Plant Nutrient Reference
What each nutrient does in the plant, how it moves, and where a shortage shows first — with the arithmetic for turning a label percentage into an actual quantity.
What the three numbers mean
Nitrogen
Leafy growth and green colour
Nitrogen is part of chlorophyll — the green pigment in leaves — and an essential constituent of all proteins. FAO records it as responsible for the dark green colour of stem and leaves, vigorous growth, branching and tillering, leaf production, size enlargement and yield formation. It is the most abundant mineral nutrient in plants.
Phosphorus
Roots, energy and fruit formation
Phosphorus is essential for growth, cell division, root lengthening, seed and fruit development, and early ripening. It is part of several compounds including oils and amino acids, and its compounds ADP and ATP act as the energy carriers within the plant. It is far less abundant than nitrogen or potassium — about one-fifth to one-tenth the concentration of nitrogen.
Potassium
Water, quality and resilience
Potassium is the second most abundant mineral nutrient in plants after nitrogen. It is involved in the working of more than 60 enzymes, in photosynthesis and in moving its products to storage organs — seeds, tubers, roots and fruits — in water economy, and in providing resistance against a number of pests, diseases and stresses such as frost and drought. It regulates stomatal opening and therefore the plant's internal water relations.
Macro and micro — the difference in scale
- N · K about 80% of the plant's mineral nutrients
- P · S · Ca · Mg 19% together
- All micronutrients under 1% combined — the thin sliver at the end
To put the gap in scale: the ratio of nitrogen to molybdenum in plants is about 10,000 : 1, and plants need roughly forty times more magnesium than iron.
Where a deficiency shows — and why there
Direction mobile nutrients travel under shortage
-
Growing points
- B Boron
- Ca Calcium
- Cu Copper
The nutrient cannot move at all — new growth is hit first and cannot be rescued from the old leaves.
-
Younger leaves
- Cl Chlorine
- Fe Iron
- Mn Manganese
- S Sulphur
- Zn Zinc
The nutrient is barely mobile in the phloem, so the plant cannot draw it out of an old leaf to feed a new one.
-
Middle and older leaves
- Mo Molybdenum
Moderate mobility — the symptom appears in the middle of the plant rather than at either end.
-
Older leaves
- Mg Magnesium
- N Nitrogen
- P Phosphorus
- K Potassium
The nutrient is mobile, so the plant moves it out of the old leaves into the new ones — the old yellow first while the top stays green.
From percentage to quantity
How much nutrient is actually in what you are holding?
The percentage on the bag is by weight: 20% N means 20 kg of nitrogen in every 100 kg of product. Enter a weight and the declared percentages to see the actual quantity.
| Nutrient | As declared on the label | Expressed as the element |
|---|---|---|
| Nitrogen N | 200 g | same value |
| Phosphorus P | 200 g P₂O₅ | 87.2 g P × 0.436 |
| Potassium K | 200 g K₂O | 166 g K × 0.83 |
Notice the result: a bag marked 20-20-20 does not supply equal amounts of the three elements. The label declares phosphorus and potassium as oxides rather than as elements — which is why the two columns disagree.
This is arithmetic only. It tells you what is in the bag, not what you should apply. Deciding an appropriate quantity needs a soil and water analysis, a specific plant and growth stage, and the product's own label as its authority. We found no Kuwait institutional source stating fertiliser rates, and we do not invent one.
Basis of the calculation and the conversion factors: FAO Fertilizer and Plant Nutrition Bulletin 16 (2006), Chapter 5 and the units-and-conversion-factors table.
The nutrient reference
Macronutrients
3NitrogenDeficiency shows on: Older leaves
What it does in the plant
Nitrogen is part of chlorophyll — the green pigment in leaves — and an essential constituent of all proteins. FAO records it as responsible for the dark green colour of stem and leaves, vigorous growth, branching and tillering, leaf production, size enlargement and yield formation. It is the most abundant mineral nutrient in plants.
