Farmers’ Guide to Soybean Production in Northern Nigeria

Abstract

Soybean is among the major industrial and food crops grown in every
continent. The crop can be successfully grown in many states in Nigeria
using low agricultural input. Soybean cultivation in Nigeria has expanded
as a result of its nutritive and economic importance and diverse domestic
usage. IITA along with partners has developed improved technologies for
soybean production. This handbook outlines crop production practices
that farmers may use to grow soybean profitably in Nigeria.

Full text

i
www.iita.org
Farmers’ Guide to Soybean
Production in Northern Nigeria
I.Y. Dugje, L.O. Omoigui, F. Ekeleme, R. Bandyopadhyay,
P. Lava Kumar, and A.Y. Kamara

ii
Farmers’ Guide to Soybean Production
in Northern Nigeria
I.Y. Dugje1,2, L.O. Omoigui1, F. Ekeleme1,3,
R. Bandyopadhyay1, P. Lava Kumar1,
and A.Y. Kamara1
May 2009
1. International Institute of Tropical Agriculture, Ibadan, Nigeria
2. University of Maiduguri, Nigeria
3. Michael Okpara University of Agriculture, Umudike, Nigeria

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© International Institute of Tropical Agriculture (IITA) 2009
Ibadan, Nigeria
To Headquarters from outside Nigeria:
IITA, Carolyn House
26 Dingwall Road, Croydon CR9 3EE, UK
Within Nigeria:
PMB 5320, Oyo Road
Ibadan, Oyo State
ISBN 978-131-333-1
Printed in Nigeria by IITA
Citation: Dugje, I.Y., L.O. Omoigui, F. Ekeleme, R. Bandyopadhyay,
P. Lava Kumar, and A.Y. Kamara. 2009. Farmers’ Guide to Soybean
Production in Northern Nigeria. International Institute of Tropical
Agriculture, Ibadan, Nigeria. 21 pp.
Disclaimer: Mention of any proprietary product or commercial applications
does not constitute an endorsement or a recommendation for its use by IITA.
Cover: Soybean production eld.
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in 1967, governed by a Board of Trustees, and supported primarily by the
CGIAR.

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Contents
Introduction .......................................................................................... 1
Importance of soybean in the global economy .............................. 1
Why grow soybean? ...................................................................... 1
Conditions necessary for soybean production ............................... 2
Preparing to plant ................................................................................ 2
Land preparation ............................................................................ 2
Choice of variety ............................................................................ 3
Seed cleaning and preparation ...................................................... 3
Soybean germination test .............................................................. 4
Planting................................................................................................ 4
Date of planting .............................................................................. 4
Seed rate ....................................................................................... 5
Seed dressing ................................................................................ 5
Plant spacing and sowing .............................................................. 5
Fertilizer ............................................................................................... 6
Soil fertility enhancement ............................................................... 6
Pests and diseases ............................................................................. 7
Weeds and their control ................................................................. 7
Insects and their control ................................................................. 7
Diseases and their control ............................................................. 9
Harvesting soybean ............................................................................. 14
Postharvest operations ........................................................................ 15
Threshing ....................................................................................... 15
Storage .......................................................................................... 16
References ........................................................................................... 17

