grass (Australia), five-year sorghum, sorgo negro, Sudan negro (Argentina). A more robust species than S. halepense (q.v.), sometimes reaching 4.5 m in height. It is a short- term perennial. The most satisfactory method of distinguishing between the two is by the articulation of the pedicelled spikelet. In S. almum the spikelet breaks off with the uppermost portion of the pedicel at maturity; in S. halepense there is a clean abscission at the base of the spikelet. S. almum usually produces short rhizomes, more or less pointing upwards, which are not as extensive or aggressive as those of S. halepense, but reach a depth of 50 cm (Chippendall, 1955; Pritchard, 1964). It originated in Argentina as a probable hybrid between Sorghum halepense and a member of the series Arundinacea. It has now been introduced into several tropical countries. Spring to autumn. Sea-level to 700 m. It is usually grown within the annual rainfall range of 460-760 mm, but may be grown under irrigation, or in areas with up to 1 900 mm annual rainfall (Russell & Webb, 1976). It is more tolerant to drought than maize, Sudan grass and Johnson grass, and has survived in areas receiving 200 mm of annual rainfall. It prefers a soil of high fertility, from light loams to heavy clays, with a pH range from 5 to 8.5. It does not spread quickly and is dependent on seeding into a cultivated seed-bed or ashes; shattered seed will germinate to fill gaps in a stand.Land preparation for establishment Use a fine, cultivated seed-bed, or the ashes from a recent scrub burn. This gives a seed-bed free from weed competition in the early seedling stage and aids even germination. It is sown through a seed drill adapted to small seeds. Wheat drills can be fitted with a smaller driving sprocket or the seed chutes reduced in diameter by longitudinal strips of leather nailed inside the seedbox and hanging down the chutes. Aerial seeding is used for the ashes of a scrub burn. It is planted at 2-4 cm, depending on soil moisture, and lightly covered with harrows. Rolling following seeding will improve germination in drier soils. Usually spring to early summer when the soil temperature is above 15°C. For aerial seeding it must be sown at the beginning of the wet season. Rate, 1.25-2 kg/ha. About 143 000 (Queensland).Seed treatment before planting Dust with a combined fungicidal and insecticidal dust. Germinate pre-chilled seeds at 20-35°C, moistened with water (Prodonoff, 1966). If Columbus grass does become a weed it can be eradicated by ploughing in most cases. If this is ineffective or not possible, control can be effected by post-emergence sprays as explained for Johnson grass (Sorghum halepense) by Marley (1978). Excellent. It was ranked first of the Sorghum species in Texas, United States.Vigour of growth and growth rhythm It grows rapidly during spring and summer and begins flowering seven to eight weeks after planting. It persisted for three years at Samford, Queensland (Pritchard, 1964; Russell & Coaldrake, 1970). It stands heavy stocking and will give several grazings in a season, but it does not stand heavy trampling. Cutting at 5 cm every six to 12 weeks gave higher yields than cutting at 15 cm. Cutting every three weeks reduced yields (Santhirasegaram, Coaldrake & Salih, 1966). S. almum should be grazed heavily once the crop is 50 cm high to prevent it from growing too coarse and from growing away from the grazing animals. Precautions must be taken to avoid prussic acid poisoning. It is advisable with any young Sorghum spp. crop to use a tester animal to graze the crop first for 20 minutes; if no toxicity is evident then the whole herd can be put on to the crop. It is best to give the herd only half an hour's grazing the first day, an hour the second, and then two to three hours the third, with a full day's grazing from then on. A rain-grown crop should provide two to three grazings per season. For maximum regrowth, stubble is left at 15 cm to renew growth. It is rarely necessary to burn, but an established crop would survive a quick fire.Dry-matter and green-matter yields Available dry-matter yields of 12 320, 10 640 and 5 040 kg/ha from nitrogen-fertilized S. almum were recorded when stocked at one beast to 0.6, 0.4 and 0.8 hectares, respectively (Yates et al., 1964). At Taroom, Queensland (lat. 26°20'S, 550 mm rainfall) S. almum yielded 5 345 kg DM/ha (Russell & Coaldrake, 1970).Suitability for hay and silage It gives quite a good, though coarse, hay which is useful in the dry season. Mature crops (nine to 11 weeks old) make good silage in dry weather, and reasonable silage during the wet season if it is not wet by rain while ensiling it. Young crops up to seven or eight weeks old decompose badly during ensilage (Catchpoole, 1972).Value as a standover or deferred feed It is not very useful for standover