How it moves inside the plant Mobile
Mobile in the phloem. Under deficiency the plant re-translocates nitrogen from older leaves to younger ones — which is precisely why the lowest leaves yellow first while the top of the plant still looks green.
Deficiency symptoms
A marked reduction in growth rate; plants look short and spindly, tillering is poor and leaf area is small. Because nitrogen is a constituent of chlorophyll, deficiency appears as a general yellowing. FAO: the yellowness usually appears first on the lower leaves while upper leaves remain green, as they receive nitrogen relayed from the older ones. In severe deficiency leaves turn brown and die.
Excess and toxicity
The effects of excess are less evident than those of deficiency: a prolonged vegetative period and delayed maturity. High ammonium in solution can be toxic to growth, particularly where the solution is alkaline, because ammonia diffuses through plant membranes and interferes with plant metabolism.
On dry, alkaline, calcareous soil
FAO's account of soils of the subtropical arid regions lists low to very low organic matter and a low content of available and mobilizable nitrogen, and states that nitrogen fertilization is almost always necessary. It also warns that losses of nitrogen as gaseous ammonia occur in the neutral to alkaline range where nitrogen fertilizers — particularly urea — are applied to the soil surface and left unincorporated. Practical consequence: scattering urea on a dry alkaline surface loses part of it to the air. This is general arid-region guidance, not a Kuwait measurement.
- Absorbed as
- NH₄⁺ / NO₃⁻
- Typical concentration in dry matter
- 1.5% (2–4%)
Source: FAO — Fertilizer and Plant Nutrition Bulletin 16, Plant nutrition for food security: A guide for integrated nutrient management. R.N. Roy, A. Finck, G.J. Blair, H.L.S. Tandon. FAO, Rome, 2006. ISBN 92-5-105490-8. Chapter 3 (nutrient functions, mobility, deficiency) and Chapter 4 (soils of the subtropical arid regions). https://www.fao.org/4/a0443e/a0443e.pdf — accessed 26 August 2026.
Last reviewed: 26 August 2026
PhosphorusDeficiency shows on: Older leaves
What it does in the plant
Phosphorus is essential for growth, cell division, root lengthening, seed and fruit development, and early ripening. It is part of several compounds including oils and amino acids, and its compounds ADP and ATP act as the energy carriers within the plant. It is far less abundant than nitrogen or potassium — about one-fifth to one-tenth the concentration of nitrogen.
How it moves inside the plant Mobile
Readily mobile within the plant, in both xylem and phloem — unlike its mobility in the soil. Under shortage, phosphorus is translocated out of old leaves into young tissue: shoot tips, root tips, expanding leaves and later the developing seed.
Deficiency symptoms
Growth is markedly restricted: growth, tillering and root development are retarded and ripening is delayed. Symptoms usually start on older leaves, where a bluish-green to reddish colour develops that can lead to bronze tints and red colour. A decreased shoot-to-root ratio is characteristic, as is lower overall growth of the tops.
Excess and toxicity
Extremely high levels can produce toxicity symptoms, generally manifesting as a watery edge on the leaf tissue which subsequently becomes necrotic. In very severe cases phosphorus toxicity can result in the death of the plant.
On dry, alkaline, calcareous soil
FAO lists phosphate deficiency in sandy soils among the nutrient-management problems of arid soils, and notes that on coarse-textured soils fertilization with phosphorus and potassium is often necessary to obtain high yields, but less so on medium- and fine-textured soils. General arid-region guidance, not a Kuwait measurement.
- Absorbed as
- H₂PO₄⁻ / HPO₄²⁻
- Typical concentration in dry matter
- 0.1–0.4%
Source: FAO — Fertilizer and Plant Nutrition Bulletin 16, Plant nutrition for food security: A guide for integrated nutrient management. R.N. Roy, A. Finck, G.J. Blair, H.L.S. Tandon. FAO, Rome, 2006. ISBN 92-5-105490-8. Chapter 3 and Chapter 4. https://www.fao.org/4/a0443e/a0443e.pdf — accessed 26 August 2026.
