Calcium (Ca) deficiency is a plant disorder that can be caused by insufficient level of available calcium in the growing medium, but is more frequently a product of low transpiration of the whole plant or more commonly the affected tissue. Plants are susceptible to such localized calcium deficiencies in low or non-transpiring tissues because calcium is not transported in the phloem. This may be due to water shortages, which slow the transportation of calcium to the plant, poor uptake of calcium through the stem, or too much nitrogen in the soil.

Phosphorus deficiency is a plant disorder associated with insufficient supply of phosphorus. Phosphorus refers here to salts of phosphates (PO), monohydrogen phosphate (HPO), and dihydrogen phosphate (HPO). These anions readily interconvert, and the predominant species is determined by the pH of the solution or soil. Phosphates are required for the biosynthesis of genetic material as well as ATP, essential for life. Phosphorus deficiency can be controlled by applying sources of phosphorus such as bone meal, rock phosphate, manure, and phosphate-fertilizers.

Calcium deficiency symptoms appear initially as localized tissue necrosis leading to stunted plant growth, necrotic leaf margins on young leaves or curling of the leaves, and eventual death of terminal buds and root tips. Generally, the new growth and rapidly growing tissues of the plant are affected first. The mature leaves are rarely if ever affected because calcium accumulates to high concentrations in older leaves.

Crop-specific symptoms include:

- Apple : 'Bitter pit' – fruit skins develop pits, brown spots appear on skin and/or in flesh and taste of those areas is bitter. This usually occurs when fruit is in storage, and Bramley apples are particularly susceptible. Related to boron deficiency, "water cored" apples seldom display bitter pit effects.

- Cabbage and Brussels sprouts : Internal browning and "tip burn"

- Carrot : 'Cavity spot' – oval spots develop into craters which may be invaded by other disease-causing organisms.

- Celery : Stunted growth, central leaves stunted.

- Tomatoes and peppers: 'Blossom end rot' – Symptoms start as sunken, dry decaying areas at the blossom end of the fruit, furthest away from the stem, not all fruit on a truss is necessarily affected. Sometimes rapid growth from high-nitrogen fertilizers may exacerbate blossom end rot. Water management and preventing water stress is key to minimizing its occurrence.

Potassium deficiency, also known as potash deficiency, is a plant disorder that is most common on light, sandy soils, because potassium ions (K) are highly soluble and will easily leach from soils without colloids. Potassium deficiency is also common in chalky or peaty soils with a low clay content. It is also found on heavy clays with a poor structure.

All plants require sufficient supplies of macronutrients for healthy growth, and nitrogen (N) is a nutrient that is commonly in limited supply. Nitrogen deficiency in plants can occur when organic matter with high carbon content, such as sawdust, is added to soil. Soil organisms use any nitrogen to break down carbon sources, making N unavailable to plants. This is known as "robbing" the soil of nitrogen. All vegetables apart from nitrogen fixing legumes are prone to this disorder.

Nitrogen deficiency can be prevented in the short term by using grass mowings as a mulch, or foliar feeding with manure, and in the longer term by building up levels of organic matter in the soil. Sowing green manure crops such as grazing rye to cover soil over the winter will help to prevent nitrogen leaching, while leguminous green manures such as winter tares will fix additional nitrogen from the atmosphere.

Physiological plant disorders are caused by non-pathological conditions such as poor light, adverse weather, water-logging, phytotoxic compounds or a lack of nutrients, and affect the functioning of the plant system. Physiological disorders are distinguished from plant diseases caused by pathogens, such as a virus or fungus. While the symptoms of physiological disorders may appear disease-like, they can usually be prevented by altering environmental conditions. However, once a plant shows symptoms of a physiological disorder it is likely that that season’s growth or yield will be reduced.

Manganese (Mn) deficiency is a plant disorder that is often confused with, and occurs with, iron deficiency. Most common in poorly drained soils, also where organic matter levels are high. Manganese may be unavailable to plants where pH is high.

Affected plants include onion, apple, peas, French beans, cherry and raspberry, and symptoms include yellowing of leaves with smallest leaf veins remaining green to produce a ‘chequered’ effect. The plant may seem to grow away from the problem so that younger

leaves may appear to be unaffected. Brown spots may appear on leaf surfaces, and severely affected leaves turn brown and wither.

