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on the surfaces of soil particles bind positively-charged atoms or molecules (cations), but allow these to exchange with other positively charged particles in the surrounding soil water. This is one of the ways that solid materials in soil alter the chemistry of the soil. CEC affects many aspects of
177:
The cation-exchange capacity of a soil is determined by its constituent materials, which can vary greatly in their individual CEC values. CEC is therefore dependent on parent materials from which the soil developed, and the conditions under which it developed. These factors are also important for
139:
The amount of negative charge from deprotonation of clay hydroxy groups or organic matter depends on the pH of the surrounding solution. Increasing the pH (i.e. decreasing the concentration of H cations) increases this variable charge, and therefore also increases the cation-exchange capacity.
168:
at a particular pH value. If this pH differs from the natural pH of the soil, the measurement will not reflect the true CEC under normal conditions. Such CEC measurements are called "potential CEC". Alternatively, measurement at the native soil pH is termed "effective CEC", which more closely
116:
Cations are adsorbed to soil surfaces by the electrostatic interaction between their positive charge and the negative charge of the surface, but they retain a shell of water molecules and do not form direct chemical bonds with the surface. Exchangeable cations thus form part of the
156:
Cation-exchange capacity is measured by displacing all the bound cations with a concentrated solution of another cation, and then measuring either the displaced cations or the amount of added cation that is retained. Barium (Ba) and ammonium
101:. The replacement of aluminium or silicon atoms by other elements with lower charge (e.g. Al replaced by Mg) can give the clay structure a net negative charge. This charge does not involve deprotonation and is therefore
294:
and iron and aluminium oxides often carry positive charges. In most soils the cation-exchange capacity is much greater than the anion-exchange capacity, but the opposite can occur in highly weathered soils, such as
524:
Ramos, F.T.; Dores E.F.G.C.; Weber O.L.S.; Beber D.C.; Campelo Jr J.H.; Maia J.C.S. (2018) "Soil organic matter doubles the cation exchange capacity of tropical soil under no-till farming in Brazil".
109:
groups that are deprotonated to leave negative charges at the pH levels in many soils. Organic matter also makes a very significant contribution to cation exchange, due to its large number of charged
278:
Base saturation expresses the percentage of potential CEC occupied by the cations Ca, Mg, K or Na. These are traditionally termed "base cations" because they are non-acidic, although they are not
113:. CEC is typically higher near the soil surface, where organic matter content is highest, and declines with depth. The CEC of organic matter is highly pH-dependent.
487:
Holmgren, G.G.S.; Meyer, M.W.; Chaney, R.L.; Daniels, R.B. (1993). "Cadmium, Lead, Zinc, Copper, and Nickel in
Agricultural Soils of the United States of America".
1203:
858:
821:
121:
above the charged surface. The binding is relatively weak, and a cation can easily be displaced from the surface by other cations from the surrounding solution.
282:
in the usual chemical sense. Base saturation provides an index of soil weathering and reflects the availability of exchangeable cationic nutrients to plants.
554:
1171:
1115:
82:/kg could hold 10 cmol of Na cations (with 1 unit of charge per cation) per kilogram of soil, but only 5 cmol Ca (2 units of charge per cation).
1258:
1073:
1103:
70:
Cation-exchange capacity is defined as the amount of positive charge that can be exchanged per mass of soil, usually measured in cmol
1279:
547:
1151:
1136:
1131:
908:
188:
1198:
1193:
1141:
888:
118:
873:
584:
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Positive charges of soil minerals can retain anions by the same principle as cation exchange. The surfaces of kaolinite,
893:
868:
878:
540:
918:
853:
680:
655:
1166:
752:
665:
650:
605:
452:
85:
Cation-exchange capacity arises from various negative charges on soil particle surfaces, especially those of
1284:
1093:
816:
811:
702:
670:
1161:
1146:
1088:
1083:
838:
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762:
579:
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977:
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1222:
1058:
848:
707:
660:
496:
421:
105:-independent, and called permanent charge. In addition, the edges of these sheets expose many acidic
54:, Ca) in plant-available form. It also indicates the capacity to retain pollutant cations (e.g. Pb).
675:
90:
1229:
1234:
1156:
982:
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197:
528:
466:
826:
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110:
94:
1063:
1021:
913:
804:
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697:
504:
448:
279:
148:
1038:
774:
508:
165:
42:
1246:
500:
425:
74:/kg. Some texts use the older, equivalent units me/100g or meq/100g. CEC is measured in
17:
994:
161:) are frequently used as exchanger cations, although many other methods are available.
47:
169:
reflects the real value, but can make direct comparison between soils more difficult.
1273:
1188:
1053:
1011:
957:
779:
600:
86:
1108:
967:
942:
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645:
50:, as it indicates the capacity of the soil to retain several nutrients (e.g. K, NH
1098:
1033:
1016:
989:
962:
947:
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635:
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75:
789:
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615:
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727:
291:
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106:
62:
1048:
1004:
972:
300:
125:
1026:
952:
620:
610:
98:
38:
439:
Carroll, D. (1959). "Cation exchange in clays and other minerals".
164:
CEC measurements depend on pH, and therefore are often made with a
1043:
147:
131:
130:
61:
934:
722:
536:
376:
Zech, Wolfgang; Schad, Peter; Hintermeier-Erhard, Gerd (2014).
532:
78:
of electric charge, so a cation-exchange capacity of 10 cmol
102:
453:
10.1130/0016-7606(1959)70[749:ieicao]2.0.co;2
178:
determining soil pH, which has a major influence on CEC.
