Science and management of Ca and Mg

Calcium (Ca) has an atomic number of 20

and an atomic weight of 40.08

What does Ca share in common

with other elements in group IlA?

Calcium (Ca) has an atomic number of 20

and an atomic weight of 40.08

Ca+2

The plume from the burning reactor initially traveled in a northwest direction toward Sweden,

Finland and eastern Europe, exposing the public to levels up to 100 times the normal

background radiation. Contamination of grain and dairy products was a serious concern.

Both Sr-90 and I-131 migrate to vital organs in the body where they are impossible to

remove, serving as a constant source of unnecessary radiation and as a cause of cancer or

other diseases

Radioactive fall-out from Chernobyl

Sr can

substitute for

Ca with very

unhealthy

consequences

element atomic number % by weight

oxygen 8 46.60

silicon 14 27.72

aluminum 13 8.13

iron 26 5.00

calcium 20 3.63

sodium 11 2.83

potassium 19 2.59

magnesium 12 2.09

titanium 22 0.44

hydrogen 1 0.14

phosphorus 15 0.12

manganese 25 0.10

fluorine 9 0.08

sulfur 16 0.05

chlorine 17 0.05

Calcium is the 5th most abundant element in the earth’s crust

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As a result, most young soils contain

large amounts of calcium

Old soils that are highly weathered and soils

that formed from parent materials low in Ca

tend to contain much less Ca.

Young Ca rich soil in IL Old Ca deficient soil in NC

The highly weathered soils of Brazil’s

Cerrado region naturally had such low

Ca levels that cattle ranchers lost cattle

due to brittle Ca deficient bones and

large scale crop production was

considered impossible.

The highly weathered soils of Brazil’s

Cerrado region naturally had such low

Ca levels that cattle ranchers lost cattle

due to brittle Ca deficient bones and

large scale crop production was

considered impossible.

> 150 million acres converted to ag since 1985,

Brazil is now the #1 soybean exporter

Enormous quantities of lime have been applied!!

Brazilian soybean breeders have also developed well

adapted soybeans varieties with high tolerance of Al toxicity

Ca+2

Ca+2

Forms of calcium in soil

Ca-rich minerals

CaSO4 * 2H2O

CaAl2Si2O8

Calcium-organo-mineral complexes

Exchan

geable

Ca

+2

Most of the Ca in soil

So

lutio

n

Ca

+2

Plant

available

Ca

All of these forms of

Ca are linked but the

ones on the right side

of the slide are much

more dynamic

CaCO3

plagioclase

gypsum

calcium carbonate

For most soils, Ca+2 is the dominant

exchangeable cation and cation in solution

exchangeable

cations

Ca+2

Ca+2

Ca+2

Ca+2 Ca+2

Ca+2

Ca+2

Ca+2

Ca+2

Ca+2

cations in solution

Ca+2

Ca+2

Ca+2

Ca+2

Ca+2 Ca+2

Ca+2

Ca+2

Solution concentrations of Ca in temperate region

soils tend to range from ~30 to ~300 ppm.

Solution concentrations are not the same as

extractable (soil test) concentrations.

15 ppm Ca

is adequate

for most

crops

How many lbs of Ca arrive at the roots of a

corn crop that transpires 20” of water during a

growing season if the average soil solution

concentration is 15 ppm Ca?

1 acre-inch = 27,000 gallons

1 gallon = 8.3 lbs

27,000 gal/ac-in * 20 inches * 8.3 lbs/ gal = 4,482,000 lbs of H2O/ac

4,482,000 lbs * 15 / 1,000,000 = 67 lbs of Ca

Very few crops need more than 67 lb of Ca/ac

Multi-valent

cations such

as Ca+2, Al+3

and Fe+3 are

important

binding

agents at this

scale.

Impact of cations on flocculation

of clay particles

In contrast,

monovalent

cations such

as Na+ and

K+ cause

clay domains

to disperse.

Impact of cations on flocculation

of clay particles

What about Mg+2?

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Plant uptake of Ca commonly exceeds all other

elements except for N and K

Monocots generally contain less Ca (0.15-0.5% of dry plant tissue).

Dicots generally contain more Ca (1-3% of dry plant tissue)

Woody plants store large amounts of Ca

and often have similar uptake of Ca and N.

Ca movement within plants occurs mostly through the

transpirational stream (water moving upward through the

xylem) as opposed to in the phloem.

Ca movement to growing tissues that are not transpiring

(e.g.., fruits) is very restricted.

