Farmers' Guide to Soybean Production in Northern Nigeria - icrisat
Farmers' Guide to Soybean Production in Northern Nigeria - icrisat
Farmers' Guide to Soybean Production in Northern Nigeria - icrisat
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Farmers’ <strong>Guide</strong> <strong>to</strong> <strong>Soybean</strong> <strong>Production</strong><br />
<strong>in</strong> <strong>Northern</strong> <strong>Nigeria</strong><br />
I.Y. Dugje 1,2 , L.O. Omoigui 1 , F. Ekeleme 1,3 ,<br />
R. Bandyopadhyay 1 , P. Lava Kumar 1 ,<br />
and A.Y. Kamara 1<br />
1. International Institute of Tropical Agriculture, Ibadan, <strong>Nigeria</strong><br />
2. University of Maiduguri, <strong>Nigeria</strong><br />
3. Michael Okpara University of Agriculture, Umudike, <strong>Nigeria</strong><br />
May 2009<br />
i
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from agriculture. IITA is an <strong>in</strong>ternational non-profit R4D organization established<br />
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CGIAR.<br />
© International Institute of Tropical Agriculture (IITA) 2009<br />
Ibadan, <strong>Nigeria</strong><br />
To Headquarters from outside <strong>Nigeria</strong>:<br />
IITA, Carolyn House<br />
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ISBN 978-131-333-1<br />
Pr<strong>in</strong>ted <strong>in</strong> <strong>Nigeria</strong> by IITA<br />
Citation: Dugje, I.Y., L.O. Omoigui, F. Ekeleme, R. Bandyopadhyay,<br />
P. Lava Kumar, and A.Y. Kamara. 2009. Farmers’ <strong>Guide</strong> <strong>to</strong> <strong>Soybean</strong><br />
<strong>Production</strong> <strong>in</strong> <strong>Northern</strong> <strong>Nigeria</strong>. International Institute of Tropical<br />
Agriculture, Ibadan, <strong>Nigeria</strong>. 21 pp.<br />
Disclaimer: Mention of any proprietary product or commercial applications<br />
does not constitute an endorsement or a recommendation for its use by IITA.<br />
Cover: <strong>Soybean</strong> production field.<br />
ii
Contents<br />
Introduction.......................................................................................... 1<br />
Importance of soybean <strong>in</strong> the global economy............................... 1<br />
Why grow soybean?....................................................................... 1<br />
Conditions necessary for soybean production............................... 2<br />
Prepar<strong>in</strong>g <strong>to</strong> plant................................................................................. 2<br />
Land preparation............................................................................ 2<br />
Choice of variety............................................................................. 3<br />
Seed clean<strong>in</strong>g and preparation...................................................... 3<br />
<strong>Soybean</strong> germ<strong>in</strong>ation test............................................................... 4<br />
Plant<strong>in</strong>g................................................................................................ 4<br />
Date of plant<strong>in</strong>g.............................................................................. 4<br />
Seed rate........................................................................................ 5<br />
Seed dress<strong>in</strong>g................................................................................ 5<br />
Plant spac<strong>in</strong>g and sow<strong>in</strong>g............................................................... 5<br />
Fertilizer............................................................................................... 6<br />
Soil fertility enhancement............................................................... 6<br />
Pests and diseases.............................................................................. 7<br />
Weeds and their control................................................................. 7<br />
Insects and their control................................................................. 7<br />
Diseases and their control.............................................................. 9<br />
Harvest<strong>in</strong>g soybean............................................................................. 14<br />
Postharvest operations........................................................................ 15<br />
Thresh<strong>in</strong>g....................................................................................... 15<br />
S<strong>to</strong>rage........................................................................................... 16<br />
References............................................................................................ 17<br />
iii
Tables<br />
1. Recommended soybean varieties for Gu<strong>in</strong>ea and Sudan savanna<br />
ecological zones <strong>in</strong> <strong>Nigeria</strong>.............................................................. 3<br />
2. Recommended dates for plant<strong>in</strong>g soybean <strong>in</strong> <strong>Nigeria</strong>..................... 5<br />
