Nutrients

N Nitrogen
P Phosphorus
K Potassium
Mg Magnesium
Ca Calcium
S Sulfur
B Boron
Cu Copper
Fe Iron
Mn Manganese
Mo Molybdenum
Zn Zinc

Lettuce - Growth retardation

Symptoms
Growth of the plants is stunted with delayed heading or no heading at all. The leaves are darker green than normal, but no clear symptoms can be found. If the variety contains anthocyanine, the leaves may have a purple flush.

Reasons
Phosphorus Deficiency Symptomes may be confused with excessive nitrogen supply. Excess nitrogen leads also to dark green lettuce plants, but in this case the leaves are more rounded and the underside of the leaves does not turn purple. Low temperatures may inhibit the uptake of P.

Lettuce - Growth retardation

Symptoms
Due to strongly restricted growth and delayed heading, or no heading at all (rosetting), phosphorus deficiency causes high yield losses. The leaves become dark green and can look fallow. Sometimes reddish discoloration appears. Older leaves show paper-like necrotic areas and finally die off. With phosphorus deficiency plants develop less secondary roots than normal. Often roots show reddish discoloration .

Reasons
Phosphorus deficiency on leaves and roots Symptoms may be confused with excessive nitrogen supply. Excess nitrogen leads also to dark green lettuce plants, but in this case the leaves are more rounded and the underside of the leaves does not turn purple. Low temperatures may inhibit the uptake of P.

Lettuce - Growth retardation

Symptoms
Due to strongly restricted growth, and delayed heading, or no heading at all (rosetting), phosphorus deficiency causes high yield losses. The leaves become dark green and can look crinkled. Sometimes reddish discoloration appears. Older leaves show paper-like necrotic areas and finally die off.

Reasons
Phosphorus deficiency (right) compared to optimum supply Symptoms may be confused with excessive nitrogen supply. Excess nitrogen leads also to dark green lettuce plants, but in this case the leaves are more rounded and the underside of the leaves does not turn purple. Low temperatures may inhibit the uptake of P.

Phosphorus deficiency made worse by

  • Acidic or very alkaline (calcareaus) soils
  • Low organic matter
  • Cold or wet conditions
  • Crops with a poorly developed root system
  • Soils with low P reserves
  • Soils with a high phosphate capacity
  • Iron rich soils

Phosphorus is important for

  • Proper growth and head formation
  • Healthy green leaves