Crop Yield N P205 K20 Ca Mg S

Lbs/acre

Corn (grain) 150 bu 110 53 40 2 8 10

Corn (stover) 4.5 tons 100 37 145 26 20 14

Wheat (grain) 40 bu 50 25 15 1 6 3

Wheat (straw) 1.5 tons 20 5 35 6 3 5

Soybeans (beans)

50 bu 188 41 74 19 10 23

Soybeans (stover)

6,100 lb 89 16 74 30 9 12

http://www.soil.ncsu.edu/publications/Soilfacts/AG-439-16/

Calcium content of grain and stover for corn, wheat and soybeans

Location

N P2O5 K2O Ca Mg S

lb/ton

Alabama 52 12 50 19 4.5 3.3

N. Carolina 45 15 45 28 5.3 4.8

IPNI – N. Central 51 12 49 -na- 5.4 5.4

Alberta, Canada -na- 10-15 50-65 30 5-7 5-7

P. Northwest 50-70 8-16 48-72 28-35 5-8 4-6

http://www.aces.edu/pubs/docs/A/ANR-0449/

http://www.soil.ncsu.edu/publications/Soilfacts/ag-439-16W.pdf

http://nanc.ipni.net/articles/NANC0005-EN

http://www1.agric.gov.ab.ca/$department/deptdocs.nsf/all/agdex10073

http://grant-adams.wsu.edu/agriculture/forage/pubs/PNW0611NutrientManagementGuideforDrylandandIrrigated%20AlfalfaintheInlandNorthwest.pdf

Variation in nutrient levels in alfalfa

So how much Ca is removed by a typical alfalfa crop?

100 to > 300 lbs/ac

Physiological importance of Ca

Cell division and elongation

Cell wall development

Cell membrane function

Cell protection against toxins

Nitrate uptake and metabolism

Activity of key enzymes

Starch metabolism

Many fruits and vegetables have dramatic Ca deficiency symptoms such as

Black Heart in celery and broccoli, Tipburn in lettuce and cabbage, White Heart

or Hollow Heart in cucurbits, Blossom End Rot in tomatoes and peppers, and

Pops in peanuts. Tree fruit with low calcium exhibit storage problems such as

bitter-pit in apples, cork-spot in apples and pears, cracking in cherries, and other

degradation of the fruit while in storage.

Ca deficiency is usually associated with growing points (aka meristems)

For example: buds, unfolding leaves, fruits and root tips

Lack of moisture or non-uniform moisture availability is frequently

associated with symptoms of calcium deficiency

Most commercial fruit producers in

the Pacific NW spray their apple and

pear trees with CaCl2 or Ca(NO3)2.

Some varieties receive 3-4

treatments, others 6-7. The

application of foliar Ca is cost

effective and can dramatically

improve fruit quality.

High Response Crops

The following crops have been found to be especially

sensitive to Ca availability:

apples, broccoli, brussel sprouts, cabbage, carrots,

cauliflower, celery, cherries, citrus, conifers, cotton,

curcurbits, melons, grapes, legumes, lettuce, peaches,

peanuts, pears, peppers, potatoes, tobacco, and tomatoes

http://www.spectrumanalytic.com/support/library/ff/Ca_Basics.htm

According to the U of I, Ca deficiency does not occur in Illinois when soil pH is greater

than 5.5.

“Calcium deficiency associated with acidic soils should be corrected using limestone. The laboratory procedure used for Ca is easy and reliable—probably

more accurate than the K test— but since the deficiency does not exist, there is no reason to

recommend the test”.

According to Tiedjens,

pH measurements do not give a true

picture of the need for Ca additions

Low Ca and Mg levels in plant tissue were not always associated

with low pH levels. High Ca and Mg levels in plant tissue were not

always associated with higher pH levels. Other factors which may

have influenced plant tissue levels of Ca and Mg include competitive

cations, crop disease/injury and sub-soil pH.

Soil pH was clearly not the only factor

impacting plant uptake of Ca and Mg

Interactions with other nutrients

Competitive cations: The relative amounts of other cations such as

Na+, K+, Mg+2, NH4+, Fe+2, and Al+3 impact plant uptake of Ca+2. Additions

of large amounts of Ca+2 displace other cations from exchange sites

which may temporarily increase their availability to crops but also

increase their tendency to leach. High K applications have been known

to reduce the Ca uptake in apples, which have inefficient Ca uptake and

translocation within the tree.

Phosphorus: Free or un-combined Ca is normally present in alkaline

soils. This Ca is available to interact with other nutrients. Free Ca reacts

with P to form insoluble (or very slowly soluble) Ca-P compounds that

are not readily available to plants.