3. Recommended fertilizer rates for soybean production <strong>in</strong> <strong>Nigeria</strong>.... 7<br />
4. Recommended herbicide rates for weed control <strong>in</strong> soybean.......... 8<br />
Figures<br />
1. Prepar<strong>in</strong>g land for soybean production us<strong>in</strong>g a trac<strong>to</strong>r.................... 2<br />
2. Use good seeds for plant<strong>in</strong>g............................................................ 4<br />
3. Do not use poorly sorted seeds....................................................... 4<br />
4. <strong>Soybean</strong> <strong>in</strong> rotation with maize....................................................... 6<br />
5. (a) Rust <strong>in</strong>fected soybean leaves with large number<br />
of small tan lesions................................................................... 9<br />
(b). Large number of spores on the lower surface of<br />
tan lesions of soybean rust....................................................... 9<br />
6. Small spots and coalesc<strong>in</strong>g lesions of bacterial pustule disease......... 10<br />
7. Phy<strong>to</strong>phthora seedl<strong>in</strong>g blight caus<strong>in</strong>g wilt<strong>in</strong>g of older seedl<strong>in</strong>gs..... 10<br />
8. Initial symp<strong>to</strong>ms of frogeye leaf spot............................................... 11<br />
9. Mosaic disease-affected soybean plants........................................ 12<br />
10. Bright yellow mosaic symp<strong>to</strong>ms caused by begomovirus<br />
<strong>in</strong>fection <strong>in</strong> soybean plants.............................................................. 13<br />
11. Dwarf-disease affected soybean..................................................... 13<br />
12. Manual thresh<strong>in</strong>g of soybean.......................................................... 15<br />
13. A multipurpose soybean thresh<strong>in</strong>g mach<strong>in</strong>e.................................... 16<br />
iv
Introduction<br />
Importance of soybean <strong>in</strong> the global economy<br />
<strong>Soybean</strong> is among the major <strong>in</strong>dustrial and food crops grown <strong>in</strong> every<br />
cont<strong>in</strong>ent. The crop can be successfully grown <strong>in</strong> many states <strong>in</strong> <strong>Nigeria</strong><br />
us<strong>in</strong>g low agricultural <strong>in</strong>put. <strong>Soybean</strong> cultivation <strong>in</strong> <strong>Nigeria</strong> has expanded<br />
as a result of its nutritive and economic importance and diverse domestic<br />
usage. It is also a prime source of vegetable oil <strong>in</strong> the <strong>in</strong>ternational<br />
market. <strong>Soybean</strong> has an average prote<strong>in</strong> content of 40% and is more<br />
prote<strong>in</strong>-rich than any of the common vegetable or animal food sources<br />
found <strong>in</strong> <strong>Nigeria</strong>. <strong>Soybean</strong> seeds also conta<strong>in</strong> about 20% oil on a dry<br />
matter basis, and this is 85% unsaturated and cholesterol-free.<br />
The rapid growth <strong>in</strong> the poultry sec<strong>to</strong>r <strong>in</strong> the past five years has also<br />
<strong>in</strong>creased demand for soybean meal <strong>in</strong> <strong>Nigeria</strong>. It is believed that<br />
soybean production will <strong>in</strong>crease as more farmers become aware of<br />
the potential of the crop, not only for cash/food but also for soil fertility<br />
improvement and Striga control. The market for soybean <strong>in</strong> <strong>Nigeria</strong> is<br />
grow<strong>in</strong>g very fast with opportunities for improv<strong>in</strong>g the <strong>in</strong>come of farmers.<br />
Currently, SALMA Oil Mills <strong>in</strong> Kano, Grand Cereals <strong>in</strong> Jos, ECWA Feeds<br />
<strong>in</strong> Jos, AFCOT Oil Seed Processors, Ngurore, Adamawa State, and PS<br />
Mandrides <strong>in</strong> Kano all process soybean.<br />
IITA along with partners has developed improved technologies for<br />
soybean production. This handbook outl<strong>in</strong>es crop production practices<br />
that farmers may use <strong>to</strong> grow soybean profitably <strong>in</strong> <strong>Nigeria</strong>.<br />
Why grow soybean?<br />
• It is good for food—soy-milk, soy-cheese, dadawa, Tom Brown<br />
(<strong>in</strong>fant wean<strong>in</strong>g food),<br />
• It is the source of an excellent vegetable oil,<br />
• It is used <strong>in</strong> <strong>in</strong>dustry,<br />
• It improves soil fertility and controls the parasitic weed, Striga<br />
hermonthica,<br />
• <strong>Soybean</strong> cake is an excellent lives<strong>to</strong>ck feed, especially for poultry,<br />
• The haulms provide good feed for sheep and goats.<br />
1
Figure 1. Prepar<strong>in</strong>g land for soybean production us<strong>in</strong>g a trac<strong>to</strong>r.<br />
Conditions necessary for soybean production<br />
