Essential Plant Nutrients
A Short Summary

CALCIUM (Ca) 40.08 Atomic weight
Calcium is absorbed by plants as the calcium Ion (Ca++). It is essential part of cell wall structure and must be present for the formation of new cells. Calcium is non-mobile in plants. Young tissue is affected first under conditions of deficiency.

POTASSIUM (K) 39.09 Atomic weight
Potassium is taken up by plants in the form of potassium Ions (K+). it is not synthesized into compounds as with nitrogen and phosphorus but tends to remain in ionic form within cells and tissues.

Potassium is essential for translocation of sugars and for starch formation. it is required in the opening and closing of stomata by guard cells. Potassium encourages root growth and increases crop resistance to disease. It produces larger, more uniformly distributed xylem vessels throughout the root system. Potassium increases size and quality of fruit and grains and is essential for high quality forage crops, unless there is an abundant microbial population present.

Potassium has been found to be the element most required by tree crops such as prunes with a very high carbohydrate production. The most responsive vegetable has been the potato, which again is a high producer of carbohydrate as starch in the tubers. Potassium is mobile in the plant tissues.

PHOSPHORUS (P) 30.79 Atomic weight
Phosphorus is absorbed by plants as H2PO4-, HPO4- -, PO4- -, depending on soil pH. Most of the total soil phosphorus is tied up chemically in compounds of limited solubility. In neutral to alkaline soils, calcium phosphate is formed, while in acid soils, iron and aluminum phosphates are produced. Phosphorus is present in all living cells. It is utilized by plants to form nucleic acids (DNA and RNA). It is used in the storage and transfer of energy through energy-rich linkages (ATP and ADP).

Phosphorus stimulates early growth and root formation. It hastens maturity and promotes seed production. Phosphorus supplementation is required most by crops under these circumstances: (1) growth in cold weather, (2) limited root growth, and (3) fast top growth.

MAGNESIUM (Mg) 24.30 Atomic weight
Plant uptake of magnesium is in the form of the magnesium Ion (Mg++). The chlorophyll molecule contains magnesium. It is therefore essential for photo synthesis. Magnesium serves as an activator for many plant enzymes required in growth processes.

Magnesium is mobile within plants and can be readily translocated from older to younger tissue under conditions of deficiency.

NITROGEN (N) 14.0 Atomic weight
Nitrogen is taken up by plants primarily as nitrate (NO3-) or ammonium (NH4+) Ions. Plants can utilize both of these forms of nitrogen in their growth process. Most of the nitrogen taken up in plants is in the nitrate form.

There are two basic reasons for this:
  1. First, nitrate nitrogen is mobile in the soil and moves with the soil water to plant roots where uptake can occur. Ammonic nitrogen, on the other hand, is bound to the surfaces of soil particles and cannot move to the roots.
  2. Secondly, all form of nitrogen added to soils are changed to nitrate under proper conditions of temperature, aeration, moisture, etc. by soil organisms.

Nitrogen is used by plants to synthesize amino acids which in turn form proteins. The protoplasm of all living cells contains protein. Nitrogen is also required by plants for utilizing other vital compounds such as chlorophyll, nucleic acids and enzymes.

SULFUR (S) 32.06 Atomic weight
Uptake of sulfur in plants is in the form of sulfate Ions (SO4- - -). Sulfur may also be absorbed from the air through the leaves in areas where the atmosphere has been enriched with sulfur compounds from industrial sources.

Sulfur is a constituent of two amino acids (methionine and cysteine) and is therefore essential for protein synthesis. It is also essential for nodule formation on legume roots. Sulfur is present in oil compounds responsible for the characteristic odors of plants such as garlic and onion.

BORON (B) 10.81 Atomic weight
Boron is taken up by plants as borate. It functions in plants in the differentiation of meristem cells. With boron deficiency, cells may continue to divide but structural components are not differentiated. Boron is non-mobile in plants, and a constant supply is necessary at all growing points. Deficiency is first found in the youngest tissues of the plant.

