What is cec in agriculture


Cation exchange capacity (CEC) is a useful indicator of soil fertility because it shows the soil’s ability to supply three important plant nutrients: calcium, magnesium and potassium.

What is CEC in soil?

Sandy soils rely heavily on the high CEC of organic matter for the retention of nutrients in the topsoil. Cation exchange capacity ( CEC) is a measure of the soil’s ability to hold positively charged ions.

What does CEC stand for?

Soil cation exchange capacity (CEC) is a significant number for an important soil characteristic.

What is the CEC of a container?

This is true on a weight basis as the CEC is expressed as meq / 100 grams. However, containers are filled based on their volume and not the weight of the growing medium they hold.

What is effective CEC (ECEC)?

This ‘exchange acidity’ needs to be included when summing the base cations and this measurement is referred to as effective CEC ( ECEC ). Different laboratories use various methods to measure CEC, and can return contrasting results depending on the fraction of the soil measured.


What is a good CEC in soil?

Soils are predominately upland, well-drained red soils with a CEC of 6 to 12 meq/100 g. Soils in their native state are acid and low in phosphorus but higher in potassium than the Coastal Plain soils.

What is CEC method?

A new implementation of the Competing Enantioselective Conversion (CEC) method was developed to qualitatively determine the absolute configuration of enantioenriched secondary alcohols using thin-layer chromatography.

How do you calculate CEC in soil?

To determine the cation exchange capacity (CEC), calculate the milliequivalents of H, K, Mg, and Ca per 100g of soil (meq/100g soil) by using the following formulas: H, meq/100g soil = 8 (8.00 – buffer pH) K, meq/100g soil = lbs/acre extracted K ÷ 782. Mg, meq/100g soil = lbs/acre extracted Mg ÷ 240.

What is CEC and AEC?

Cation exchange capacity (CEC) represents the quantity of negative charge available to attract cations. Anion exchange capacity (AEC) represents the positive charge available to attract anions in solution.

How does CEC affect soil fertility?

As CEC measures a soils ability to hold nutrients it is a key determinant of soil fertility. Soils with high CEC have the ability to hold more cations making them sufficient in calcium, magnesium and other cations. On the contrary, soils with low CEC are easily deficient in cations.

What is a cation in soil?

Cations are positively charged ions such as calcium (Ca2+), magnesium (Mg2+), and potassium (K+), sodium (Na+) hydrogen (H+), aluminum (Al3+), iron (Fe2+), manganese (Mn2+), zinc (Zn2+) and copper (Cu2+). The capacity of the soil to hold on to these cations called the cation exchange capacity (CEC).

Why does CEC increase with pH?

The higher the pH of the surrounding solution, i.e. higher OH ion concentration more H ions are attracted from the OH bonds of the clay structure and the higher the CEC of the clay.

What does low CEC mean?

If the CEC number is low, not many molecules are able to bind (react) to the particle surface. If the number is high, a larger number of molecules can bind to the particle’s surface.

What is CEC in clay?

Cation exchange capacity (CEC) is the amount of a cation that can be exchanged by another cation on the surface of a clay mineral. It is expressed in cmol(+)/kg, which is numerically equivalent to meq/100 g, where mol(+) represents moles of electrical charge.

What is the soil pH?

Most soils have pH values between 3.5 and 10. In higher rainfall areas the natural pH of soils typically ranges from 5 to 7, while in drier areas the range is 6.5 to 9. Soils can be classified according to their pH value: 6.5 to 7.5—neutral.

What is high activity clay?

High activity clays have a high ‘cation exchange capacity’ (CEC), due to their large surface area. This means that these clays have a great capacity to retain and supply large quantities of nutrients, such as calcium, magnesium, potassium, and ammonium.

What is soil electrical conductivity?

Soil electrical conductivity (EC) is a measure of the amount of salts in soil (salinity of soil). It is an excellent indicator of nutrient availability and loss, soil texture, and available water capacity.

How does CEC relate to farming?