Boron: High soil or plant tissue levels of Ca can inhibit B uptake and

utilization. Calcium sprays and soil applications have been effectively

used to help detoxify B over-applications.

SOIL TEXTURE CALCIUM MAGNESIUM

Sandy 400 60-75

Silt loam 800 150-200

Levels of soil test Ca and Mg (lbs/A)

considered adequate for crop production Illinois Agronomy Handbook

A state wide (598 fields in 52 IL counties)

soil fertility survey conducted in 2007/2008

reported average Ca and Mg levels of

4,452 and 732 lbs/ac, respectively.

4500 >> 800 !!

Portion of nutrients taken up by corn that are typically supplied by 3 main mechanisms

Nutrient Root

interception Mass flow Diffusion

% of uptake

Nitrogen <1 80 19

Phosphorous 2 5 93

Potassium 2 18 80

Calcium 150 375 0

Magnesium 33 600 0

Sulfur 5 300 0

Why are some of these #s greater than 100%???

The amount of Ca and Mg brought to roots by the transpirational

stream is often much greater than crop uptake

Why isn’t Ca uptake higher, when more is available?

In contrast with most other nutrients, Ca is taken up

almost exclusively by young root tips.

K uptake is generally higher than Ca uptake even though

solution concentrations of Ca are often 10 times greater

than K concentrations.

Impact of clay mineralogy on Ca availability

Ca Saturation, %

High CEC clays generally need > 70% Ca saturation to provide adequate Ca availability

Low CEC clays generally only need 40-50% Ca saturation

Calc

ium

availa

bili

ty

Review of factors affecting Ca nutrition

Total Ca supply

Soil pH

CEC

% Ca saturation

Relative abundance of other cations

Clay mineralogy

Moisture availability and uniformity of uptake

New root growth

Many crop consultants promote Ca products!

Most claims do not appear to be supported by

research but Ca supplementation programs

merit consideration, especially when growing

“high response” crops

http://www.turfformula.com/images/images-new/super-cal.jpg

A wide range of calcium

products are available on the market.

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Tissue testing can help identify situations when

Ca supplementation is likely to be of value.

Liming Material Approx. % Ca

Calcitic Limestone 32

Dolomitic Limestone 22

Hydrated Limestone 46

Precipitated Lime 60

Blast Furnace Slag 29

Ca fertilizers Approx. % Ca.

Gypsum 22

CaCI2 36

Ca(NO3) 2 19

Ca-Chelates 3-5

Calcium amendments

When evaluating Ca

products, carefully

consider price,

application method

and whether a liming

material is

appropriate.

Does gypsum improve soil structure ??

Ca+2 is a stronger flocculator than Mg+2

but Mg+2 is not a weak flocculator

Ca saturated Mg saturated

Which of these soils is Ca saturated?

Thin sections showing different degrees of surface crust formation

Are these soils representative of real field soils?

Ca saturated Mg saturated

Thin sections showing different degrees of surface crust formation

Some crust prone soils are likely to benefit from additional Ca+2 but care should be

taken to avoid creating K or Mg deficiencies through excessive Ca saturation.

Definitely not !

Ca+2 is a stronger flocculator than Mg+2 but other cations like

Fe+3 and Al+3 are even stronger!

Recent article in Journal of Soil and Water Conservation (peer reviewed scientific journal)

(Norton, 2009)

(Norton, 2009)

+

Large additions of Ca can cause

large losses of other cations

Jack Maloney, IN farmer

Keith Schlapkohl, IA Farmer

Routine applications of gypsum are used by some successful farmer innovators

in the Midwest region.

Mike Starkey, IN Farmer

STOCKTON, IA — Keith Schlapkohl concedes he doesn't know everything about farming. That hasn't stopped him from trying new things on his Scott County farm. "It seems for every one question I get answered, 10 more are raised," he says. Schlapkohl has been trying different ideas dealing with improving nitrogen efficiency and using gypsum on his Eastern Iowa fields. During this time, his yields have averaged close to 300 bushels per acre for corn and 60 bushels for soybeans.

Excerpt from the Iowa Farmer Today article: “Schlapkohl believes gypsum increases production by improving water infiltration. "Its chemical tillage," says Schlapkohl about gypsum. By using gypsum, he has been able to lower the magnesium levels in his soils. Higher magnesium levels tighten up the soil, he explains. Using gypsum also has increased the amount of oxygen in the soil and increased N efficiency, Schlapkohl notes. (he has harvested >300 bu of corn/acre with less than 100 lbs of fertilizer N) He uses a calcium-sulfate product from Cedar Rapids that has a higher ratio — 3:1 — of calcium to sulfur, compared with other sources that have a 1:1 ratio. Schlapkohl says there is more available calcium and less heavy metals in this product compared with regular gypsum. This substance is not as powdery as typical gypsum. He has a business that spreads the gypsum product over the winter. Because he also farms, Schlapkohl likes to spread the product between harvest and planting and stay close to home.”

