Form taken up by plant:                               NH4+, NO3-

Mobility in soil:                                                NH4+: no;  NO3-: yes

                                                                             NO3- water soluble, not influenced by soil colloids

Mobility in plant:                                             Yes

Deficiency symptoms:                                  Chlorosis in older leaves, under severe deficiency lower leaves are brown, beginning at the leaf tip and proceeding along the midrib.       

Soil pH where deficiency will occur:         None due to nitrate's mobility

Role of nutrient in plant growth:                N assimilation into amino acids for protein and amino acid synthesis, component of chlorophyll, vegetative growth          

Enzymes that require N:                               Nitrate reductase, nitrite reductase, nitrogenase         

Role of nutrient in microbial growth:        Necessary for the synthesis of amino acids     

Concentration in plants:                               Wheat  1.7 - 3.0%

                                                                                    Grain  2.0%

                                                                                    Forage 3.0 %


                                                                             Corn  2.7 - 3.5%

                                                                             Soybeans  4.2 - 5.5%

                                                                             Grain sorghum 3.3 - 4.0%

                                                                             Peanuts 3.5 - 4.5%

                                                                             Alfalfa 4.5 - 5.0%

                                                                             Bermudagrass 2.5 - 3.0%          

Effect of pH on availability:

            Precipitated forms (low pH):                      none

            Precipitated forms (high pH):                    none

     at pH>8, no nitrification;  at pH>7, NO2- accumulates   

Interactions with other nutrients:               Si: enhances leaf erectness, thus neutralizing the negative effects of high nitrogen supply on light interception (leaf erectness usually decreases with increasing nitrogen supply); P: symbiotic legume fixation needs adequate P or a N deficiency can result; Mo: component of nitrogenase therefore could have Mo induced N deficiency in N2 fixing legumes (especially under acid soils conditions); Fe: necessary for nitrogenase and ferredoxin (electron carrier), legume hemoglobin, deficiency reduces nodule mass, and nitrogenase;           

Fertilizer sources:                                          ammonium sulfate, anhydrous ammonia, ammonium chloride, ammonium nitrate, ammonium nitrate-sulfate, ammonium nitrate with lime, ammoniated ordinary superphosphate, monoammonium phosphate, diammonium phosphate, ammonium phosphate-sulfate, ammonium polyphosphate solution, ammonium thiophosphate solution, calcium nitrate, potassium nitrate, sodium nitrate, urea, urea-sulfate, urea-ammonium nitrate, urea-ammonium phosphate, urea phosphate.       


Burford, J.R., and J.M. Bremner.  1975.  Relationships between the denitrification capacities of soils and total, water-soluble and readily decomposable soil organic matter.  Soil Biochem. 7:389-394.

Marschner, Horst.  1995.  Mineral Nutrition in Higher Plants.  Academic Press, London.

Tisdale, S.L., W.L. Nelson, J.D. Beaton, and J.L. Havlin.  1993.  Soil Fertility and Fertilizers.  MacMillan Publishing Co., New York, N.Y.

Authors: Heather Lees, Shannon Taylor, Joanne LaRuffa and Wade Thomason



Form taken up by plant:                               H2PO4-, HPO4=

Mobility in soil:                                                None; roots must come in direct contact with orthophosphate P

Mobility in plant:                                             Yes

Deficiency symptoms:                                  Lower leaves with purple leaf margins

            Deficiency pH range:                                 <5.5 and >7.0

Toxicity symptoms:                                       None

            Toxicity pH range:                                       Non toxic (optimum availability pH 6.0-6.5)

Role of nutrients in plant growth:              Important component of   phospholipids and nucleic acids (DNA and RNA)

Role of nutrient for microbial growth:       Accumulation and release of       energy during cellular metabolism

Concentration in plants:                               1,000 – 5,000 ppm (0.1 –0.5%)

Effect of pH on availability:                          H2PO4 at pH < 7.2

                                                                             HPO4 2- at pH > 7.2

Interactions with other nutrients:               P x N, P x Zn at high pH, in anion exchange P displaces S, K by mass action displaces Al inducing P deficiency (pH<6.0)

Phosphorus fertilizer sources:                   Rock phosphate, phosphoric acid, Ca orthophosphates, ammoniumphosphates, ammonium poly-phosphates, nitric phosphates, K phosphates, microbial fertilizers (phosphobacterins) increase P uptake

Additional categories:

Mineralization/immobilization:                    C:P ratio of < 200: net mineralization of organic P; C:P ratio of 200-300: no gain/loss of inorganic P; C:P ratio of >300: net immobilization of inorganic P

P fixation:                                                         Formation of insoluble Ca, Al, and Fe phosphates

                                                                             Al(OH)3 + H2PO4- -à Al(OH)2HPO4

                                                                             (Soluble)                           (Insoluble)

Organic P sources:                                        Inositol phosphate (Esters of orthophosphoric acid), phospholipids, nucleic acids, phosphate sugars

Inorganic P sources:                                     Apatite and Ca phosphate (unweathered soils) and Fe and Al sinks from P fixation (weathered soils)

Waste:                                                               Poultry litter (3.0 to 5.0%), steel slag (3.5%), electric coal ash (<1.0%)

Total P levels in soil:                                      50 – 1500 mg/kg

Solution concentration range:                    < 0.01 to 1.0 ppm

Applied fertilizer:                                            < 30% recovered in plants, more P must be added than removed by crops


Alexander, M., 1977.  Introduction to Soil Microbiology. 2nd Edition. John Wiley and Sons, NY.

Brady, N.C., 1990.  The Nature and Properties of Soils.  10th Edition. Macmillan Publishing Co.,


Brigham Young University. 1997.  The Phosphorus Cycle.

Harrison, A.F., 1987.  Soil Organic Phosphorus. A Review of World Literature. C.A.B. p.39.

Pierre, W.H., 1948.  The Phosphorus Cycle and Soil Fertility.  J. Amer. Soc. of Agron., 40:1-14.

Pierzynski, G.M., Sims, J.T., and Vance, G.F., 1994.  Soil and Environmental Quality. Lewis

   Publishers, FL.

Stewart, J.W.B., and Sharpley, A.N., 1987.  Controls on Dynamics of Soil and Fertilizer

   Phosphorus and Sulfur in Soil Fertility and Organic Matter as Critical

   Components of Production Systems, SSSA Spec. Pub. No.19, 101-121.

Tiessen, H., 1995.  Phosphorus in the Global Environment – Transfers, Cycles and Management.

   John Wiley and Sons, NY.

Tisdale, S.L., Nelson, W.L., Beaton, J.D. and Havlin, J.L., 1993.  Soil Fertility and Fertilizers.

   Macmillan Publishing Co., NY.

Authors:  Clyde Alsup and Michelle Armstrong, 1998, Asrat Shiferaw 1994, Jerry Speir, 1996



Form taken up by the plant:




Mobility in the soil:



Mobility in the plant:



Deficiency symptoms:

Since K is mobile in the plant, visual deficiency symptoms usually appear first in the lower leaves, and progress to the top as the severity of the deficiency increases. Necrotic lesions on broadleaf plants, chlorotic and necrotic leaf margins on grasses, straw lodging in small grains, and stalk breakage in corn.


Role of nutrient in plant growth:

Enzyme activation, carbohydrate transportation, amino acid synthesis, starch synthesis, water relations, stomatal opening and closing, transpiration, photosynthesis, mass flow in absorpton, energy relations, ATP synthesis, translocation of assimilates, nitrogen uptake, protein synthesis, grain formation, tuber development, nutrient balancing, chlorophyll, disease and insect resistance, strengthening of roots and stems.


Role of nutrient in microbial growth:

Fulfillment of biological requirements similar to other organisms.



Enzyme activation is regarded as the most important function of potassium.  Over 80 plant enzymes require K for activation.


Concentration in plants:

5,000 to 60,000 mg/g (0.5 – 6.0%)


Distribution in the soil:




Soil solution:


5,000 – 25,000  mg/g

50 – 750  mg/g

40 – 600  mg/g

1 – 10  mg/g

Effect of pH on availability:

In very acid soils, toxic amounts of exchangeable Al3+ and Mn2+ create an unfavorable root environment for uptake of K+.  The use of lime on acid soils low in exchangeable K+ can induce a K+ deficiency through ion competition.


Interactions with other nutrients:

K+ enhances NH4+, NO3- and Cu2+ uptake, K+ decreases Ca2+ and Mg2+ in plant tissue, Ca2+ and Mg2+ decreases K+ in plant tissue, K+ reduces B uptake,  K+ reduces Fe2+ toxicity, K+ enhances Mn2+ uptake when Mn is deficient and decreases uptake when Mn is present in toxic amounts, Na+ is capable of substituting for K+.  K+ reduces Mo uptake, high NH4+ with inadequate K+ may cause toxicity symptoms.


Fertilizer sources:

Potassium Chloride (KCl); Potassium Sulfate (K2SO4); Potassium Magnesium Sulfate (K2SO4, MgSO4); Potassium Nitrate (KNO3); Potassium Phosphates (KPO3, K4P2O7, KH2PO4, K2HPO4); Potassium Carbonate (K2CO3), Potassium Bicarbonate (KHCO3), Potassium Hydroxide (KOH); Potassium Thiosulfate (K2S2O3), Potassium Polysulfide (KSx).


Alexander, M.A. 1977. Introduction to Soil Microbiology. 2nd Edition. John Wiley & Sons, Inc. New York, NY pp. 382-385.