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Introduction .......................................................................................... 1
Importance of soybean in the global economy .............................. 1
Why grow soybean? ...................................................................... 1
Conditions necessary for soybean production ............................... 2
Preparing to plant ................................................................................ 2
Land preparation ............................................................................ 2
Choice of variety ............................................................................ 3
Seed cleaning and preparation ...................................................... 3
Soybean germination test .............................................................. 4
Planting................................................................................................ 4
Date of planting .............................................................................. 4
Seed rate ....................................................................................... 5
Seed dressing ................................................................................ 5
Plant spacing and sowing .............................................................. 5
Fertilizer ............................................................................................... 6
Soil fertility enhancement ............................................................... 6
Pests and diseases ............................................................................. 7
Weeds and their control ................................................................. 7
Insects and their control ................................................................. 7
Diseases and their control ............................................................. 9
Harvesting soybean ............................................................................. 14
Postharvest operations ........................................................................ 15
Threshing ....................................................................................... 15
Storage .......................................................................................... 16
References ........................................................................................... 17
Tables
1. Recommended soybean varieties for Guinea and Sudan savanna
ecological zones in Nigeria ............................................................. 3
2. Recommended dates for planting soybean in Nigeria .................... 5
3. Recommended fertilizer rates for soybean production in Nigeria ... 7
4. Recommended herbicide rates for weed control in soybean .......... 8
Figures
1. Preparing land for soybean production using a tractor ................... 2
2. Use good seeds for planting ........................................................... 4
3. Do not use poorly sorted seeds ...................................................... 4
4. Soybean in rotation with maize ....................................................... 6
5. (a) Rust infected soybean leaves with large number
of small tan lesions ................................................................... 9
(b) Large number of spores on the lower surface of
tan lesions of soybean rust ...................................................... 9
6.
Small spots and coalescing lesions of bacterial pustule disease
........ 10
7. Phytophthora seedling blight causing wilting of older seedlings ..... 10
8. Initial symptoms of frogeye leaf spot .............................................. 11
9. Mosaic disease-affected soybean plants ........................................ 12
10. Bright yellow mosaic symptoms caused by begomovirus
infection in soybean plants ............................................................. 13
11. Dwarf-disease affected soybean .................................................... 13
12. Manual threshing of soybean .......................................................... 15
13. A multipurpose soybean threshing machine ................................... 16

1
Introduction
Importance of soybean in the global economy
Soybean is among the major industrial and food crops grown in every
continent. The crop can be successfully grown in many states in Nigeria
using low agricultural input. Soybean cultivation in Nigeria has expanded
as a result of its nutritive and economic importance and diverse domestic
usage. It is also a prime source of vegetable oil in the international
market. Soybean has an average protein content of 40% and is more
protein-rich than any of the common vegetable or animal food sources
found in Nigeria. Soybean seeds also contain about 20% oil on a dry
matter basis, and this is 85% unsaturated and cholesterol-free.
The rapid growth in the poultry sector in the past ve years has also
increased demand for soybean meal in Nigeria. It is believed that
soybean production will increase as more farmers become aware of
the potential of the crop, not only for cash/food but also for soil fertility
improvement and Striga control. The market for soybean in Nigeria is
growing very fast with opportunities for improving the income of farmers.
Currently, SALMA Oil Mills in Kano, Grand Cereals in Jos, ECWA Feeds
in Jos, AFCOT Oil Seed Processors, Ngurore, Adamawa State, and PS
Mandrides in Kano all process soybean.
IITA along with partners has developed improved technologies for
soybean production. This handbook outlines crop production practices
that farmers may use to grow soybean protably in Nigeria.
Why grow soybean?
It is good for food—soy-milk, soy-cheese, • dadawa, Tom Brown
(infant weaning food),
It is the source of an excellent vegetable oil,•
It is used in industry,•
It improves soil fertility and controls the parasitic weed, • Striga
hermonthica,
Soybean cake is an excellent livestock feed, especially for poultry,•
The haulms provide good feed for sheep and goats.•

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Conditions necessary for soybean production
Soybean growth is inuenced by climate and soil characteristics.
Soybean performs well in the southern and northern Guinea savannas
of Nigeria where rainfall is more than 700 mm.
However, short-duration varieties can thrive in the much drier Sudan
savanna when sown early and with an even distribution of rainfall
throughout the growing period. The time for planting soybean depends
upon temperature and day length. Soybean is a short-day plant and
owers in response to shortening days. It can be grown on a wide range
of soils with pH ranging from 4.5 to 8.5. Soybean should not be planted
in sandy, gravelly, or shallow soils to avoid drought stress. It should not
be grown in waterlogged soils or soils with surfaces that can crust, as
this will lead to poor seedling emergence.
Preparing to plant
Land preparation
Clear all vegetation before land preparation. The seedbed may be
prepared manually with a hoe or animal-drawn implement or tractor
(Fig. 1). Well-prepared land ensures good germination and reduces
weed infestation. You can plant on ridges or on a at seedbed.
Figure 1. Preparing land for soybean production using a tractor.

