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Cultivation of Sweet Sorghum

Climate and soil requirements:
Sweet sorghum is a warm-season crop that matures earlier under high temperatures and short days.
It tolerates drought and high-temperature stress better than many crops, but it does not grow well, under low temperatures.
It can be grown on soils ranging from heavy clay to light sand. Loam and sandy loam soils generally allow the best syrup production.

Sweet sorghum is ideally shown during June, coinciding with the south - west monsoon.
Rainfall of 500 – 600 mm distributed ideally across growing period is the best, unless the soil can hold much water (deep).
The crop does not prefer high rainfall as high soils moisture or continuous heavy rain after flowering may hamper sugar increase.
If irrigation is available, sowing can be done before June so that the crop does not face heavy rains after flowering and more so during the last half of grain maturing period.
Sowing during rabi or summer season may result in low biomass and sugar yield.

All India Coordinated Sorghum Improvement Project by the National Research Center for Sorghum at Hyderabad has released SSV 84, a sweet stalk variety.

SSV 84 has average yielding ability of 40.4 t/ha green cane, 1.38 t grain, and 12-13% sucrose.
It is able to produce 15% fermentables at 50-60% recovery and can yield up to 2000 l/ha ethanol.


Seed rate:
A good crop may have about 1,00,000 to 1,20,000 plants/ha. This can be achieved with 8 kg seed/ha.
Sowing:
Sowing can be done on ridges or in furrows at a spacing of 60 cm between rows and 15 cm within rows.
Three to four seeds are dibbled in each hill/planting hole and the seedlings are to be eventually thinned to one per hill.
If a planter is used, then the existing seed rate will be reduced.


Fertilizer application:
Like other crops, sweet sorghum needs adequate nutrients to produce good yields.
Fertilization practices may also affect syrup quality.
Soil testing should be used to determine the need for lime, phosphorus, potassium, calcium, and magnesium.
Recommended dose of fertilizer for sweet sorghum in soils with normal fertility levels is 80kg of nitrogen, 60 kg of phosphorous and 40 kg of potassium.
Half of N and whole of P and K are applied as basal.
Remaining N is top-dressed during 25-35 days after germination, following weeding and inter-cultivated.
Excessive nitrogen reduces syrup quality.
So, recommended amounts of nitrogen should not be exceeded.
When sweet sorghum is grown immediately after a legume crop, the nitrogen application rate can be reduced or eliminated without harming yields.


Crop Protection:
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     Observe dead hears and
       tillering of the plant due
          to shoot fly attack.
Shoot fly and Stem borer are major pests.
Shoot fly infestation occurs soon after germination and up to 30 days.
Shoot fly attack can be noticed by the dead hearts and profuse tillering by the plant.
Shoot fly can be managed by the soil application of Carbofuran 3G at 8 to 10 kg/ha.


The first indication that a sorghum plant is infested by the stem borer is the appearance of small elongated holes in young whorl leaves .

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                                    Windows due to stem borer attack. Subsequently larvae bore into the stem and shot-holes appear.


Consequent to eating the central stem portion, the growing point is killed and dead heart symptoms appear in whorl leaves .

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A large number of predators attack this pest. Chemical control is required only when the infestation is very severe.
2 to 3 granules of Carbofuran 3G are placed in the leaf whorls immediately after observing the shot holes on the leaves to prevent stem tunneling.


Harvesting:
Most of the sweet sorghum varieties mature between 115-125 days during rainy season.
The highest-quality syrup is produced when the sorghum is harvested before the mature or ripe seed stage.
Sucrose percentage and syrup yields generally increase as the stalk matures to the ripe seed stage.
To obtain high-quality syrup and high yields, the crop should be harvested when the seed is in the soft dough stage.
Stalks can be harvested either along with the grain, or 4-5 weeks after the grain harvest.
The ear-head and peduncle (between the base of the seed head and the top node) should be removed before processing the stalks.
Ear-heads may be dried and threshed so the seeds can be used for the next year's crop.
Excellent-quality syrup can be made without removing (stripping) the leaves.
However, the stalks should not be crushed while the leaves are still wet. Delay milling for 3 to 5 days.
This delay will allow the leaves to dry out, the stalks to lose some water, and natural enzymes within the stalk to invert
some of the sucrose. These changes will make the syrup easier to cook and less likely to crystallize.
A crop yielding 40 t fresh stalk/ha and 60% extractability would yield about 3 t jaggery and 3.5 t syrup.
The same stalk in fermentation may yield 2500 l of ethanol.
The stalk residue left over after processing is about 12-15 t/ha, which may be used either as fuel or feed.


Sweet sorghum varieties:

SPV 422

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  • A high yielding variety for cultivation in post-rainy season

  • Flowers in 90 to 95 days and matures in 25 to 130 days, grows to a height of 2.6 to 3.0 m

  • Juicy stalks with 19% sugar

  • Produces millable cane yield of 40 t/ ha It gives a grain yield of 3.0 to 3.2 t/ ha with pearly white bold grains

  • Resistant to leaf diseases.


NTJ2

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  • A high yielding variety for cultivation in post-rainy season

  • Flowers in 68 to 75 days and matures in 110 to 115 days and grows to a plant height of 2.0 to 2.5 m

  • Flowers in 70 to 75 days and matures in 105 to 110 days with a plant height of 2.0 to 2.5 m in the post-rainy season

  • Stems are thick and juicy with 18.5% sugar 

  • Produces millable cane yield of 50 t/ ha

  • It gives a grain yield of 3.5 to 4.0 t/ha with creamy white bold grains 

  • Resistant to leaf diseases


SPV 1411

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  • A high yielding variety for cultivation in post-rainy season

  • Released as “Parbhani Moti” for post rainy season

  • Flowers in 79 to 85 days and matures in 120 to 129 days and grows to a plant height of 2.0

  • Stems are juicy with 21% sugar Produces millable cane yield of 30 t/ ha

  • It gives a grain yield of 3.0 to 4.0 t/ha with pearly white lustrous bold grains

  • Tolerant to shoot fly, stem borer and leaf diseases.                                                     


ICSR 93034

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  • A high yielding variety for cultivation in post-rainy season

  • Flowers in 75 to 80 days and matures in 110 to 115 days during post-rainy season

  • Matures late in 120 to 125 days during rainy season

  • Grows to a plant height of 2.0 to 2.8 m

  • Stems are juicy with 18% sugar

  • Produces millable cane yield of 43 t/ ha

  • It gives a grain yield of 3.0 to 3.4 t/hawith lustrous and bold grains.


ICSV 93046

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  • Flowers in 75 to 80 days and matures in 115 to 120 days during post-rainy season

  • Matures late in 120 to 125 days during rainy season

  • Grows to a plant height of 2.0 to 2.5 m

  • Stems are juicy with 15% sugar

  • Produces millable cane yield of 43 t/ ha

  • It gives a grain yield of 3.2 to 3.5 t/ha with lustrous and bold grains.

  • Stays green even after physiological maturity

  • Tolerant to shoot fly, stem borer and leaf diseases.


ICSV 700

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  • Flowers in 80 to 85 days and matures in 120 to 125 days during post-rainy season

  • Matures late in 120 to 125 days during rainy season

  • Grows to a plant height of 3.0 to 3.2 m

  • Stems are juicy with 18% sugar

  • Produces millable cane yield of 40 t/ ha

  • Lustrous, creamy and small sized grains.

  • Resistant to stem borer.

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