Transcript 5.3 Sorghum - Spate Irrigation Network

5.3
Sorghum
SORGHUM: THE HARDY PLANT SOME FACTS
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.
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.
Hydrocyanic Acid Poisoning
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.
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.
Rotations
Sorghum follows other crops readily, but care should be
exercised in the choice of the crop to follow sorghum
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)