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Variety Ecology Characteristics Striga control
TGX 1448-2E Southern and northern
Guinea savannas
Medium maturing, high yield,
low shattering, high oil
content, excellent grain color
Good
TGX 1835-10E
TGX 1485-1D
Guinea savanna
Guinea savanna
Early maturing, rust resistant,
pustule resistant
Early maturing, pustule
resistant, rust susceptible
Not known
Not known
Table 1. Recommended soybean varieties for Guinea savanna
ecological zones in Nigeria.
N.B. Early and extra-early maturing varieties are strongly recommended in the Sudan savanna
because of the low amount and duration of rainfall in the zone.
Choice of variety
Selected soybean varieties grown in Nigeria are presented in Table 1.
Choose a variety suited to your agroecological zone. Soybean variety
selection should be based on maturity, yield potential, lodging, drought
tolerance, and resistance to pests and diseases. The maturity period
should be the rst consideration when choosing a variety suited to your
geographical zone. Consider varieties that are earlier maturing rather
than late maturing in areas with low rainfall. Although later maturity
increases the yield potential, it is risky to grow late-maturing varieties in
drier environments because of late-season drought.
Seed cleaning and preparation
Use high quality seeds of the selected variety (Fig. 2). Soybean seeds
easily lose their viability. It is common for soybean, even when stored
properly, not to germinate after 12 –15 months in storage. Therefore,
use seeds that are not more than 12 months old to ensure good
germination. Sort out the good seeds for planting to ensure that they
are free from insects, disease infestation, and weed seeds. Do not
purchase seeds from the open market as the germination potential
is not guaranteed. Planting poor quality seeds will not produce a
good yield (Fig. 3). Always buy seeds from seed companies or seed
producers nearest to you.

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Soybean germination test
Test seeds for germination before planting. The germination rate
should be 85% or more to obtain a good stand. To conduct a quick
seed germination test, select 400 seeds randomly and sow 100 seeds
each in four wooden or plastic boxes or a prepared seedbed. Sow one
seed/hole at a distance of 10 cm between the seeds. Soak cloth- or
paper-lined germination boxes or the seedbed well with water before
sowing and provide water every morning and evening. Start counting
the seedlings 5 days after sowing and complete the counting within
10 days. A total count of 320 germinated seeds or more indicates a
germination rate of 80% and above. When the percentage germination
is 80% or less, the seed rate has to be increased accordingly to achieve
100% germination.
Planting
Date of planting
Soybean produces well over a wide range of planting dates, if moisture
is available. The recommended dates for planting soybean in different
ecological zones in Nigeria are presented in Table 2. Do not plant too early
Figure 2. Use good
seeds for planting.
Figure 3. Do not use poorly
sorted seeds.

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because a prolonged dry spell after planting may result in permanent wilting
of the crop and the need for replanting. Late planting, on the other hand,
may expose the crop to attack by some late season pests and also deprive
the crop of sufcient moisture if the rains stop early. Plant soybean as soon
as the rains are well established.
Seed rate
About 50–70 kg (20–28 standard mudus) are required to obtain a
population of 444,444 plants/ha for soybean varieties. Since soybean
seed size varies among varieties, it is essential to consider planting in
terms of seeds/unit area. It is not uncommon to see sizes ranging from
12.6 to 18.9 g/100 seeds
Seed dressing
Treat seeds with fungicides, such as Captan, Apron Plus, or Thiram, at the
rate of 1 sachet/8 kg of seeds before planting for protection against soil-
borne fungal diseases.
Plant spacing and sowing
Sow soybean by hand, planter, or by drilling. Plant 3 to 4 seeds/hole at a
spacing of 75 cm between rows and 10 cm between stands. Alternatively,
drill seeds at 50–75 cm between rows and 5 cm within rows. For the early
maturing varieties, a spacing of 50 cm between rows and 5–10 cm within
rows is recommended because they respond better to narrow spacing
than the late-maturing varieties. Do not sow seeds more than 2–5 cm
deep. Deeper planting may result in loss of vigor or failure of seedlings to
emerge.
Ecological zone Suggested time of planting
Table 2. Recommended dates for planting soybean in Nigeria.
Moist savanna/southern Guinea savanna Early June–early July
Northern Guinea savanna–Sudan savanna Mid-June–early July
Sudan savanna July, weeks 1–2