<strong>Soybean</strong> growth is <strong>in</strong>fluenced by climate and soil characteristics.<br />
<strong>Soybean</strong> performs well <strong>in</strong> the southern and northern Gu<strong>in</strong>ea savannas<br />
of <strong>Nigeria</strong> where ra<strong>in</strong>fall is more than 700 mm.<br />
However, short-duration varieties can thrive <strong>in</strong> the much drier Sudan<br />
savanna when sown early and with an even distribution of ra<strong>in</strong>fall<br />
throughout the grow<strong>in</strong>g period. The time for plant<strong>in</strong>g soybean depends<br />
upon temperature and day length. <strong>Soybean</strong> is a short-day plant and<br />
flowers <strong>in</strong> response <strong>to</strong> shorten<strong>in</strong>g days. It can be grown on a wide range<br />
of soils with pH rang<strong>in</strong>g from 4.5 <strong>to</strong> 8.5. <strong>Soybean</strong> should not be planted<br />
<strong>in</strong> sandy, gravelly, or shallow soils <strong>to</strong> avoid drought stress. It should not<br />
be grown <strong>in</strong> waterlogged soils or soils with surfaces that can crust, as<br />
this will lead <strong>to</strong> poor seedl<strong>in</strong>g emergence.<br />
Prepar<strong>in</strong>g <strong>to</strong> plant<br />
Land preparation<br />
Clear all vegetation before land preparation. The seedbed may be<br />
prepared manually with a hoe or animal-drawn implement or trac<strong>to</strong>r<br />
(Fig. 1). Well-prepared land ensures good germ<strong>in</strong>ation and reduces<br />
weed <strong>in</strong>festation. You can plant on ridges or on a flat seedbed.<br />
2
Table 1. Recommended soybean varieties for Gu<strong>in</strong>ea savanna<br />
ecological zones <strong>in</strong> <strong>Nigeria</strong>.<br />
Variety Ecology Characteristics Striga control<br />
TGX 1448-2E<br />
Southern and northern<br />
Gu<strong>in</strong>ea savannas<br />
Medium matur<strong>in</strong>g, high yield,<br />
low shatter<strong>in</strong>g, high oil<br />
content, excellent gra<strong>in</strong> color<br />
Good<br />
TGX 1835-10E<br />
Gu<strong>in</strong>ea savanna<br />
Early matur<strong>in</strong>g, rust resistant,<br />
pustule resistant<br />
Not known<br />
TGX 1485-1D<br />
Gu<strong>in</strong>ea savanna<br />
Early matur<strong>in</strong>g, pustule<br />
resistant, rust susceptible<br />
Not known<br />
N.B. Early and extra-early matur<strong>in</strong>g varieties are strongly recommended <strong>in</strong> the Sudan savanna<br />
because of the low amount and duration of ra<strong>in</strong>fall <strong>in</strong> the zone.<br />
Choice of variety<br />
Selected soybean varieties grown <strong>in</strong> <strong>Nigeria</strong> are presented <strong>in</strong> Table 1.<br />
Choose a variety suited <strong>to</strong> your agroecological zone. <strong>Soybean</strong> variety<br />
selection should be based on maturity, yield potential, lodg<strong>in</strong>g, drought<br />
<strong>to</strong>lerance, and resistance <strong>to</strong> pests and diseases. The maturity period<br />
should be the first consideration when choos<strong>in</strong>g a variety suited <strong>to</strong> your<br />
geographical zone. Consider varieties that are earlier matur<strong>in</strong>g rather<br />
than late matur<strong>in</strong>g <strong>in</strong> areas with low ra<strong>in</strong>fall. Although later maturity<br />
<strong>in</strong>creases the yield potential, it is risky <strong>to</strong> grow late-matur<strong>in</strong>g varieties <strong>in</strong><br />
drier environments because of late-season drought.<br />
Seed clean<strong>in</strong>g and preparation<br />
Use high quality seeds of the selected variety (Fig. 2). <strong>Soybean</strong> seeds<br />
easily lose their viability. It is common for soybean, even when s<strong>to</strong>red<br />
properly, not <strong>to</strong> germ<strong>in</strong>ate after 12 –15 months <strong>in</strong> s<strong>to</strong>rage. Therefore,<br />
use seeds that are not more than 12 months old <strong>to</strong> ensure good<br />
germ<strong>in</strong>ation. Sort out the good seeds for plant<strong>in</strong>g <strong>to</strong> ensure that they<br />
are free from <strong>in</strong>sects, disease <strong>in</strong>festation, and weed seeds. Do not<br />
purchase seeds from the open market as the germ<strong>in</strong>ation potential<br />
is not guaranteed. Plant<strong>in</strong>g poor quality seeds will not produce a<br />
good yield (Fig. 3). Always buy seeds from seed companies or seed<br />
producers nearest <strong>to</strong> you.<br />
3
Figure 2. Use good<br />
seeds for plant<strong>in</strong>g.<br />
Figure 3. Do not use poorly<br />
sorted seeds.<br />
<strong>Soybean</strong> germ<strong>in</strong>ation test<br />
Test seeds for germ<strong>in</strong>ation before plant<strong>in</strong>g. The germ<strong>in</strong>ation rate<br />
should be 85% or more <strong>to</strong> obta<strong>in</strong> a good stand. To conduct a quick<br />
seed germ<strong>in</strong>ation test, select 400 seeds randomly and sow 100 seeds<br />