Dibb, D.W. and W.R. Thompson, Jr. 1985. Interaction of potassium with other nutrients. pp. 515-533 in R.D. Munson (ed.) Potassium in agriculture. Am. Soc. Agron.- Crop Sci. Soc. Am.- Soil Sci. Soc. Am. Madison, WI.

Kramer, P.J. and J.S. Boyer. 1995. Water relations of plants and soils, 2nd Edition. Academic Press, Inc., San Diego, CA. pp. 263-264.

Raven, P.H., R.F. Everet, and S.E. Eiichhorn. 1986. Biology of Plants, 4th Edition. Worth Publishing, Inc., New York, NY. p. 519.

Salisbury, F.B. and C.W. Ross. 1985. Plant physiology, 3rd Edition. Wadsworth Publishing Co., Belmont, CA. p. 108.

Tisdale, S.L., W.L. Nelson, and J.D. Beaton. 1985. Soil fertility and fertilizers, 4th Edition. Macmillan Publishing Co., New York, NY pp. 249-291.

Tisdale, S.L., W.L. Nelson, J.D. Beaton, and J.L. Havlin. 1993. Soil fertility and fertilizers, 5th Edition. Macmillan Publishing Co., New York, NY pp. 230-263.

Authors: Dallas Geis 1994, Michael Goedeken 1996, Todd Heap and Matt Barnes 1998



Forms taken up by plants:                           Fe+2 (Ferrous), while Fe+3 (Ferric) is reduced to Fe+2 at the root surface before it is absorbed

Mobility in soil                                                  No

Mobility in plant                                               No

Deficiency symptom in plant                       Interveinal chlorosis

Role in Plant nutrition                                    Iron is a component of cells, proteins, and enzymes.  It is involved in nitrogen fixation, respiration and photosynthesis.

Typical concentration in plant tissue        20-300 ppm

Fe Soil Test                                                      Chelation with EDDHA (ethylenediamineedi-o-hydroxyphenylacetic acid)

Fe is 100% complexed with EDDHA over a broad range of soil pH.

Fertilizer sources                                            Foliar application of FeEDDHA or FeSO4.7H2O

Oxidation/Reduction                                      Oxidation Fe+2 + 1/4O2 + H+ àFe+3 + ½ H2O

                                                                             Reduction  Fe+3 + e- à Fe+2

Fe+3 Forms of Iron                                           Fe(OH)3 amorphous

                                                                 Fe(OH)3 (soil)

                                                                             Hematite Fe2O3    Goethite FeOOH

                                                                             Soil Fe(OH)3 is usually the most soluble form of iron in soils and, therefore, typically controls the solubility of iron in aerobic soils.

Fe+2 Forms of Iron                                          A common iron mineral in nature is pyrite (FeS2).  Pyrite is often associated with bituminous coal and other ores.  Bacterial oxidation of pyrite generates acid and is the cause of acid mine drainage.

FeS2 + 31/2O2 +  H2O à  Fe+2 + 2SO4-2 + 2H+ .  Fe+2 hydrolyzes to form hydrolysis products common under reduced conditions.  FeOH+ predominates in solution at pH< 6.75, while Fe(OH)20 prdeominates at pH >9.3.  Magnetite (Fe304) is a stable mineral under reduced conditions

Microbial use of iron                                      Many organisms use Fe+3 as an electron acceptor such as some fungi and and chemoorganotrophic or chemolithtropic bacteria.  This bacterial reduction of ferric to ferrous is a major way iron is solubilized.    Reduction takes place under anaerobic conditions (waterlogged).   Shewenella putrefaciens is one organism capable of reducing iron.  Oxidation occurs under aerobic conditions.  At neutral pH, organisms such as Gallionella ferruginea or Leptothrix oxidize iron.  Under acidic conditions, Thiobacillus ferrooxidans is the primary organism responsible for iron oxidation.  This organism is typical in acid mine drainage areas.


Brock, T. D.; M. T. Madigan; J. M. Martinko; J. Parker. (1994).  Biology of Microorganisms.  Prentice Hall Englewood Cliffs, NJ.

Lindsay, W. L. (1979).  Chemical Equilibria in Soils.  John Wiley & Sons, NY.

Raun, W. R.; G. V. Johnson; R. L. Westerman.  (1998).  Soil-Plant Nutrient Cycling and Environmental Qualtiy.  Plant & Soil Sciences 5813 class notes.

Tisdale, S. L.; W. L. Nelson; J. D. Beaton; J. L. Havlin. (1985).  Soil Fertility and Fertilizers 5th edition.  MacMillan Publishing Co. NY.

Walsh, L. M.; J. D. Beaton. (1973).  Soil Testing and Plant Analysis.  Soil Science Society of America, Inc.  Madison, WI.

Authors: Fred Kanampiu 1994, Jing Chen, Jason Yoder 1996 and Libby Dayton 1998




Form taken up by plants:                             SO42-, SO2- (low levels adsorbed through leaves)       

Mobility in plant:                                             Yes

Mobility in soil:                                                Yes

Deficiency symptoms:                                  Leaves chlorotic (upper leaves), reduced plant growth, weak stems                                                

Role of nutrient in plant

and microbial growth                                    Synthesis of the S-containing amino acids cystein, cystine, and methionine; Synthesis of other metabolites, including CoA, biotin, thiamine, and glutathione; Main function in proteins is the formation of disulfide bonds between polypeptide chains; Component of other S-containing substances, including S-adenosylmethionine, formylmethionine, lipoic acid, and sulfolipid; About 2% of the organic reduced sulfur is in the plant is present in the water soluble thiol (-SH) fraction; Vital part of ferredoxin; Responsible for the characteristic taste and smell of plants in the mustard and onion families; Enhances oil formation in flax and soybeans; Sulfate can be utilized without reduction and incorporated into essential organic structures; Reduced sulfur can be reoxidized in plants           

Enzymes needing sulfur:                             Coenzyme A, ferredoxin, biotin, thiamine pyrophosphates, urease and sulfotransferases     

Concentration in plants:                               0.1 and 0.5% of the dry weight of plants           

Effect of pH on availability:                          pH<6.5, AEC increases with decreasing pH   

Interaction with other nutrients:                 Associated with salts and exchangeable cations, can be replaced by phosphorus on exchange sites     

Fertilizer sources:                                          Organic matter, ammonium bisulfite, ammonium nitrate-sulfate, ammonium phosphate-sulfate, ammonium polysulfide, ammonium sulfate, ammonium thiosulfate, ferrous sulfate, gypsum, magnesium sulfate, potassium sulfate, pyrites, potassium-magnesium sulfate, potassium thiosulfate, potassium polysulfide, sulfuric acid (100%), sulfur, sulfur dioxide, single superphoshate, triple superphosphate, urea-sulfur, urea-sulfuric acid and zinc sulfate        


Hartmann, H.T., Kofranek, A.M., Rubatzky, V.E., Flocker, W.J. (1988). Plant Science. 2nd ed. Prentice Hall. Englewood Cliffs, N.J.

Marschner, H. (1995). Mineral Nutrition of Higher Plants. 2nd ed. Institute of Plant Nutrition Univ. Hohenheim. Academic Press. San Diego, Ca.

Tisdale, S.L., Nelson, W.L., Beaton, J.D., and Havlin, J.L. (1993). Soil Fertility and Fertilizers. 5th ed. Macmillan Pub. Co. New York, NY.

Vaughan, D., Malcolm, R.E. (1985). Soil Organic Matter and Biological Activity. Martinus Nijhoff/Dr W. Junk Publishers, Dordrecht.

Authors: Xin Li, Dale Keahey and Jeremy Dennis


Form taken up by the plant:                        CO2

Mobility in soil:                                                CO2 mobile in soil pore space.

                                                                             HCO3- mobile in soil solution.                 

Mobility in plant:                                             --

Deficiency symptoms:                                  --

Toxicity symptoms:                                       --

Role in plant growth:                                     Basic energy source and building block for plant tissues.  Converted through photosynthesis into simple sugars.  Used by plants in building starches, carbohydrates, cellulose, lignin, and protein. CO2 given off by plant respiration.

Role in microbial growth:                             Main food of microbial population.  Utilization by microbes is closely related to C:N ratio.

Concentration in plants:                               --

Effect of pH on availability:                          None

Interactions with other nutrients:               10:1 C:N ratio needed for stable soil organic matter.  High C:N ratios lead to nitrogen immobilization.  Low C:N ratios lead to nitrogen mineralization.  N rates in excess of those required for maximum yield can lead to increased soil organic carbon.

Fertilizer sources:                                          Crop residues, green manures and animal wastes can be significant sources of soil organic carbon.                       


Detwiler, R.P., and C.A.S. Hall. 1988. Tropical Forests and the global carbon cycle. Science. 239:42-47.

Dixon, R.K., S. Brown, R.A. Houghton, A.M. Solomon, M.C. Trexler, and J. Wisniewski. Carbon pools and flux of global forest ecosystems. Science. 263:185 190.

Gillis, A.M. 1991. Why can’t we balance the globe’s carbon budget?. Bioscience. 41:442-447.

Schlesinger, W.H. 1998. “Chapter 2:  An overview of the carbon cycle”. Soil processes and the carbon cycle. Boca Raton, Fla: CRC Press, c1998.