Last reviewed: 26 August 2026
PotassiumDeficiency shows on: Older leaves
What it does in the plant
Potassium is the second most abundant mineral nutrient in plants after nitrogen. It is involved in the working of more than 60 enzymes, in photosynthesis and in moving its products to storage organs — seeds, tubers, roots and fruits — in water economy, and in providing resistance against a number of pests, diseases and stresses such as frost and drought. It regulates stomatal opening and therefore the plant's internal water relations.
How it moves inside the plant Mobile
Mobile in the phloem. Deficiency symptoms therefore show on the older tissues — the plant moves potassium out of old leaves into new ones when supply is short.
Deficiency symptoms
The general symptom is chlorosis along the leaf boundary followed by scorching and browning of the tips of older leaves; the affected area moves inwards as the deficiency worsens. Affected plants are generally stunted with shortened internodes, slow growth, weak stalks susceptible to lodging, a greater incidence of pests and diseases, low yield, shrivelled grain and generally poor quality. Potassium-deficient plants may lose control over the rate of transpiration and suffer internal drought.
Excess and toxicity
The source we read does not describe specific potassium toxicity symptoms in the plant. Absence of a statement is not evidence of safety.
On dry, alkaline, calcareous soil
FAO describes arid-region soils as rather well supplied with potassium, sulphur, calcium, magnesium, boron and molybdenum. Potassium deficiency is therefore less expected in these soils than nitrogen, iron or zinc deficiency — with the exception of coarse-textured soils, where fertilization with phosphorus and potassium is often necessary. General arid-region guidance, not a Kuwait measurement, and no substitute for a soil analysis.
- Absorbed as
- K⁺
- Typical concentration in dry matter
- 1–5%
Source: FAO — Fertilizer and Plant Nutrition Bulletin 16, Plant nutrition for food security: A guide for integrated nutrient management. R.N. Roy, A. Finck, G.J. Blair, H.L.S. Tandon. FAO, Rome, 2006. ISBN 92-5-105490-8. Chapter 3 and Chapter 4. https://www.fao.org/4/a0443e/a0443e.pdf — accessed 26 August 2026.
Last reviewed: 26 August 2026
Secondary nutrients
3CalciumDeficiency shows on: Growing points and youngest leaves
What it does in the plant
Calcium is part of the architecture of cell walls and membranes, and is involved in cell division, growth, root lengthening, and the activation or inhibition of enzymes.
How it moves inside the plant Immobile
Immobile in the phloem. This is the decisive point: the plant cannot draw calcium out of an old leaf to rescue a new one, so deficiency shows first at the growing tips and youngest leaves. The problems concentrate in organs that do not transpire readily — that is, large, fleshy developing fruits.
Deficiency symptoms
Deficiency is seen first on growing tips and the youngest leaves, as with all nutrients that are not very mobile in the plant. Calcium-deficient leaves become small, distorted, cup-shaped, crinkled and dark green; they cease growing, become disorganized and twisted, and under severe deficiency die. Although all growing points are sensitive, those of the roots are affected more severely.
Excess and toxicity
The source we read does not describe specific calcium toxicity symptoms in the plant. Absence of a statement is not evidence of safety.
On dry, alkaline, calcareous soil
FAO describes arid-region soils as rather well supplied with calcium, and notes that calcareous soils sometimes contain more than 25 percent calcium. Soil calcium shortage is therefore unlikely in such soils — which does not mean calcium-deficiency symptoms in fruit are impossible, because getting calcium into a fruit is a matter of transport within the plant and of water relations, not of soil supply alone. General arid-region guidance, not a Kuwait measurement.