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Fertilizer
A good fertilizer recommendation for soybean production depends
on a good soil test. Under normal conditions, soybean as a legume
should provide itself with nitrogen through biological nitrogen xation.
Until nodulation occurs, the soybean plant depends on soil nitrogen for
growth. Phosphorus is often the most decient nutrient, therefore, apply
optimum phosphorous fertilizer for good yield. Apply phosphorus at the
rate of 30 kg p/ha in the form of single super phosphate fertilizer (SUPA)
(3 × 50 kg bags) in addition to 2½ × 50 kg bags of compound fertilizer
NPK 15:15:15. Nitrogen and potassium fertilizers are needed only
when there are obvious deciencies. Incorporate the fertilizer into the
soil at land preparation during harrowing and leveling the eld. Use the
recommendations (Table 3) as a guide for fertilizing your soybean crop.
Soil fertility enhancement
Soybean improves soil fertility and xes nitrogen in the soil for the
succeeding maize (Fig. 4). When grown in rotation with maize, it serves as
a catch crop in controlling Striga hermonthica, a parasitic weed that attacks
maize, by causing suicidal germination of Striga.
Figure 4. Soybean in rotation with maize.

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Recommended fertilizer rates (kg/ha) Materials
20 kg N
40 kg P2O5
20 kg K2O
2½ × 50 kg bags of NPK (15-15-15)
plus 3 × 50 kg bags of SSP (SUPA)
Table 3. Recommended fertilizer rates for soybean production in Nigeria.
Pests and diseases
Weeds and their control
Perennial and most annual weeds are a problem in soybean in its early
growth stages. A properly timed weed control program can minimize the
effects of weeds. Weed control in soybean could be manual or chemical
or both.
Manual weed control: Carry out the rst weeding at 2 weeks after
planting and the second at 5–6 weeks after planting. Avoid weeding
immediately after a rainfall as this would lead to transplanting the weeds.
Poor hoe weeding or delay in weeding could cause signicant reductions
in soybean yields.
Chemical weed control: Herbicides, if used properly, are safe and
effective in controlling weeds in soybean. The choice of herbicide,
however, depends on the predominant weed species and the availability
of the herbicide. Herbicides are available for pre-emergence or post-
emergence weed control in soybean. If herbicide is applied at planting,
one weeding may be required at 5–6 weeks after planting. Use
herbicides as presented in Table 4.
Insect pests and their control
Several different insects occur in soybean elds but few are normally
of any economic importance, and the species that cause damage
are usually not abundant enough to warrant control measures. In
the vegetative stage, the crop is very tolerant of caterpillars but very
susceptible to silverleaf whitey attack.

