Plant uptake as Mg2+ at root tip

Crop removal

Plant residue and Microbial population

Mineralizatio

nIm

mobilizatio

n

Erosion

CEC

Leaching MgSO4

Chelates in solution

Secondary clay and humus

Weathering

PPTSoil Solution

Mg fertilizer

Mg 2+

Magnesium Cycle

Authors: Jeffrey Ball, Mark Everett, Rick Kochenower, and Heather Qualls

Click on green circle to return to main cycle

More Info.

Where you can goWhere you have been

Dolomite, MgSO4, MgO, Mangesite,Magnesia, Kainite,

Langbeinite, Epsom salts

OxidesSilicatesSulfides

Etc

Plant uptake as Mg2+ at root tip

Secondary clay and humus

Mg fertilizer

Soil Solution

Where you can goWhere you have been

More Info.

Soil Solution

Plant uptake as Mg2+ at root tip

Crop removal

Plant residue and Microbial population

Chelates in solution

Mg fertilizer

Dolomite, MgSO4, MgO, Mangesite,Magnesia, Kainite,

Langbeinite, Epsom salts

Where you can goWhere you have been

More Info.

Crop removal

Plant uptake as Mg2+ at root tip

Where you can goWhere you have been

More Info.

Plant uptake as Mg2+ at root tip

Plant residue and Microbial population

Mineralizatio

nIm

mobilizatio

n

Erosion

Chelates in solution

Soil Solution

Where you can goWhere you have been

More Info.

Plant residue and Microbial population

ErosionSoil Solution

Where you can goWhere you have been

More Info.

Leaching MgSO4

Chelates in solution

Soil Solution

Where you can goWhere you have been

More Info.

OxidesSilicatesSulfides

Etc

Plant uptake as Mg2+ at root tip

Plant residue and Microbial population

Leaching MgSO4

Chelates in solution

Secondary clay and humus

Soil Solution

Where you can goWhere you have been

More Info.

Parent materialnon-exchangeable 2% of all rock

Dolomite MagnesiteSerpentine BiotiteOlivine FosteritePyrope IoliteDiopside AugiteEnstatite ActinoliteHornblende TalcPhlogopite Clinochlore

OxidesSilicatesSulfides

Etc

Secondary clay and humus

Weathering

Soil Solution

Where you can goWhere you have been

More Info.

Secondary clay and humus

Weathering

PPT

Mg fertilizer

Soil Solution

OxidesSilicatesSulfides

Etc

Parent materialnon-exchangeable 2% of all rock

Dolomite MagnesiteSerpentine BiotiteOlivine FosteritePyrope IoliteDiopside AugiteEnstatite ActinoliteHornblende TalcPhlogopite Clinochlore

Dolomite, MgSO4, MgO, Mangesite,Magnesia, Kainite,

Langbeinite, Epsom salts

Where you can goWhere you have been

More Info.

Plant uptake as Mg2+ at root tip

Plant residue and Microbial population

Mineralizatio

nIm

mobilizatio

n

Erosion

CEC

Leaching MgSO4

Chelates in solution

Secondary clay and humus

Weathering

PPTSoil Solution

Mg fertilizer

Mg 2+Parent material

non-exchangeable 2% of all rock

Dolomite MagnesiteSerpentine BiotiteOlivine FosteritePyrope IoliteDiopside AugiteEnstatite ActinoliteHornblende TalcPhlogopite Clinochlore

OxidesSilicatesSulfides

Etc

Dolomite, MgSO4, MgO, Mangesite,Magnesia, Kainite,

Langbeinite, Epsom salts

Where you can goWhere you have been

More Info.

CEC

Soil Solution

Mg 2+

Where you can goWhere you have been

More Info.

Deficiencies:pH 5.0 is best for Mg availability. A higheror lower pH depresses Mg uptake. High Kand Ca levels also interfere with uptake.

Where deficiencies occur:Highly leached humus acid soils or onsandy soils which have been limed heavily(due to Ca2+ competition). Deep sandysoils. Soils with high forage production (8-10ton/ac/yr) removal. Sometimes on soilshigh in K, Mg deficiencies are indicated bysoil test index values less than 100lbs/acre.

Toxicity Symptoms:none

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

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Form taken up by plant: Mg2+

Mobility in Soil: yes/no

Mobility in Plant:yes as Mg2+ or Mg Citrate

Deficiency Symptoms: Interveinal chlorosis, necrosis, andGeneral withered appearance. Leaves arestiff and brittle and intercostal veins aretwisted. Observed in lower leaves first.Between veins striping, mottling, andblotching.

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Role of Mg in Plant Growth: Responsible for electron transfer inphotosynthesis. Central element ofchlorophyll molecule (6-25% of total plantMg). Required for starch degradation in thechloroplast. Involved in regulating cellularpH. Required for protein synthesis.Required to form RNA in the nucleus, Mgpectate in the middle lamella.

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

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

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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 plantlimits Mg2+ uptake. H+ (low pH) can limitMg2+ uptake. Mg salts increasephosphorus adsorption.

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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)

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

Radioactive Isotopes: 23Mg t 1/2 = 11.6 sec27Mg t 1/2 = 9.6 min28Mg t 1/2 = 21.3 hr

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Enzymes that require Mg2+: Magnesium is a co-factor for manyenzymes. This includes enzymes involvedin glycolysis, carbohydrate transformationsrelated to glycolysis, Krebs cycle, themonophosphate shunt, lipid metabolism,nitrogen metabolism, “phosphate pool”reactions, photosynthesis, and othermiscellaneous reactions.

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

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Ionic Radius: 0.78 Angstroms

Hydration Energy: 1908 J mol-1

Toxicity Symptoms:none

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

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References:

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

Brady, Nyle C. and Ray R. Weil. 1996. The Nature and Properties of Soils. 11th

Edition. Prentice Hall, Upper Saddle River, N.J.

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 FertilityHandbook. 3rd

ed. Okla. Plant Food Educational Society and Okla. State Univ. Dept. ofAgronomy, Stillwater, OK.

Johnson, G.V., W.R. Raun, Hailin Zhang, and Jeffrey A. Hattey. 1997.Oklahoma Soil

Fertility Handbook. 4th Edition. Oklahoma State University Department ofAgronomy, Oklahoma Agricultural Experiment Station, Oklahoma

CooperativeExtension Service, And Oklahoma State University Division of AgriculturalSciences and Natural Resources, 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. InternationalPotash

Institute, Bern.

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

Authors: Jeffrey Ball, Mark Everett and Rick Kochenower, and Heather Qualls

More Information

Form taken up by plant

Mobility in soil

Mobility in plant

Deficiency symptoms

Deficiencies

Where deficiencies occur

Toxicity symptoms/Toxicities

Role of nutrient in microbial and plant growth

Concentration in plants

Effect of pH on availability

Precipitated forms at pH

Interactions with other nutrients

Fertilizer sources

Location in plants

Radioactive isotopes

Enzymes that require Mg2+

Ionic radius/Hydration energy References Back to cycle

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More Info.

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

Where deficiencies occur:Highly leached humus acid soils or onsandy soils which have been limes heavily(due to Ca2+ competition). Deep sandysoils. Soils with high forageproduction (8 –10ton/ac/yr) removal.Sometimes on soils high in K, Mg deficiencies areindicated by soil test index values less than 100lbs/ac.