SORGHUM

INTRODUCTION

Sorghum  plays  an  important   role  in  the  development  and  evolution  of dedicated  energy  crops.  This  work  focuses  on  sorghum  growth  and development,  composition,  relevant  production  issues  and  varieties.  As  an energy  crop,  sorghum  is  unique  in  that  there  several  types  of  sorghum  that  are  and  can  be  used  biofuel  and  bioproduct  production,with  the  defining  factor  in  these  crops  being  the  primary  source  of  carbohydrates.

Sorghum (sorghum bicolor (L)moench)  is  an  indigenous  crop  to  Africa  , and  though  commercial  needs  and  uses  may  charge  over  time,  sorghum  will  remain  a  basic  staple  food  for  many  rular  communities.  The  latter  is  especially  true  in  the  more  drought  prone  areas of South Africa  where  this  crops provide  better household  food  security  than  maize.

Sorghum  is  mainly  cultivated  in  drier  areas,  especially  in  shallow  and heavy  clay  soil.  The production  of  sorghum  in  South Africa  varies  from  100,000 ton (13,000 ha to 180,000 ha)  per  annum. The  free  state  and  Mpumalanga  provinces  are the largest contributors  to  the  area planted  to n Sorghum  and  Sorghum  production.

In  recent  years,  there has  been  a  shift  in  Sorghum  production  from  the  drier  western  production  areas  to  the  wetter  eastern  areas.  This  change  has  resulted  in  the  identification  and  development  of  cultivars  which  are  more  tolerant  to  lower  temperature.

SORGHUM  CULTIVATION

Sorghum is a cultivated  grass  native  to  sub-saharan  Africa,  several  varieties  of  which  are  widely  grown  for  the  grain,  as  forage,  as  a  source  of  syrup.

Sorghum  belongs to  the  grass  family,  Graminea.  It  is  essential   that  producers  know  the  crop  they  are  cultivating  in  order  to  develope the  most  effective  production  practices.

planting  sorghum

Planting  time  usually  varies  from  September  to  January ,  depending on  planting  rain  and  soil  temperature  early  in  the  season. Crop  failures  are  likely  in  central  and  southern  regions from  very  early  plantings  in  August - September  and  very  late  plantings  in  February- March  due  to  cold  conditions.  Planting  at  the  early  end  of  the  range  is preferred  to  avoid  midge  bproblems   and  to  allow  the  option  to  double-crop  a  winter  crop  if  sufficient  rainfall  is  received.  Best  yields  usually  follow  October  plantings.  These  crops  usually  miss  insect   damage  by  midge.  With late crops,  midge  resistant  sorghum  hybrids and/or  with  the  use  of  insecticide  sprays.  Generally, mid-season  hybrids  are  the  best  over all  performance.  Sorghum ergot  disease  risk  can  be  minimized  by  planting  from  mid-October  to  mid-January  in  southern  Queenland  so  that  flowering  occurs  between  mid-January  to  mid-March  when  the  probability  of  ergot  developing  in  sorghum  florets  is  lowest.

Plant population

DRYLAND

 Expected yields largely determine the population required. Lower populations are required

in the  marginal areas and high populations where  conditions are good. 

Planting population - dryland

Yield  expectation(t/ha)	Plant/ha
1-3	30000-50000
3-5	50000-75000
5-7	75000-150000

Quick-maturing hybrids planted in good conditions require higher plant populations than

slower hybrids to realise the yield potential for a particular environment.

IRRIGATED

 In irrigated crops, the choice of target plant population is dependent on row spacing.

Increase populations to 150,000-200,000 plants/ha for partial irrigation, or 220,000-250,000

for full irrigation.

Planting population - irrigated

Row spacing (m)	Plants/ha
0.15-0.30	250,000
0.75	150,000
1.0 (single rows)	120,000
1.0 (twin rows)	200,000

Average seeding rate

·        Dryland 3-4 kg/ha

·        Irrigated 10 kg/ha.

The rate depends on seed size, target population, expected establishment and germination

percentage.