Wallace, A., G.A. Wallace, and J.W. Cha. 1990. Soil organic matter and the global carbon cycle. Journal of Plant Nutrition. 13:459-466

Author: Tyson Ochsner


Form taken up by plants:                             Ca+2

Mobility in soil:                                                No, slight mobility in soil solution

Mobility in plant:                                             Movement occurs in xylem to the leaves (one way ticket)

Role of nutrient in plant growth:                Required for cell wall rigidity, cell division of meristems and root tips, normal mitosis, membrane function, acts as a secondary messenger, aids in storage of phosphates in vacuoles, actively involved in photosynthesis and found in the endoplasmic reticulum

Role in microbial growth:                             Needed for Rhizobium and Azotobacter

Concentration in plants:                               Fresh weight of plants typically contains 0.1-5.0%, can contain up to 10% dry weight in leaves before plant experiences toxicity

Content present in soils:                              Tropical soils: 0.1-0.3%

                                                                             Temperate soils:  0.7-1.5%

                                                                             Calcareous soils:  >3.0%

                                                                             Largely dependent on parent material of soil and rainfall              

Deficiency symptoms:                                  First seen in the younger leaves of plants, loss in plant structure, under extreme deficiencies gel-like conditions, root development no longer takes place, stunted plant growth

Effect of pH on availability:                          Depends on mineral

Interactions with other nutrients:               Since Ca+2 is so directly related to pH in solution, it effects all of the other nutrients.  When NO3-N is applied to soil, Ca+2 absorption increases in the plant.   Increases in Ca+2 in soil decreases Al+3 in acid soils, as well as decreasing Na+ in sodic soils.  Increases in Ca+2 taken up by plants cause deficiencies of Mg+2 and K+.  MoO4-2 and H2PO4- availability increases with increases in Ca+2 concentrations.

Sources of Calcium:                                      Lime (CaO) (Ca(OH)2), Calcite (CaCO3), Dolomite (CaMg(CO3)2, Gypsum (CaSO4.2H2O), any Phosphorus fertilizer, Anorthite (CaAl2Si2O3), biotite, apatite, augite & hornblende.


Amjad, Z. (ed.) 1998. Calcium Phosphates in Biological and Industrial Systems.  Klower

      Academic Press.  Boston, MA.

Lindsay, W.L. 1979.  Chemical Equilibria in Soils.  John Wiley & Sons. New York, NY. 

      pp. 86-102.

Marschner, H. 1995.  Mineral Nutrition of Higher Plants.  Academic Press.  New York,

 NY. pp. 285-298.

Tisdale, S.L., Nelson, W.L., Beaton, J.D. and Havlin, J.L. 1993.  Soil Fertility and

Fertilizers.  Macmillan Publishing Company.  pp. 289-296.

Authors: James Johnson, Derrel White, Lori Gallimore and Micah DeLeon


Form taken up by plant:                               Mg++

Mobility in Soil:                                                yes/no

Mobility in Plant:                                             yes as Mg++ or Mg Citrate

Deficiency Symptoms:                                  Interveinal chlorosis, necrosis, general withered appearance, leaves are stiff and brittle and intercostal veins are twisted.

Deficiencies:                                                    pH 5.0 is best for Mg availability.  A higher or lower pH depresses Mg uptake.  High K and Ca levels also interfere with uptake.

Where deficiencies occur:                           Highly leached humus acid soils or on sandy soils which have been limed heavily (due to Ca2+ competition).  sometimes on soils high in K; Mg deficiencies are indicated by soil test index values less than 100 lbs/A.

Toxicity Symptoms:                                       none

Toxicities:                                                         Grass Tetany when K/(Ca+Mg)> 2.2

Role of Mg in Plant Growth:                         Responsible for electron transfer in photosynthesis; Central element of chlorophyll molecule (6-25% of total plant Mg); Required for starch degradation in the chloroplast;  Involved in regulating cellular pH; Required for protein synthesis; Required to form RNA in the nucleus; Mg-pectate in the middle lamella

Role of Nutrient in Microbial Growth:        Important for phosphorus metabolism; Helps to regulate the colloidal condition of the cytoplasm.

Concentration in plants:                               0.15% - 0.35%  (1500-3500 ppm)

Effect of pH on Availability:                         Highest Mg availability at pH 5.0.

Precipitated forms at low pH:                      MgCl2 , MgSO4 , Mg(NO3)2

Precipitated forms at high pH:                    MgO, MgCO3, Mg(OH)2, MgCa(CO3)2

Interactions with other nutrients:               Uptake of K+, NH4+, Ca 2+ , Mn2+ by plant limits Mg2+ uptake; H+ (low pH) can limit Mg2+ uptake;  Mg salts increase phosphorus adsorption

Fertilizer Sources:                                          Dolomite (MgCa(CO3)2) (most common); Magnesium sulfate (MgSO4 x H2O) (Kieserite); Magnesium oxide (Mg(OH)2) (Brucite); Magnesite (MgCO3); Magnesia (MgO); Kainite (MgSO4 x KCl x 3H2O); Langbeinite (2MgSO4K2SO4); Epsom Salts (MgSO4 x 7H2O)

Additional categories:                                                                 

Location in Plants:                                         In corn, 34% of total Mg is in grain                     

Radioactive Isotopes:                                   23Mg           t 1/2 = 11.6 sec

                                                                             27Mg           t 1/2 = 9.6 min

                                                                             28Mg           t 1/2 = 21.3 hr

Enzymes that require Mg++:                       Magnesium is a co-factor for many enzymes.  This includes enzymes involved in glycolysis, carbohydrate transformations related to glycolysis, Krebs cycle, the monophosphate shunt, lipid metabolism, nitrogen metabolism, “phosphate pool” reactions, photosynthesis, and other miscellaneous reactions.

Examples:                                                        ATPase (phosphorylation), phosphokinases; RuBP carboxylase (photosynthesis); Fructose 1,6-phosphatase (starch synthesis in chloroplasts);  Glutamate synthase (ammonia assimilation in the  chloroplasts); Glutathione synthase; PEP carboxylase

Ionic Radius:                                                   0.78 Angstroms

Hydration Energy:                                          1908 J mol-1


Ball, Jeffrey. 1994. Magnesium Cycle. As presented to SOIL 5813.

Jacob, A. 1958. Magnesium - the fifth major plant nutrient. Staples Press Limited, London.

Johnson, G.V., W.R. Raun, and E.R. Allen. 1995. Oklahoma Soil Fertility Handbook. 3rd ed. Okla. Plant Food Educational Society and Okla. State Univ. Dept. of Agronomy, Stillwater, OK.

Lauchli, A. and R.L. Bieleski (editors). 1983. Inorganic Plant Nutrition. Springer-Verlag, Berlin.

Marschner, H. 1986. Mineral Nutrition of Higher Plants. 2nd ed. Academic Press, London.

Mengel, K. and E.A. Kirkby. 1978. Principles of Plant Nutrition. International Potash Institute, Bern.

West Virginia Univ. 1959. Magnesium and agriculture symposium. Morgantown, WV.

Authors: Jeffrey Ball, Mark Everett and Rick Kochenower



Form taken up by plant:                               H3BO30

Mobility in soil:                                                Yes

Mobility in plant:                                             No

Deficiency symptoms:                                  Boron deficient plants exhibit a wide range of deficiency symptoms, but the most common symptoms include necrosis of the young leaves and terminal buds.  Structures such as fruit, fleshy roots and tubers may exhibit necrosis or abnormalities related to the breakdown of internal tissues

Interactions with O.M.:                                  Boron is complexed by O.M. and can be a major source of B to plants.  Mineralization  of O.M. releases boron to soil solution.  The mineral source of boron in soils is Tourmaline, which is a very insoluble borosilicate mineral.

Effect of pH on availability:                          Boron availability decreases with increasing pH. Overliming acid soils can cause boron deficiency because of interaction with calcium.                                                                                                  

Role of Soil  characteristics                         Boron is generally less available on sandy soils in humid regions, because of more leaching.  This is especially true in acid soils with low O.M.  Boron availability increases with increasing O.M.   Most alkaline and calcareous soils contain sufficient Boron because the primary  boron minerals have not been highly weathered  and, more important, B products of weathering (H3BO3) have not been leached out as in humid region soils.                                                                                    

Role of Boron in plants:                               Cell growth and formation. The action  appears to be in binding sugars together. Indirect evidence also suggests involvement in carbohydrate transport.      

Concentrations in Soil:                                 Total Boron in soils is small (20-200 ppm)                                                                                                

Deficiency levels in plants:                          Monocots: 5-10 mg/kg

                                                                             Dicots: 50-70 mg/kg                                                                                                

Toxic levels in plants:                                   Corn: 100 mg/kg

                                                                             Cucumber: 400 mg/kg                                                                                               

Toxic levels in soil & water:                         Boron can be toxic on some alkaline soils when  soil test or extractable boron exceeds 5 ppm.  Irrigation water that contains > 1ppm boron can also produce toxicity.

Boron availability index:                               Soil test is “hot water soluble” B

                                                                                    <0.3 ppm boron

                                                                                    0.3-0.5 ppm boron

                                                                                    > 0.5 ppm boron

                                                                                    >5.0 ppm boron

Boron fertilizers:                                             Borax: (Na4B4O7 10H2O) 10-11% B

                                                                             Boric acid (H3BO3) 17 % B

                                                                             Colemanite (Ca2B6O11 5H2O) 10 % B

                                                                             Sodium pentaborate (Na2B10O1610H2O) 18%B

                                                                             Sodium tetraborate (Na2B4O7 5H2O) 14 % B

                                                                             Use low rates, generally  < 3 lbs/acre.  Do not reapply without soil testing.

Other  Sources of B:                                      Animal wastes: 0.01 to 0.09 lb/ton of  waste @ 72-85% moisture.


