www.3rlighting.com/tutorial

Nitrogen: Lack of Nitrogen stunts growth, the leaves turn yellow and die. The older leaves seem to be affected first (usually the lower leaves). Needed for leafing and building proteins. Too much Nitrogen will bum the leaves, browning the tips.

Phosphorus: Lack of Phosphorus stunts growth, the leaves and stems turn purple on a subtle subtone sometimes as purple or brown spots--thin stems small leaves. Usually shows up as deep green on older leaves first, needed for fruiting as well as energy storage and transfer. Too much Phosphorus in solution can combine with Calcium and form into small rocks--unavailable to plants.

Potassium: Lack of Potassium turns plants spindly with weak stalks and small leaves, which curl downward. The older leaves often yellow at the tips first, then between leaf veins, then whole leaf browns and falls off. Sometimes a cause of fruit or flower drop. Needed for stomates on leaves, rooting, budding, and growing tips.

Calcium: The growing tip and young leaves turn brown or are malformed from lack of Calcium. Root growth is stunted; root tips grow black spots. Blossom end rot in the fruit is a calcium deficiency--but can also result from humidity problems or too high a ratio of Nitrogen, Potassium, or Magnesium. Growth slows or stops, used to build cell walls.

Magnesium: This is necessary for the chloroplasts to do their job. Green color drains from the center of the leaves, turning to yellow, then to black accompanied by upward curling of leaves along edges. Often shows up in the lower leaves first, sometimes turns growing tip lime green. Sometimes a sign of pH kept too low. Often the leaf veins stay green longer than the rest of the leaf. A moveable mineral.

Sulfur: Looks similar to Nitrogen deficiency, but tends to hit young leaves first Older leaves may be thicker than new leaves. Unusual in hydroponics.


Trace Elements

Iron: Iron deficiency shows up in the growing tip first, the veins stay green while the new leaves yellow and even turn to beige. Fruit and flowers will drop.

Manganese: Shows up on new growth, leaves turn yellow while the veins stay green, creating a lacing pattern. Growth is stunted, leaves turn black. Leaves curl up, brown, and drop off. Very little Manganese is needed. A moveable mineral.

Boron: Growing point dies, side shoots begin to grow then die. Leaves grow thick, curl in, and turn yellow to brown.

Zinc: Older leaves turn yellow between the veins; they grow closely together with little spacing. Upward curl to leaves which grows worse under stronger light

Copper: Young leaves curl up, may take on a bluish hue.

Molybdenum: Leaves turn pale green then yellow. Without molybdenum, plants cannot use Nitrogen.

Chlorine: Roots are stunted. Leaves wilt then slowly die. Unusual in U.S. hydroponics.