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Vegetable Plant Nutrients: Sources and Deficiencies

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Plant nutrients
Plant nutrients are essential for strong seedling growth.

When vegetables and other plants lack essential nutrients or elements they will not look themselves; they will look unhealthy and they may even die. The symptom of a nutrient deficiency can range from yellowing and poor growth to flower and fruit failure.

Nutrient deficiency symptoms in plants can be confusing. Many plant nutrient deficiencies share the same or very similar symptoms. Whatismore, symptoms of nutrient deficiency can be similar to symptoms of many plant diseases.

A certain way to know if a plant or crop is suffering from a nutrient deficiency is to have a soil test. Ask the tester to recommend the nutrients and amount necessary to rectify the deficiency.

Here are important mineral plant nutrients, their function, symptoms of deficiency, and fertilizers to help correct deficiencies:

Guide to Plant Nutrients and Deficiencies:

Nitrogen (N)

  • Function: Necessary for rapid green, leafy growth; part of chlorophyll necessary for photosynthesis; part of protein.
  • Sign of deficiency: Lower leaves pale green or bluish then turn yellow (chlorosis); leaves drop, the oldest leaves fall first; leaves are small; stems thin; plant lacks vigor; growth is spindly or stunted.
  • Sign of excess: Leaves dark green; plant has excessive leaf growth at the expense of buds and fruits.
  • Source: Manure, bonemeal, blood meal (dried blood), fish meal, fish emulsion (also contain phosphorus and potassium, in small amounts), conttonseed meal (also contains small amount of phosphorus and even smaller amount of potassium), coffee grounds (also contains very small amounts of phosphorus and potassium), soybean meal (also contains small amount of potassium and even smaller amount of phosphorus), composted legumes (peas, beans, peanuts), ammonium sulfate or nitrate.

Phosphorus (P)

  • Function: Essential to photosynthesis; enables strong growth; encourages blooming and root development, cell wall structure development; moisture conservation; necessary for photosynthesis.
  • Sign of deficiency: Lower leaves and stem look reddish or purplish; young leaves look pale; shoots are thin; plants don’t flower or form fruits; premature fruit drop; roots are stunted; cell division is slowed.
  • Sign of excess: Essential elements may be tied up.
  • Sources: Bonemeal, colloidal phosphate, rock phosphate (contains slightly more phosphorus than colloidal phosphate, breaks down more slowly), New Jersey greensand, superphosphate.

Potassium (K)

  • Function: Promotes disease resistance; necessary for root development and cell wall structure development; moisture conservation; promotion of photosynthesis.
  • Sign of deficiency: Lower leaves spotted, mottled or curled; leaf tips and edges turn yellow and bronze, then brown and appear dry and scorched; stems are weak; root system is small; plant vigor reduced; plant susceptible to wilting and wilt diseases; fruit is small; fruit is thin skinned; fruit color is poor; flavor is poor..
  • Sign of excess: Fruit coarse and poorly colored fruit; reduced absorption of magnesium and calcium.
  • Sources: Potash rock, manure, granite dust or meal (also contains trace elements), greensand (also contains trace elements), New Jersey greensand, fish meal, seaweed, kelp meal (also contains small amounts of nitrogen, smaller amounts of phosphorus and trace elements) wood ashes (also contains some phosphorous, raises soil pH), potassium sulfate or nitrate.

Calcium (Ca)

  • Function: Cell division, building plant proteins, flowering, fruiting.
  • Sign of deficiency: Growing tip of plant is damaged or dies back; tips of new leaves yellow and appear scorched; young leaves and buds die back; stems are weak; blossom-end of fruit rots; cavities in tomatoes; black heart; black roots.
  • Sign of excess: Intake of potassium and magnesium is reduced.
  • Sources: Calcitic limestone, dolomitic limestone, gypsum, eggshells, oyster shells, fish meal, wood ashes, slag.

Magnesium (Mg)

  • Function: Plant strength.
  • Sign of deficiency: Lower leaves and older leaves mottled–yellow and white patches between green veins of leaves; brownish or purplish patches may form on leaves; old leaves white or yellow; leaves fall prematurely; growth is stunted; poor flower and fruit quality.
  • Sign of excess: Absorption of calcium and potassium is reduced.
  • Sources: Dolomitic limestone, manure, New Jersey greensand, talc, magnesium sulfate (Epsom salts), green plants.

Sulfur (S)

  • Function: Healthy growth.
  • Sign of deficiency: Deficiency is rare; young leaves are pale green to yellow; growth stunted.
  • Sign of excess: Sulfur burn from too low pH.
  • Sources: Gypsum, composted legumes, composted cabbage leaves; sulfur, superphosphate.

Boron (B)

  • Function: Important to plant growth.
  • Sign of deficiency: Young leaves are pale green at base, develop yellow spots, then become twisted, thickened and curl under; leaves are small; multiple buds; dieback from terminal buds; heart rot (corkiness); internal cork of apples, cracked stem in celery, heart rot and girdle of beets.
  • Sign of excess: Leaves turn yellowish red.
  • Sources: Clover, composted melon plants, borax (add only if prescribed), granite dust.

Copper (Cu)

  • Function: Plant growth, utilization of iron.
  • Sign of deficiency: Young leaves turn pale and may become mottled and wilt; leaves develop brown spots; leaf tips dieback; leaves may not grow; growth slows or stops; multiple buds; gum pockets; lack of leaf development in citrus.
  • Sign of excess: Iron uptake blocked.
  • Sources: Manure, rock powders, copper sulfate (use with care), neutral copper, composted dandelions, grass clippings, sawdust.

Iron (Fe)

  • Function: Plant growth, chlorophyll and carbohydrate production.
  • Sign of deficiency: Young leaves turn yellow or very pale but veins remain green (chlorosis); growth is weakened and stunted.
  • Sign of excess: None known.
  • Sources: Humus, manure, compost, blood meal, New Jersey greensand; chelated iron, iron sulfate (copperas).

Manganese (Mn)

  • Function: Growth and plant maturation.
  • Sign of deficiency: Leaves mottled yellow and white; brown spots may develop on leaves; plant growth stunted or plant slow to mature.
  • Sign of excess: Tissue dieback in the leaves; dieback surrounded by yellow border.
  • Sources: Oak leaves, leaf mold, carrot tops, alfalfa; manganese sulfate (tecmangam).

Molybdenum (Mo)

  • Function: Esstential to many plant functions, converting nitrates into amino acids, conversion of phosphorus into plant forms.
  • Sign of deficiency: Leaves turn yellow and pale between veins; leaves may become bluish green; leaves do not open completely; plant growth is stunted.
  • Sign of excess: Poisonous to livestock.
  • Sources: Sodium molybdate.

Zinc (Zn)

  • Function: Fruit development.
  • Sign of deficiency: Young leaves mottled yellow, plant tips stop growing; plants wilt easily. Occurs in peat and alkaline soils: abnormally long, narrow, mottled, yellowed leaves, poor fruiting, dieback. Small, thin, and yellow leaves; yield low; Deficiency leads to iron deficiency, which it resembles. Also leaves are thickened and malformed, small and narrow. Growth is stunted.
  • Sign of excess: None known.
  • Sources: manure, composted corn, ragweed, vetch; zinc sulfate.

More tips: Plant Nutrients for Vegetable Gardens

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. has more than 10 million visitors each year.

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