Mortvedt, J.J.  1972. Micronutrients in Agriculture.  Soil Science Society of Americia, Madison, Wisconsin.

Philipson, Tore. 1953. Boron in Plant and Soil with special regard to Swedish Agriculture.  Acta Agriculturae Scandinavica. III:2.

Raun, W.R., G.V. Johnson, and S.L. Taylor. 1996.  Soil-Plant Relationships, Oklahoma State University  Agronomy 5813 class notes.

Taiz, Lincoln and Eduardo Zeiger. 1991. Plant Physiology.

Tisdale S.L., W.L. Nelson, J.D. Beaton, and J.L. Havlin. 1993. Soil Fertility and Fertilizers.  5th ed. MacMillan Publishing Co. New York, NY.

Authors: Andrew Bennett and Jason Kelley


Form taken up by the plant:                        Absorbed by plants as Mn2+ from the soil, or Mn2+ from foliar sprays of MnSO4, or foliar chelates as MnEDTA.

Mobility in soil:                                                Relatively immobile; concentration in soils generally ranges from 20 to 3000 ppm and averages 600 ppm; total soil Mn is an inadequate predictor of Mn availability; Mn is highest in the surface horizon, minimal in the B horizon, and generally increases in the C horizon; Mn2+ can leach from soils over geological time, particularly acid spodizols.                                                                                               

Mobility in plant:                                             Relatively immobile; Mn moves freely with the transpiration stream in the xylem sap in which its concentration and ionic form may vary widely; Mn accumulated in leaves cannot be remobilized while that in roots and stems can.                                                                                             

Deficiency symptoms:                                  Interveinal chlorosis (yellowish to olive-green) with dark-green veins first showing up in the younger leaves; patterns of chlorosis can be easily confused with Fe, Mg, or N deficiencies; under severe deficiencies, leaves develop brown speckling and bronzing in addition to interveinal chlorosis, with abscission of developing leaves; characterizations—gray speck of oats, marsh spot of peas, speckled yellows of sugar beets, stem streak necrosis in potato, streak disease in sugar cane, mouse ear in pecan, and internal bark necrosis in apple; most common micronutrient deficiency in soybeans; deficiencies are common in cereal grains, beans, corn, potatoes, sugar beets, soybean and many vegetables; some crops are more sensitive to deficiencies; may cause susceptibility to root rot diseases such as “take-all” in wheat.

deficiency at pH (.7.0)                                    Mn tends to become limiting at a high pH.

Toxicity symptoms:                                       Sometimes observed on highly acidic soils; crinkle leaf of cotton.

Toxic at pH (< 5.5)                                           Toxicity occurs in low pH soils (<5.5).

Role of Mn in plant growth:                         Water splitting role in photosynthesis resulting in evolution of O2; redox reactions; decarboxylation and hydrolysis reactions; dehydrogenase and transferase reactions; can substitute for Mg2+ in many phosphorylating & group-transfer reactions; influences auxin in plants; activates many enzymes involved in the metabolisms of organic acids, phosphorus, and nitrogen (in dispute); activator in enzymes involved in carboxylic acid cycle and carbohydrate metabolism, but frequently replaced by Mg.

Enzymes                                                           Mn-containing protein in photosystem II involved in H2O splitting; Mn-containing superoxide dismutases catalyze the dismutation of the toxic superoxide; often implicated as affecting purple acid phosphatases which catalyze the hydrolysis of phosphoric acid monoesters and anhydrides, but more recent evidence suggest a dominant role by Fe; affects indole acetic acid oxidase; C4 plants—requirement for NAD-malic and phosphoenolpyruvate (PEP) carboxykinase (two of three alternate forms of decarboxylating enzymes); C4 plants—NADP-malic enzyme (third type of decarboxylating enzyme) requires either Mn2+ or Mg2+ ; C4 plants—phosphoenolpyruvate (PEP) carboxylase requires either Mn2+ or Mg2+; earlier evidence of a role in nitrate and nitrite reductase activity has been disputed; excess causes depression of net photosynthesis by inhibiting the RuBP carboxylase reaction; excess Mn2+ is sequestered in the vacuole to prevent saturation of ATPs which require Mg for normal functioning.

Role of Mn for microbial growth:                Used by many microbes in biological oxidation; Bacteria—Arthrobacter, Bacillus; Fungi—Cladisporium, Curvularia.

Concentration in plants:                               Typically ranges from 20 to 500 ppm ; concentrations <20 ppm generally cause deficiencies, and >500 ppm cause toxicities, but vary with crop, culture, and tissue.

Effect of pH on availability:                          Mn decreases 100-fold for each unit increase in pH; concentration of Mn2+ in solution is increased under acid, low-redox conditions; high pH also promotes the formation of less available organic complexes; activity of soil microorganisms that oxidize soluble Mn to unavailable forms reaches a maximum near pH 7.0; liming and burning can produce alkaline conditions causing deficiency; high pH favors oxidation to Mn+4, from which insoluble oxides are formed (MnO2, Mn2O3, and Mn3O4); pH < 6.0 favors reduction of Mn and formation of more available divalent form Mn+2

precipitated forms (low pH)                         Typically precipitated as Mn and Fe oxides, often as concretions.

precipitated forms (high pH)                        Complexation occurs with organic matter at high pH; precipitated as Mn carbonates and MnOH.

Other factors:                                                  Poor aeration increases Mn availability; soil waterlogging will reduce O2 and lower redox potential, which increases soluble Mn2+; dry soils allow rapid oxidation and deficiency may result; local accumulation of CO2 around roots increases Mn availability; high organic matter (particularly if basic soil) forms unavailable chelated Mn2+  compounds, particularly in peat and muck soils; pronounced seasonal variations, with wet weather increasing Mn2+  and warm, dry weather encouraging the formation of less available oxidized forms; some deficiencies are caused by soil organisms oxidizing Mn2+  to Mn3+ ; Mn- efficient and Mn-inefficient plants

Interactions with other nutrients:               High levels of Cu, Fe or Zn can reduce Mn uptake; high levels of Mn can reduce Fe concentrations and induce Fe deficiencies and vice versa; ratio of Fe to Mn should be between 1.5 to 2.5; Mn and Al toxicities frequently occur together on acid soils

Fertilizer sources:                                          Manganese sulfate (MnSO4*4H2O, 26-28%)—most common; Manganese oxide (MnO, 41-68%); Manganese chloride (MnCl2, 17%); Organic complexes (5-9%); Synthetic chelates (MnEDTA, 5-12%)



Adriano, D.C. 1986.  Trace elements in the terrestrial environment.  Springer-Verlag. New York, NY.

Boyles, F.W. Jr, and W.L. Lindsay.  1986.  Manganese phosphate equilibrium relationships in soils. Soil Sci. Soc. Am. J.  50: 588-593.

Davis, J.G.  1996.  Soil pH and magnesium effects on manganese toxicity in peanuts.  Journal of Plant Nutrition.  19:535-550.

Graham, R. D., R.J. Hannam, and N.C. Uren.  1988.  Manganese in soils and plants.  Kluwer Academic Pub. Dordrecht, Netherlands.

Marschner, H.  1995.  Mineral nutrition of higher plants.  Academic Press.  2nd Ed. London, New England.

Stevenson, F.J.  1986.  Cycles of soil:  carbon, nitrogen, phosphorus, sulfur, micronutrients.  John Wiley & Sons.  New York, NY.

Tisdale, S.L., W.L. Nelson, J.D. Beaton, J.L. Havlin.  1993.  Soil fertility and fertilizers. MacMillan Publishing Co.  5th Ed.  New York, NY.

Authors:  John Koemel, Robert Zupancic and Johnny Roberts


Plant available forms:                                    Co2+, Co3+, Co(OH)3-, organic chelates of Co [6]; plant uptake increases as pH decreases. [2]             

Role in plant nutrition:                                  Micronutrient, required for symbiotic nitrogen fixation by Rhizhobium bacteria in root nodules.  No conclusive evidence of requirement by higher plants. [1] [2] [8] [9]

Plant Mobility:                                                  Intermediate mobility. [2]

Plant Deficiency symptoms:                       Necrosis of leguminous plants with deficient soil nitrogen and cobalt. [8]  

Role in animal nutrition:                               Vitamin B12 nutrition. [2]

Enzymes:                                                         Cyanocobalamin (Vitamin B12), essential metal for humans and mammals. [4]

Mammalian toxicity:                                       Critical organs include skin, heart, and respiratory tract.  Reported toxicity occurred in miners that worked in cobalt rich ore, developed dermatitis, cardiomyopathy, and hard metal lung disease. [4]          

Mobility in soil:                                                Low mobility of inorganic Co, High mobility of organic chelates of Co. [6]

Common soil types with deficiencies:      Acidic and highly leached sandy soils, calcareous soils, and peat soils. [2] [9]

Interactions with other nutrients:               Co2+ ion is strongly adsorbed on Mn nodules and goethite, and adsorption increases with pH. [6] [7]  High adsorption by Fe and Mn oxides. [2] [6]


            Earth’s crust:                                       25 mg kg-1 [5], 40 mg kg-1 [3]

            Soil:                                                        1-50 mg kg-1 [7], 1-40 mg kg-1 [3], 0.1-70 mg kg-1        [6]

            Plants:                                                   0.05-0.5 mg kg-1 [3]  0.02-0.5 mg kg-1 [9]

Fertilizer sources:                                          Foliar feeding of Co solution [6], CoSO4  and cobaltized superphosphate (trace amounts of CoSO4). [9

Geologic Sources:                                         Associated with mafic and ultramafic deposits.  Primary Co minerals are cobaltite (CoZnS-FeAsS) and skutterudite (CoAs3-NiAs3).  Primary minerals with trace levels of Co include:  olivine, hornblende, augite biotite, ilmenite, and magnetite. [2]

Industrial uses:                                               Metal alloys, used for hard metal alloys due to high melting point, strength, and resistance to oxidation. Formerly added to beer (cobalt chloride) to improve the quality of beer froth. [4]  Used in paints, enamels, and inks as a pigment, and as a catalyst in the petroleum industry. [1]



Adriano, D.C.  1986.  Trace elements in the terrestrial environment, Springer-Verlag, New York.