Now that you understand (I hope) CEC, how does knowing the number and understanding the concept relate to your farming practices? The basic aspect to remember is CEC indicate s how well soil holds on to anything applied to it (emphasis on anything) and how difficult it is for plants to take it away. Soils with low CEC grab hold of very little. Water passes through beach sand at 20 inches an hour, but in clay or organic soil, it could be less than an inch an hour. This indicates how to irrigate different soils. Low CEC soils need quick but often irrigation, while high CEC soils need slow irrigation less often. If growers have drip irrigation on a sandy site, it is best to irrigate twice a day using high flow emitters, but only for an hour or less each time. If soil has greater clay content, it may be best to irrigate with low flow emitters for a longer time (six or more hours) every three of four days.

What does CEC mean in soil?

CEC is short for cation exchange capacity, but what is that? What does CEC mean for you as a grower and how does soil with a low number differ from soil with a high number? Soil particles are negatively charged and attract positively charged molecules. These molecules can be nutrients, water, herbicides and other soil amendments.

What is the CEC value of Michigan soil?

Michigan soils have a wide range of CEC values with sand-based soils having numbers below 10, clay and silt soils having values of 15 to 25 and organic soils approaching 100.

How to determine CEC?

The only way CEC can be determined is by conducting a soil test.

When applying nutrients to low CEC soil, it is best to apply a little at a time?

When applying nutrients to low CEC soil, it is best to apply a little at a time otherwise you run the risk of leaching them through the soil and into ground water, especially on seasonally high water table sites.

What is the CEC of soil?

Cation exchange capacity (CEC) is a useful indicator of soil fertility because it shows the soil’s ability to supply three important plant nutrients: calcium, magnesium and potassium.

How to improve CEC in weathered soil?

You can improve CEC in weathered soils by adding lime and raising the pH. Otherwise, adding organic matter is the most effective way of improving the CEC of your soil. This can be done with permanent pasture, regular slashing, green manure crops, leaving crop stubbles to rot, rotating crops or pasture, and the addition of mulch and manure.

What happens if the CEC is low?

If a soil has a low CEC and high sodium levels, up to half the cations in the soil may be in the water around the soil particles, and not actually held by the particles. These cations are very susceptible to being leached or drained away in the soil water.

What are the most exchangeable cations in soil?

The five most abundant exchangeable cations in the soil are calcium (Ca ++ ), magnesium (Mg ++ ), potassium (K + ), sodium (Na +) and aluminium (Al +++ ).

Why is soil pH important for CEC?

Soil pH is important for CEC because as pH increases (becomes less acid), the number of negative charges on the colloids increase, thereby increasing CEC.

What is the term for the capacity of a colloid to hold and exchange cations?

The stronger the colloid’s negative charge, the greater its capacity to hold and exchange cations, hence the term cation exchange capacity (CEC).

What is CEC in soil?

CEC is a measure of the ability of a soil to hold cations by electrostatic attraction. Cations are positively charged; they are held by negatively charged sites on clay and humus particles called colloids. These consist of thin, flat plates and, for their size, have a comparatively large surface area. For this reason they are capable of holding very large quantities of cations. The stronger the negative charge on the colloid, the greater its capacity to hold and exchange cations, hence the term CEC. In a research study of equilibrium partitioning of heavy metals in Dutch field soils, it was found that the solid/aqueous phase partition coefficients for Cd, Cu, Ni, Pb, and Zn correlated well with CEC ( Janssen et al., 1997 ). In a study on Pb bioavailability and toxicity to earthworms significant negative relationships between mortality and pH and between mortality and CEC were demonstrated ( Bradham et al., 2006 ). In the same study statistically significant negative relationships emerged between internal Pb and CEC and pH. Furthermore, the relationship between earthworm internal Pb concentration and soil properties such as pH and CEC was also significant ( Bradham et al., 2006 ).

What is the CEC of a plant?

The CEC of plant roots was once regarded as the basis for crops to exchange cations with those held in soil colloid, and crops with high root CEC could take up more calcium from soil and thus liberate P bound with calcium for crop use. Our study with wheat and pea showed that the root CEC of pea was several times higher than that of wheat in terms of per kilogram dry root or root weight per pot. However, the P uptake amounts by the two crops did not follow the same pattern as root CEC. In relation to root CEC, crop uptake of the calcium amount was considered a mechanism for P release and for crop uptake, and the ratio of CaO to P2 O 5 in plant tissue was proposed as the index for indicating the plant’s ability to absorb P from RPs. However, later researchers have rejected this hypothesis.