- Absorbed as
- Ca²⁺
- Typical concentration in dry matter
- 0.2–1.0%
Source: FAO — Fertilizer and Plant Nutrition Bulletin 16, Plant nutrition for food security: A guide for integrated nutrient management. R.N. Roy, A. Finck, G.J. Blair, H.L.S. Tandon. FAO, Rome, 2006. ISBN 92-5-105490-8. Chapter 3 and Chapter 4. https://www.fao.org/4/a0443e/a0443e.pdf — accessed 26 August 2026.
Last reviewed: 26 August 2026
MagnesiumDeficiency shows on: Older leaves
What it does in the plant
Magnesium occupies the centre-spot of the chlorophyll molecule and is therefore vital for photosynthesis. It is associated with enzyme activation, energy transfer, maintenance of electrical balance, protein production and carbohydrate metabolism.
How it moves inside the plant Mobile
Mobile within the plant and readily translocated from older to younger parts. Deficiency symptoms therefore appear first in the older parts — and that is the distinguishing mark separating it from iron and manganese deficiency, which look similar but appear on young leaves.
Deficiency symptoms
The typical symptom is interveinal chlorosis of older leaves: the veins remain green while the area between them turns yellow. As deficiency worsens the leaf tissue becomes uniformly pale, then brown and necrotic. Leaves are small and brittle, twigs become weak and leaves drop early. However, the variety of symptoms across plant species is so great that a generalised description is harder for magnesium than for other nutrients.
Excess and toxicity
The source we read does not describe specific magnesium toxicity symptoms in the plant. Absence of a statement is not evidence of safety.
On dry, alkaline, calcareous soil
FAO describes arid-region soils as rather well supplied with magnesium. Interveinal yellowing on an alkaline arid soil therefore deserves careful checking before it is attributed to magnesium: the position of the symptom decides it — magnesium on the older leaves, iron and manganese on the younger ones, and those two are the more expected on alkaline calcareous soils. General arid-region guidance, not a Kuwait measurement.
- Absorbed as
- Mg²⁺
- Typical concentration in dry matter
- 0.1–0.4%
Source: FAO — Fertilizer and Plant Nutrition Bulletin 16, Plant nutrition for food security: A guide for integrated nutrient management. R.N. Roy, A. Finck, G.J. Blair, H.L.S. Tandon. FAO, Rome, 2006. ISBN 92-5-105490-8. Chapter 3 and Chapter 4. https://www.fao.org/4/a0443e/a0443e.pdf — accessed 26 August 2026.
Last reviewed: 26 August 2026
SulphurDeficiency shows on: Younger leaves
What it does in the plant
Sulphur is part of the amino acids cysteine, cystine and methionine, and is therefore essential for protein production. It is involved in chlorophyll formation and enzyme activation, is part of the vitamins biotin and thiamine, and is needed for the formation of mustard oils and the sulphydryl linkages that are the source of pungency in onion and oils.
How it moves inside the plant Immobile
Mobility is low under low-sulphur conditions, because sulphur locked into structural compounds cannot be translocated; as the plant's sulphur status rises, so does its mobility. The consequence: in a well-supplied plant sulphate is preferentially sent to young, actively growing leaves, but as supply becomes limiting it is the young leaves that lack it and show the symptoms.
Deficiency symptoms
In many ways sulphur deficiency resembles nitrogen deficiency: it starts with pale yellow or light-green leaves. But it differs in where it appears — sulphur symptoms in most cases appear first on the younger leaves, and are present even after nitrogen has been applied. Sulphur-deficient plants are small and spindly with short slender stalks, growth is retarded, maturity in cereals is delayed, nodulation in legumes is poor and nitrogen fixation reduced. Fruits often do not mature fully and remain light green.
Excess and toxicity
Toxicity can occur under highly reduced conditions, possibly from hydrogen sulphide injury. Most plants are susceptible to high atmospheric sulphur dioxide: normal concentrations range from 0.1 to 0.2 mg/m³, and toxicity symptoms are observed when these exceed 0.6 mg/m³. Symptoms appear as necrotic spots on leaves which then spread over the whole leaf.