each <strong>in</strong> four wooden or plastic boxes or a prepared seedbed. Sow one<br />
seed/hole at a distance of 10 cm between the seeds. Soak cloth- or<br />
paper-l<strong>in</strong>ed germ<strong>in</strong>ation boxes or the seedbed well with water before<br />
sow<strong>in</strong>g and provide water every morn<strong>in</strong>g and even<strong>in</strong>g. Start count<strong>in</strong>g<br />
the seedl<strong>in</strong>gs 5 days after sow<strong>in</strong>g and complete the count<strong>in</strong>g with<strong>in</strong><br />
10 days. A <strong>to</strong>tal count of 320 germ<strong>in</strong>ated seeds or more <strong>in</strong>dicates a<br />
germ<strong>in</strong>ation rate of 80% and above. When the percentage germ<strong>in</strong>ation<br />
is 80% or less, the seed rate has <strong>to</strong> be <strong>in</strong>creased accord<strong>in</strong>gly <strong>to</strong> achieve<br />
100% germ<strong>in</strong>ation.<br />
Plant<strong>in</strong>g<br />
Date of plant<strong>in</strong>g<br />
<strong>Soybean</strong> produces well over a wide range of plant<strong>in</strong>g dates, if moisture<br />
is available. The recommended dates for plant<strong>in</strong>g soybean <strong>in</strong> different<br />
ecological zones <strong>in</strong> <strong>Nigeria</strong> are presented <strong>in</strong> Table 2. Do not plant <strong>to</strong>o early<br />
4
Table 2. Recommended dates for plant<strong>in</strong>g soybean <strong>in</strong> <strong>Nigeria</strong>.<br />
Ecological zone<br />
Suggested time of plant<strong>in</strong>g<br />
Moist savanna/southern Gu<strong>in</strong>ea savanna Early June–early July<br />
<strong>Northern</strong> Gu<strong>in</strong>ea savanna–Sudan savanna Mid-June–early July<br />
Sudan savanna July, weeks 1–2<br />
because a prolonged dry spell after plant<strong>in</strong>g may result <strong>in</strong> permanent wilt<strong>in</strong>g<br />
of the crop and the need for replant<strong>in</strong>g. Late plant<strong>in</strong>g, on the other hand,<br />
may expose the crop <strong>to</strong> attack by some late season pests and also deprive<br />
the crop of sufficient moisture if the ra<strong>in</strong>s s<strong>to</strong>p early. Plant soybean as soon<br />
as the ra<strong>in</strong>s are well established.<br />
Seed rate<br />
About 50–70 kg (20–28 standard mudus) are required <strong>to</strong> obta<strong>in</strong> a<br />
population of 444,444 plants/ha for soybean varieties. S<strong>in</strong>ce soybean<br />
seed size varies among varieties, it is essential <strong>to</strong> consider plant<strong>in</strong>g <strong>in</strong><br />
terms of seeds/unit area. It is not uncommon <strong>to</strong> see sizes rang<strong>in</strong>g from<br />
12.6 <strong>to</strong> 18.9 g/100 seeds<br />
Seed dress<strong>in</strong>g<br />
Treat seeds with fungicides, such as Captan, Apron Plus, or Thiram, at the<br />
rate of 1 sachet/8 kg of seeds before plant<strong>in</strong>g for protection aga<strong>in</strong>st soilborne<br />
fungal diseases.<br />
Plant spac<strong>in</strong>g and sow<strong>in</strong>g<br />
Sow soybean by hand, planter, or by drill<strong>in</strong>g. Plant 3 <strong>to</strong> 4 seeds/hole at a<br />
spac<strong>in</strong>g of 75 cm between rows and 10 cm between stands. Alternatively,<br />
drill seeds at 50–75 cm between rows and 5 cm with<strong>in</strong> rows. For the early<br />
matur<strong>in</strong>g varieties, a spac<strong>in</strong>g of 50 cm between rows and 5–10 cm with<strong>in</strong><br />
rows is recommended because they respond better <strong>to</strong> narrow spac<strong>in</strong>g<br />
than the late-matur<strong>in</strong>g varieties. Do not sow seeds more than 2–5 cm<br />
deep. Deeper plant<strong>in</strong>g may result <strong>in</strong> loss of vigor or failure of seedl<strong>in</strong>gs <strong>to</strong><br />
emerge.<br />
5
Figure 4. <strong>Soybean</strong> <strong>in</strong> rotation with maize.<br />
Fertilizer<br />
A good fertilizer recommendation for soybean production depends<br />
on a good soil test. Under normal conditions, soybean as a legume<br />
should provide itself with nitrogen through biological nitrogen fixation.<br />
Until nodulation occurs, the soybean plant depends on soil nitrogen for<br />
growth. Phosphorus is often the most deficient nutrient, therefore, apply<br />
optimum phosphorous fertilizer for good yield. Apply phosphorus at the<br />
rate of 30 kg p/ha <strong>in</strong> the form of s<strong>in</strong>gle super phosphate fertilizer (SUPA)<br />
(3 × 50 kg bags) <strong>in</strong> addition <strong>to</strong> 2½ × 50 kg bags of compound fertilizer<br />
NPK 15:15:15. Nitrogen and potassium fertilizers are needed only<br />
when there are obvious deficiencies. Incorporate the fertilizer <strong>in</strong><strong>to</strong> the<br />
soil at land preparation dur<strong>in</strong>g harrow<strong>in</strong>g and level<strong>in</strong>g the field. Use the<br />
recommendations (Table 3) as a guide for fertiliz<strong>in</strong>g your soybean crop.<br />