How does biochar affect soil?

Biochars can potentially increase the cation exchange capacity (CEC) of soils especially for highly weathered, nutrient-poor sandy soils; however, this is dependent on biochar properties and aging of applied biochar in the soil. The lack of standardized methodology of assessment of CEC in biochars makes it difficult to compare materials from different feedstocks and temperatures of production. In some cases, increasing pyrolysis temperature has been shown to decrease CEC of the biochar (Gaskin et al., 2008 ), while in other cases, CEC increases with increasing temperature ( Singh et al., 2010b ). The lower temperature biochar described by Gaskin et al. (2008) was shown to have a higher degree of oxygen surface functional groups, resulting in increased CEC. The published data suggest that biochars from woody materials tend to provide low CEC values, while nonwoody plant materials such as sugarcane trash (leaf) or tree bark tend to have higher CEC values (Chan et al., 2007; Gaskin et al., 2008; Gundale and DeLuca, 2006; Major et al., 2009; Singh et al., 2010b; Van Zwieten et al., 2010b; Yamamoto et al., 2006 ).

What is the median effective CEC?

The median value for effective cation-exchange capacity (effective CEC) was 1.1 cmol c /dm 3 (ranging from 0.35 to 8.10 cmol c /dm 3 ( Fig. 11 ). By the time this survey was done, there were no criteria in Brazil being used to interpret such a data, yet 96.5% of the samples presented <4 cmol c /dm 3, a category proposed by Buol et al. (1975) as the upper limit for the low class of effective CEC (measured by a neutral unbuffered salt extraction) ( Fig. 11 ).

What determines the CEC of a soil?

The CEC of a soil is largely determined by the mineral composition of the clay-sized fraction. The source of the negative charge in clay minerals can be either permanent or variable. Permanent charge results from isomorphous substitution among cations with differing valences within the crystalline clay structure, and is a permanent characteristic of the mineral. Smectite, vermiculite, and illite are commonly occurring clay minerals with permanent charge. Variable charge results from the protonation and deprotonation of OH groups on the surfaces of Al and Fe oxides, crystalline or amorphous, and exposed edges of layer-silicate minerals. Kaolinite, hydroxy-interlayered vermiculite, goethite, gibbsite, quartz, and allophane are some of the clay minerals with variable charge. Carboxyl and OH groups in soil organic matter also have a variable-charge behavior, wherein the amount of negative charge increases with soil pH.

What does 240 mean in CEC?

240. The high CEC values mean that peat has a good capacity to store cationic nutrients for plants. However, by contrast, the anion exchange capacity is very low. This means, for instance, that, unlike in most soils, phosphate can easily be leached from peat growing media as will N present in nitrate form.

Is root CEC higher than wheat?

Our study with wheat and pea showed that the root CEC of pea was several times higher than that of wheat in terms of per kilogram dry root or root weight per pot. However, the P uptake amounts by the two crops did not follow the same pattern as root CEC.

What is CEC in soil?

Fundamentals of Soil Cation Exchange Capacity (CEC) David B. Mengel, Department of Agronomy, Purdue University. Soils can be thought of as storehouses for plant nutrients. Many nutrients, such as calcium and magnesium, may be supplied to plants solely from reserves held in the soil. Others like potassium are added regularly to soils as fertilizer …

What is the cation exchange capacity of soil?

The cation exchange capacity of a soil determines the number of positively-charged ions cations-that the soil can hold. This, in turn, can have a significant effect on the fertility management of the soil.

How to measure cation exchange capacity?

The direct method is to replace the normal mixture of cations on the exchange sites with a single cation such as ammonium (NH 4+ ), to replace that exchangeable NH 4+ with another cation, and then to measure the amount of NH 4+ exchanged (which was how much the soil had held).

What are the cations that are exchangeable?

Cations held on the clay and organic matter particles in soils can be replaced by other cations; thus, they are exchangeable. For instance, potassium can be replaced by cations such as calcium or hydrogen, and vice versa.