 How to calculate planting rate (kg/ha)

Planting rate = Target population (plants/ha) x100 x 100

                             No. of seeds/kg x expected field establishment (%) x germination (%)

No of seeds/kg = 28,000 (depending on variety, marked on bag)

Germination % = marked on bag

Expected field establishment (depending on insects, seedbed, machinery):

       Precision planter 70-80%

       Airseeder (press wheels) 50-70%

       Airseeder (no press wheels) 40-60%

Row spacing

·        25 cm optimum for yields exceeding 4 t/ha.

·        50 cm for expected yields of 3-4 t/ha.

·        75 cm for expected yields of 1-3 t/ha.

Under good growing conditions, narrow rows out-yield wide rows. This advantage decreases

as soil moisture reserves decline. There may be situations where it is necessary to row crop

even though expected yield indicates narrow rows are superior (e.g. where inter-row

cultivation is used for weed control).

In dry areas where yields are less than 1.0 t/ha, the row spacing may be as wide as 2m.

Depending on the planter, twin rows spaced 18-45 cm apart with wide centre give a less

cramped spatial arrangement of seedlings and have regularly shown yield benefits.

Seed placement depth

50-75 mm into moisture. It is only necessary to plant seed deep enough to

give it moisture to germinate and allow its roots to grow down through moist soil into

subsoil moisture, ahead of the drying front.

Suitability for zero tillage

Sorghum is the most widely grown zero tillage summer crop in the Burnett. It tolerates

compacted subsoil and can stand high presswheel pressure at planting. Good grass control

in the crop is essential to achieve high yields but this can be expensive with herbicides.

Some farmers are now using shielded sprayers and knock down herbicides prior to planting.

The longer the paddock is under zero tillage the easier it is to establish the following crops.

GROWTH  AND  DEVELOPMENT

The  growth  and  development of sorghum are divided into the vegetative and reproductive growth stages

Vegetative growth stages:  Identification of the sorghum growth stage during vegetative growth is done according to leaf development.

Reproductive growth stages: The identification of the reproductive growth stage is done according to the development of grain kernels.

GROWTH REQUIREMENTS AND ADAPTATION

The optimum growth requirements of sorghum plants, in order to exploit its inherit yield potential, are a deep well-drained fertile soil, a medium to good and fairly stable rainfall pattern during the growing season, temperate to warm weather (20 – 30 °C) and a frost-free period of approximately 120 to 140 days.

Soil requirements

Sorghum is mainly grown on low potential, shallow soils with high clay content, which usually are not suitable for the production of maize. Sorghum usually grows poorly on sandy soils, except where a heavy textured subsoil is present. Sorghum is more tolerant of alkaline salts than other grain crops and can therefore be successfully cultivated on soils with a pH (KCl) between 5,5 and 8,5. Sorghum can better tolerate short periods of waterlogging compared to maize. Soils with a clay percentage of between 10 and 30 % are optimal for sorghum production.

Climatic requirements

The climatic requirements for the production of sorghum are divided into temperature, day length and water needs.

Temperature

Sorghum is a warm-weather crop, which requires high temperatures for good germination and growth. The minimum temperature for germination varies from 7 to 10 °C. At a temperature of 15 °C, 80 % of seed germinate within 10 to 12 days. The best time to plant is when there is sufficient water in the soil and the soil temperature is 15 °C or higher at a depth of 10 cm. Temperature plays an important role in growth and development after germination. A temperature of 27 to 30 °C is required for optimum growth and development. The temperature can, however, be as low as 21 °C, without a dramatic effect on growth and yield.  Exceptionally high temperatures cause a decrease in yield.

Day length

Sorghum is a short-day plant, which means that the plant requires short days (long nights) before proceeding to the reproductive stage. The optimum photoperiod, which will induce flower formation, is between 10 and 11 hours. Photoperiods longer than 11 to 12 hours stimulate vegetative growth. The tropical varieties are usually more sensitive to photoperiod than the quick, short-season varieties. Sorghum plants are most sensitive to photoperiod during flower initiation.

Water requirements

Sorghum is produced in South Africa on a wide range of soils, and under fluctuating rainfall conditions of approximately 400 mm in the drier western parts to about 800 mm in the wetter eastern parts.

