Plant nutrition, Botany Course, Master Gardener Training, Extension Service, Oregon State University

Table 3. Plant macronutrients.

Element Absorbed as Leaches from soil/ Mobility in plant Signs of excess Signs of deficiency Notes

Nitrogen (N) NO₃-,
(nitrate),
NH₄+
(ammonium) Leachable, especially NO₃-. Mobile in plants. Succulent growth; dark green color; weak, spindly growth; few fruits. May cause brittle growth, especially under high temperatures. Reduced growth, yellowing (chlorosis). Reds and purples may intensify in some plants. Reduced lateral bud breaks. Symptoms appear first on older growth. In general, the best NH₄+:NO₃- ratio is 1:1. Under low sugar conditions (low light), high NH₄+ can cause leaf curl. Uptake is inhibited by high P levels. The N:K ratio is extremely important. Indoors, the best N:K ratio is 1:1 unless light is extremely high. In soils with a high C:N ratio, more N should be supplied.

Phosphorus (P) H₂PO₄-, HPO₄-
(phosphate) Normally not leachable, but may leach from soil high in bark or peat. Not readily mobile in plants. Shows up as micronutrient deficiency of Zn, Fe, or Co. Reduced growth. Color may intensify; browning or purpling of foliage in some plants. Thin stems, reduced lateral bud breaks, loss of lower leaves, reduced flowering. Rapidly bound (fixed) on soil (P) particles. Under acid conditions, fixed with Fe, Mg, and Al. Under alkaline conditions, fixed with Ca. Important for young plant and seedling growth. High P interferes with micronutrient absorption and N absorption. Used in relatively small amounts when compared to N and K.

Potassium (K) K+ Can leach in sandy soils. Mobile in plants. Causes N deficiency in plant and may affect the uptake of other positive ions. Reduced growth, shortened inter-nodes. Marginal burn or scorch (brown leaf edges), necrotic (dead) spots in leaves. Reduction of lateral bud breaks, tendency to wilt readily. N:K balance is important. High N:low K favors vegetative growth; low N:high K promotes reproductive growth (flowers, fruit).

Magnesium (Mg) Mg++ Leachable. Mobile in plants. Interferes with Ca uptake. Reduction in growth. Marginal chlorosis, interveinal chlorosis (yellow between the veins) in some species (may occur on middle or lower leaves). Reduction in seed production, cupped leaves. Mg commonly is deficient in foliage plants because it is leached and not replaced. Epsom salts at a rate of 1 teaspoon per gallon may be used two times per year. Mg also can be absorbed by leaves if sprayed in a weak solution. Dolomitic limestone can be applied in outdoor situations to correct a deficiency.

Calcium (Ca) Ca++ Normally not leachable. Moderately limited mobility in plants. Interferes with Mg absorption. High Ca usually causes high pH, which then precipitates many micronutrients so that they become unavailable to plants. Inhibition of bud growth, death of root tips. Cupping of maturing leaves, weak growth. Blossom-end rot of many fruits, pits on root vegetables. Ca is important to pH control and rarely is deficient if the correct pH is maintained. Water stress (too much or too little) can affect Ca relations within plants, causing deficiency in the location where Ca was needed at the time of stress.

Sulfur (S) SO₄- (sulfate) Leachable, not mobile in plants. Sulfur excess usually is in the form of air pollution. General yellowing of affected leaves or the entire plant. S often is a carrier or impurity in fertilizers and rarely is deficient. It also may be absorbed fro the air and is a by-product of combustion.

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Other Tables

Element	Absorbed as	Leaches from soil/ Mobility in plant	Signs of excess	Signs of deficiency	Notes
Nitrogen (N)	NO₃-, (nitrate), NH₄+ (ammonium)	Leachable, especially NO₃-. Mobile in plants.	Succulent growth; dark green color; weak, spindly growth; few fruits. May cause brittle growth, especially under high temperatures.	Reduced growth, yellowing (chlorosis). Reds and purples may intensify in some plants. Reduced lateral bud breaks. Symptoms appear first on older growth.	In general, the best NH₄+:NO₃- ratio is 1:1. Under low sugar conditions (low light), high NH₄+ can cause leaf curl. Uptake is inhibited by high P levels. The N:K ratio is extremely important. Indoors, the best N:K ratio is 1:1 unless light is extremely high. In soils with a high C:N ratio, more N should be supplied.
Phosphorus (P)	H₂PO₄-, HPO₄- (phosphate)	Normally not leachable, but may leach from soil high in bark or peat. Not readily mobile in plants.	Shows up as micronutrient deficiency of Zn, Fe, or Co.	Reduced growth. Color may intensify; browning or purpling of foliage in some plants. Thin stems, reduced lateral bud breaks, loss of lower leaves, reduced flowering.	Rapidly bound (fixed) on soil (P) particles. Under acid conditions, fixed with Fe, Mg, and Al. Under alkaline conditions, fixed with Ca. Important for young plant and seedling growth. High P interferes with micronutrient absorption and N absorption. Used in relatively small amounts when compared to N and K.
Potassium (K)	K+	Can leach in sandy soils. Mobile in plants.	Causes N deficiency in plant and may affect the uptake of other positive ions.	Reduced growth, shortened inter-nodes. Marginal burn or scorch (brown leaf edges), necrotic (dead) spots in leaves. Reduction of lateral bud breaks, tendency to wilt readily.	N:K balance is important. High N:low K favors vegetative growth; low N:high K promotes reproductive growth (flowers, fruit).
Magnesium (Mg)	Mg++	Leachable. Mobile in plants.	Interferes with Ca uptake.	Reduction in growth. Marginal chlorosis, interveinal chlorosis (yellow between the veins) in some species (may occur on middle or lower leaves). Reduction in seed production, cupped leaves.	Mg commonly is deficient in foliage plants because it is leached and not replaced. Epsom salts at a rate of 1 teaspoon per gallon may be used two times per year. Mg also can be absorbed by leaves if sprayed in a weak solution. Dolomitic limestone can be applied in outdoor situations to correct a deficiency.
Calcium (Ca)	Ca++	Normally not leachable. Moderately limited mobility in plants. Interferes with Mg absorption.	High Ca usually causes high pH, which then precipitates many micronutrients so that they become unavailable to plants.	Inhibition of bud growth, death of root tips. Cupping of maturing leaves, weak growth. Blossom-end rot of many fruits, pits on root vegetables.	Ca is important to pH control and rarely is deficient if the correct pH is maintained. Water stress (too much or too little) can affect Ca relations within plants, causing deficiency in the location where Ca was needed at the time of stress.
Sulfur (S)	SO₄- (sulfate)	Leachable, not mobile in plants.	Sulfur excess usually is in the form of air pollution.	General yellowing of affected leaves or the entire plant.	S often is a carrier or impurity in fertilizers and rarely is deficient. It also may be absorbed fro the air and is a by-product of combustion.