On dry, alkaline, calcareous soil
FAO describes arid-region soils as rather well supplied with sulphur. General arid-region guidance, not a Kuwait measurement, and no substitute for a soil analysis.
- Absorbed as
- SO₄²⁻
- Typical concentration in dry matter
- 0.12–0.35%
Source: FAO — Fertilizer and Plant Nutrition Bulletin 16, Plant nutrition for food security: A guide for integrated nutrient management. R.N. Roy, A. Finck, G.J. Blair, H.L.S. Tandon. FAO, Rome, 2006. ISBN 92-5-105490-8. Chapter 3 and Chapter 4. https://www.fao.org/4/a0443e/a0443e.pdf — accessed 26 August 2026.
Last reviewed: 26 August 2026
Micronutrients
7IronDeficiency shows on: Younger leaves
What it does in the plant
Iron is generally the most abundant of the micronutrients in the plant. It plays a role in the synthesis of chlorophyll, carbohydrate production, cell respiration, the chemical reduction of nitrate and sulphate, and nitrogen assimilation. For chelated iron to be used, iron must be separated from the organic ligand at the root surface after Fe³⁺ is reduced to Fe²⁺.
How it moves inside the plant Immobile
Absorbed iron is immobile in the phloem. Deficiency therefore begins on the younger leaves first: the plant cannot draw iron out of an old leaf to supply a new one.
Deficiency symptoms
Deficiency begins on younger leaves first and appears as yellowing of the interveinal areas — commonly called iron chlorosis. In severe deficiency leaves become almost pale white from loss of chlorophyll, and complete leaf fall and shoot death can occur. Its symptoms are somewhat similar to those of manganese, as both lead to a failure in chlorophyll production.
Excess and toxicity
Iron toxicity in rice is known as bronzing: leaves are first covered by tiny brown spots that develop into a uniform brown colour. It is a problem in highly reduced rice soils and in highly weathered lowland acid soils — that is, in conditions the opposite of alkaline calcareous soils.
On dry, alkaline, calcareous soil
This is the most important micronutrient in Kuwait-type soils. FAO's account of soils of the subtropical arid regions states: owing to the high soil pH, micronutrient availability poses several problems; in particular, acute iron deficiency occurs frequently in the form of lime chlorosis. It explains that this is caused by immobilization of iron in the soil and also in the roots and leaves, and that the calcareousness of these soils plays an additional detrimental role. FAO lists frequent iron and zinc deficiencies because of fixation under alkaline reaction among the characteristic problems of these soils. The practical conclusion: interveinal yellowing on young leaves in an alkaline calcareous soil is an expected pattern with a known explanation — it is not evidence that the soil lacks iron, but that the iron present is not available. General arid-region guidance, not a Kuwait measurement.
- Absorbed as
- Fe²⁺
- Typical concentration in dry matter
- 50–250 µg/g
Source: FAO — Fertilizer and Plant Nutrition Bulletin 16, Plant nutrition for food security: A guide for integrated nutrient management. R.N. Roy, A. Finck, G.J. Blair, H.L.S. Tandon. FAO, Rome, 2006. ISBN 92-5-105490-8. Chapter 3 (Iron) and Chapter 4 (Soils of the subtropical arid regions). https://www.fao.org/4/a0443e/a0443e.pdf — accessed 26 August 2026.
Last reviewed: 26 August 2026
ManganeseDeficiency shows on: Younger leaves
What it does in the plant
Manganese activates several enzymes and functions as an auto-catalyst. It is essential for splitting the water molecule during photosynthesis, has certain properties similar to magnesium, and is important in nitrogen metabolism and carbon dioxide assimilation.
How it moves inside the plant Immobile
Like iron, generally immobile in the phloem. Its symptoms therefore appear first on the younger leaves — the decisive difference from magnesium, which affects the older leaves first despite the symptom looking similar.