Alloway, B.J.  1990.  Heavy metals in soils, Blackie Press, Glasgow. 

Bohn, H.L., B.L. McNeal, and G.A. O’Connor.  1985.  Soil Chemistry, 2nd Ed., John Wiley, New York.

Gerhardsson, Lars, and Staffan Skerfving.  1996.  Concepts on biological markers and biomonitoring for metal toxicity.  In Toxicology of metals, L.W. Chang, L. Magos, and S. Tsuguyoshi, Eds., CRC Press, Boca Raton, FL.

Huheey, J.E.  1983.  Inorganic chemistry: Principles of structure and reactivity, 3rd Ed. Harper Collins Publishers, New York. 

Kabata-Pendias, A., and H. Pendias.  1992.  Trace elements in soils and plants, 2nd Ed., CRC Press, Boca Raton, FL. 

Khattak, R.A. and A.L. Page.  1992.  Mechanism of manganese Adsorption on soil constitiuents.  In Biogeochemistry of trace metals, D.C. Adriano, Ed., Lewis Publishers, Boca Raton, FL.

Saliisbury, F.B., and C.W. Ross.  1992.  Plant Phisiology, 4th Ed., Wadsworth, Belmont, CA.  

Tisdale, S.L., W.L. Nelson, J.D. Beaton. 1985.  Soil Fertility and Fertilizers, 4th Ed., MacMillan Publishsers, New York.

Author: Steve McGowen


Form taken up by the plant:                        Cl-

Mobility in the soil:                                         Mobile                   

Mobility in the plant:                                      Mobile                   

Deficiency Symptoms:                                  pH unknown. Reduced growth, wilting, development of necrotic and chlorotic spots on leaves, with leaves eventually attaining a bronze color.  Roots become stunted in length but thickened or club shaped near the tips.  Acts as a counter ion during rapid K+ fluxes, contributes to turgor of leaves.  Deficiency occurs in soils, <2ppm.

Toxicity Symptoms:                                       pH unknown.  Can reduce yield and quality of crops.  High levels will increase total leaf water potential and cell sap osmotic potential in wheat.  Improves moisture relations in some crops.  Leaves of tobacco and potatoes become thickened and tend to roll when excessive Cl concentrations occur.  Storage quality of potato tubers are adversely affected by surplus uptake of Cl.        

Role of Nutrient in Plant Growth:               Stimulates splitting of water in photosynthesis, essential for roots, cell division in leaves and as an osmotically active solute.  Winter Wheat: Suppresses take-all, stripe rust, tan spot.               

                                                                             Wheat: Suppresses leaf rust and tan spot.       

                                                                             Oats: Suppresses leaf rust                     

                                                                             Corn: Suppresses stalk rot                     

Role of nutrient for microbial growth:       Unknown

Concentration in Plants:                              Normal concentration is 0.2 - 2.0 % of dry matter.  Cereal grain concentrations are 10-20 ppm, sugarbeet leaves 100-200 ppm. Tobacco plants require concentrations in soil of 10-15 ppm.  <70-700 ug/g in tissue is deficient.                   

Effect of pH on availability:                          Non adsorbed at pH >7              

                                                                             Non specific adsorption pH <7              

                                                                             No effect on availability               

Interactions of Cl with other nutrients:     Uptake of NO3 and SO4 can be reduced by the competitive effects of Cl.  Lower protein concentrations in winter wheat are attributed to strong competitive relationships between Cl and NO3 when Cl levels are high.  Negative interaction between Cl and NO3  has been attributed to competition for carrier sites at root surfaces.                   

Fertilizer sources:                                          Source                                  %Cl             

                                                                             Ammonium Chloride           66    

                                                                             Calcium Chloride                 65

                                                                             Potassium Chloride            47

                                                                             Magnesium Chloride           74    

                                                                             Sodium Chloride                 60

Origins of Cl in Soil and Plants:                  Most Cl in soil comes from salt trapped in parent material, marine aerosols, and volcanic emissions.  Most often found in apatite, hornblende, and some feldspars.  Nearly all soil Cl has been in the oceans at least once and returned to land by uplift and subsequent leaching of marine sediments or by oceanic salt spray carried in rain or snow.  Sea spray near coastal regions provides about 100 kg/ha/yr and for inland regions accumulations are 1-2 kg/ha/yr.  For inland regions these amounts are adequate since no deficiencies have been reported.  Salt droplets and dust particles can be absorbed by plant leaves in adequate amounts for plant requirements.             

Other:                                                                 In recent years water softening, industrial brines, and road deicing have contributed significant amounts of Cl to local areas.  Irrigation water that is highly mineralized, salt water spills associated with extraction of oil, natural gas, some coal deposits and improper disposal of feedlot wastes can supply Cl to soil.  Wind erosion of salt evaporites can also affect enrichment of soils.               

Forms in soil:                                                   Most Cl exists as soluble salts of NaCl, CaCl2, or  MgCl2.             

Behavior in Soil:                                             Cl anion is very soluble in most soils.  It is rapidly cycled through soil systems due to mobility (except in extremely acid soils). Exchangeable Cl can occur in acid, kaolinitic soils which have pH dependent positive charges. In humid climate zones Cl is leached through the soil system and in Arid to Semi-arid zones it is concentrated in the soil horizon.                    

Accumulations of Cl in Soil:                        Accumulates where internal drainage of soils is restricted and in shallow groundwater where Cl can move by capillary action into the root zone and be deposited at or near the soil surface.   

Effects:                                                              Primary effect is an increase of osmotic pressure of soil water and thereby lowers the availability of water to plants.              


Bohn, H.L., B.L. McNeal and G.A. O’Connor.  1979.  Soil Chemistry, Wiley-Interscience, New York, 219, 232, 286 pp.

Pendias-Kabata, Alina and Henryk Pendias.  1992.  Trace Elements in Soils and Plants.  2nd ed.  CRC Press, Florida, 251-252pp.

Salisbury, Frank B. and Cleon W. Ross.  1992.  Plant Physiology, 4th ed. Wadsworth Inc., California, 120, 129, 133, 135, 148, 215, 217 pp.

Tisdale, S.L., W.L. Nelson, J.D. Beaton and J.L. Havlin.  1993.  Soil Fertility and Fertilizers.  5th ed.  Macmillan, New York, 73-75, 342-344 pp.

Authors: David Gay, Justin Carpenter, Mark Wood and Curt Woolfolk


Form taken up by the plant:                        Cu2+

Mobility in the soil:                                         Immobile, pH dependent, forms strong complexes with organic matter, oxides of Fe, Al, Mn, phenolic carboxyl., and hydroxyl groups, and clay minerals. Undergoes specific adsorption.  Can be isomorphically substituted for Fe or Mn.  Cu can leach through the soil profile in humus-poor, acidic peat, or in very acidic mineral soils, such as those around Ni and Cu smelters. Concentration of natural Cu in soil is 34 to 55 ppm.


Mobility in the plant:                                      Immobile

Deficiency symptoms:                                  Stunted growth, terminal dieback first in young shoots, necrosis of the apical meristem, bleaching of young leaves, impaired lignification of cell walls;  impaired pollen formation and fertilization, delayed flowering and maturation, shortened internodes, stem deformation, yellowing, curling of leaves, seed and fruit growth dramatically reduced

Toxicity symptoms:                                       Stunting, reduced shoot vigor, reduced branching, thickening, poorly developed and discolored roots, leaf chlorosis resemble Fe deficiencies

Role of nutrient in plant growth:                Copper can not be replaced by any other metal ion in its involvement in enzymes.  It is required for synthesis of quinones in chloroplasts, and makes up the electron transporter, plastocyanin in PSII

Enzymes containing Cu:                              Superoxide Dimutase (CuZnSOD), Cytochrome oxidase, Ascorbate oxidase, Phenol Oxides, Tryosinase, Laccase, Diamine oxidase, Plastocyanin, Amine oxidase, Stellacyanin

Role in microbial growth:                             Used in electron transport

Concentration in plants:                               2-30 ppm dry weight (Adriano, 1986); 5-20 ppm (Tisdale, 1985)

Effect of pH on availability:

High pH (> 7.0)                                                 Formation of hydrolysis products which adsorb to exchange sites (lower availability), CuOH+ is the primary form

Middle pH (6.9 - 7.0)                                        Predominate form is Cu(OH)20

Low pH ( < 6.0)                                                 Exchange sites taken up by Al3+ and H+ allowing the Cu2+  form to remain soluble

Interactions with other nutrients:               Nitrogen and phosphorus (especially where Cu deficiencies exist), sulfur, iron, zinc, manganese, and molybdenum


Fertilizer sources:                                          Copper sulfate, copper nitrate, copper chelate, copper ammonium phosphate, copper carbonate, animal waste, copper hydroxide, copper acetate, copper oxalate, copper oxychloride, copper polyflavanoids, copper-sulfur frits, copper-glass fusions, chalcanthite, azurite, malachite, chalcopyrite, chalcocite, covellite, tenorite, cuprite (Loneragan, 98)


Adriano, D.C.  1986.  Trace Elements in the Terrestrial Environment.  Springer-Verlag, New York, NY.

