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Soybean - Necrosis
Symptoms
Beginning on older leaves, numerous small brown spots give the plant a mottled appearance.
Furthermore, the blotches expand and coalesce to irregularly shapened, light brown necrosis.
Reasons
Potassium deficiency
Large amounts of K are necessary for adequate nutrition of soybeans.
Potassium deficiency made worse by
- Acidic soils (low pH)
- Sandy or light soils (leaching)
- Drought conditions
- High rainfall (leaching)
- or heavy irrigation
- Heavy clay (illite) soils
- Soils with low K reserves
- Magnesium rich soils
Potassium is important for
- Increased activation of enzymes and co-enzyme functions
- Improved protein synthesis
- Better stomatal function, turgor potential