Deficiency symptoms
Manganese deficiency resembles iron and magnesium deficiency in that interveinal chlorosis occurs. However, manganese symptoms are first visible on the younger leaves, whereas in magnesium deficiency the older leaves are affected first. In dicots such as legumes, younger leaves develop chlorotic patches between the veins somewhat resembling magnesium deficiency.
Excess and toxicity
Toxicity leads to the development of brown spots, mainly on older leaves, and uneven green colour.
On dry, alkaline, calcareous soil
FAO states that available soil manganese decreases with increases in soil pH and calcareousness. This is the same logic that explains iron deficiency on alkaline calcareous soils: the element is present but not available. General guidance, not a Kuwait measurement.
- Absorbed as
- Mn²⁺
- Typical concentration in dry matter
- 20–500 µg/g
Source: FAO — Fertilizer and Plant Nutrition Bulletin 16, Plant nutrition for food security: A guide for integrated nutrient management. R.N. Roy, A. Finck, G.J. Blair, H.L.S. Tandon. FAO, Rome, 2006. ISBN 92-5-105490-8. Chapter 3 and Chapter 4. https://www.fao.org/4/a0443e/a0443e.pdf — accessed 26 August 2026.
Last reviewed: 26 August 2026
ZincDeficiency shows on: Younger leaves
What it does in the plant
Zinc is required directly or indirectly by several enzyme systems, by auxins, and in protein synthesis, seed production and rate of maturity. It is believed to promote RNA synthesis, which in turn is needed for protein production.
How it moves inside the plant Immobile
The mobility of zinc is low, and its rate of movement to younger tissue is particularly depressed in plants that are already zinc-deficient — the deficiency compounds itself.
Deficiency symptoms
Common symptoms are stunted growth, poor tillering, light green, yellowish or bleached spots, chlorotic bands on either side of the midrib in monocots (particularly maize), and brown rusty spots on leaves in some crops. In fruit trees the shoots may fail to extend and small leaves bunch together at the tip in a rosette-type cluster; little-leaf is also a common symptom. Internodes are short, flowering, fruiting and maturity can be delayed, shoots may die off and leaves fall prematurely. Symptoms are not the same in all plants.
Excess and toxicity
Zinc toxicity can result in reduced root growth and leaf expansion followed by chlorosis, and is generally associated with tissue concentrations greater than 200 µg/g.
On dry, alkaline, calcareous soil
FAO lists frequent iron and zinc deficiencies because of fixation under alkaline reaction among the nutrient-management problems of arid soils, and states explicitly that zinc deficiency is frequent, but copper deficiency is rare in these soils. Zinc is therefore — after iron — the second micronutrient to expect on an alkaline calcareous soil. General arid-region guidance, not a Kuwait measurement.
- Absorbed as
- Zn²⁺
- Typical concentration in dry matter
- 21–150 µg/g
Source: FAO — Fertilizer and Plant Nutrition Bulletin 16, Plant nutrition for food security: A guide for integrated nutrient management. R.N. Roy, A. Finck, G.J. Blair, H.L.S. Tandon. FAO, Rome, 2006. ISBN 92-5-105490-8. Chapter 3 and Chapter 4. https://www.fao.org/4/a0443e/a0443e.pdf — accessed 26 August 2026.
Last reviewed: 26 August 2026
BoronDeficiency shows on: Growing points and youngest leaves
What it does in the plant
Boron in a plant is like the mortar in a brick wall, the bricks being the cells of growing parts such as meristems. Its key roles relate to membrane integrity and cell-wall development — affecting permeability, cell division and extension — and to pollen tube growth, which affects seed and fruit set and hence yield.
How it moves inside the plant Immobile
Relatively immobile in plants, and its content frequently increases from the lower to the upper parts of the plant. Much of its uptake appears to follow water flow through the roots.
