Potassium deficiency - Lettuce

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Nutrients

Lettuce - Chlorosis

Symptoms
Tips and margins of older leaves get chlorotic spots with increasing size which become necrotic later on. On account of scorched leaf margins leaves are deformed. With more severe deficiency the leaf color turns to mottled dark green and the plant appears wilted. Occasionally leaves are less crinkled than normal and shape of the leaves becomes more rounded. Growth of the plants is restricted, they do not form heads or the heads remain loose.

Reasons
Potassium deficiency Symptomes may be confused with high salt concentration of the growing substrate. In this case the veins of the leaves become brown in addition to dry leaf margins.

Lettuce - Discolouration

Symptoms
Potassium deficiency causes longer main roots than normal and only few secondary roots. They show yellowish color. Often roots are slimy .

Reasons
Potassium deficiency on roots

Lettuce - Chlorosis

Symptoms
Tips and margins of older leaves get chlorotic spots with increasing size which become necrotic later on. On account of scorched leaf margins leaves are deformed. With more severe deficiency the leaf color turns to mottled dark green and the plant appears wilted. Maybe leaves are less crinkled than normal and shape of the leaves becomes more rounded. Growth of the plants is restricted, they do not form heads or the heads remain loose. Potassium deficiency causes longer main roots than normal and only few secondary roots. Often roots are slimy and yellowish in color.

Reasons
Potassium deficiency on head and roots

Lettuce - Necrosis

Symptoms
Symptoms of potassium deficiency start on older leaves. The leaf color turns to mottled dark green and the plant appears wilted. Tips and margins get chlorotic spots with increasing size which become necrotic later on. On account of scorched leaf margins leaves are deformed. On the photo necrotic areas appear along the main veins. More typical are scorched zones on the margins. Occasionally leaves are less crinkled than normal and shape of the leaves becomes more rounded.

Reasons
Potassium deficiency on leaves

Lettuce - Deformation

Symptoms
Tips and margins of older leaves get chlorotic spots with increasing size which become necrotic later on. On account of scorched leaf margins leaves are deformed. With more severe deficiency the leaf color turns to mottled dark green and the plant appears wilted. Maybe leaves are less crinkled than normal and shape of the leaves becomes more rounded. Growth of the plants is restricted, they do not form heads or the heads remain loose.

Reasons
Potassium deficiency (right) compared to optimum supply(left) Symptoms may be confused with high salt concentration of the growing substrate. In this case the veins of the leaves become brown in addition to dry leaf margins.

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

Internal water regulation
Vigorous growth and healthy foliage
Required in large amounts

Yara recommended fertilizers for Potassium

YaraVita FOLIAR POTASH

Lettuce (field grown): 5 l/ha 14 to 20 days after the 4 to 6 leaf stage. Repeat if necessary at 10 day intervals. Note: Final application to be made at least one month before harvest. Water rate: 500 l/ha.

Other recommended products

YaraMila COMPLEX

Lettuce (field grown): 416 kg/ha applied as a base dressing

YaraVita MAGPHOS K

Lettuce (Field Grown)): 5 l/ha. Apply 10 to 14 days after transplanting or emergence. One or two repeat applications may be made at 10 to 14 day intervals. Water rate: 500 l/ha

YaraTera KRISTA K PLUS

Lettuce (fertigated): Crop specific recipes for 2 tank (A & B tank) systems can be produced for protected crops using the Yara Fertigation Plan, for more details contact your local Yara area manager.

YaraTera KRISTA MKP

Lettuce (fertigated): Crop specific recipes for 2 tank (A & B tank) systems can be produced for protected crops using the Yara Fertigation Plan, for more details contact your local Yara area manager.

YaraTera KRISTA SOP

Lettuce (fertigated): Crop specific recipes for 2 tank (A & B tank) systems can be produced for protected crops using the Yara Fertigation Plan, for more details contact your local Yara area manager.