Alloway, G.J.  1995.  Heavy Metals in Soils.  John Wiley and Sons, Inc., New York, NY.

Brady, N.C.  1990.  The Nature and Property of Soils.  MacMillan Publishing Co., New York, NY.

Committee on Medical and Biological Effects of Environmental Pollutants.  1977.  Copper.  National Academy of Sciences, Washington, D.C.

Hung, J.J.  1984.  Effects of pH and other solution parameters on the Activities of Cadmium, Copper,  and

Zinc Cations in Soil Solutions.  University Microfilms International, Ann Arbor, Michigan

Loneragan, L.F., A.D. Robson, R.D. Graham, eds.  1981.  Copper in Soils and Plants.  Academic Press, Sydney, Australia.

Narschner, Horst.  1986.  Mineral Nutrition of Higher Plants.  Academic Press, Inc., San Diego, CA.

Nriagu, J.O.  1979.  Copper in the Environment, Part 1 and 2.  John Wiley and Sons, Inc., New York, NY.

Stevenson, F.J.  1986.  Cycles of Soil Carbon, Nitrogen, Phosphorus, Sulfur, and Micronutrients.  John Wiley and Sons, Inc., New York, NY.

Authors: Tracy Johnston, Gary Strickland and Shawn Zupancic




Form taken up by plant:                               Zn2+ at pH < 7.7; Zn(OH)+ at pH > 7.7 (less available to plants).

Mobility in soil:                                                No (Low solubility): Soluble by chelation by mobile ligands. Highly soluble at pH < 6.

Mobility in Plants:                                           Low: Mobility in plants does not coincide with water flow. Zn is absorbed by plants as Zn2+ and transported as citrate, malate and malonate complexes.

Deficiency found in:                                      Acidic, sandy soils with high leaching, calcareous soils pH>8.0, exposed subsoil horizons (erosion), Deficiency symptoms are purple margins similar to phosphorus deficiency, but also inward toward the center of leaves (purple blotching), and brown spots on rice leaves. Deficiency is rarely observed in wheat.  Zn deficiency can be corrected by application of 2.5-25 kg/ha of ZnSO4 (depending on soil pH and texture) or 0.3-6 kg/ha as chelates in broadcast or band application.  Foliar application of 0.5-2.0% ZnSO4*7H2O effective for fruit trees for the growing season; 2% solution is used for seed soaking. Soil application corrects Zn deficiency for 2-5 years.

Toxicity symptoms:                                       Most plant species have high tolerance to excessive amounts of Zn. However, on acid and heavily sludged soils Zn toxicity can take place. Zn toxicity symptoms as follow: Inhibited root elongation, photosynthesis in leaves, depresses RuBP carboxylase activity, chlorosis in young leaves due to induced deficiency of Fe2+ and/or Mg2+. Zn2+ has ion radius similar to Fe2+ and Mg2+, which creates unequal competition for these elements when zinc supply is high.  The critical toxicity level in leaves is 100-300 mg per kg of dry weight.

Role of Zn in the plant:                                  1.  Component of ribosomes.

                                                                             2.  Carbohydrate metabolism

a)        a cofactor of carbonic anhydrase, which converts CO2 into HCO3-

b)        activity of photosynthetic enzymes: ribulose 1,5 bisphosphate carboxylase (RuPPC)

c)         Chlorophyll content decreases and abnormal chloroplast structure occurs when Zn is deficient

d)        Sucrose and starch formation by activating aldolase and starch synthetase

3.    Protein metabolism: Stabilizes DNA and RNA structures

4.    Membrane integrity: Stabilizes biomembranes and neutralizes free oxigen radicals, as a part of superoxide dismutase

5.    Auxin metabolism: Controls tryptophane synthetase, which produces tryptophane, a source for IAA

6.    Reproduction: Flowering and seed production are depressed by Zn deficiency.

Role of Zn in microbial growth:                  Indispensability of Zn in metabolism of living organisms, microflora also is highly dependent on concentrations of zinc present. Some heterotrophs can tolerate high concentration of Zn and behave as bioaccumulators of Zn, among them Zoogloea-producing bacteria, Ephiphytic bacteria, Nonsporing bacteria. Different genera of Green Algae respond differently to Zn contamination. Microspora, Ulothrix, Hormidium, and Stigeoclonium are resistant to high Zn concentrations, whereas genera such as Oedogonium and Cladophora are rather sensitive to the presence of Zn.

Concentration in plants:                               Depending on genotype, Zn concentration varies in the range 25-150 ppm (0.0025-0.015% of dry weight) of Zn sufficient plant.

Concentration in soils:                                 10-300 ppm (0.001-0.03%). Concentration of total Zn increases with depth, whereas extractable Zn content decreases. Concentration of Zn in the upper horizon also depends on organic matter content, which can hold up to 13% Zn. In soils, 30-60% Zn can be found in iron oxides, 20-45% in the lattice of clay minerals, and 1-7% on clay exchange complex. Highest Zn concentration is in solonchaks – saline soils in Asia, lowest in light textured soils with low organic matter.

Origin in soils:                                                 Zinc composition of soils defined by parent material. Magmatic rocks have 40 and 100 mg/kg Zn in granites and basalt, respectively. Sedimentary rock composition varies in the range 10 to 30 mg/kg in sandstones and dolomites, and 80-120 mg/kg in clays,

Effect of pH on availability:                          pH is the most important parameter of Zn solubility. General equation for soil Zn is

                                                                                    pZn = 2pH – 5.8

                                                                             The form of Zn predominant at

·        pH<7.7 – Zn2+

·        pH>7.7 – ZnOH+

·        pH<7.7 – Zn(OH)2

Interaction of Zn with other nutrients:      Increase in available P content can considerably decrease availability of Zn in the soil due to the high antagonism between these two elements. However, some authors suggest that symptoms considered as a Zn deficiency are actually P toxicity.  Presence of other nutrients such as iron, copper, manganese and calcium may also inhibit Zn uptake by plants, probably due to the competition for the carrier sites on roots. Application of high rates of NPK fertilizers can aggravate Zn deficiency.

Fertilizer sources:                                          Zinc sulfate with 25-36%Zn, Zinc oxide – 50-80% Zn, Zinc Chloride - 48% Zn, Zinc Chelate – 9-14.5% Zn, and manure are used in agriculture.

Soil Test:                                                           For available Zn determination four extractants are generally used:

                                                                             0.1M HCL, EDTA-(NH4)2CO3, Dithizone - NH4OAC, and DTPA-TEA.

                                                                             Soil content of Zn of 2ppm (0.0002%) and higher are sufficient for most of the crops, <2 ppm is deficient for pecans, <0.8 ppm is deficient for corn. When Zn concentration is less than 0.3 ppm, deficiency symptoms are observed in less sensitive crops such as cotton, wheat, soybean, etc.


Allowey, B.J. (ed.).  1990.  Heavy Metals in Soils. John Wiley and Sons. New York.

Johnson, G.V., W. R. Raun, H.Zang, and J.A. Hattey.  1997  Oklahoma Soil Fertility Handbook.  4th ed.  Department of Agronomy Oklahoma State University.

Kabata-Pendias, A., H. Pendias.  1991. Trace elements in soils and plants. 2nd ed.  CRC Press Boca Raton Ann Arbor London.

Nriagu, J.O. (ed.).  1980.  Zinc in the Environment. John Wiley and Sons. New York.

Prasad, R., and J.F. Power.  1997.  Soil Fertility Management for Sustainable Agriculture. CRC Press LLC. New York.

Raun, W.R., G.V. Johnson, R.L. Westerman.  1997.  Soil - Plant Nutrient Cycling and Environmental Quality.  Oklahoma State University.

Robson, A.D. (ed.).  1993. Zinc in Soils and Plants. Kluwer Academic Publishers. Australia.

Marschner, H.  1995.  Mineral Nutrition of Higher Plants. 2nd ed. Academic Press. London.

Tisdale, S.L., W.L. Nelson, J. D. Beaton, and J.L. Havlin.  1993.  Soil Fertility and Fertilizers.  5th ed. MacMillian. USA.

Authors: Francisco Gavi, Chad Dow, John Ringer and Erna Lukina


Form taken up by plants:                             MoO42-

Mobility in soil:                                                Immobile.  Solution concentrations below 4 ppb transfer by diffusion.  Above 4 ppb by mass flow.

Mobility in plant:                                             It is readily translocated and deficiency symptoms generally appear in the whole plant.        

Deficiency symptoms:                                  Deficiency symptoms are closely related to N metabolism because Mo is needed for nitrogenase. General deficiency symptoms are varied between plants and range from yellowing, stunting, interveinal mottling and cupping of older leaves followed by necrotic spots at the tips and margins.

Deficiencies occur in:                                   Soils with low pH and high Fe and Al oxides.

                                                                             Deficiency usually resolved by addition of lime.

Plants most susceptible to deficiencies: Legumes, Brassica sp., Lycopersicon esculentum, Beta vulgaris, Crucifers, Citrus

Toxicity symptoms:           PLANTS             Not readily toxic and marked toxicity is not known in the field.  When it does occur, toxicity symptoms are yellow or orange-yellow chlorosis, with some brownish tints that start in the youngest leaves.  Further symptoms include moribund buds, thick stems, development of auxillary buds and succulent older leaves.  However, when toxicity does occur, it is normally found in high pH soils in the western regions of North America and Australia.

