Soybean Crop Disorders A Presentation To IPM Course/FFS

Participants By

Mr. Allah Dad Khan Provincial Coordinator IPM KPK For

MINFAL Pakistan

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

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

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

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

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

Symptoms

Pale green to yellow leaflets without prominent veins or necrosis.

Sulphur deficiency

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

Symptoms

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

Zinc deficiency

Symptoms

Symptoms are prominent interveinal chlorosis or necrosis; veins are prominent over length of leaf.

Iron Deficiency

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

Symptoms

Pale yellow leaves with mottled interveinal chlorosis leading to dark brown necrosis.

Manganese deficiency

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

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