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Magnesium Cycle
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Crop removal
Plant uptake as Mg2+ at root tip
Plant residue and
Microbial population
Chelates in solution
Leaching MgSO4
Mg fertilizer
PPT
Soil Solution
Erosion
Secondary clay
and humus
Weathering
Authors: Jeffrey Ball, Mark Everett, Rick Kochenower, and Heather Qualls
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CEC
More Info.
Plant uptake as Mg2+ at root tip
Dolomite, MgSO4, MgO,
Mangesite,Magnesia, Kainite,
Langbeinite, Epsom salts
Mg fertilizer
Soil Solution
Secondary clay
and humus
Oxides
Silicates
Sulfides
Etc
Where you can go
Where you have been
More Info.
Crop removal
Plant uptake as Mg2+ at root tip
Plant residue and
Microbial population
Chelates in solution
Mg fertilizer
Dolomite, MgSO4, MgO,
Mangesite,Magnesia, Kainite,
Langbeinite, Epsom salts
Soil Solution
Where you can go
Where you have been
More Info.
Crop removal
Plant uptake as Mg2+ at root tip
Where you can go
Where you have been
More Info.
Plant uptake as Mg2+ at root tip
Plant residue and
Microbial population
Chelates in solution
Soil Solution
Erosion
Where you can go
Where you have been
More Info.
Plant residue and
Microbial population
Soil Solution
Erosion
Where you can go
Where you have been
More Info.
Chelates in solution
Leaching MgSO4
Soil Solution
Where you can go
Where you have been
More Info.
Plant uptake as Mg2+ at root tip
Plant residue and
Microbial population
Chelates in solution
Leaching MgSO4
Soil Solution
Secondary clay
and humus
Oxides
Silicates
Sulfides
Etc
Where you can go
Where you have been
More Info.
Parent material
non-exchangeable 2% of all rock
Dolomite
Magnesite
Serpentine
Biotite
Olivine
Fosterite
Pyrope
Iolite
Diopside
Augite
Enstatite
Actinolite
Hornblende
Talc
Phlogopite Clinochlore
Soil Solution
Secondary clay
and humus
Where you can go
Where you have been
Weathering
Oxides
Silicates
Sulfides
Etc
More Info.
Dolomite, MgSO4, MgO,
Mangesite,Magnesia, Kainite,
Langbeinite, Epsom salts
Parent material
non-exchangeable 2% of all rock
Dolomite
Magnesite
Serpentine
Biotite
Olivine
Fosterite
Pyrope
Iolite
Diopside
Augite
Enstatite
Actinolite
Hornblende
Talc
Phlogopite Clinochlore
Mg fertilizer
Soil Solution
PPT
Secondary clay
and humus
Where you can go
Where you have been
Weathering
Oxides
Silicates
Sulfides
Etc
More Info.
Plant uptake as Mg2+ at root tip
Plant residue and
Microbial population
Dolomite, MgSO4, MgO,
Mangesite,Magnesia, Kainite,
Langbeinite, Epsom salts
Chelates in solution
Leaching MgSO4
Mg fertilizer
Soil Solution
PPT
Erosion
Secondary clay
and humus
Where you can go
Where you have been
Parent material
non-exchangeable 2% of all rock
Dolomite
Magnesite
Serpentine
Biotite
Olivine
Fosterite
Pyrope
Iolite
Diopside
Augite
Enstatite
Actinolite
Hornblende
Talc
Phlogopite Clinochlore
Weathering
Oxides
Silicates
Sulfides
Etc
CEC
More Info.
Soil Solution
Where you can go
Where you have been
CEC
More Info.
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). Deep sandy
soils. Soils with high forage production (8
-10ton/ac/yr) removal. Sometimes on soils
high in K, Mg deficiencies are indicated by
soil 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, and
General withered appearance. Leaves are
stiff and brittle and intercostal veins are
twisted. Observed in lower leaves first.
Between veins striping, mottling, and
blotching.
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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 colloidal condition of the
cytoplasm.
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 plant
limits Mg2+ uptake. H+ (low pH) can limit
Mg2+ uptake. Mg salts increase
phosphorus 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:
23
Mg
t 1/2 = 11.6 sec
27
Mg
t 1/2 = 9.6 min
28
Mg
t 1/2 = 21.3 hr
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Enzymes that require Mg2+:
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
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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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More Info.
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 Fertility
Handbook. 3rd
ed. Okla. Plant Food Educational Society and Okla. State Univ. Dept. of
Agronomy, 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 of
Agronomy, Oklahoma Agricultural Experiment Station, Oklahoma
Cooperative
Extension Service, And Oklahoma State University Division of Agricultural
Sciences and Natural Resources, Stillwater, OK.
Lauchli, A. and R.L. Bieleski (editors). 1983. Inorganic Plant Nutrition. SpringerVerlag,
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, and Heather Qualls
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More Information
Form taken up by plant
Effect of pH on availability
Mobility in soil
Precipitated forms at pH
Mobility in plant
Interactions with other nutrients
Deficiency symptoms
Fertilizer sources
Deficiencies
Location in plants
Where deficiencies occur
Radioactive isotopes
Toxicity symptoms/Toxicities
Enzymes that require Mg2+
Concentration in plants
Ionic radius/Hydration energy
Role of nutrient in microbial
and plant growth
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References
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 limes heavily
(due to Ca2+ competition). Deep sandy
soils. Soils with high forage
production (8 –10ton/ac/yr) removal.
Sometimes on soils high in K, Mg deficiencies are
indicated by soil test index values less than 100lbs/ac.
Back to cycle
More Info.