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Product Product rate/ha (L) Time of application Remarks
Paraquat plus
Pendimethalin
(50EC)
3 L of Paraquat
plus 3 L of
Pendimethalin (250
mL of each/20-L
sprayer)
Applied within 2
days of planting
Where grasses,
e.g., Rottboellia
are common
Paraquat plus
Dual Gold
3 L of Paraquat plus
2 L of Dual Gold
(= 250 mL of
Paraquat plus 200
mL of Dual Gold in
15-L sprayer (= 1½
milk tins of
Paraquat plus 3/4
milk tins of Dual
Gold)
Applied within 2
days of planting
Controls most grasses
and broadleaf weeds.
Where sowing is
done after 1 week
of land preparation,
application must be
within 12 h after
planting.
Paraquat plus
Butachlor
3 L of Paraquat plus
4 L of Butachlor
(= 250 mL of
Paraquat plus 350
mL of Butachlor in
15-L sprayer) (= 1½
milk tins of
Paraquat plus 2½
milk tins of
Butachlor)
Applied within 2
days of planting
Controls most grasses
and broadleaf weeds
and sedges
Fusilade forte 1–1½ L (150 mL
(= 1 milk tin)/15-L
sprayer
Postemergence
Apply 21–28 days
after sowing
For grass weed
control
Round-up
or other
Glyphosate
products
4 L (= 350 mL/15-L
sprayer)
Preemergence
(before land
preparation)
Used under no-tillage
system, applied at
least 2 weeks before
sowing also to control
perennial weeds
Note: (1) About 12 loads of a 15-L sprayer are required for 1 ha. (2) Where animal power is used for land
preparation, allow rain to fall on the prepared land before planting and spray herbicides within 2 days of
planting to enhance effectiveness. (3) 150 mL of chemical will ll a standard sized container of liquid Peak milk.
Table 4. Recommended herbicide rates for weed control in soybean.
From owering onwards, soybean becomes attractive to pod-sucking
bugs that can seriously reduce seed quality. Insect pests can be
controlled with a single spray of Cypermethrin + Dimethoate 10 EC at
the rate of 100 mL in 15 L of water.

9
Diseases and their control
Soybean diseases normally result in
major yield losses in Nigeria. Some
of the common diseases caused
by fungi, bacteria, and viruses are
mentioned below.
Fungal and bacterial diseases
Rust: Asian soybean rust, caused
by Phakopsora pachyrhizi, is one of
the most important foliar diseases
in Nigeria. The infected leaves
have small tan to dark brown or
reddish brown lesions (Fig. 5a)
on which small raised pustules (or
‘bumps’) occur on the lower surface
of the leaves (Fig. 5b). Pustules
produce a large number of spores.
Brown or rust-colored powder falls
when severely infected leaves are
tapped over a white paper or cloth.
Severe infection leads to premature
defoliation and yield losses up
to 80%. The disease is of great
economic importance in the derived
savanna and southern Guinea
savanna zones where rainfall and
humidity are high.
Bacterial pustule: The disease is
caused by Xanthomonas axonopodis
pv. glycines. Symptoms appear as
specks to large, irregular spots with
raised light-colored pustules in the
elevated centers of the spots on
Figure 5a. Rust-infected
soybean leaves with large number
of small tan lesions.
Figure 5b. Large number of spores
on the lower surface of tan lesions of
soybean rust.
Product Product rate/ha (L) Time of application Remarks
Paraquat plus
Pendimethalin
(50EC)
3 L of Paraquat
plus 3 L of
Pendimethalin (250
mL of each/20-L
sprayer)
Applied within 2
days of planting
Where grasses,
e.g., Rottboellia
are common
Paraquat plus
Dual Gold
3 L of Paraquat plus
2 L of Dual Gold
(= 250 mL of
Paraquat plus 200
mL of Dual Gold in
15-L sprayer (= 1½
milk tins of
Paraquat plus 3/4
milk tins of Dual
Gold)
Applied within 2
days of planting
Controls most grasses
and broadleaf weeds.
Where sowing is
done after 1 week
of land preparation,
application must be
within 12 h after
planting.
Paraquat plus
Butachlor
3 L of Paraquat plus
4 L of Butachlor
(= 250 mL of
Paraquat plus 350
mL of Butachlor in
15-L sprayer) (= 1½
milk tins of
Paraquat plus 2½
milk tins of
Butachlor)
Applied within 2
days of planting
Controls most grasses
and broadleaf weeds
and sedges
Fusilade forte 1–1½ L (150 mL
(= 1 milk tin)/15-L
sprayer
Postemergence
Apply 21–28 days
after sowing
For grass weed
control
Round-up
or other
Glyphosate
products
4 L (= 350 mL/15-L
sprayer)
Preemergence
(before land
preparation)
Used under no-tillage
system, applied at
least 2 weeks before
sowing also to control
perennial weeds
Note: (1) About 12 loads of a 15-L sprayer are required for 1 ha. (2) Where animal power is used for land
preparation, allow rain to fall on the prepared land before planting and spray herbicides within 2 days of
planting to enhance effectiveness. (3) 150 mL of chemical will ll a standard sized container of liquid Peak milk.
Table 4. Recommended herbicide rates for weed control in soybean.

