Soybean crop disorders A Lecture By Mr Allah Dad Khan

2. Soybean Crop Disorders
A Presentation To IPM Course/FFS Participants
By
Mr. Allah Dad Khan
Provincial Coordinator IPM KPK For MINFAL
Pakistan

3. Symptoms
 Pale green plants, pale
yellow leading to brown
older leaves, veins are not
prominent.
 Lower leaves turn pale
green. One of the causes of
chlorotic leaves is
ineffective N fixation under
cooler and wet soil
conditions. Drainage tiles
instillation in heavy soils
can alleviate N deficiency.
Nitrogen deficiency

4. Phosphorus
 Dark green to bluish green leaves, often with
interveinal, small lesions; Soybean may have
marginal chlorosis.
 Older leaves begin to show deficiency symptoms of
growth stunting, dark green coloration of the leaves
with necrotic spots, and leaf cupping. Additionally, P
deficiency can delay blooming and maturity. Cool
and wet soils decrease P uptake by the root system.
 Symptoms

5. Symptoms
 Green plants with chlorosis along the
leaf margins - leading to brown
interveinal necrosis in soybean; veins
stay green.
 Similar to P deficiency, K deficiency
symptoms occur first on older, lower
leaves, although under severe
deficiency all but the very young,
newly developed leaves may show
symptoms. Leaf margins and
between the veins show signs of
yellow and brown coloration. The
causes of K deficiencies are
insufficient application of K fertilizer
and cool/wet conditions.
Potassium deficiency

6. Symptoms
 Soybean typically requires
large amounts of
potassium. Like
phosphorus deficiency,
potassium deficiency
occurs first on older leaves.
Symptoms are chlorosis at
the leaf margins and
between the veins. In
severe cases, all but the
very youngest leaves may
show symptoms.

Potassium deficiency

7. Soil pH
 The pH of a soil is a measure of the acidity or
concentration of hydrogen ions in the soil solution.
Many chemical and biological processes in the soil
are affected by pH, and maintaining pH in the
proper range will maximize the efficiency of other
crop inputs and decrease the risk of yield losses.
Soybeans thrive in the pH range of 6.0 to 6.8 (in
mineral soils). Figure 1 shows the availability of
essential nutrients as a function of soil pH
 Symptoms

8. Symptoms
 Pale green to yellow
leaflets without
prominent veins or
necrosis.
Sulphur deficiency

9. Symptoms
 Pale green plants with
interveinal pale yellow
mottling of the leaves
followed by interveinal
necrosis - or necrosis
along the underside of
the main veins in
drybean.
Magnesium deficiency

10. Symptoms
 Pale green plants;
interveinal mottling (or
interveinal chlorosis in
drybean) of older
leaves leading to
bronze necrosis; green
veins.
Zinc deficiency

11. Symptoms
 Symptoms are
prominent interveinal
chlorosis or necrosis;
veins are prominent
over length of leaf.
Iron Deficiency

12. Symptoms
 Chlorosis between the veins of
young, upper leaves is the
typical Fe deficiency
symptom. Calcareous soils
with high Ca levels and high
pH cause Fe to tightly bound
to the soil particle and
become unavailable for the
plant. Deficiency can be
managed by installing
drainage tiles in heavier soils
and planting high tolerant
varieties.
Iron Deficiency

13. Symptoms
 Pale yellow leaves with
mottled interveinal
chlorosis leading to
dark brown necrosis.
Manganese deficiency

14. Symptoms
 Stunted plants with
interveinal chlorosis. Can be a
problem in soils with high pH
(>7), or on soils that are
sandy or with a high organic
matter content. Manganese
activates enzymes which are
important in photosynthesis,
as well as nitrogen
metabolism and synthesis.
Symptoms are hard to
distinguish from iron
chlorosis.
Manganese deficiency

15. Symptoms
 Plants turn a light
green color due to lack
of nitrogen fixation.
This deficiency is not
common, but can occur
on acidic, highly
weathered soils.
Molybdenum deficiency