Soil fertility enhancement<br />
<strong>Soybean</strong> improves soil fertility and fixes nitrogen <strong>in</strong> the soil for the<br />
succeed<strong>in</strong>g maize (Fig. 4). When grown <strong>in</strong> rotation with maize, it serves as<br />
a catch crop <strong>in</strong> controll<strong>in</strong>g Striga hermonthica, a parasitic weed that attacks<br />
maize, by caus<strong>in</strong>g suicidal germ<strong>in</strong>ation of Striga.<br />
6
Table 3. Recommended fertilizer rates for soybean production <strong>in</strong> <strong>Nigeria</strong>.<br />
Recommended fertilizer rates (kg/ha)<br />
20 kg N<br />
40 kg P 2<br />
O 5<br />
20 kg K 2<br />
O<br />
Materials<br />
2½ × 50 kg bags of NPK (15-15-15)<br />
plus 3 × 50 kg bags of SSP (SUPA)<br />
Pests and diseases<br />
Weeds and their control<br />
Perennial and most annual weeds are a problem <strong>in</strong> soybean <strong>in</strong> its early<br />
growth stages. A properly timed weed control program can m<strong>in</strong>imize the<br />
effects of weeds. Weed control <strong>in</strong> soybean could be manual or chemical<br />
or both.<br />
Manual weed control: Carry out the first weed<strong>in</strong>g at 2 weeks after<br />
plant<strong>in</strong>g and the second at 5–6 weeks after plant<strong>in</strong>g. Avoid weed<strong>in</strong>g<br />
immediately after a ra<strong>in</strong>fall as this would lead <strong>to</strong> transplant<strong>in</strong>g the weeds.<br />
Poor hoe weed<strong>in</strong>g or delay <strong>in</strong> weed<strong>in</strong>g could cause significant reductions<br />
<strong>in</strong> soybean yields.<br />
Chemical weed control: Herbicides, if used properly, are safe and<br />
effective <strong>in</strong> controll<strong>in</strong>g weeds <strong>in</strong> soybean. The choice of herbicide,<br />
however, depends on the predom<strong>in</strong>ant weed species and the availability<br />
of the herbicide. Herbicides are available for pre-emergence or postemergence<br />
weed control <strong>in</strong> soybean. If herbicide is applied at plant<strong>in</strong>g,<br />
one weed<strong>in</strong>g may be required at 5–6 weeks after plant<strong>in</strong>g. Use<br />
herbicides as presented <strong>in</strong> Table 4.<br />
Insect pests and their control<br />
Several different <strong>in</strong>sects occur <strong>in</strong> soybean fields but few are normally<br />
of any economic importance, and the species that cause damage<br />
are usually not abundant enough <strong>to</strong> warrant control measures. In<br />
the vegetative stage, the crop is very <strong>to</strong>lerant of caterpillars but very<br />
susceptible <strong>to</strong> silverleaf whitefly attack.<br />
7
Table 4. Recommended herbicide rates for weed control <strong>in</strong> soybean.<br />
Product Product rate/ha (L) Time of application Remarks<br />
Paraquat plus<br />
Pendimethal<strong>in</strong><br />
(50EC)<br />
Applied with<strong>in</strong> 2<br />
days of plant<strong>in</strong>g<br />
3 L of Paraquat<br />
plus 3 L of<br />
Pendimethal<strong>in</strong> (250<br />
mL of each/20-L<br />
sprayer)<br />
Where grasses,<br />
e.g., Rottboellia<br />
are common<br />
Paraquat plus<br />
Dual Gold<br />
Paraquat plus<br />
Butachlor<br />
Fusilade forte<br />
3 L of Paraquat plus<br />
2 L of Dual Gold<br />
(= 250 mL of<br />
Paraquat plus 200<br />
mL of Dual Gold <strong>in</strong><br />
15-L sprayer (= 1½<br />
milk t<strong>in</strong>s of<br />
Paraquat plus 3/4<br />
milk t<strong>in</strong>s of Dual<br />
Gold)<br />
3 L of Paraquat plus<br />
4 L of Butachlor<br />
(= 250 mL of<br />
Paraquat plus 350<br />
mL of Butachlor <strong>in</strong><br />
15-L sprayer) (= 1½<br />
milk t<strong>in</strong>s of<br />
Paraquat plus 2½<br />
milk t<strong>in</strong>s of<br />
Butachlor)<br />
1–1½ L (150 mL<br />
(= 1 milk t<strong>in</strong>)/15-L<br />
sprayer<br />
Applied with<strong>in</strong> 2<br />
days of plant<strong>in</strong>g<br />
Applied with<strong>in</strong> 2<br />
days of plant<strong>in</strong>g<br />
Postemergence<br />
Apply 21–28 days<br />
after sow<strong>in</strong>g<br />
Controls most grasses<br />
and broadleaf weeds.<br />
Where sow<strong>in</strong>g is<br />
done after 1 week<br />
of land preparation,<br />
application must be<br />
with<strong>in</strong> 12 h after<br />
plant<strong>in</strong>g.<br />
Controls most grasses<br />
and broadleaf weeds<br />
and sedges<br />
For grass weed<br />
control<br />
Round-up<br />
or other<br />
Glyphosate<br />
products<br />
4 L (= 350 mL/15-L<br />
sprayer)<br />
Preemergence<br />
(before land<br />
preparation)<br />
Used under no-tillage<br />
system, applied at<br />
least 2 weeks before<br />
sow<strong>in</strong>g also <strong>to</strong> control<br />
perennial weeds<br />
Note: (1) About 12 loads of a 15-L sprayer are required for 1 ha. (2) Where animal power is used for land<br />
preparation, allow ra<strong>in</strong> <strong>to</strong> fall on the prepared land before plant<strong>in</strong>g and spray herbicides with<strong>in</strong> 2 days of<br />