Prevention can be achieved by improving soil structure. Do not over-lime.

Symptoms include dying growing tips and bushy stunted growth, extreme cases may prevent fruit set. Crop-specific symptoms include;

- "Apple"- interacting with calcium, may display as "water core", internal areas appearing frozen

- "Beetroot"- rough, cankered patches on roots, internal brown rot.

- "Cabbage"- distorted leaves, hollow areas in stems.

- "Cauliflower"- poor development of curds, and brown patches. Stems, leafstalks and midribs roughened.

- "Celery"- leaf stalks develop cracks on the upper surface, inner tissue is reddish brown.

- "Celeriac"- causes brown heart rot

- "Pears"- new shoots die back in spring, fruits develop hard brown flecks in the skin.

- "Strawberries"- Stunted growth, foliage small, yellow and puckered at tips. Fruits are small and pale.

- "Swede (rutabaga)" and "turnip"- brown or gray concentric rings develop inside the roots.

- "Arecaceae" ("Palm Tree") - brown spots on fronds & lower productivity.

Bitter pit is a disorder in apple fruits, now believed to be induced by calcium deficiency. It occurs less commonly in pears.

The disease was probably first reported in Germany where it was known as "Stippen". It was also known as "Baldwin spot" and "blotchy cork" in North America. The name "bitter pit" was first used by Cobb in Australia in 1895. The disease has been shown as non-pathological and is now known as a disorder. When it occurs on the tree, it is known as "tree pit"; it may also occur in storage, when it is known as "storage pit".

Boron deficiency is a common deficiency of the micronutrient boron in plants. It is the most widespread micronutrient deficiency around the world and causes large losses in crop production and crop quality. Boron deficiency affects vegetative and reproductive growth of plants, resulting in inhibition of cell expansion, death of meristem, and reduced fertility.

Plants contain boron both in a water-soluble and insoluble form. In intact plants, the amount of water-soluble boron fluctuates with the amount of boron supplied, while insoluble boron does not. The appearance of boron deficiency coincides with the decrease of water-insoluble boron. It appears that the insoluble boron is the functional form while the soluble boron represents the surplus.

Boron is essential for the growth of higher plants. The primary function of the element is to provide structural integrity to the cell wall in plants. Other functions likely include the maintenance of the plasma membrane and other metabolic pathways.

The affected fruit have dark spots, about ½ cm diameter, which occur on the skin and/or in the flesh The cells in the spots are dead (necrotic), and turn brown-black.

Magnesium (Mg) deficiency is a detrimental plant disorder that occurs most often in strongly acidic, light, sandy soils, where magnesium can be easily leached away. Magnesium is an essential micro nutrient found from 0.2-0.4% dry matter and is necessary for normal plant growth. Excess potassium, generally due to fertilizers, further aggravates the stress from the magnesium deficiency, as does aluminium toxicity.

Magnesium has an important role in photosynthesis because it forms the central atom of chlorophyll. Therefore, without sufficient amounts of magnesium, plants begin to degrade the chlorophyll in the old leaves. This causes the main symptom of magnesium deficiency, chlorosis, or yellowing between leaf veins, which stay green, giving the leaves a marbled appearance. Due to magnesium’s mobile nature, the plant will first break down chlorophyll in older leaves and transport the Mg to younger leaves which have greater photosynthetic needs. Therefore, the first sign of magnesium deficiency is the chlorosis of old leaves which progresses to the young leaves as the deficiency continues. Magnesium also is a necessary activator for many critical enzymes, including ribulosbiphosphate carboxylase (RuBisCO) and phosphoenolpyruvate carboxylase (PEPC), both essential enzymes in carbon fixation. Thus low amounts of Mg lead to a decrease in photosynthetic and enzymatic activity within the plants. Magnesium is also crucial in stabilizing ribosome structures, hence, a lack of magnesium causes depolymerization of ribosomes leading to pre-mature aging of the plant. After prolonged magnesium deficiency, necrosis and dropping of older leaves occurs. Plants deficient in magnesium also produce smaller, woodier fruits.

