5.3Sorghum

Sorghum is grown in warm or hot regions that have summer rain-fall, even if rainfall is as low as 400-600 mm.

The most favorable mean temperature is about 37oC. The minimum temperature for growth is 15oC. The sorghum plants seems to withstand extreme heat better than other crops.

Sorghum is practically dormant during periods of drought but resume growth as soon as there is sufficient water to wet the soil . This characteristic accounts in large part for the success of sorghum in a dry season

As compared with corn of similar seasonal requirements , sorghum has more roots and a smaller leaf area per plant . A waxy cuticle retards drying.

Sorghum is grown successful on all types of soil.

SORGHUM: THE HARDY PLANT SOME FACTS

Botanical description

Sorghum belongs to the family Graminea. Sorghum is a coarse grass with grows 0.5 to 5.0 meters in height. A leaf arises at each node. Crown buds give rise to tillers

The total number of leaves on the main stalks , including those formed during the seedling stages , averaged 16 to 27 per stalk . Early maturing varieties have few leaves and consequently are limited in plant yield .

The sorghum inflorescence is a loose to dense panicle having many primary branches borne on a hairy axis

Central Issue:Sorghum yields in Pakistan are very low – 0.2- 0.6 ton/ ha

compared to other countries but esp compared to Eritrea where they reach >2ton/ha

Cultivation

Seedbed preparation Irrigation Hydrocyanic poisoning Planting density Weed control Use of fertilizers

Harvesting Ratooning

Rotationsا

Seedbed cultivation

Moldboard plowing is common practice for seedbed preparation in humid and irrigated areas.

The yields may be increased from 25 to 30 % by thorough tillage of medium –heavy soils.

Weed control before planting is desirable.

Most of the fields in the semiarid region are tilled by stubble –mulch.

Irrigation

From 50 to 60 cm of water consisting of stored soil moisture, rainfall and irrigation is required for a maximum yield of sorghum . Of this amount ,some 20 to 50 cm of water must be supplied by irrigation in the sub humid , semiarid and arid regions .Preplanting irrigation wets the soil to its field-carrying capacity to a depth of 180 to 200 cm will reduce the number of summer irrigations . The maximum water usage is during the boot stage of plant growth when 2.5 cm of water is consumed during 3 or 4 days. Yield may more than double on providing additional spate irrigation turns – as the plant is no longer stressed.

Planting density

Sorghum for grain, fodder or silage is usually planted in rows 0.5 to 1.0 meters apart. A sorghum planter or other types of row planters with special sorghum seed plates can work satisfactory.

The amount of seed to plant per hectare depends upon the condition of the seed size and weather conditions at seeding time.

Young plants including the roots and especially the leaves of sorghum contain a glucoside, which upon breaking down releases the poisonous hydrocyanic acid (HCN).

Losses of cattle, sheep and goats occur each year from sorghum poisoning when they graze upon the green plants. Small plants, and young branches and tillers are high in hydrocyanic acid.

Hydrocyanic Acid Poisoning

Weed control

From two to four cultivations are required to control the weeds in sorghum that is planted in rows.

Fewer cultivations are required when the sorghum is planted in furrows.

Weed control with herbicides is less satisfactory in sorghum than in maize for instance, because the sorghum plants are more sensitive to the chemicals.

The killer weed - stryga

A BIG PROBLEM IN SORGHUM BUT ONLY IN RAINFED SORGHUM:NOT IN IRRIGATED SORGHUM!

Use of fertilizers

In semi-arid areas sorghum responds strongly to applications of farm yard manure or nitrogen.

This is an argument to intercrop sorgum with guar

Harvesting

Cut the plants at ground level and laid them on the ground between the rows. Leave the cut plants for 4-5 days to dry up. This conserves soil moisture to be used use by the ratooned crop.

If the plants are left on the ground for longer period, the grains will start to change color and develop an unpleasant smell.

Cut off the ear heads and transport to the threshing ground. Leave there there for 1-2 weeks, until the plant is dry enough to be threshed easily.

Sorghum is harvested when the crop is matured ,

but not when it is fully dry . This is done to allow

enough time for the ratoon crop develop . So some

farmers harvest the main crop 10- 15 days ahead of the normal harvesting time .

The process of harvesting is :

cut the plants at ground level and laid them on the ground

between the rows

left the laid plants for 4-5 days to dry up . This conserves soil

moisture to use by crop ratoon . If the plants are left on the ground

for longer period , the grains started to change color and develop

an unpleasant smell .

cut off the ear heads and transport to threshing ground , and leave

there for 1- 2 weeks until they are dry enough to be threshed

easily .

RATOONING

Crop ratooning is highly practiced in the spate irrigation in many areas. It has short growing period requirement ( 20 -30 days).

Ratoon yields are lower than the first yield (30%). Sometimes a second ratoon is also harvested – often for fodder only. Varieties are selected on their capacity to ratoon.

Sorghum follows other crops readily, but care should be exercised in the choice of the crop to follow sorghum

Rotations

Livestock

Close link with livestock: Fodder Tilling land Construction and maintenance of structures and

field bunds Transport “Money deposit” (buy in good year, sell in bad year)