10
the lower surface (Fig. 6). The elevated
pustules sometimes have cracks in
them. Later lesions join together and the
dead areas tear away to give a ragged
appearance to the leaves. Symptoms
of rust and bacterial pustule sometimes
appear similar.
Phytophthora seedling blight and
root and stem rot: Phytophthora sojae
causes seedling blight, and root and
stem rot. Young seedlings that appear
to be established turn off-color to yellow,
wilt, and die (Fig. 7). The stems of these
plants may show a brown discoloration
that begins at the soil line and extends
up the stem. The brown, dead leaves
remain attached to the plant, and the
dead seedlings are obvious symptoms
of the disease in the eld.
The root rot phase of the disease is
rapidly becoming a very destructive
disease in Nigeria. The Phytophthora
fungus can kill plants at all stages of
growth. Infected stands may survive
but are less productive than healthy
stands. Infection generally occurs in
elds with poor drainage, but it can occur
in normally well-drained elds that are
waterlogged for 7–14 days after irrigation
or very heavy or prolonged rainfall.
Frogeye leaf spot: The fungus
Cercospora sojina that survives in
infected soybean residue and seeds
causes this disease. Symptoms appear
Figure 7. Phytophthora
seedling blight causing
wilting of older seedlings.
Figure 6. Small spots
and coalescing lesions
of bacterial pustule
disease.

11
as brown, circular to irregular spots
with narrow reddish brown margins on
the leaf surfaces (Fig. 8). The central
areas of the spots turn ash gray to
light brown. Sometimes lesions can
develop on stems and pods from
where mature seeds are infected.
Infected seeds may show discoloration
of the seed coat that ranges from
small specks to large blotches of light
to dark gray or brown.
To control these diseases:
Plant resistant varieties. This is the •
best option to control disease.
Plant in a good seedbed. Avoid •
poorly drained or compacted soil.
Plant seeds treated with fungicides
•
as mentioned earlier under ‘seed
dressing’.
Rotate crops with maize to prevent
•
the increase in inoculum levels in a
Figure 8. Initial symptoms of
frogeye leaf spot.
eld.
Use of a foliar fungicide is seldom warranted, except on high-value •
elds (e.g., seed production elds) or in years when the weather is
especially favorable for disease development.
Virus diseases
Soybean is susceptible to several viruses transmitted by aphids, beetles
and whiteies prevailing in Nigeria. Most of the virus infection results
in foliar symptoms such as mosaic and mottling, thickening/brittling of
older leaves, puckering, leaf distortion, severe reduction in leaf size,
and stunting of plants. Mixed infection with more than one virus is
common under eld conditions. Features of the three most common
virus diseases on soybean in Nigeria are presented here.

12
Mosaic disease: Cowpea mild mottle
virus (CPMMV; genus Carlavirus,
family Flexiviridae) transmitted by
whitey (Bemisia tabaci Gennidius) is
the most prevalent virus associated
with soybean mosaic disease in
Nigeria. In addition, Bean pod
mottle virus (genus Comovirus,
family Comoviridae), Alfalfa mosaic
virus (genus Alfamovirus, family
Bormoviridae), Cucumber mosaic
virus (genus Cucumovirus, family
Bormoviridae), and Southern bean
mosaic virus (genus Sobemovirus)
were also detected in mosaic disease-
affected plants either singly or in
mixed infections, particularly with
CPMMV. Depending on genotype
and age of infection symptoms range
from mosaic and mottling, leaf curling,
green vein banding, and stunting
(Fig. 9). Most severe symptoms are
observed in plants infected at early
stages of growth (preowering) and
signicant reduction in pods.
Yellow mosaic disease: It is caused
by whitey (B. tabaci)-transmitted
different viruses belonging to
the genus Begomovirus, family
Geminiviridae. Soybean yellow
mosaic virus was found to be the most
prevalent virus associated with this
disease. Soybean mottle mosaic virus,
which also causes similar symptoms,
Figure 9. Mosaic disease-
affected soybean plants.