Magnesium deficiency may be confused with zinc or chlorine deficiencies, viruses, or natural ageing since all have similar symptoms. Adding Epsom salts (as a solution of 25 grams per liter or 4 oz per gal) or crushed dolomitic limestone to the soil can rectify magnesium deficiencies. For a more organic solution, applying home-made compost mulch can prevent leaching during excessive rainfall and provide plants with sufficient amounts of nutrients, including magnesium.

Plants look thin, pale and the condition is called "general starvation".

Iron (Fe) deficiency is a plant disorder also known as "lime-induced chlorosis". It can be confused with manganese deficiency. A deficiency in the soil is rare but iron can be unavailable for absorption if soil pH is not between about 5 and 6.5. A common problem is excessive alkalinity of the soil (the pH is above 6.5). Also, iron deficiency can develop if the soil is too waterlogged or has been overfertilised. Elements like calcium, zinc, manganese, phosphorus, or copper can tie up iron if they are present in high amounts.

Iron is needed to produce chlorophyll, hence its deficiency causes chlorosis. For example, iron is used in the active site of glutamyl-tRNA reductase, an enzyme needed for the formation of 5-Aminolevulinic acid which is a precursor of heme and chlorophyll.

Grass tetany or hypomagnesemic tetany, also known as grass staggers and winter tetany, is a metabolic disease involving magnesium deficiency, which can occur in such ruminant livestock as beef cattle, dairy cattle and sheep, usually after grazing on pastures of rapidly growing grass, especially in early spring.

The main role of potassium is to provide the ionic environment for metabolic processes in the cytosol, and as such functions as a regulator of various processes including growth regulation. Plants require potassium ions (K) for protein synthesis and for the opening and closing of stomata, which is regulated by proton pumps to make surrounding guard cells either turgid or flaccid. A deficiency of potassium ions can impair a plant's ability to maintain these processes. Potassium also functions in other physiological processes such as photosynthesis, protein synthesis, activation of some enzymes, phloem solute transport of photoassimilates into source organs, and maintenance of cation:anion balance in the cytosol and vacuole.

Cobalt poisoning is intoxication caused by excessive levels of cobalt in the body. Cobalt is an essential element for health in animals in minute amounts as a component of Vitamin B. A deficiency of cobalt, which is very rare, is also potentially lethal, leading to pernicious anemia.

Symptoms include leaves turning yellow or brown in the margins between the veins which may remain green, while young leaves may appear to be bleached. Fruit would be of poor quality and quantity. Any plant may be affected, but raspberries and pears are particularly susceptible, as well as most acid-loving plants such as azaleas and camellias.

Manganese deficiency can be easy to spot in plants because, much like magnesium deficiency, the leaves start to turn yellow and undergo interveinal chlorosis. The difference between these two is that the younger leaves near the top of the plant show symptoms first because manganese is not mobile while in magnesium deficiency show symptoms in older leaves near the bottom of the plant.

Detecting phosphorus deficiency can take multiple forms. A preliminary detection method is a visual inspection of plants. Darker green leaves and purplish or red pigment can indicate a deficiency in phosphorus. This method however can be an unclear diagnosis because other plant environment factors can result in similar discoloration symptoms. In commercial or well monitored settings for plants, phosphorus deficiency is diagnosed by scientific testing. Additionally, discoloration in plant leaves only occurs under fairly severe phosphorus deficiency so it is beneficial to planters and farmers to scientifically check phosphorus levels before discoloration occurs. The most prominent method of checking phosphorus levels is by soil testing. The major soil testing methods are Bray 1-P, Mehlich 3, and Olsen methods. Each of these methods are viable but each method has tendencies to be more accurate in known geographical areas. These tests use chemical solutions to extract phosphorus from the soil. The extract must then be analyzed to determine the concentration of the phosphorus. Colorimetry is used to determine this concentration. With the addition of the phosphorus extract into a colorimeter, there is visual color change of the solution and the degree to this color change is an indicator of phosphorus concentration. To apply this testing method on phosphorus deficiency, the measured phosphorus concentration must be compared to known values. Most plants have established and thoroughly tested optimal soil conditions. If the concentration of phosphorus measured from the colorimeter test is significantly lower than the plant’s optimal soil levels, then it is likely the plant is phosphorus deficient. The soil testing with colorimetric analysis, while widely used, can be subject to diagnostic problems as a result of interference from other present compounds and elements. Additional phosphorus detection methods such as spectral radiance and inductively coupled plasma spectrometry (ICP) are also implemented with the goal of improving reading accuracy. According to the World Congress of Soil Scientists, the advantages of these light-based measurement methods are their quickness of evaluation, simultaneous measurements of plant nutrients, and their non-destructive testing nature. Although these methods have experimental based evidence, unanimous approval of the methods has not yet been achieved.

