Nutrient

Function

Deficiency symptoms

Sources

Nitrogen
(N)

Required for all phases of growth and development

Lower leaves light green or yellowish; stalk short & slender, plant is stunted.

Blood meal, composted poultry manure, feather meal, worm castings.

Phosphorus
(P)

Strengthens stems, helps in resistance to pests and diseases, fruiting and flowering

Lower leaves and stem are reddish; upper leaves are dull, pale or dark green, plants stunted; failure to flower or produce fruit, premature dropping of fruit.

Bone meal & rock phosphate (slow release), colloidal (soft) rock phosphate, fish meal, fish hydrolysate - Other sources

Potassium
(K)

Required for formation of all sugars, starches and proteins; contributes to cold-hardiness; root development.

Lower leaves spotted with dead tissue (usually at tips and between veins), mottled or curled; underdeveloped roots, stem tissue may appear weak

Composted manure, wood chips, greensand, seaweed (kelp), wood ashes (use with caution). Beware of excess K

Calcium
(Ca)

Required for cell growth and division, helps plants use nitrogen

Tip burn on lettuce, blossom-end rot in pepper and tomatoes, development of thick woody stems. Young leaves of terminal bud hooded. Die back at tips and margins of leaf

Bone meal, gypsum, lime, ground oyster shells. Soluble Ca may be helpful during growth. More

Sulfur (S)

Constituent of protein and certain vitamin complexes.

New leaves are yellowish. Veins and tissue between veins are light green.

Composted manure, gypsum, Sul-Po-Mag.

Magnesium (Mg)

Constituent of chlorophyll; required for enzyme action.

Whitish patches appear first on older leaves, between leaf veins due to insufficient chlorophyll (chlorosis). Leaf tips & margins turned or cupped upward

Dolomitic limestone, Sul-Po-Mag, Epsom salts

Boron   Young leave of terminal bud are light green at the base, the bud eventually dies. Hollow stems Boric acid
Iron (Fe) Often caused by alkaline soil Leaf veins green, rest of leave yellow (chlorotic), stalks short & slender, yellow leaves on upper parts of plants, poor growth of new shoots Acidify soil if too alkaline, Greensand, manure
Copper (Cu)   Slow growth, died-back of shoot tips, spotty or marked chlorosis, susceptible to fungal diseases Grass clippings, sawdust, wood shavings
Manganese (Mg)   Slow growth, sporodic maturing of plants, yellowing of areas between leaf veins, spots of dead tissue scattered over leaf Add organic matter to correct pH
Selenium (Se)   deficiency rare Manure
Zinc (Zn)   Leaves abnormally long and narrow, turning yellow or spotting; thick leaves; stalks with shortened internodes Manure, rock phosphate

Adapted from Organic Gardening Magazine archives that were at http://www.organicgardening.com/

Deficiencies in tomatoes http://www.ext.colostate.edu/PUBS/Garden/02949.html (mostly about diseases and controls),  
      tomato cracks , catfacing

Deficiencies in tomatoes   X   Y   Z

http://www.ehow.com/info_8203173_symptoms-nutrient-deficiency-bell-peppers.html

Guide to Nutrient Deficiencies in Your Vegetable Garden - Gardens Alive article

Blossom end rot discussion http://forums.gardenweb.com/forums/load/pepper/msg061225038414.html 

Several charts, etc. http://bigpictureagriculture.blogspot.ca/2015/12/plant-nutrient-deficiency-leaf.html 

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