plant<strong>in</strong>g <strong>to</strong> enhance effectiveness. (3) 150 mL of chemical will fill a standard sized conta<strong>in</strong>er of liquid Peak milk.<br />
From flower<strong>in</strong>g onwards, soybean becomes attractive <strong>to</strong> pod-suck<strong>in</strong>g<br />
bugs that can seriously reduce seed quality. Insect pests can be<br />
controlled with a s<strong>in</strong>gle spray of Cypermethr<strong>in</strong> + Dimethoate 10 EC at<br />
the rate of 100 mL <strong>in</strong> 15 L of water.<br />
8
Diseases and their control<br />
<strong>Soybean</strong> diseases normally result <strong>in</strong><br />
major yield losses <strong>in</strong> <strong>Nigeria</strong>. Some<br />
of the common diseases caused<br />
by fungi, bacteria, and viruses are<br />
mentioned below.<br />
Fungal and bacterial diseases<br />
Rust: Asian soybean rust, caused<br />
by Phakopsora pachyrhizi, is one of<br />
the most important foliar diseases<br />
<strong>in</strong> <strong>Nigeria</strong>. The <strong>in</strong>fected leaves<br />
have small tan <strong>to</strong> dark brown or<br />
reddish brown lesions (Fig. 5a)<br />
on which small raised pustules (or<br />
‘bumps’) occur on the lower surface<br />
of the leaves (Fig. 5b). Pustules<br />
produce a large number of spores.<br />
Brown or rust-colored powder falls<br />
when severely <strong>in</strong>fected leaves are<br />
tapped over a white paper or cloth.<br />
Severe <strong>in</strong>fection leads <strong>to</strong> premature<br />
defoliation and yield losses up<br />
<strong>to</strong> 80%. The disease is of great<br />
economic importance <strong>in</strong> the derived<br />
savanna and southern Gu<strong>in</strong>ea<br />
savanna zones where ra<strong>in</strong>fall and<br />
humidity are high.<br />
Figure 5a. Rust-<strong>in</strong>fected<br />
soybean leaves with large number<br />
of small tan lesions.<br />
Figure 5b. Large number of spores<br />
on the lower surface of tan lesions of<br />
soybean rust.<br />
Bacterial pustule: The disease is<br />
caused by Xanthomonas axonopodis<br />
pv. glyc<strong>in</strong>es. Symp<strong>to</strong>ms appear as<br />
specks <strong>to</strong> large, irregular spots with<br />
raised light-colored pustules <strong>in</strong> the<br />
elevated centers of the spots on<br />
9
the lower surface (Fig. 6). The elevated<br />
pustules sometimes have cracks <strong>in</strong><br />
them. Later lesions jo<strong>in</strong> <strong>to</strong>gether and the<br />
dead areas tear away <strong>to</strong> give a ragged<br />
appearance <strong>to</strong> the leaves. Symp<strong>to</strong>ms<br />
of rust and bacterial pustule sometimes<br />
appear similar.<br />
Figure 6. Small spots<br />
and coalesc<strong>in</strong>g lesions<br />
of bacterial pustule<br />
disease.<br />
Figure 7. Phy<strong>to</strong>phthora<br />
seedl<strong>in</strong>g blight caus<strong>in</strong>g<br />
wilt<strong>in</strong>g of older seedl<strong>in</strong>gs.<br />
Phy<strong>to</strong>phthora seedl<strong>in</strong>g blight and<br />
root and stem rot: Phy<strong>to</strong>phthora sojae<br />
causes seedl<strong>in</strong>g blight, and root and<br />
stem rot. Young seedl<strong>in</strong>gs that appear<br />
<strong>to</strong> be established turn off-color <strong>to</strong> yellow,<br />
wilt, and die (Fig. 7). The stems of these<br />
plants may show a brown discoloration<br />
that beg<strong>in</strong>s at the soil l<strong>in</strong>e and extends<br />
up the stem. The brown, dead leaves<br />
rema<strong>in</strong> attached <strong>to</strong> the plant, and the<br />
dead seedl<strong>in</strong>gs are obvious symp<strong>to</strong>ms<br />
of the disease <strong>in</strong> the field.<br />
The root rot phase of the disease is<br />
rapidly becom<strong>in</strong>g a very destructive<br />
disease <strong>in</strong> <strong>Nigeria</strong>. The Phy<strong>to</strong>phthora<br />
fungus can kill plants at all stages of<br />
growth. Infected stands may survive<br />
but are less productive than healthy<br />
stands. Infection generally occurs <strong>in</strong><br />
fields with poor dra<strong>in</strong>age, but it can occur<br />
<strong>in</strong> normally well-dra<strong>in</strong>ed fields that are<br />
waterlogged for 7–14 days after irrigation<br />
or very heavy or prolonged ra<strong>in</strong>fall.<br />
Frogeye leaf spot: The fungus<br />
Cercospora soj<strong>in</strong>a that survives <strong>in</strong><br />
<strong>in</strong>fected soybean residue and seeds<br />
causes this disease. Symp<strong>to</strong>ms appear<br />
10
as brown, circular <strong>to</strong> irregular spots<br />
with narrow reddish brown marg<strong>in</strong>s on<br />
the leaf surfaces (Fig. 8). The central<br />
areas of the spots turn ash gray <strong>to</strong><br />
light brown. Sometimes lesions can<br />
develop on stems and pods from<br />
where mature seeds are <strong>in</strong>fected.<br />
Infected seeds may show discoloration<br />