What is the purpose of cations in soil?

Cations on the soil’s exchange sites serve as a source of resupply for those in soil water which were removed by plant roots or lost through leaching. The higher the CEC, the more cations which can be supplied. This is called the soil’s buffer capacity .

Can I use potash on low CEC soil?

Also, multi-year potash applications are not recommended on low-CEC soils. Higher-CEC soils (greater than 10 meg/100g), on the other hand, experience little cation leaching, thus making fall application of N and K a realistic alternative. Applying potassium for two crops can also be done effectively on these soils.

Do high CEC soils need lime?

Therefore, high-CEC soils generally do not need to be limed as frequently as low-CEC soils; but when they do become acid and require liming, higher lime rates are needed to reach optimum pH. CEC can also influence when and how often nitrogen and potassium fertilizers can be applied.

What is the CEC in soil?

Cation exchange capacity ( CEC) is a measure of the soil’s ability to hold positively charged ions. It is a very important soil property influencing soil structure stability, nutrient availability, soil pH and the soil’s reaction to fertilisers and other ameliorants (Hazleton and Murphy 2007).

Which soil fraction tends to have a higher CEC?

Soils with a higher clay fraction tend to have a higher CEC.

What is the CEC of soil?

Cation exchange capacity (CEC) is a measurement of soil’s ability to hold positively charged ions (cations) by using electrical attraction. When soil can hold onto essential nutrients and minerals, they are more available to plant roots that need them for survival.

Why is CEC important for soil fertility?

That means CEC is a very useful gauge for soil fertility, because if the soil is efficiently storing cations, plants have access to the nutrition they need.

What is the electrical conductivity of soil?

Electrical Conductivity (EC) Soil contains ions: cations (positively charged ions) and anions (negatively charged ions). The attraction of these opposingly charged particles allows soil to transmit a measurable electrical current. This current is the highway system through which nutrients can move through the soil and become available …

How are cations held in soil?

Cations can be held and stored in the soil by negatively charged colloids: These colloid particles consist of flat, thin plates with a lot of negatively charged surface area to hold and store large quantities of cations. A plant can then trade for the nutrients it can’t produce with hydrogen cations it can produce.

What is the EC of a patch of soil?

The EC of a patch of soil is measured in miliSiemens per meter (mS/m) or deciSiemens per meter (dS/m) and can provide a lot of helpful information about soil health.

Can you get EC measured for soil?

If you have your soil regularly tested, you can also request an EC measurement for your samples as well. Just remember that EC levels can greatly vary within an expanse of soil (especially due to changing water levels). Some crops tolerate a wider range of EC levels, while others prefer a more narrow threshold.

What does it mean when a soil has a higher CEC?

This usually means that high CEC (clay) soils have a greater water holding capacity than low CEC (sandy) soils.

What are the cations in soil?

Cations are positively charged ions such as calcium (Ca2+), magnesium (Mg2+), and potassium (K+), sodium (Na+) hydrogen (H+), aluminum (Al3+), iron (Fe2+), manganese (Mn2+) , zinc (Zn2+) and copper (Cu2+). The capacity of the soil to hold on to these cations called the cation exchange capacity (CEC). These cations are held by the negatively charged clay and organic matter particles in the soil through electrostatic forces (negative soil particles attract the positive cations). The cations on the CEC of the soil particles are easily exchangeable with other cations and as a result, they are plant available. Thus, the CEC of a soil represents the total amount of exchangeable cations that the soil can adsorb. The cations used by plants in the largest amounts are calcium, magnesium, and potassium. In most soils within humid regions such as in New York, sodium is not present in sufficient quantities to occupy a significant amount of the CEC. However, in dry climates, sodium can occupy an important portion of the CEC. Other cations that can occupy cation exchange sites in New York soils are hydrogen, aluminum, iron and manganese. Cations such as zinc and copper are typically present in the soil in too low a concentration to occupy much of the CEC.

What is the CEC of a soil?

Cation exchange capacity (CEC) is the amount of exchangeable cations per unit weight of dry soil. It is measured in milliequivalents (me) of cations per 100 gms of soil (recently C mol (P +) kg -1 soil).