Mike Starkey says his background in accounting helped him to

prioritize information gathering functions at the farm, including a

heavy use of on-farm trials to evaluate the impact of various

inputs.

“We are not afraid to change things when we find something that

works better,” Mike Starkey says.

The Starkey family has been a no-till operation since 2000 after

trying it briefly in the early '90s. Once he and his family learned

how to properly set up no-till planting equipment, place nitrogen

efficiently and monitor calcium and magnesium levels in soils, the

operation was successful in using no-till.

Starkey echoes Maloney’s comments about water infiltration

improvements after using Gypsoil. “It is amazing how water does

not stand anymore. When it rains hard, water is just gone now.”

Figure 1. Varying degrees of clay dispersion in soils. The higher amounts of dispersal (4 and 5) indicate a soil's suitability for gypsum application. No.0 displays slaking (breaking off of soil particles), compared to 1 to 5 which show clay dispersion

What about the jar test?

A tablespoon of any soluble salt (including table

salt) will flocculate clay in a quart jar!

Without the addition of a flocculating agent, it is normal for fine clay to

stay in suspension after soil is shaken vigorously with water.

Excellent review of research on the value

of gypsum in humid regions

Soils which respond positively to gypsum have greater ability

to adsorb both Ca+2 and SO4-2 than soils which are not

responsive. This could be developed into a routine soil test.

Green data points

represent soils that

responded positively to

gypsum

Magnesium (Mg) has an atomic number of 12

and an atomic weight of 24.3

What does Mg share in common

with other elements in group IlA?

Magnesium (Mg) has an atomic number of 12

and an atomic weight of 24.3

Mg+2

According to the U of I, Mg deficiency occasionally occurs in IL for both corn and

soybean but is limited to sandy, low organic matter soils.

Southern Illinois University research has shown no response to applied Mg even when the Mg test from the surface soil

was below recommended levels. They observed that Mg levels below the surface 7-inch level were adequate and apparently met the needs for optimum crop production

even when surface levels were considered deficient.

Magnesium deficient corn

Magnesium deficient tomato leaves

Physiological role of Mg in plants

Central element of the chlorophyll molecule

Enzyme activator and a constituent of many enzymes

Sugar synthesis

Starch translocation

Plant oil and fat formation

Nutrient uptake control

Increase Fe utilization

Aids N fixation in legume nodules

The basic structure of a chlorophyll molecule is a porphyrin

ring, coordinated to a central atom. This is very similar in

structure to the heme group found in hemoglobin, except that

in heme the central atom is iron, whereas in chlorophyll it is

magnesium.

High Response Crops

The following crops have been found to be especially sensitive

to availability of Mg:

alfalfa, blueberry, beet, broccoli, cabbage, cauliflower,

celery, clover, conifers, cotton, cucumber, eggplant, lettuce,

onion, pepper, potatoes, pumpkin, spinach, squash,

tobacco, tomato and watermelon

http://www.spectrumanalytic.com/support/library/ff/Mg_Basics.htm

Spectrum Analytic Inc (a plant and soil testing lab in OH) analyzed

thousands of plant tissue samples in 2010. The results indicate that

many crops would benefit from more magnesium. In looking at the

data, keep in mind that this is a biased survey. Plant samples are

more often than not submitted to find out why a crop is

underperforming.

http://www.spectrumanalytic.com/doc/_media/library/newsletter/spectrum_ag_winter_2010.pdf

Sources of Mg

Dolomitic limestone is a mixture of CaCO3 and MgCO3 and is the

lowest cost source of Mg but should only be applied when lime is

needed. The Mg content of dolomitic limestone varies from 8-10%.

To be most effective as a source of Mg, dolimitic lime should be

broadcast and incorporated.

Neutral salt sources of Mg

Sul-po-mag has a Mg content of 11%. The sulfur (S) and K2O

concentrations are ~22%.

Epsom salts = MgSO4·7H2O = 9.9% Mg

MgCl2, Mg(NO3)2 and Mg chelates can be used as solutions and

foliar sprays

Cation Balancing??