of the seed coat that ranges from<br />
small specks <strong>to</strong> large blotches of light<br />
<strong>to</strong> dark gray or brown.<br />
To control these diseases:<br />
• Plant resistant varieties. This is the<br />
best option <strong>to</strong> control disease.<br />
• Plant <strong>in</strong> a good seedbed. Avoid<br />
poorly dra<strong>in</strong>ed or compacted soil.<br />
• Plant seeds treated with fungicides<br />
as mentioned earlier under ‘seed<br />
•<br />
dress<strong>in</strong>g’.<br />
Rotate crops with maize <strong>to</strong> prevent<br />
Figure 8. Initial symp<strong>to</strong>ms of<br />
frogeye leaf spot.<br />
the <strong>in</strong>crease <strong>in</strong> <strong>in</strong>oculum levels <strong>in</strong> a<br />
field.<br />
• Use of a foliar fungicide is seldom warranted, except on high-value<br />
fields (e.g., seed production fields) or <strong>in</strong> years when the weather is<br />
especially favorable for disease development.<br />
Virus diseases<br />
<strong>Soybean</strong> is susceptible <strong>to</strong> several viruses transmitted by aphids, beetles<br />
and whiteflies prevail<strong>in</strong>g <strong>in</strong> <strong>Nigeria</strong>. Most of the virus <strong>in</strong>fection results<br />
<strong>in</strong> foliar symp<strong>to</strong>ms such as mosaic and mottl<strong>in</strong>g, thicken<strong>in</strong>g/brittl<strong>in</strong>g of<br />
older leaves, pucker<strong>in</strong>g, leaf dis<strong>to</strong>rtion, severe reduction <strong>in</strong> leaf size,<br />
and stunt<strong>in</strong>g of plants. Mixed <strong>in</strong>fection with more than one virus is<br />
common under field conditions. Features of the three most common<br />
virus diseases on soybean <strong>in</strong> <strong>Nigeria</strong> are presented here.<br />
11
Figure 9. Mosaic diseaseaffected<br />
soybean plants.<br />
Mosaic disease: Cowpea mild mottle<br />
virus (CPMMV; genus Carlavirus,<br />
family Flexiviridae) transmitted by<br />
whitefly (Bemisia tabaci Gennidius) is<br />
the most prevalent virus associated<br />
with soybean mosaic disease <strong>in</strong><br />
<strong>Nigeria</strong>. In addition, Bean pod<br />
mottle virus (genus Comovirus,<br />
family Comoviridae), Alfalfa mosaic<br />
virus (genus Alfamovirus, family<br />
Bormoviridae), Cucumber mosaic<br />
virus (genus Cucumovirus, family<br />
Bormoviridae), and Southern bean<br />
mosaic virus (genus Sobemovirus)<br />
were also detected <strong>in</strong> mosaic diseaseaffected<br />
plants either s<strong>in</strong>gly or <strong>in</strong><br />
mixed <strong>in</strong>fections, particularly with<br />
CPMMV. Depend<strong>in</strong>g on genotype<br />
and age of <strong>in</strong>fection symp<strong>to</strong>ms range<br />
from mosaic and mottl<strong>in</strong>g, leaf curl<strong>in</strong>g,<br />
green ve<strong>in</strong> band<strong>in</strong>g, and stunt<strong>in</strong>g<br />
(Fig. 9). Most severe symp<strong>to</strong>ms are<br />
observed <strong>in</strong> plants <strong>in</strong>fected at early<br />
stages of growth (preflower<strong>in</strong>g) and<br />
significant reduction <strong>in</strong> pods.<br />
Yellow mosaic disease: It is caused<br />
by whitefly (B. tabaci)-transmitted<br />
different viruses belong<strong>in</strong>g <strong>to</strong><br />
the genus Begomovirus, family<br />
Gem<strong>in</strong>iviridae. <strong>Soybean</strong> yellow<br />
mosaic virus was found <strong>to</strong> be the most<br />
prevalent virus associated with this<br />
disease. <strong>Soybean</strong> mottle mosaic virus,<br />
which also causes similar symp<strong>to</strong>ms,<br />
12
Figure 10. Bright yellow mosaic symp<strong>to</strong>ms caused by begomovirus<br />
<strong>in</strong>fection <strong>in</strong> soybean plants.<br />
was found <strong>to</strong> be less frequent <strong>in</strong> the<br />
fields. Virus-<strong>in</strong>fected plants produce<br />
bright yellow mosaic or specks, and<br />
develop <strong>in</strong><strong>to</strong> large blotches on the leaf<br />
lam<strong>in</strong>a (Fig. 10), but this <strong>in</strong>fection does<br />
not result <strong>in</strong> leaf dis<strong>to</strong>rtion or reduction<br />
<strong>in</strong> lam<strong>in</strong>a size. Mixed <strong>in</strong>fection of these<br />
two begomoviruses and CPMMV<br />
are common <strong>in</strong> the fields and such<br />
<strong>in</strong>fection results <strong>in</strong> bright yellow<br />
mosaic symp<strong>to</strong>ms and leaf pucker<strong>in</strong>g.<br />
Dwarf disease: The causal virus<br />
responsible for soybean dwarf<strong>in</strong>g<br />
disease is not known. This disease<br />
occurs <strong>in</strong> low frequency <strong>in</strong> the fields.<br />
Leaves and shoots of the <strong>in</strong>fected<br />
plants are severely stunted with<br />
severe reduction <strong>in</strong> leaf lam<strong>in</strong>a<br />
(Fig. 11). Infected plants do not<br />
produce any pods.<br />
Figure 11. Dwarf disease-affected<br />