Zinc deficiency may manifest as acne, eczema, xerosis (dry, scaling skin), seborrheic dermatitis, or alopecia (thin and sparse hair). There may also be impaired wound healing.

Zinc deficiency can manifest as non-specific oral ulceration, stomatitis, or white tongue coating. Rarely it can cause angular cheilitis (sores at the corners of the mouth) and burning mouth syndrome.

Exposure to cobalt metal dust is most common in the fabrication of tungsten carbide. Another potential source is wear and tear of metal-on-metal hip prostheses; however, this is a relatively uncommon phenomenon with 18 reported cases being documented in the medical literature.

Progressive symptoms may include grazing away from the herd, irritability, muscle twitching, staring, incoordination, staggering, collapse, thrashing, head thrown back, and coma, followed by death. However, clinical signs are not always evident before the animal is found dead.

The condition results from hypomagnesemia (low magnesium concentration in blood) which may reflect low magnesium intake, low magnesium absorption, unusually low retention of magnesium, or a combination of these. Commonly, apparent symptoms develop only when hypomagnesemia is accompanied by hypocalcemia (blood Ca below 8 mg/dL).

Low magnesium intake by grazing ruminants may occur especially with some grass species early in the growing season, due to seasonally low magnesium concentrations in forage dry matter. Some conserved forages are also low in magnesium and may be conducive to hypomagnesemia.

High potassium intake relative to calcium and magnesium intake may induce hypomagnesemia. A K/(Ca+Mg) charge ratio exceeding 2.2 in forages has been commonly considered a risk factor for grass tetany. Potassium fertilizer application to increase forage production may contribute to an increased K/(Ca+Mg) ratio in forage plants, not only by adding potassium to soil, but also by displacing soil-adsorbed calcium and magnesium by ion exchange, contributing to increased susceptibility of calcium and magnesium to leaching loss from the root zone during rainy seasons. In ruminants, high potassium intake results in decreased absorption of magnesium from the digestive tract.

Trans-aconitate, which accumulates in some grasses, can be a risk factor for hypomagnesemia in grazing ruminants. (Tetany has been induced in cattle by administration of trans-aconitate and KCl, where the amount of KCl used was, by itself, insufficient to induce tetany.) Relatively high levels of trans-aconitate have been found in several forage species on rangeland sites conducive to hypomagnesemia. Although at least one rumen organism converts trans-aconitate to acetate, other rumen organisms convert trans-aconitate to tricarballylate, which complexes with magnesium. Using rats as an animal model, oral administration of tricarballylate has been shown to reduce an animal's magnesium retention. Potassium fertilizer application results in increased concentration of aconitic acid in some grass species.

Poor growth and a variety of disorders such as leaf discolouration (chlorosis) can be caused by a shortage of one or more plant nutrients. Poor plant uptake of a nutrient from the soil (or other growing medium) may be due to an absolute shortage of that element in the growing medium, or because that element is present in a form that is not available to the plant. The latter can be caused by incorrect pH, shortage of water, poor root growth or an excess of another nutrient. Plant nutrient deficiencies can be avoided or corrected using a variety of approaches including the consultation of experts on-site, the use of soil and plant-tissue testing services, the application of prescription-blend fertilizers, the application of fresh or well-decomposed organic matter, and the use of biological systems such as cover crops, intercropping, improved fallows, ley cropping, permaculture, or crop rotation.

Nutrient (or mineral) deficiencies include:

- Boron deficiency

- Calcium deficiency

- Iron deficiency

- Magnesium deficiency

- Manganese deficiency

- Molybdenum deficiency

- Nitrogen deficiency

- Phosphorus deficiency

- Potassium deficiency

- Zinc deficiency