or deferred feed because the mature stem is not very palatable. In common with other Sorghum species, Columbus grass contains dhurrin, a cyanogenetic glucoside which can be toxic. The Queensland Department of Primary Industries recorded HCN equivalents of 0.06 and 0.081 percent in the plants. Danger is greatest in plants carrying young shoots, either from the base or from old stems. Hungry animals turned on to wet pasture are most susceptible. Affected animals breathe heavily, they stagger about and display muscle tremor, become anchored and lie down. They die if not treated. Their mucous membranes remain red and do not become blue (Knott, personal communication).Three treatments are effective for animals showing early signs of HCN poisoning: Inject a mixture of sodium nitrate and sodium thiosulphate (photographic hypo) in water into a vein or under the skin. Recommended dose rates vary, but are approximately 3 g sodium nitrite and 15 g sodium thiosulphate in 20 ml water for cattle; l g sodium nitrite and 2 g sodium thiosulphate in 15 ml water for sheep. Excessive doses can cause nitrite poisoning. 2. Inject sulphuric ether under the skin; 10 ml for cattle, 5 ml for sheep. 3. Drench with sodium thiosulphate (photographic hypo) in water, 55 g in 550 ml for cattle; 10 g in 100 ml for sheep (Everist, 1974). This is the usual farm treatment. Potentially toxic amounts of nitrite have been noted in some S. almum plants but no cases of nitrite poisoning have been reported. 350-1 600 kg/ha.
Optimum temperature for growth Mean 19.1 + 3.3°C (Russell & Webb, 1976).¿Minimum temperature for growth About 15°C. Minimum temperature of the coldest month 7 + 5.3°C (Russell & Webb, 1976).0 It is susceptible to frost, and winter killing occurs on the high plains of the United States. Regrowth from rhizomes occurs after light frosts. About 25°N and 30°S. Mean 28.9 + 6.3° (Russell & Webb, 1976).žà It does not grow well in the shade. S. almum cv. Crooble is able to suppress weeds (Pritchard, 1964).Maximum germination and quality required for sale 70 percent germinable seed, 97.3 percent purity in Queensland (Prodonoff, 1966). It can be attacked periodically by grasshoppers, army-worms and wild predators. It is quite palatable, but not as readily eaten as annual sorghums (Pritchard, 1964). It is a short-day plant.Chemical analysis and digestibility In addition Minson and Milford (1966) and Minson (1972) carried out digestibility trials which included Sorghum almum at various stages of growth. It will not tolerate prolonged flooding. It requires a high level of nutrition for yields to be maintained, and does well as a pioneer species sown in the ashes of burnt brigalow (Acacia harpophylla) in Queensland where there is a high initial nitrogen status after years of growth of this leguminous tree. It also responds very well to applied nitrogen. It also requires adequate phosphorus and perhaps potash, as revealed by soil tests. The critical value for phosphorus in the dry matter at pre-flowering is 0.2 percent.Compatibility with other grasses and legumes It is usually sown alone as a grazing crop, but in aerial seeding of newly burnt brigalow country in Queensland, Australia, a light seeding of S. almum is made with Chloris gayana, Panicum maximum var. trichoglume or Cenchrus ciliaris. The S. almum provides quick feed with little competition from the other grasses in the first year and helps to provide an early return in terms of beef production on the outlay for initial pasture establishment. The somatic chromosome number is 2n=40 (Fedorov, 1974). It is predominantly cross-pollinated, but is also self-fertile.Seed production and harvesting It seeds heavily, but some seed may shatter. Harvesting is accomplished with a combine harvester using riddles suitable for the seed size and adjusting the blast to clean but not blow away the seed. Fields for seed production should be at least 1 km away from Johnson grass (S. halepense), with which it readily cross-pollinates. One of the most valuable summer forage and fodder crops in semi-arid to subhumid areas with rainfalls of 450-750 mm. In the Chaco Salteno in the province of Salta, northern Argentina, S. almum pastures have allowed Criollo x zebu cross animals to be grown to 400 kg live weight in two-and-a-half years, instead of four to five years under natural pastures. The pasture is grazed from November to April (Tothill, 1978). Stocked at 2.5 beasts per hectare, live-weight gain was 717 kg/ ha over 23 months. When only green forage was considered, live-weight gain fell to zero when approximately 1 120 kg DM/ha still remained for the animals at the end of the growing season. This contained 83 percent S. almum stem and 15 percent other material, mainly S. almum leaf (Yates et al., 1964).
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