13
was found to be less frequent in the
elds. Virus-infected plants produce
bright yellow mosaic or specks, and
develop into large blotches on the leaf
lamina (Fig. 10), but this infection does
not result in leaf distortion or reduction
in lamina size. Mixed infection of these
two begomoviruses and CPMMV
are common in the elds and such
infection results in bright yellow
mosaic symptoms and leaf puckering.
Dwarf disease: The causal virus
responsible for soybean dwarng
disease is not known. This disease
occurs in low frequency in the elds.
Leaves and shoots of the infected
plants are severely stunted with
severe reduction in leaf lamina
(Fig. 11). Infected plants do not
produce any pods.
Figure 10. Bright yellow mosaic symptoms caused by begomovirus
infection in soybean plants.
Figure 11. Dwarf disease-affected
soybean.

14
Cultivate virus disease-resistant varieties. This is the most convenient,
economical, and effective approach for controlling soybean virus
diseases. If resistant varieties are not available, the following
approaches can contribute to the management of virus diseases
in the eld.
Many viruses involved in mosaic disease are seed transmitted •
in soybean. Use certied seed to avoid seed-borne
infection or use seed that are produced away from the
infection source.
Do not plant seeds obtained from mosaic-affected plants.•
Rouge (uprooting and destruction) symptomatic plants. •
This can reduce the incidence of insect-transmitted viruses.
Eradicate the weeds and voluntary plants in the vicinity of •
the soybean farms.
Treat seeds with systemic insecticides and apply one or two •
foliar sprays of insecticides to reduce the insect vector activity
during preowering stage (most vulnerable to virus infections)
of the plant.
Harvesting soybean
Soybean matures within 3–4 months after planting and requires timely
harvesting to check excessive yield losses. At maturity, the pod is straw-
colored. It is recommended that soybean be harvested when about 85%
of the pods have turned brown for a non-shattering variety but 80% for
shattering varieties. Alternatively, the crop can be harvested when the
seeds are at the hard-dough stage, when the seed moisture content is
between 14 and 16%. Newer varieties are resistant to shattering but
losses in yield may occur from other causes if harvesting is delayed.
Harvesting can be done with a cutlass, a hoe, or sickles. Cut the mature
plants at ground level. Stack them loosely on tarpaulin and allow them
to dry in the open for 2 weeks before threshing. Do not harvest by hand
pulling because this may remove the nutrient that the soybean has
added to the soil.

15
Postharvest operations
Threshing soybean
Thresh manually or mechanically when the plants are properly dry and
as soon as possible. Manual threshing is mainly recommended for
small-scale production. It involves piling soybean plants on tarpaulin or
putting dry soybean pods in sacks and beating them with a stick.
The material is then winnowed to remove the seeds from the
debris (Fig. 12).
Use mechanical threshers in large-scale production. Such
threshers are equipped with blowers that separate the grains from
the chaff (Fig. 13).
Figure 12. Manual threshing of soybean.

16
Figure 13. A multipurpose soybean threshing machine.
Storage
Soybean should be stored at a moisture content of 10% or less. A
soybean seed is sufciently dry when it cannot be dented with the teeth
or ngernails. At harvest, the grains usually contain about 14% moisture.
Dry to 13% moisture for storage of 6–12 months and to 10–11% for
longer storage. Open-air drying is the most practical way to protect
soybean in storage. Place 50-kg or 100-kg bags of clean soybean on
a rack in the cold room or in shade. High moisture content in stored
soybean encourages the development of various agents of deterioration,
such as insects and microorganisms. Good storage management can
greatly inuence the storability of soybean and subsequent germination
when planted in the eld. Do not leave soybean exposed to high
temperatures, as it will increase deterioration and reduce seed viability.

17
References
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