                                            ANIMALS           Toxicity occurs in livestock when they intake

                                                                             feeds and forages with high Mo content of 10-50 ppm.  Ruminant animals are particularly sensitive and develop the disease molybdenosis. 

Role of Mo in plants:                                      Needed in nitrate reductase for the reduction of NO3-  to NO2-, biological nitrogen fixation, influences nitrogen content in plants,  aids in

                                                                             purine catabolism,  aids in oxidation of sulfite to sulfate, influences the utilization of carbohydrates, and promotes root flavonoids.

Role of Mo for microbes:                              Needed in nitrogenase for fixation of N2 by Rhizobium, Azotobacter, Rhodospirillum,  Klebsiella, and blue-green algae 

Enzymes that require Mo:                            Nitrate reductase, molybdoenzyme, nitrogenase, sulfite oxidase, Xanthine oxidase, and aldehyde oxidase. 

Effect of pH on availability:                                

Precipitated forms at low  pH                      FeMoO4, PbMoO4

Precipitated forms at high pH                     CaMoO4

Soil solution forms:                                       MoO42-, HMoO4-, H2MoO4 (MoO42- is the most dominant species.)

Concentration in soil:                                    Average concentration is about 2 ppm and ranges between 0.2 and 5 ppm.

Interactions with other nutrients:               P additions increase Mo uptake by replacements on the exchange complex and release to solution.  S depressed Mo uptake by direct competition on root adsorption sites.  Mo, with Mn, affects Fe uptake in tomatoes.

Fertilizer sources:                                          Na42MoO4×2H2O (39%), (NH4)6Mo7O24×4H2O (54%), MoO3 (66%), and MoS2 (60%).


Adriano, D. C.  1986.  Trace elements in the terrestrial environment.  Springer-Verlag New York Inc.  pp. 329-361.

Barber, S.A.  1995.  Soil nutrient bioavailability:  a mechanistic approach.  2nd Edition.  John Wiley & Sons Inc.  New York, NY.  pp. 345-352.

Bohn, H.L, B.L. McNeal, and G. A. O’Connor.  1985.  Soil chemistry.  2nd Edition.  John Wiley & Sons Inc. New York, NY.  pp.  226, 308.

Brady, N.C.  1990.  The nature and properties of soil.  10th Edition.  Macmillian.  New York, NY.  pp.  381-398.

Brown, J.C., Ambler, J.E., Chaney, R.L. and Foy, C.D.  1972.  Micronutrients in agriculture.  SSSA, Inc.  Madison, WI. pp.  401-402.

Gupta, U.C.  1997.  Molybdenum in agriculture.  Cambridge University Press.  United Kingdom.

Gupta, U.C. and J. Lipsett.  1981.  Molybdenum in soils, plants, and animals.  Advances in Agronomy 34:73-115.

Lindsay, W. L.  1979.  Chemical equilibria in soils.  John Wiley & Sons.  New York, NY.  pp.  365-372.

Stevenson, F.J.  1986.  Cycles of soil.  John Wiley & Sons Inc.  New York, NY.

Tisdale, S.L., W.L. Nelson, and J.D. Beaton.  1985.  Soil fertility and fertilizers. 5th Edition.  Macmillian. New York, NY.  pp. 378-381.

Authors:  Matt Rowland and Renee’ Albers 1998, Steven Phillips and Eric Hanke



Form taken by plants:                                   Al3+, Al(OH)2+, Al(OH)2+

Mobility in soil:                                                Mass flow at low pH (< 5.5). Otherwise immobile.

Mobility in plants:                                           No

Deficiency symptoms:                                  Unknown.

Toxic forms:                                                     Al3+, aluminum hydroxides, “Al13” hydroxy-polymer.

Toxicity symptoms for plants:                    Phytotoxicity (monomeric Al forms): Limited root branching and rooting depths. Browning of root tips. Inhibited shoots growth. Phosphorus deficiency symptoms.

                                                                             Rhyzotoxicity (polymeric Al forms):  Impaired germination of seeds.

Toxicity for humans:                                     Neurotoxicity. Impaired motor functions. Aggravation of Alzheimer disease and parkinsonism.

Toxicity for wildlife:                                        Forest die-backs in North America and Europe (red spruce, various firs, pines, sugar maple). Al accumulator plants are toxic to herbivores. Embriotoxicity for oysters. Neurotoxicity for mammals.

Al as a nutrient in plant growth:                 Very low Al levels can benefit some plants. Otherwise unknown.

Effect of pH on availability:                          Availability of inorganic complexes of Al is greatest at low pH (< 5.5). Organic complexes of Al is released at high pH (> 7.0)

Soluble species:                                             Al3+        pH  < 5.5

                                                                             Al(OH)2+  pH 4.7 – 6.5

                                                                             Al(OH)2+   pH 6.5 – 8.0

                                                                             Al(OH)4-   pH > 8.0

Precipitated forms:                                        AlPO4 , Al2SiO5 , Al2(OH)6 (gibbsite)

Anions ameliorating toxicity:                      PO43-, F-, SO42-, hydroxides, organic carboxylates.


Bertsch, P.M., and Bloom, P.R., 1996. Aluminum. In: Methods of Soil Analysis. Part 3, Chemical Methods, 517 – 550. D.L. Sparks et al. (Eds.). Soil Science Society of America, Inc. Madison, Wisconsin, 1996

Hargrove, W.L. 1986. The solubility of aluminum-organic matter and its implication in plant uptake of aluminum. Soil Sci. 142: 179-181.

Lewis, T.E. (Editor). 1989. Environmental chemistry and toxicity of aluminum. 1989, Lewis Publishers, Inc., 344 P.

Sparling, D.W. and Lowe, T.P. 1996. Environmental hazards of aluminum to plants, invertebrates, fish and wildlife. Rev. Environ. Contam. Toxicol., 145: 1-127.

Strid, H. 1996. Aluminum toxicity effects on growth and on uptake and distribution of some mineral nutrients in two cultivars of spring wheat

Authors: Olga Kachurina and Alan O'Dell


Status:                                                               Micronutrient required only by  some plants.

Form taken up by plant:                               Na+

Mobility in plant:                                             Relatively mobile.

Deficiency symptoms:                                  In C4 plants - chlorosis in leaves and necrosis in the leaf margins and tips; lower chlorophyll a/b ratios and lowered photosystem II activity

Plant most susceptible to deficiencies:   Some desert and salt-marsh species and C4 species, succulents; Australian Atriplex species.

Toxicity symptoms:                                       Causes decrease in growth and yield, yellowing and withering of the plants; Na salts retards germination amount of Na-containing substance needed to kill the plant: NaCl -1.8%, NaBr - 1.2%, NaNO3 - 1.7%, Na2SO4 - 0.8%, Na2PO4 - 1.5%, Na2CO3 - 1.1%.

Adverse effects on plants:                           Pronounced under low concentrations of  other components of soil solution; at high concentrations impedes water uptake by plants; may enter the plant in preference to K ions depriving the plant of an essential nutrient and inhibiting some enzymes; decreases absorption of Ca++, Mg++, and K+ in some plants; impairs cell membrane.

Role of nutrient in plant growth:                Readily taken up by plant; function is similar to that of potassium - activator for a wide variety of important enzymes; activates ATPase (membrane transport); is involved in osmosis balance; facilitates absorption of N, P, K in some plants due to enhancing permeability of cells to salts (in sugar beets, carrots), favors the accumulation of fructose, promotes conversion of fructose to glucose, increases sucrose content in some plants, reduces the motility of stomatal openings; uptake of Na when K is sufficient can improve vigor and color of foliage, increase disease resistance, and decrease wilting in hot dry weather in  celery, mangel, sugar beet, Swiss chard, table beet, turnip, barley, carrot, cotton, flax, oat, pea, tomato, vetch, wheat; in C4 plants Na is needed for transporting CO2 to the cells where it is reduced to carbohydrates; activates membrane translocator system.

Role of Na for microbes:                              Inhibits initiation of glycolysis, inhibits intracellular enzymes, activates few extracellular enzymes; specifically required by blue green algae, Aerobacter species (activates fermentative enzymes); actively required by halobacteria and halococci; required by nitrogen fixing microorganisms

Concentrations in plants:                            0.0013-3.51% of dry matter, 0.016 - 16.78 % in ash; halophytes are very rich in Na; buckwheat, corn and sunflower have unusually low content of Na;

Origin in soils and plants:                            1) parent material: silicate minerals- alkali feldspars (albite, microcline), hornblende, tourmaline, sodium sulfate minerals - thenardite (Na2SO4), aphthitalite - (Na,K)2SO4, glauberite (Na2SO4.CaSO4),  hanksite (9Na2SO4.2Na2CO3.KCl); 2)ocean spray, 3) salts precipitated via rain, 4) ground  water, 4) loess , 5) brines (for 1 barrel of crude oil 10 barrels of brine produced).

Concentration in atmosphere:                    1500-5500mg/m3

Concentration in biosphere:                       1.65 mol/hectare (average composition of living matter).

Concentration in seawater:                         10500 ppm

Concentration in lithosphere:                     750-7500 mg/kg dry matter

Accumulations of Na in soil:                       Accumulates under restricted internal drainage, or shallow water table and high evaporation when Na+ can move upwards and accumulate at or near soil surface.

