Sorghum is a coarse perennial grass but is usually treated as an annual. It is a hardy crop that is well adapted to drought and therefore requires less water to grow compared to maize. It can be grown under a wide range of soils in different ecological zones and therefore offer a good option in supplementing animal feeds during dry seasons. It can also be ratooned (harvested and left to grow again).
Sorghum is one of the most important crops in Kenya that can be used both for grain and forage. While some varieties are used solely for grain, other varieties have been developed for fodder while others are dual purposes. Forage sorghum comprises 20% grain and 80% herbage, while dual-purpose sorghum has about 40% grain and 60% herbage. Dual-purpose sorghum is used as human food and livestock feed, while forage sorghum is used for livestock feed only. Both have the potential to supply quality feeds to ruminants in dry areas.
Unlike other fodder, such as Napier grass, sorghum is easy to ensile because it is not necessary to add sugar to facilitate fermentation. Both E1291 variety and E6518 do well in cold dry highlands, 1500–2000 meters altitude, and minimum 650 mm annual rainfall. Other sorghum varieties developed at Kenya Agricultural Research Institute, Lanet, are Ikinyaruka, BJ28, BM30, and Lanet 1. BM30 is 10% more digestible than the other varieties, as it was developed with a gene that gave it the brown midrib, brown seed, and is associated with high digestibility. E6518 and E1291 have white midrib and brown seed.
Forage sorghum is relished by ruminants. It has between 20 and 24% crude proteins while Napier grass has between 10 and 12% crude proteins. It can be grazed on (young or as deferred fodder), cut fresh, made into hay or ensiled.
Select a suitable site for growing forage sorghum. Forage sorghum grows mainly in the cold dry highlands, 1500-2000 metres above sea level and receiving average annual rainfall of minimum 650mm. It is drought resistant and can grow well under less fertile soils, with quick growth, high biomass accumulation and dry matter content.
Prepare land using either a hand hoe or oxen/tractor drawn plough. Deep cultivation (at least 15cm) improves aeration, water infiltration and ensures good drainage. Harrowing may be necessary to ensure an appropriate tilth or alternatively practise zero tillage using herbicides.
Ratooning is the practice of cutting, after harvest, most of the above –ground portion of a monocot crop so as to allow the plants to regenerate and produce a fresh crop in the next season.
Dual purpose varieties include: E1291, Ikinyaruka and BJ 28; and Forage: E6518, BM30 and Lanet 1. Dual-purpose sorghum are used as food and feed while Forage types are used for Livestock feed only.
Drill seeds along the furrows. Sow 3 cm deep if dry planted so that seeds don’t germinate in false rains at the beginning of the season; sow 2 cm deep if ground is wet. The seed rate is 6–10 kg/ha, depending on variety. For example, E1291 at 6-8kg and E6518 at 8-10kg. Space forage sorghum seed at 75 x 10 cm, and dual-purpose sorghum seed at 60 x 20 cm. This spacing for dual-purpose sorghum allows for a high grain-to-herbage ratio.
Apply 10 – 30 tons/ha of well-decomposed, organic manure in soil at planting to enhance water holding capacity, soil texture and to supply nutrients for healthy crop establishment.
Apply 25 kg DAP per acre at sowing. Top-dress using 80 kg CAN per acre at knee height.
Hand weed at least twice, depending on weed growth, or apply herbicides either pre- or post-emergence, or practise zero tillage. Thin when crop is 30 cm high or 30 days old, whichever comes first, to achieve spacing within rows of 10 cm for forage or 20 cm for dual-purpose. Forage sorghum has a high ability to tiller, especially if the mother plant is damaged or ample space is provided. .
Variety E1291 takes170 days to maturity and grows up to1.7 metres high. Variety E6518 takes 230 days to maturity and grows up to 3 metres high depending on the growing season. Varietyy BJ-28 takes 110 days and grows up to 1 metre high..
To harvest dual-purpose sorghum, cut the head with a knife or with a combine harvester;To harvest forage variety, cut the stalk with a machete or a forage harvester. Observe hygiene and ensure soil particles don’t mix with the fodder To feed fresh by the cut-and-carry method, wilt the green chop. All fresh sorghum herbage must be wilted first for at least 12 hours. Feed the forage as green chop or ensile it for future use.
The ability of sorghum to ratoon (regrow) increases the total annual yield of herbage per unit area and also provides reserve feed for cut-and-carry during the dry period when lack of soil moisture makes reseeding impossible. Depending on how the crop is well managed, three or more ratoons are possible.
Dual-purpose sorghum E1291 yields 5–7 t/ha of grain, 26 tones/ha fresh biomass (forage) and 14–18 t/ha dry matter; Forage sorghum E6518 yields 4–5 t/ha of grain, 33 tones/ha fresh biomass (forage) and 17–22 t/ha dry matter. .
Sorghum feed is primarily a source of energy, with an estimated 65% total digestible nutrients (TDN); it also contains about 13% TDN of protein. When fed to ruminants as either silage or wilted green chop, it can provide up to 67% of required roughage and up to 20% of the total diet as a ground grain supplement. When fed to lactating dairy cows, brown-seeded sorghum must be supplemented with adequate levels of minerals and vitamins to minimize deficiencies associated with it. Brown-midrib sorghum is more digestible than white-midrib; for example, variety BM30 is 10% more digestible than most other varieties..
Sorghum contains hydrogen cyanide (prussic acid), high levels of which may poison ruminants. Although acid levels are low in the varieties developed by KALRO, it is prudent to wilt the herbage for at least 12 hours before feeding it. When wilted, sorghum can be fed ad lib, although the animal will require other protein and mineral supplements...
Sorghum is both cold tolerant and drought resistant as compared with other fodder crops such as maize and Napier grass. It can replace maize one-to-one as green chop, silage and grain for feeding to both ruminants (cows and goats) and non-ruminants (pigs and poultry). Sorghum grain has an energy level comparable with that of other common cereals, such as maize. It can survive dry-spell conditions then resume growth once moisture becomes available because of its morphology and physiology. Brown seeded sorghum can toralerate bird damage compared to white seeded sorghum (E1291 and E6518) as the birds will first eat the white seeded sorghum before eating the brown seeded. Some varieties, especially those with brown seeds contain high levels of tannins, which are anti-nutrients. Some sorghum varieties are high in hydrogen cyanide (prussic acid), which can poison ruminants; hence the need to wilt it before feeding it as green chop. Sorghum grain should be ground for optimal digestibility. At its early stage, sorghum does not compete well with weeds so a weed-free field is necessary. Bird damage can lead to serious, even total loss of grain; thus scaring birds is necessary from milky stage to grain maturity. ..