Proposed by Firman Bear, William Albrecht and

others prior to the advent of soil test calibration

Claims associated w/ “balanced” Ca:Mg ratios

• Improves soil structure

• Reduces weed populations

• Stimulates populations of earthworms and beneficial microorganisms

• Improves forage quality

• Excess soil Mg “ties up” and promotes leaching of other plant nutrients

• Better “balance” of soil nutrients

• Improved plant and animal health

• “Cows milk easier”

U of WI Conclusions

• Alfalfa yield related to exchangeable K and soil pH, not Ca:Mg ratio

• Neither Ca or Mg additions affected weeds

• Earthworms related to organic matter, not Ca:Mg ratio

• Alfalfa quality related to pH and stand, not Ca:Mg ratio

• No justification to use calcitic over dolomitic lime or adding extra Ca

NCR 103 Committee NC Regional Publication 533 Soil Cation Ratios for Crop Production

– Ca and Mg levels can be balanced but too low

– Field research does not support “optimal” Ca:Mg ratio concept

Concludes:

“A sufficient supply of nutrient cations is the most important consideration in making economic fertilizer recommendations”

Bear, F.E., and S.J. Toth. 1948. Influence of calcium on availability of other soil cations. Soil

Sci. 65:67-74.

Eckert, D.J., and E.O. McLean. 1981. Basic cation saturation ratios as a basis for fertilizing and

liming agronomic crops: 1. Growth chamber studies. Agron. J. 73:795-799.

Eckert, D.J. 1987. Soil test interpretations: Basic cation saturation ratios and sufficiency levels.

In J.R. Brown (ed.) Soil Testing: Sampling, Correlation, Calibration, and Interpretation. Special

Publication No. 21. Soil Science Society of America. Madison, WI.

Graham, E.R. 1959. An explanation of theory and methods of soil testing. Missouri Agric. Ext.

Stn. Bull. 734.

Hunter, A.S. 1949. Yield and composition of alfalfa as affected by various calcium -magnesium

ratios in the soil. Soil Sci. 67:53-62.

Liebhardt, W.C. 1981. The basic cation saturation concept and lime and potassium

recommendations on Delaware’s Coastal Plain soils. Soil Sci. Soc. Am. J. 45:544-549.

McLean, E.O., R.C. Hartwig, D.J. Eckert, and G.B. Triplett. 1983. Basic cation saturation ratios

as a basis for fertilizing and liming agronomic crops. II. Field studies. Agron. J. 75:635-639.

Simson, C.R., R.B. Corey, and M.E. Sumner. 1979. Effect of varying Ca:Mg ratios on yield and

composition of corn and alfalfa. Commun. Soil Sci. and Plant Anal. 10:153-162.

Many studies have evaluated the base saturation ratio concept -

none have concluded that specific optimum ratios exist

Why no crop response to “Ca:Mg ratio” ?

• Ca and Mg levels in the soil solution are normally high compared to plant uptake

• Plant K uptake is 2-4 times that of Ca and Mg despite much lower levels of K in the soil solution

• Roots preferentially take up K and exclude Ca and Mg.

K:Mg ratio may be more important than Ca:Mg ratio

A number of studies (e.g., Rahmatullah and Baker (1981)

and Stout and Baker (1981) have reported an inverse

relationship between K:Mg ratio and Mg uptake by corn

seedlings

Wilkinson et al. (1987) reported that applications of high

rates of K to cool season grass pastures, whether from

manure or inorganic fertilizers, increased the incidence of

grass tetany.

.

Johannsonn and Hahlin (1977) reported a strong

inverse relationship between K:Mg ratio and Mg

uptake by oats, and only a minor effect of Ca

saturation on K and Mg uptake.

1. When the soil test K to soil test Mg ratio exceeds 1.5 many crops will have

trouble taking up Mg, almost regardless of the soil Mg test level.

2. When the ratio is between 1 and 1.5 some grasses will have occasional Mg

problems, and corn is the most sensitive grass species.

3. When the ratio is less than 1, there are few Mg problems in any crop,

assuming that the soil Mg is not initially deficient.

4. When the soil pH is less than 6.0, situations described in points 1 through 3

will occur at a lower soil K:Mg ratio and the Mg shortage will be more severe.

5. It is rare to find an example where the soil levels of K or Mg have any effect on

Ca uptake.

6. It is very rare to find poor Ca uptake when the soil Ca saturation is higher than

50%. Some exceptions to this can be found with some crops, such as apples,

that use Ca inefficiently.

http://www.spectrumanalytic.com/support/library/ff/Is_Magnesium_a_Hidden_Problem_in_your_area.htm

From the Spectrum Analytic, Inc website:

Good overview of

Mg concepts

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