Why is the term equivalent used for CEC?

For the measurement of CEC, the term equivalent or more especially “Milliequivalent” is used because the number of negative charge sites in a given soil sample does not change, but the weights of the cations that may be adsorbed to those sites at one time do change because they have different weights.

What is the CEC of 100 g of clay?

If 100 g of a certain clay is capable of exchanging a total of 250 mg of calcium (Ca 2+ ), the cation exchange capacity (CEC) is 250/20 or 12.5 me/100 g or 12.5 C mol (P +) kg -1.

Which soils have higher cation exchange capacities?

As for example, soils with large amounts of clay and organic matter will have higher cation as well as anion exchange capacities as sandy soils low in organic matter. Also, soils with predominately 2: 1 colloids will have higher exchange capacities than soils with predominately 1: 1 mineral colloids.

How much hydrogen can a clay cation exchange?

Thus, if a clay has a cation exchange capacity of 1 milliequivalent (1 me/100 g); it is capable of exchanging 1 mg of hydrogen or its equivalent for every 100 g of clay. The weight of one hectare furrow slice (depth 0-15 cm) is 2.2 × 10 6 kilograms. Therefore, one hectare furrow slice. (0-15 cm) soil is capable of exchanging 22 kilograms of hydrogen.

What does CEC mean in soil?

The numerical value for CEC represents how much nutrition can be held by a given amount of soil. For example one pound of a clay loam soil with a CEC value of 20 will hold 4 times as many nutrients as a sandy soil with a CEC value of 5. 20/4 = 5.

What soil is good for pecan trees?

Growing Pecan Trees in Western Alkaline Soil. It’s common to see nutrient and water inhibition compromise the production of pecans in the arid western states, particularly where the soils are high pH, which can tie up nutrients such as zinc, iron, phosphorus and more.

Is CEC a limiting factor?

CEC may be the limiting factor for having a fertile soil. In order to improve the fertility of your soil when CEC is limiting you, add Humic Acids as the most effective tool. However, don’t be fooled by “New and Improved” formulations of Humic Acids that claim you only need a few gallons or pounds per acre, as that’s not how the math works and CEC and the ability to hold onto the hundreds of pounds of nutrients needed by a crop is all about math.



  • Soils (Fertility)Purdue University Cooperative Extension Service West Lafayette, IN 47907
    Soils are composed of a mixture of sand, silt, clay and organicmatter. Both the clay and organic matter particles have a net negativecharge. Thus, these negatively-charged soil particles will attract andhold positively-charged particles, much like the opposite poles of amagnet attract ea…

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Forms of Nutrient Elements in Soils

  • The most common soil cations (including their chemical symbol andcharge) are: calcium (Ca++), magnesium (Mg++), potassium (K+),ammonium (NH4+), hydrogen (H+) and sodium (Na+). Notice that somecations have more than one positive charge. Common soil anions (with their symbol and charge) include: chlorine(Cl-), nitrate (NO3-), sulfate (S04=) and phosphate (PO43-). Noteals…

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Defining Cation Exchange Capacity

  • The total number of cations a soil can hold–or its total negativecharge–is the soil’s cation exchange capacity. The higher the CEC,the higher the negative charge and the more cations that can be held. CEC is measured in millequivalents per 100 grams of soil (meq/100g).A meq is the number of ions which total a specific quantity ofelectrical charge…

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Measuring Cation Exchange Capacity

  • Table 1. Normal Range of CEC Values for Common Color/Texture SoilGroups.
    More commonly. the soil testing labs estimate CEC by summing thecalcium, magnesium and potassium measured in the soil testingprocedure with an estimate of exchangeable hydrogen obtained from thebuffer pH. Generally, CEC values arrived at by this summation methodwill be sl…
  • Buffer Capacity and Percent Base Saturation
    Cations can be classified as either acidic (acid- forming) orbasic. The common acidic cations are hydrogen and aluminum; commonbasic ones are calcium, magnesium, potassium and sodium. Theproportion of acids and bases on the CEC is called the percent basesaturationand can be cal…

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