Deficiency symptoms
Deficiency usually appears at the growing points of roots, shoots and youngest leaves. Young leaves are deformed and arranged in a rosette; there may be cracking and cork formation in stalks, stems and fruits, thickening of stem and leaves, shortened internodes, withering or dying of growing points, and reduced bud, flower and seed production. Other symptoms include premature seed or fruit drop and unsatisfactory pollination. Death of the growing tip leads to sprouting of auxiliary meristems and a bushy broom-type growth. Roots become thick, slimy and develop brownish necrotic spots.
Excess and toxicity
Toxicity can arise from excessive boron application, in arid or semi-arid areas, and where irrigation water is rich in boron — FAO gives the threshold as more than 1–2 ppm. Symptoms are yellowing of the leaf tip followed by gradual necrosis of the tip and leaf margins spreading towards the midrib; leaves become scorched and may drop early. This is the clearest case in this reference of a nutrient whose risk in this region lies in excess rather than shortage.
On dry, alkaline, calcareous soil
Boron cuts both ways in arid soils. FAO describes them as rather well supplied with boron, while also listing an occasional excess of soluble salts, adsorbed sodium and boron among their problems. Set alongside FAO's statement that boron toxicity arises where irrigation water carries more than 1–2 ppm, the practical conclusion is clear: in a region depending on irrigation that may be saline, the better question about boron is whether there is too much, not too little. That can only be answered by an analysis of the irrigation water. General arid-region guidance, not a Kuwait measurement.
- Absorbed as
- H₃BO₃ / H₂BO₃⁻
- Typical concentration in dry matter
- 6–60 µg/g
Source: FAO — Fertilizer and Plant Nutrition Bulletin 16, Plant nutrition for food security: A guide for integrated nutrient management. R.N. Roy, A. Finck, G.J. Blair, H.L.S. Tandon. FAO, Rome, 2006. ISBN 92-5-105490-8. Chapter 3 (Boron) and Chapter 4 (Soils of the subtropical arid regions). https://www.fao.org/4/a0443e/a0443e.pdf — accessed 26 August 2026.
Last reviewed: 26 August 2026
CopperDeficiency shows on: Growing points and youngest leaves
What it does in the plant
Copper is involved in chlorophyll formation and is part of several enzymes. As much as 70 percent of the copper in plants may be present in the chlorophyll, largely bound to chloroplasts. It participates in lignin formation and in protein and carbohydrate metabolism, and is possibly required for symbiotic nitrogen fixation.
How it moves inside the plant Immobile
Not readily mobile in the plant, and its movement is strongly dependent on the plant's own copper status.
Deficiency symptoms
Deficiency symptoms are first visible as narrow, twisted leaves and pale white shoot tips. At maturity, ears are poorly filled or even empty where deficiency is severe. In fruit trees, dieback of the terminal growth can occur. In citrus the leaves appear mottled and there is dieback of new twigs.
Excess and toxicity
Copper toxicity symptoms are more variable with species and less established than its deficiency symptoms. Excess copper induces iron deficiency, so chlorosis is a common symptom — a diagnostically important point: leaf yellowing can be caused by an excess of another element rather than by a shortage of iron.
On dry, alkaline, calcareous soil
FAO states explicitly that copper deficiency is rare in arid-region soils, in contrast to iron and zinc. General arid-region guidance, not a Kuwait measurement.
- Absorbed as
- Cu⁺ / Cu²⁺
- Typical concentration in dry matter
- 5–20 µg/g
Source: FAO — Fertilizer and Plant Nutrition Bulletin 16, Plant nutrition for food security: A guide for integrated nutrient management. R.N. Roy, A. Finck, G.J. Blair, H.L.S. Tandon. FAO, Rome, 2006. ISBN 92-5-105490-8. Chapter 3 and Chapter 4. https://www.fao.org/4/a0443e/a0443e.pdf — accessed 26 August 2026.