CHLORINE (Cl) 35.45 Atomic weight
Chlorine is required in the photosynthetic reaction of plants. Deficiency is not seen in the field due to its universal presence in nature.

MANGANESE (Mn) 54.93 Atomic weight
Manganese serves as an activator for enzymes in growth processes. It assists iron in chlorophyll formation. High manganese concentration may induce iron deficiency. Manganese uptake is primarily in the form of the Ion (Mn++).

IRON (Fe) 55.84 Atomic weight
Iron is required for the formation of chlorophyll in plants cells. Iron is taken up by plants either as ferrous (Fe++) or (Fe+++) Ions. It serves as an activator for biochemical processes such as respiration, photosynthesis and symbiotic nitrogen fixation. Iron deficiency can be induced by high levels of manganese or high lime content in soils.

COPPER (Cu) 63.54 Atomic weight
Copper is an activator of several enzymes in plants, and it plays a role in vitamin A production. Vitamin A deficiency interferes with protein syntheses. Plant uptake is in the form of Ions (Cu+, Cu++).

ZINC (Zn) 65.38 Atomic weight
Zinc is an essential component of several important enzyme systems in plants. It controls the synthesis of indoleacetic acid, and important plant growth regulator. Terminal growth areas are affected first when zinc is deficient. Zinc is absorbed by plants as the zinc Ion (Zn++).

MOYLBDENUM (Mo) 95.94 Atomic weight
Molybdenum is required by plants for the utilization of nitrogen. Plants cannot transform nitrate nitrogen into amino acids without molybdenum. Legumes cannot fix atmospheric nitrogen symbiotically unless molybdenum is present.

CARBON (C) 12.011 Atomic weight
Even though carbon is the number one building block of all life, it is rarely mentioned as a plant nutrient. Carbon is taken in through the plant's leaves directly from the air as carbon dioxide (CO2).

The lack of soil organic carbon is a sure sign of a lack of organic matter in the form of humus which is food for bacteria.

When too much nitrogen is added to the soil, it induces a carbohydrate deficiency and reduces bacterial populations. Carbohydrates are the sugar, (carbon, hydrogen, oxygen), energy source for bacterial populations to thrive.

Bacteria are most abundant at a soil carbon to nitrogen ratio of 30 to 1. Added nitrogen induces a sugar deficiency that reduces bacterial competition to fungi root diseases and nematodes.

Carbon leaves the Earth's soils and goes to the atmosphere as (CO2) in a constant cycle known as the Carbon cycle. Vegetation collects carbon dioxide from the air, releases the oxygen (O2) and returns the carbon (C) to the earth.

All photo synthetic forms can reduce atmospheric CO2 but not all can use CO2 as their sole source of carbon. In the non-sulfur purple bacteria, organic substances such as acetate act as hydrogen donors for CO2 reduction. In contrast, other microbes, such as nitrifying bacteria, utilize inorganic substances exclusively and must therefore use atmospheric CO2 as their only carbon source.

Most microbial forms oxidize organic materials which serve not only as substrates in energy yielding reactions but also as sources of carbon for nutrition.

The range of organic compounds from which carbon is extracted by organisms is endless. Microorganisms, as a group, are especially versatile in this respect, in fact, for every naturally occurring organic material; there is a microbe capable of decomposing it. This is the reason why microorganisms play such a vital role in the geochemical cycling of the elements, especially carbon and nitrogen.

Carbohydrates are among the most readily available sources of carbon for microorganisms. Monosaccharide's, (simple sugars), are widely used but alcohols, such as mannitol and glycerol are good sources too, especially for fungi and actinomycetes.

Amino acids are readily used as carbon sources b most microorganisms while some can utilize fatty acids.

Hydrocarbons, (oils), can serve as a carbon source for few bacteria of the genera corynebacterium, mycobaterium and pseudomas.

Utilization of compounds such as lignin is quite extensive under aerobic (O2) conditions, but when oxygen is limited such compounds are not decomposed. Instead they accumulate, for example, as peat or coal. The major lignin decomposers are fungi, pseudomonas and actinomycetes.