FERTILISATION

 To assess the correct quantity  of fertiliser to be applied for optimal yield, soil samples should be taken according to the recommendations of an accredited soil laboratory.

Fertiliser recommendations made according to the soil analysis should be applied accordingly.

 Symptoms of deficiencies that may be observed in the field are as follows:

·        Nitrogen (N) deficiency—young plants are light green or yellow- green, at a more mature stage the older leaves start yellowing first, with a characteristic inverted V-shape.

·        Phosphorus (P) deficiency—under wet, cool conditions leaves of young plants may turn dark green with reddish-purple margins and tips.

·        Potassium (K) deficiency—a deficiency of K is initially noted as yellow or necrotic leaf margins, beginning at the lower leaves and spreading to the upper leaves.

WEEDS

Weed control during the first 6 to 8 weeks after planting is crucial, as weeds compete vigorously with the crop for nutrients and water during this period. The root parasite Striga asiatia (L.) Kuntze or witchweed (rooiblom) can damage the crop and mainly occurs under low input farming conditions. The parasitic plants are single stemmed with bright red flowers. Most of the damage is done before the parasite emerges from the soil. The symptoms include leaf wilting, leaf rolling, and leaf scorching even though the soil may have sufficient water. The tiny seeds are disseminated by wind, water and animals, and remain viable in the soil for 15 to 20 years. rotation with cotton, groundnut, cowpea and pigeonpea will reduce the incidence of Striga. Hand pulling the plants before flowering may be useful.

MARKETING, USES AND PRODUCTS

Grading

 For grading purposes sorghum is divided into the following classes:

Class GM: This includes malt sorghum that does not have a dark testa (condensed tannins), is listed as a GM cultivar and meets the requirements of Class GM sorghum as stipulated by the grading regulations.

Class GL: This includes sorghum which does not have a dark testa (condensed tannins) and is from a GM cultivar that cannot be graded in the Class GM sorghum or from a GL cultivar as stipulated in the cultivar list, and meets the requirements of Class GL sorghum as stipulated by the grading regulations.

Class GH:This includes malt sorghum which has a dark testa (condensed tannins) and is from a GH cultivar as determined by the cultivar list, and meets the requirements of Class GH sorghum as stipulated by the grading regulations.

Other sorghum:This includes sorghum which does not meet the requirements of Class GM, Class GL and Class GH sorghum.

Sorghum products for the consumer

Malt: Commercial malt is produced from GM cultivars with specific character- istics. Industrial malt is produced from GM and GH cultivars. Condensed tannins in GH cultivars are neutralised before malting commences. The malt is used in the industrial production of sorghum beer.

Beer: Preparation of beer is a lengthy process covering 3 days. Ingredients for the preparation of beer are malt, meal and yeast.

Beer powder: Instant beer powder is a premixed product that consists mainly of sorghum malt, a starch component and brewers yeast. A 24-hour period is needed before the beer can be consumed.

Sorghum meal: Sorghum meal, also known as Mabele, directly competes with maize meal. Sorghum with condensed tannins is not used for meal production .

Sorghum rice: Sorghum rice or corn rice is whole, decorticated sorghum.

Livestock feed: and other animal products Livestock feed is the most important market for surplus sorghum, as it competes effectively with other grain products in terms of price and quality. Sorghum is an important component in poultry feed and good progress has been made in the manufacturing of dog food, as well as pigeon and  ostrich  food

SORGHUM VARIETIES

Scientific classification

Kingdom:Plantae

order:Poales

Family :Poaceae

Sub-Family:Panicoideae

Tribe: Andropogoneae

Genus: Sorghum

Species: sorghum bicolor

 The genus sorghum is divided into five sections: Parasorghum, Stiposorghum, Heterosorghum, Chaetosorghum and Sorghum.

Parasorghum: Sheath-nodes densely bearded, pedicillate spikelets staminate, panicle branches simple, awn and callus well developed, chromosomes large, n=5.

Stiposorghum: As Parasorghum except awn and callus better developed, n=5.

