Manganese deficiency
A trace-element shortage that causes yellow patches between green veins on young leaves, often on high-pH, peaty or heavily limed soils.
Also known as: Speckled yellows, Marsh spot
Symptoms and identification
Young leaves develop pale yellow areas between the veins, leaving a fine network of green veins. Brown spots may appear in the yellow areas, and beetroot and spinach show speckled yellow leaves. Peas can get dark hollow spots inside the seed, called marsh spot.
Causes
Manganese is locked up in alkaline soil, over-limed soil and soil rich in organic matter, and it is also low in very sandy, leached soils. Wet, cold soil and compacted ground make symptoms worse.
Organic treatment
Apply compost and mulches, and use a seaweed foliar feed. Lowering pH slowly using sulphur gradually releases the manganese already in the soil.
Prevention
Test soil pH and avoid liming above the level the crop needs. Use acidifying fertilisers or sulphur where soil is too alkaline, and improve drainage and soil structure.
Chemical treatment (use with care)
Spray with manganese sulphate or a chelated manganese product at the label rate. Overdoing it can cause damage, so follow the directions exactly.