Silicon (Si) 28.08 Atomic weight, Sodium (Na) 22.98 Atomic weight, Cobalt (Co) 58.93 Atomic weight, Vanadium (V) 50.94 Atomic weight, Selenium (Se) 78.96 Atomic weight, Bromine (Br) 79.90 Atomic weight, Niobium (Nb) 92.90 Atomic weight, Nickel (Ni) 58.70 Atomic weight. This group includes nutrients that are used by only a limited number of plant species. Cobalt has recently been shown to be required by legumes when fixing nitrogen, but not when fixed nitrogen is present. Vanadium is required by certain algae. Chlorine is necessary for the growth of higher plants but other halides, such as bromine, may be a substitute at higher concentrations. Selenium is needed by Astragalus spp. (a legume) can replace sulfur in certain sulfur amino acids giving selenocystathionine, selenomethionine, selenocysteine and methyselencysteine: these compounds are potentially poisonous. Some of these have also been isolated from wheat grown in seleniferous soil. Selenomethionine completes with methionine in the synthesis of protein. When high concentrations of an element not commonly found in most plants are seen in a particular species, it raises the possibility that the element is essential for that species. For example, barium is found in brazil nuts, aluminum in tea, chromium, nickel and cobalt in gramineae, silicon in rice and cucumbers.

Potassium in Soils
The following are general elemental relationships. The most overlooked element in agriculture other than carbon is potassium. Potassium levels have rarely been associated with nitrogen levels, but they should be.

Potassium is directly involved in:
  1. The synthesis of carbohydrates, proteins, oils and certain organic acids.
  2. Acceleration of certain enzymatic actions.
  3. The reductase reduction of nitrates which are fundamental for the synthesis of protein.
  4. Inceasing photosynthetic activity under low light conditions.
  5. Facilitating the transport of carbohydrates inside the plant.
  6. Cellular division.
  7. Regulation of nitrogen absorption by the plant.
  8. Increasing the resistance of plants to diseases.

We have found in corn, potatoes, and grasses that when excess nitrogen fertilizer is added to the crop during the growing season, there is a direct decline in the level of potassium present in the plant. Also, as the potassium level declines, the manganese level increases to a dangerously high amount in the plant. The same elemental relationship seems to exist whether soil applied or foliar applied nitrogen applications are made.

Potassium strengthens plant vascular tissue and under adequate levels, increases the cell wall thickness up to three times.

Potassium uptake is inhibited in most plants grown in soils with high magnesium and low oxygen levels. When potassium an d magnesium levels are too low, use of the fertilizer from Sulfate of Potash Magnesia which is 22% K and 11% Mg is about the ideal balance between these two elements.

Potassium is the plants cellular liquid antifreeze system because it remains in the liquid, increases the salt level and decreases the liquid freezing point.

Remember, the more nitrogen that is added to a crop, the busier the potassium becomes and the greater the need.

Phosphates in Soils
Several factors influence the availability of phosphates to the plant.

Soil pH influences the ionic character of phosphorus. At low pH, P is principally in the H2PO4 form. At intermediate soil pH levels, H2PO4 is predominant and at higher values P3O4 is present.

Plants can absorb all of these forms, but this ionic nature of phosphorus also influences the way it binds to soil colloid. Anions are strongly attracted to and absorbed by soil particles, phosphates, at low soil pH, can form insoluble and unavailable salts with iron and aluminum Cations.

In soils with increased calcium and a high pH, CaCO3 can greatly reduce the plants available phosphate.

Organic matter contains large amounts of the total soil phosphate but these are not readily taken up by plants unless there is an enzymatic cleavage of the phosphate bond. This cleavage is achieved by the enzyme phosphatase which is produced by microorganisms.