Behavior in soil:                                              At low concentrations, Na can deteriorate soil structure by dispersing clays and organic colloids (dispersive soils are easily erodible); causes increase in the hardness and relative impermeability of the B horizon and a decrease in thickness of the humus-enriched A horizon; in form of chloride, increases the osmotic pressure of soil water and lowers the availability of water to plants; Na-affected soils release substantially smaller   percentage of the total nitrogen than the other soils; Na reduces evaporation and increases the water- holding power of the soil, through an exchange of bases  it is capable of rendering certain relatively insoluble  nutritive salts more available to plants; high pH caused by high concentration of Na+   leads to reduced availability of some micronutrients and  contribute to aluminum and boron toxicity, Co and Mo become more soluble in alkaline soils.

Forms in soils:                                                Most Na exists as soluble salts of NaCl, Na2SO4 (white alkali), Na2CO3.

Interactions with other nutrients:               Substitutes potassium in case of a  deficiency in potassium in some species; Na prevents Al toxicity (where Ca content is decreased); prevents poisonous effect of excess K, NH4, Mg, Ca, Cu; high concentrations of Na strengthens Cl-toxicity in some plants Na stimulates absorption of N and P by  plants, in others inhibits uptake of Ca, Mg, K; in saline soils Na ions compete with the uptake of K+; CaSO4 and elemental S help in leaching Na+ out.

Fertilizer sources:                                          Sodium nitrate (NaNO3), sodium sulfate (Na2SO4), sodium chloride (NaCl).

Pesticides sources:                                       Fungicide - sodium omadine; herbicide - NaClO3 (sodium chlorate


Bibliography of the literature on sodium and iodine in relation to plant and animal nutrition. 1948. 1 ed., v.1.

Cairns, R.R., R.A. Milne, and W.E. Bowser. 1962. A nutritional disorder in barley seedlings grown on Alkali solonetz soil. Canadian Journal of Soil Science, 42, no.1:1-6.

Curtis, H.1983. Biology. Worth Publishers, Inc. New York.

Harmer, P.M., and Benne E.J. 1945. Sodium as a crop nutrient. Soil Science, 60:137-148

Harrison, P.M., and K.L. Hoare. 1980. Metals in biochemistry. Chapman and Hall. London and New York.

McBride, M.B. 1994. Environmental chemistry of soils. Oxford University Press. New York, Oxford.

Metal ions in Biological systems. 1984. Ed. by H. Sigel. Marcel Dekker, Inc.New York and Basel. vv.18, 20, 24.

Osterhout, W. J. V. 1908. The value of sodium to plants by reason of its protective action. Berkeley, The University Press.

Peil, K.L. 1968. Studies on natural microbial populations... Master of Science Thesis. Oklahoma State University.

Pipkin, H.R. 1969. Uptake and redistribution of calcium and sodium in the tomato plant. Master of Science Thesis. Oklahoma State University.

Plant physiology. 1963. Ed. by Steward, F.C. Academic Press, Inc. San Diego, New York, Boston, London, Sydney, Tokyo, Toronto.

Salisbury, F.B., and Ross, C.W. 1992. Plant physiology, 4th ed. Wadsworth Inc., California.

Wells, R.C. 1923. Sodium sulfate: its sources and uses. Washington, Government printing office.

Author: Elena Jigoulina



Form taken up by the plant:                        V2O5

Mobility in soil:                                                No/Yes (Becomes mobile at pH 5.0 with

                                                                             redox potential of –100 and at pH 8.0

                                                                             with redox potential of –330),

Deficiency symptoms:                                  None

Effect of other nutrients on uptake:          Ni, Mn, and Cu inhibit uptake and Mo

                                                                             enhances the uptake of V.

Role of nutrient in plant growth:                Still unknown

Role of Vanadium in microbe growth:      Part of vanadium nitrogenase in many Azotobacter species

Concentration in plants:                               1 ppm

Abundance on earth:                                    ~300 ppm

Effect of pH:                                                     pH of normal soils have no effect.      However, pH < 3.0 or >8.5 increases solubility.

Oxidation states:                                            +5 to -1

Soluble species:                                             VO2+, H2VO4-, and HV2O5-

Interaction with other species:                   O, N, P, C, Si, and B



Clark, R.J.H. 1968. The Chemistry of Titanium and Vanadium. Elsevier Publishing    Company, New York, NY.

Fargasova A. and E. Beinrohr 1998. Metal-Metal Interactions in Accumulation. pp 1305-1317 in Chemosphere Vol. 36 No.6. Elsevier Science Ltd, Great Britain.  

Hudson T.G. 1964. Vanadium Toxicology and Biological Significance. Elsevier Publishing Company, New York.

Lai Y.D. and J.C. Liu 1997. Leaching Behaviors of Ni and V From Spent Catalyst. Pp 213-224 in Journal of Hazardous Materials Vol. 53. Elsevier Science B.V.

Yates M.G., E.M. De Souza and J.H. Kahindi 1997. Oxygen, Hydrogen, and Nitrogen Fixation in Azotobacter. pp 863-869 in Soil Biology and Biochemistry Vol. 29 No. 5/6, Elsevier Science Ltd. Great Britain.             

Author: Bryam M. Howell



Form taken up by plants:                             O2, Diatomic oxygen

Mobility in the soil:                                        Yes                                                                                                

Mobility in the plant:                                      Yes

Deficiency symptoms:                                  Oxygen is essential for respiration, and low concentrations will stunt root growth;  microbial oxidation will be slowed

Role of the nutrient in plant:                        Respiration in roots; Redox e- acceptor

Concentration in plant:                                 Depends on conditions

Concentration in soil:                                    Depends on conditions

Effect of pH on availability:                          None

Interaction with other nutrients:                 Nitrogen (denitrification); Effects other elements oxidation states

Fertilizer sources:                                          None



Linsdsay, W.L. 1979.  Chemical Equlibria in Soils.  John Wiley & Sons, NY.

Raun, W.R., G.V. Johnson, R.L. Westerman. 1998. Soil-Plant Nutrient Cycling and Environmental Quality.  Agron 5813 Class Book.

Tisdale, S.L., W.L. Nelson, J.D. Beaton, J.L. Havlin. 1985. Soil Fertility and Fertilizers 5th edition.  Macmillan Publishing Co. NY.


Author: Doug Cossey



Form taken up by plant:                               Si(OH)4 - monosilicic acid

Mobility in soil:                                                No/Yes

Mobility in plant:                                             Forms concrete particles built of silica (Si(OH)4 . nH2O) and opaline (SiOn(OH)4-2n). Silica may complex with cell wall polymers. Monosilicic acid is mobile in xylem sap.

Deficiency symptoms:                                  Deficiency results in greater susceptibility to biophage-related diseases, lower tolerance, in some cases, of drought, salinity, and toxicity by minerals, including aluminum and manganese, and higher level of lodging in cereal stems (with possible decrease in yield)

Role of nutrient in plant growth:                Silica particles provide resistance to mechanical compression, strength to cell walls and air canals; they also decrease relative share of biomass consumed by biophages.

                                                                             Plants can be divided into four groups, according to Si uptake/influx mechanism:

                                                                                    1.         Passive

                                                                                    2.         Active

                                                                                    3.         Exclusive

                                                                                    4.         Active uptake/active exclusion depending on concentration in environmental solution

Concentration in plants:                               (SiO2 fraction of the dry weight):

                                                                             1.    High (0.1 - 0.15) - wetland grasses

                                                                             2.    Intermediate (0.01 - 0.03) - dry land grasses

                                                                             3.    Low (<0.01) - dicotyledones

Concentration in soils:                                 1 to 40 mg/l Si in soil solution


Effect of pH on availability:                          [Si(OH)4] mobility increases as pH decreases

Concentration in groundwater:                  3.5 to 28 mg/l Si

Concentration in freshwater:                      0.5 to 44 mg/l Si

Concentration in sea water:                        1 to 7 mg/l Si (bulk), 0.0001 to 0.2 (surface)

Fertilizer sources:                                          Metallurgy wastes

“As yet there is no evidence that Si has any role in [higher] plant biochemical processes but is present at low levels in many leaf cell types.” [6] p. 470.


Silicon and Siliceous Structures in Biological Systems. Edited by Tracy L. Sipson and Benjamin E. Volcani. Springer-Verlag, pp. 16-17, 387, 410.

Silicon Biochemistry. Ciba Foundation Symposium 121. John Wiley & Sons, 1986, pp. 17, 28-29, 90-93.

J. A. Raven. The transport and function of silicon in plants (review). In “Biological Reviews of the Cambridge Philosophical Society,” v. 58 (May 1983), pp. 179-207.

J. J. R. Frausto da Silva, R. J. P. Williams. The biological Chemistry of the Elements. Clarendon Press, Oxford, 1991, p. 468.

H. F. Mayland, J. L. Wright, R. E. Sojka. Silicon Accumulation and Water Uptake by Wheat. In “Plant and Soil,” v. 137 no. 2 (Nov. 1991), pp. 191-199.

M. J. Hodson, A. G. Sangster. Observations on the distribution of mineral elements in the leaf of wheat (Triticum aestivum L.), with particular reference to silicon. In “Annals of botany,” v. 62 (November 1988), pp. 463-471.

J. G. Menzies, D. L. Ehret, P. A. Bowen. Surprising Benefits of Silicon. In “American Vegetable Grower,” v. 40 (March 1992), pp. 82-84.

V. Matichenkov, E. Bocharnikova. Total Migration and Transformation of Silicon in Biochemical Subsystems. Modern Antropogenic Influence on the Global Change of Si Cycle. In “GAIM Science Conference Abstracts.” (

Author: Aleksandr Felitsiant