soybean.<br />
13
Cultivate virus disease-resistant varieties. This is the most convenient,<br />
economical, and effective approach for controll<strong>in</strong>g soybean virus<br />
diseases. If resistant varieties are not available, the follow<strong>in</strong>g<br />
approaches can contribute <strong>to</strong> the management of virus diseases<br />
<strong>in</strong> the field.<br />
• Many viruses <strong>in</strong>volved <strong>in</strong> mosaic disease are seed transmitted<br />
<strong>in</strong> soybean. Use certified seed <strong>to</strong> avoid seed-borne<br />
<strong>in</strong>fection or use seed that are produced away from the<br />
<strong>in</strong>fection source.<br />
• Do not plant seeds obta<strong>in</strong>ed from mosaic-affected plants.<br />
• Rouge (uproot<strong>in</strong>g and destruction) symp<strong>to</strong>matic plants.<br />
This can reduce the <strong>in</strong>cidence of <strong>in</strong>sect-transmitted viruses.<br />
• Eradicate the weeds and voluntary plants <strong>in</strong> the vic<strong>in</strong>ity of<br />
the soybean farms.<br />
• Treat seeds with systemic <strong>in</strong>secticides and apply one or two<br />
foliar sprays of <strong>in</strong>secticides <strong>to</strong> reduce the <strong>in</strong>sect vec<strong>to</strong>r activity<br />
dur<strong>in</strong>g preflower<strong>in</strong>g stage (most vulnerable <strong>to</strong> virus <strong>in</strong>fections)<br />
of the plant.<br />
Harvest<strong>in</strong>g soybean<br />
<strong>Soybean</strong> matures with<strong>in</strong> 3–4 months after plant<strong>in</strong>g and requires timely<br />
harvest<strong>in</strong>g <strong>to</strong> check excessive yield losses. At maturity, the pod is strawcolored.<br />
It is recommended that soybean be harvested when about 85%<br />
of the pods have turned brown for a non-shatter<strong>in</strong>g variety but 80% for<br />
shatter<strong>in</strong>g varieties. Alternatively, the crop can be harvested when the<br />
seeds are at the hard-dough stage, when the seed moisture content is<br />
between 14 and 16%. Newer varieties are resistant <strong>to</strong> shatter<strong>in</strong>g but<br />
losses <strong>in</strong> yield may occur from other causes if harvest<strong>in</strong>g is delayed.<br />
Harvest<strong>in</strong>g can be done with a cutlass, a hoe, or sickles. Cut the mature<br />
plants at ground level. Stack them loosely on tarpaul<strong>in</strong> and allow them<br />
<strong>to</strong> dry <strong>in</strong> the open for 2 weeks before thresh<strong>in</strong>g. Do not harvest by hand<br />
pull<strong>in</strong>g because this may remove the nutrient that the soybean has<br />
added <strong>to</strong> the soil.<br />
14
Figure 12. Manual thresh<strong>in</strong>g of soybean.<br />
Postharvest operations<br />
Thresh<strong>in</strong>g soybean<br />
Thresh manually or mechanically when the plants are properly dry and<br />
as soon as possible. Manual thresh<strong>in</strong>g is ma<strong>in</strong>ly recommended for<br />
small-scale production. It <strong>in</strong>volves pil<strong>in</strong>g soybean plants on tarpaul<strong>in</strong> or<br />
putt<strong>in</strong>g dry soybean pods <strong>in</strong> sacks and beat<strong>in</strong>g them with a stick.<br />
The material is then w<strong>in</strong>nowed <strong>to</strong> remove the seeds from the<br />
debris (Fig. 12).<br />
Use mechanical threshers <strong>in</strong> large-scale production. Such<br />
threshers are equipped with blowers that separate the gra<strong>in</strong>s from<br />
the chaff (Fig. 13).<br />
15
Figure 13. A multipurpose soybean thresh<strong>in</strong>g mach<strong>in</strong>e.<br />
S<strong>to</strong>rage<br />
<strong>Soybean</strong> should be s<strong>to</strong>red at a moisture content of 10% or less. A<br />
soybean seed is sufficiently dry when it cannot be dented with the teeth<br />
or f<strong>in</strong>gernails. At harvest, the gra<strong>in</strong>s usually conta<strong>in</strong> about 14% moisture.<br />
Dry <strong>to</strong> 13% moisture for s<strong>to</strong>rage of 6–12 months and <strong>to</strong> 10–11% for<br />
longer s<strong>to</strong>rage. Open-air dry<strong>in</strong>g is the most practical way <strong>to</strong> protect<br />
soybean <strong>in</strong> s<strong>to</strong>rage. Place 50-kg or 100-kg bags of clean soybean on<br />
a rack <strong>in</strong> the cold room or <strong>in</strong> shade. High moisture content <strong>in</strong> s<strong>to</strong>red<br />
soybean encourages the development of various agents of deterioration,<br />
such as <strong>in</strong>sects and microorganisms. Good s<strong>to</strong>rage management can<br />
greatly <strong>in</strong>fluence the s<strong>to</strong>rability of soybean and subsequent germ<strong>in</strong>ation<br />
when planted <strong>in</strong> the field. Do not leave soybean exposed <strong>to</strong> high<br />
temperatures, as it will <strong>in</strong>crease deterioration and reduce seed viability.<br />
16