Minerals + Organic Matter + Microbes = Transformed Products for Soil Health

The final products evolving from organic matter break down by soil microbes are polysaccharides (complex sugars) and humus. About 10% of the organic carbon in soils is in the form of carbohydrate (polysaccharides). It serves an important function by binding soil particles into water-stable aggregates. Polysaccharides are derived from plant, animal and microbial digested materials and from extracellular gums of microbial origin. The polysaccharide fraction is potentially the most readily available microbial food in the soil organic matter, but despite its abundance, utilization by microorganisms is severely curtailed until most other food sources are no longer available in adequate quantities.

The humus component consists of three substances:
  1. Humin is the black insoluble residue which has a closer association with the inorganic fraction of soils. The humin is removed from humus by and alkali solution.
  2. Humic acid is precipitated from humus by a very acid solution and is the main component in humus. The major component of humic acid consists of plant polysaccharide residues protected from further degradation by the action of phenolic protein complexes.
  3. The remaining solution from humus extraction contains the fulvic acid fraction; about half of the bulk of the fulvic acid consists of bacterial cell residues, amino acids and amino sugars. Fulvic acid generally has a lower molecular weight and a 10% higher carbon content than the acid portion, although humus represents the final stage of organic matter decomposition in soil, it would be a mistake to regard it simply as the digestion resistant residue of plants, animals and microbes. It is in fact a product of microbial biosynthesis, and furthermore, it remains subject to very slow microbial breakdown. The humus component appears to be the energy reserve for all soils, giving the soils the vitality we referred to earlier.

The development and cropping ability of the soil ecosystem is controlled by the biological attributes rather than physical factors. The physical environment sets limits as to how far development may proceed and also the pattern and rate of change but it is the microbial factor which is generally seen to be of overriding significance.


Humic acids give the soil life and vitality…or are there more?

In the universal scheme of things, there lies, somewhere between energy and matter, submicroscopic energy particles called somatids. Somatids do not have any DNA or RNA yet they maintain a kind of "genetic memory" as they develop. The somatid is considered indestructible because it has survived temperatures of 1000o C and millions of rads of radiation.

When an animal, plant or microbe cell is functioning properly, is properly nourished, the somatids live through a simple and energetic three phase cycle. This three phase cycle apparently has a function in helping cells, plants and animals maintain vitality, energy and health. However, whenever the cellular fluid deteriorates for any reason (toxins, stress, trauma, poisons or deficiencies) the somatid cycle changes into a 16-phase cycle that includes bacteria and yeast forms that do not promote robust health but actually may parasitize and contribute to the deterioration of the host condition.

Now, what is the connection between somatids and humates? Billions of living cells from massive numbers of plant, animal and bacterial bodies all containing sub microscopic somatids, (energy masses), have been concentrated through decomposition to form one gram of humic substance. These indestructible energy masses have been concentrated into a lower level energy mass waiting to awaken by the forces of the universe to revitalize the life cycle here on Earth.

Now, when we examine closely the structures of our commercial sources or humates, coal and leonardite, we will find the energy bundles called somatids. These are merely decomposed matter from Earth's biosphere that was frozen at some instant in time millions of years ago.

The first discovery of somatids was reported in the 1850-1880 period by a rival of Louis Pasteur, Antoine Bechamp. Bechamp called them microzymas. Then in 1917, a German doctor Guenther Enderlein reported on similar bodies based on the studies reported in 1901 by two other Germans, Robert Leukart and Otto Schmidt. Wilhelm Reich discovered and reported similar bodies in human blood and called them "bions". He described them as "some kind of transitional form lying between the animate and the inert."

Somatids were more recently discovered by Gaston Naessens through a special, high powered, dark field microscope. Read "The Galileo of the Microscope" by Christopher Bird for further information on somatids.