Last reviewed: 26 August 2026
MolybdenumDeficiency shows on: Middle and older leaves
What it does in the plant
Molybdenum is involved in several enzyme systems, particularly nitrate reductase, needed for the reduction of nitrate, and nitrogenase, involved in biological nitrogen fixation. It is therefore directly involved in protein synthesis and in nitrogen fixation by legumes. It is the nutrient required in the smallest amount of all.
How it moves inside the plant Moderately mobile
Appears to be moderately mobile in the plant, as suggested by the relatively high levels of molybdenum in seeds and because deficiency symptoms appear in the middle and older leaves.
Deficiency symptoms
In legumes, molybdenum deficiency can resemble nitrogen deficiency because of its role in nitrogen fixation. It can cause marginal scorching and rolling or cupping of leaves, and yellowing and stunting. Yellow spot disease in citrus and whiptail in cauliflower are commonly associated with molybdenum deficiency.
Excess and toxicity
Fodder containing more than 5 µg/g molybdenum in the dry matter is suspected of containing levels toxic to grazing animals, associated with the disease molybdenosis. The excess risk here falls on the animal eating the plant rather than on the plant itself.
On dry, alkaline, calcareous soil
FAO describes arid-region soils as rather well supplied with molybdenum. General arid-region guidance, not a Kuwait measurement.
- Absorbed as
- MoO₄²⁻
- Typical concentration in dry matter
- < 1 µg/g
Source: FAO — Fertilizer and Plant Nutrition Bulletin 16, Plant nutrition for food security: A guide for integrated nutrient management. R.N. Roy, A. Finck, G.J. Blair, H.L.S. Tandon. FAO, Rome, 2006. ISBN 92-5-105490-8. Chapter 3 and Chapter 4. https://www.fao.org/4/a0443e/a0443e.pdf — accessed 26 August 2026.
Last reviewed: 26 August 2026
ChlorineDeficiency shows on: Younger leaves
What it does in the plant
Chlorine is thought to be involved in the production of oxygen during photosynthesis, in raising cell osmotic pressure and in maintaining tissue hydration. Some workers consider it essential only for palm and kiwi fruit.
How it moves inside the plant Mobile
The source we read gives no explicit statement of chlorine mobility in the phloem. It is recorded here for completeness rather than for diagnosis.
Deficiency symptoms
Chlorine deficiency leads to chlorosis in younger leaves and overall wilting, as a consequence of its likely effect on transpiration. Chlorine deficiency is rare in practice, and especially so where irrigation water is saline.
Excess and toxicity
Toxicity symptoms are burning of the leaf tips or margins, bronzing, premature yellowing and leaf fall. Excess — not deficiency — is the side of chlorine that matters in regions with saline water, because chloride is one of the principal salts in such water.
On dry, alkaline, calcareous soil
The source we read does not include chlorine among the nutrients listed in its description of arid-region soils, so no judgement about its status in those soils is offered here. Its practical relevance to the region comes through irrigation-water salinity, which is covered by the salinity material rather than by this record.
- Absorbed as
- Cl⁻
- Typical concentration in dry matter
- 0.2–2%
Source: FAO — Fertilizer and Plant Nutrition Bulletin 16, Plant nutrition for food security: A guide for integrated nutrient management. R.N. Roy, A. Finck, G.J. Blair, H.L.S. Tandon. FAO, Rome, 2006. ISBN 92-5-105490-8. Chapter 3. https://www.fao.org/4/a0443e/a0443e.pdf — accessed 26 August 2026.
Last reviewed: 26 August 2026
No nutrient matches this search.
The limits of this page
This page explains mechanism: what each nutrient does, how it moves, and where its shortage appears and why there.
It states no application rate, recommends no product, and gives no feeding schedule for any crop. The reason is explicit: we could not reach a Kuwait institutional source stating fertiliser rates or planting dates, and an unsourced figure is worse than no figure. The authority for quantity is the product label and the result of your own soil and water analysis.
A visual symptom alone is not a confirmed diagnosis. Salinity, irrigation faults, root damage, pests and disease all produce symptoms that resemble nutrient deficiency.