Heterosorghum: Pedicellate spikelets reduced to glumes, panicle branches divided, awn and callus poorly developed, chromosomes medium, n=10 or 20.

 Chaetosorghum: Pedicellate spikelets reduced to glumes, panicle branch simple, awn well developed, callus poorly developed, chromosomes medium, n=10 or 20.

Sorghum: Sheath-nodes glabrous or finely pubescent, not bearded, pedicellate spikelet staminate, panicle branches divided, awn and callus poorly developed, chromosomes medium, n=10.

Section Sorghum includes annual cultivated forms from Asia and Africa and perennial taxa from southern Europe and Asia.

Three species are recognized:

 •S. halepense (L.) Pers. (2n=40): A rhizomatous perennial species with creeping rhizomes, pedicellate spikelets deciduous when mature, and up to 25 cm long.

•S. propinquum (Kunth) Hitchc (2n=20): A rhizomatous perennial species with creeping rhizomes, pedicelled spikelets deciduous when mature, sessile spikelets acute to acuminate, lower glume with the keels ending without or with only obscure teeth, leaf blades broad, panicles large, and 20–60 cm long.

•S. bicolor (L.) Moench: annual taxa cultivated.

Species S. bicolor comprises three subspecies: bicolor, drummondii and verticilliflorum.

•Subsp. bicolor: Plants annuals, with stout culms, often branched, frequently tillering, leaf blades up to 90 cm long and 12 cm wide, inflorescence open or contracted panicle, branches often several from lower nodes, obliquely ascending or spreading, racemes tough.

 •Subsp. drummondii: Plants annual with relatively stout culms, leaf blades lanceolate up to 50 cm long and 6 cm wide, panicles rather contracted, branches somewhat pendulous, racemes more or less crowded, mostly 3-5 noded, tardily disarticulating at maturity.

•Subsp. verticilliflorum: Plants tufted annuals or weak biannual, leaf blades linear-lanceolate up to 75 cm long and 6 cm wide, panicles usually large, somewhat contracted to loose with branches obliquely ascending or spreading, racemes 1–5 noded, fragile.

 The cultivated sorghums (Sorghum bicolor Subsp. bicolor) were classified into five basic races

•Bicolor: Grain elongate, sometimes slightly obovate, nearly symmetrical dorso-ventrally, glumes clasping the grain, which may be completely covered or exposed as much as ¼ of its length at the tip, spikelets persistent.

•Guinea: Grain flattened dorso-ventrally, sublenticular in outline, twisting at maturity nearly 90 degrees between gaping involute glumes that are from nearly as long to longer than the grain.

•Caudatum: Grain markedly symmetrical, the side next to the lower glume flat or in extreme cases somewhat concave, the opposite side rounded and bulging, the persistent style often at the tip of a beak pointing towards the lower glume, glumes ½ the length of the grain or less.

•Kafir: Grain approximately symmetrical more or less spherical, glumes clasping and variable in length.

•Durra: Grain rounded obovate, wedge-shaped at the base and broadest slightly above the middle; glumes very wide, the tip of a different texture from the base and often with a transverse crease across the middle.

These five basic races and ten intermediate combinations can account for all the variation in the cultivated forms.

CONCLUSION

sorghum  is  an  important  crop  world  wide  used  for  food(as  grain  and  in  sorghum  syrup  and  sorghum  molasses),  animal  folder,  the  production  of  alcoholic  beverages,  and  biofuel.  Most  varieties  are  drought  and  heat  tolerant  and  are  especially  important  in  arid  region,  where  the  grain  is  one  of  the  staples  for  poor  and  rural  people  .  This  varieties  form  important  component  of  pastures  in  many  tropical   regions.S.bicolor  is  an  important  food  crop  in  Africa,central America and  South  Asia,  and  is  the  fifth  most  important  cereal  crop  grown  in  the  world.

REFERENCES

Ø The  state  of  Queensland (Department  of  Agriculture  and  fisheries)  2010-2015

Queensland  Government.

Ø Sorghum  production  -  Jean  du  plessis

Ø en. m. wikipedia. org/wiki/sorghum.