Over the years, many studies have been conducted on the effects of potassium, or the lack of it, on the quality of crops. Below we share what we know today as a result of those studies:
  1. Lodging in corn and grains is induced by over application of nitrogen, made worse by applications of phosphorus, and alleviated by applications of potassium.
  2. Potassium deficiency causes an excess accumulation of iron and aluminum in plant tissue restricting the conducting vessels and leading to eventual vascular deterioration and disease.
  3. Potassium deficiency in potatoes causes low starch content and they tend to be hollow in the center and darken after cooking. When looking at potato plant tissue verses tubers, the tuber shows twice as much K as does the foliar tissue. Low potassium results in low levels of the amino acid, arginine, in the tissue and tubers which is the controlling substance for phytophthora infestants (late blight).
  4. Apples deficient in K do not color well.
  5. Potassium deficient tomato plants result in bloom drop, premature fruit drop, poor coloration and poor storage quality.
  6. Potassium deficiencies result in poor storage quality of most fruits and vegetables (onions, cabbage, tomatoes, peas, potatoes, carrots…).
Field test results have shown:
  1. Potassium deficiencies resulted in a decrease in the acidity of tomatoes and citrus fruits.
  2. Cabbage raised under low K levels formed loose heads.
  3. Soybeans, tung, sunflowers, and safflower had lower oil content when raised under reduced potassium levels.
  4. Oats and soybeans matured 25 days earlier than those with deficient potassium levels.
  5. Grapes developed less rapidly and matured less completely where potassium was deficient.
  6. In fields of cotton grown with adequate potassium, the cotton matured earlier and produced twice the weight of seed as the deficient control fields. The flowering stage was cut short for K deficient plants. Cotton with good K levels produced more mature bolls and fibers.
  7. Apple and pear trees with low potassium levels have an increased susceptibility to Ervinia amylovora ("fire blight").
  8. Potassium deficient grapes have increased susceptibility to spider mites.
  9. K deficient potatoes showed greater foliar frost damage than did potatoes with normal levels.
  10. Winter hardiness in all plants involves an accumulation of soluble carbohydrates in high concentrations. High nitrogen input without adequate levels of potassium only causes the plat to form high levels of potentially winter toxic proteinaceous substances that have not been reduced to the proper ratio of carbohydrates. The degradation of these proteinaceous materials in the winter, under snow, causes toxic effect on the leaf cells and opens up entry points for infectious diseases.
  11. In apple orchards, potassium deficient trees showed a greater loss of water than the trees with adequate levels.


Law of minimum
Plants, crops, animals and people are all dependent on a favorable combination of four environmental factors:
A) Light B) Heat C) Air D) Nutrients

With the exception of light, soils can supply each of these factors but only when they are supplied in the right combination is optimum health and growth obtained. When one factor is less than optimum, health and growth will be limited. This principle is called the "Law of Minimum" and can be stated more simply as follows: The level of productions and health can be no greater than that allowed by the most limited of the essential growth factors. In other words, there can be perfect conditions of light, air, water and temperature but if the soil is deficient in manganese for example, the health and growth of the plants will be compromised.

Law of Maximum
The level of production and health of a plant can be no greater than the deficiencies caused by an excess of any one or combination of elements.

Remember that nitrogen excess causes potassium deficiencies and manganese toxic levels. Excessive phosphorus causes toxic levels of iron and aluminum clogging the plant's vascular system.

Excessive zinc causes excessive iron uptake and deficient manganese levels.

Conclusion of the Laws of Minimum and Maximum
Nutrient deficiencies and excesses cause diseases and insect attacks by themselves. (Not saying anything about the yield and economic effect.)

MAP Sup-O-Phos are organically complexed or chelated white phosphoric acid with an analysis of 0-50-0. The organic phosphate bonding of Sup-O-Phos provides a highly stable form of phosphorus for foliar feeding and soil application. The organically complexed phosphorus in Sup-O-Phos is readily absorbed by plant roots and leaves and can safely applied directly or through sprinkler irrigation systems. When Sup-O-Phos is used for soil application, organic complexing may provide protection from chemical relations with calcium or aluminum which can produce insoluble and unavailable phosphorus form.

