Deficiency: Entire plant is light green in color; lower leaves are yellow; growth is stunted.
Toxicity: Leaves are often dark green.  In early states, plants are abundant with foliage.  If excess is severe, leaves will dry and begin to fall off.  Root system will remain under developed or deteriorate with time.  Fruit and flower set will be inhibited or deformed.

Nitrogen

Deficiency: Entire plant is bluish-green, often developing a red or purplish cast; lower leaves may be yellow, drying to a greenish-brown to black color; growth may be stunted.
Toxicity: This condition is rare and usually buffered by pH limitations.  Excess phosphorus can interfere with the availability of copper and zinc.

Phosphorous

Deficiency: Leaves have a papery appearance; dead areas along the edges of the leaves; growth is stunted.
Toxicity: Usually not absorbed excessively by plants.  Excess potassium can aggravate the uptake of magnesium, manganese, zinc and iron.

Potassium

Deficiency: Lower leaves turn yellow along the tips and margin and between the veins; the lower leaves wilt
Toxicity: Rare; not generally exhibited visibly.

Magnesium

Deficiency: Young stems and new leaves die
Toxicity: Difficult to distinguish visually.  May precipitate with sulfur in solution and cause clouding or residue in tank

Calcium

Deficiency: Leaf tissue between the veins is lighter in color; yellowed; papery in appearance
Toxicity: Zinc in excess is extremely toxic and will cause rapid death.  Excess zinc interferes with iron causing chlorosis from iron deficiency.

Zinc

Deficiency: Leaf tissue appears yellow, while the veins remain green.
Toxicity: Excess accumulation is rare but could cause bronzing or tiny brown spots on leaf surface.

Iron

Deficiency: Leaf edges appear dark green or blue; leaf edges curl upward; young leaves permanently wilt
Toxicity: Reduced growth followed by symptoms of iron chlorosis, stunting, reduced branching, abnormal darkening and thickening of roots.  This element is essential but extremely toxic in excess.

Copper

Deficiency: Young leaves turn pale green, while the older leaves remain green; plant is stunted and spindly
Toxicity: Leaf size will be reduced and overall growth will be stunted.  Leaves yellowing or scorched at edges.

Sulfur

Deficiency: Growth is stunted; lower leaves have a checkered pattern of yellow and green
Toxicity: Chlorosis, or blotchy leaf tissue due to insufficient chlorophyll synthesis.  Growth rate will slow and vigor will decline.

Manganese

Deficiency: Leaves are stunted, pale green, and malformed
Toxicity: Excess may cause discoloration of leaves depending on plant species.  This condition is rare but could occur from accumulation by continuous application.  Used by the plant in very small quantities.

Molybdenum

Deficiency: Young leaves are scorched at tips and margins
Toxicity: Yellowing of leaf tip followed by necrosis of the leaves beginning at tips or margins and progressing inward.  Some plants are especially sensitive to boron accumulation.

Boron