The importance of a readily available phosphorus source for crop nutrition cannot be over emphasized. The optimal phosphorus requirement for most crop plants is in the range of 0.3% to 0.6% of the plant dry weight as determined by tissue analysis. The most important consideration in phosphorus nutrition is the ratio of phosphorus to nitrogen in growing crops. The optimum crop response, phosphorus should be maintained at or near 10% of the nitrogen level. If a leaf sample contains 4% nitrogen, the phosphorus level should be about 0.4% of dry weight. Availability of adequate phosphorus is absolutely essential for crop development and yield.

Phosphorus is necessary for cell division (growth), energy transfer within plants, and regulation of key enzyme reactions in photosynthesis and respiration.

Crops have a peak demand for phosphorus early in the growing season when high metabolic activity occurs. Annual crops have an especially high phosphorus requirement from germination through rapid growth as the root system and leaf canopy are developing. Perennial crops including trees, vines, hay and pasture also need high levels phosphorus as the break dormancy, rebuild root systems, and grow leaf canopies.

Unfortunately, the availability of phosphorus from natural sources may be rather low early in the growing season. Cold and often water saturated or very dry soils will have reduced microbial activity and a slow decomposition rate of organic residue. Biological activity is extremely important because organic phosphorus compounds may account for 50% or more of total soil phosphorus and as much as 90% of the available phosphorus taken up by crops. Crop development will also be slow in cold and wet (or dry) soil and phosphorus nutrition is directly related to root mass. Phosphorus is practically immobile in the soil solution and crop roots must grow and expand in order to access soil phosphorus. Under early stress condition, a foliar application of phosphorus will often stimulate root growth and act as a catalyst for increased phosphorus uptake. MAP Sup-O-Phos and a balanced foliar formulation like VitaMax are excellent sources of phosphorus for foliar feeding.

An additional challenge in phosphorus nutrition is created by the chemical reactivity of the phosphate Ion in the soil. Phosphorus has a strong affinity for calcium and aluminum and will react with these elements in the soil to produce water insoluble and unavailable forms. Soil pH becomes an important factor because a high level of aluminum is present in low pH soils and a high level of calcium is present in high pH soils. Phosphorus availability is greatest at a pH of about 6.5.

The characteristics of phosphorus just reviewed suggest that the real "phosphorus nutrition problem" is one of availability and uptake and not necessarily quantity in the soil. this is the reason that soil tests for phosphorus can be misleading and when used alone, are of limited value in making fertilizer recommendation. Phosphorus fertilizer recommendations should be based on a complete examination of the soil including such characteristics as organic crop performance (tissue analysis) if available. The application of MAP Sup-O-Phos or a liquid bulk formulation such as a 10-34-0 which has been organically complexed with MAP Sup-O-Phos can increase the efficiency of phosphorus. When possible, phosphorus fertilizer should be placed in the crop root zone and application should be made as close to peak crop demand as practical.

Additional use for MAP Sup-O-Phos, which is especially important in the western United States, is maintenance of drip irrigation systems. Sup-O-Phos is effective in preventing and correcting build up of calcium and magnesium deposits in drip systems including leaky pipe systems. Addition of Sup-O-Phos to irrigation water results in release of carbon in the form of carbon dioxide and carbonic acid. These substances act to loosen calcium and magnesium deposits and flush them from the system as water soluble carbonates or bicarbonates. Regular use of Sup-O-Phos will help keep drip systems clean and trouble free.


As reported by the University of Arizona Agricultural Experiment Station an Cooperative Extension Service Bulletin A-42

  • 11-48-0 (MAP) ties up to CaHPO42H2O in 15 minutes
  • 18-46-0 (MAP) ties up to MgNH4PO46G2O in 15 minutes
  • 10-34-0 (LIQUID) ties up to Ca(NH4)2P2O7H2O in 15 minutes


  1. Using MAP Soil Applied products with phosphate applications.
  2. Apply phosphate very close to planting date.
  3. Inject phosphate in the bed or spray over the bed.
  4. Apply liquid sulfur in the row irrigation.
  5. Apply Phosphate when crop is growing not before.
  6. Keep the soil moist after phosphate has been applied.