97:
clays consist of layered sheets of aluminium and silicon
402:(2nd ed.). Cambridge: Cambridge University Press.
380:(in German) (2nd ed.). Berlin: Springer Spektrum.
1180:
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837:
634:
593:
398:Schaetzl, Randall J.; Thompson, Michael L. (2015).
347:(14th ed.). Upper Saddle River, USA: Pearson.
66:Cation exchange at the surface of a soil particle
365:(3rd ed.). Oxford: Oxford University Press.
196:Average CEC (pH 7) for some US soils based on
548:
441:Bulletin of the Geological Society of America
420:. Berlin: Springer-Verlag. pp. 709–754.
135:Effect of soil pH on cation-exchange capacity
8:
338:
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46:soil chemistry, and is used as a measure of
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41:can be retained on soil particle surfaces.
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416:Pansu, Marc; Gautheyrou, Jacques (2006).
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184:Typical ranges for CEC of soil materials
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409:
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467:"Cations and Cation Exchange Capacity"
509:10.2134/jeq1993.00472425002200020015x
343:Brady, Nyle C.; Weil, Ray R. (2008).
7:
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152:Principle of CEC measurement in soil
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1104:Environmental impact of irrigation
345:The nature and properties of soils
25:
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1217:
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489:Journal of Environmental Quality
400:Soils: Genesis and geomorphology
1172:Agriculture and the environment
909:British Agricultural Revolution
1116:Climate change and agriculture
889:Agriculture in the Middle Ages
1:
894:Arab Agricultural Revolution
361:Birkeland, Peter W. (1999).
37:) is a measure of how many
1301:
854:Agriculture in Mesoamerica
1213:
1204:Universities and colleges
822:Universities and colleges
627:
570:
418:Handbook of Soil Analysis
58:Definition and principles
27:Measure of soil chemistry
1189:Agriculturist profession
666:Agricultural engineering
651:Agricultural cooperative
31:Cation-exchange capacity
18:Cation exchange capacity
1280:Environmental chemistry
1094:Agricultural wastewater
817:Sustainable food system
812:Sustainable agriculture
703:Animal-free agriculture
671:Agricultural technology
363:Soils and geomorphology
286:Anion-exchange capacity
1194:Agricultural machinery
1152:History of agriculture
1137:Agriculture by country
1132:Agricultural machinery
1089:Agricultural pollution
1084:Agricultural expansion
859:Austronesian expansion
770:Mechanised agriculture
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136:
67:
1199:Government ministries
1142:Agriculture companies
978:Convertible husbandry
656:Agricultural supplies
606:Agricultural Engineer
151:
134:
65:
849:Neolithic Revolution
708:Cellular agriculture
661:Agricultural science
501:1993JEnvQ..22..335H
426:2006hsa..book.....P
204:Soil Taxonomy order
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91:soil organic matter
983:Rotational grazing
899:Columbian exchange
520:General References
198:USDA Soil Taxonomy
195:
154:
137:
68:
1267:
1266:
827:Urban agriculture
800:Rice-duck farming
748:Intensive farming
718:Extensive farming
529:10.1002/jsfa.8881
526:J Sci Food Agric.
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111:functional groups
16:(Redirected from
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1064:Wildlife farming
914:Green Revolution
865:Ancient history
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713:Contract farming
698:Animal husbandry
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43:Negative charges
21:
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995:Insect farming
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874:Ancient Greece
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495:(2): 335–348.
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173:Typical values
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95:Phyllosilicate
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48:soil fertility
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958:Dairy farming
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869:Ancient Egypt
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780:Paludiculture
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601:Agriculturist
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32:
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1109:Overdrafting
968:Goat farming
879:Ancient Rome
785:Permaculture
743:Horticulture
688:Agroforestry
646:Agribusiness
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470:. Retrieved
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1259:Wikiproject
1099:Overgrazing
1034:Pig farming
1017:Paddy field
990:Hydroponics
963:Fur farming
948:Aquaculture
943:Agrivoltaic
924:Monoculture
845:Prehistory
795:Polyculture
616:Farm worker
594:Occupations
564:Agriculture
144:Measurement
1274:Categories
1125:Categories
790:Plantation
738:Free range
733:Feed ratio
307:References
297:ferralsols
1157:Livestock
1000:Livestock
728:Farmhouse
292:allophane
264:Histosols
256:Vertisols
248:Mollisols
232:Spodosols
207:CEC (cmol
1223:Category
1049:Orchards
1022:Pastoral
693:Agronomy
472:June 23,
240:Entisols
224:Alfisols
216:Ultisols
107:hydroxyl
1247:Commons
1059:Terrace
1005:Pasture
973:Grazing
919:Organic
839:History
753:animals
676:Digital
636:General
580:History
575:Outline
497:Bibcode
422:Bibcode
301:oxisols
126:Soil pH
39:cations
1235:Portal
1076:impact
1027:Bocage
953:Cattle
621:Herder
611:Farmer
99:oxides
1181:Lists
1044:Ranch
1012:Mixed
763:crops
585:Index
280:bases
259:35.6
251:18.7
243:11.6
211:/kg)
76:moles
758:pigs
723:Farm
474:2017
267:128
235:9.3
219:3.5
89:and
505:doi
449:doi
303:).
157:(NH
35:CEC
1276::
503:.
493:22
491:.
445:70
443:.
408:^
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353:^
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227:9
103:pH
93:.
556:e
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507::
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299:(
209:c
159:4
80:c
72:c
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33:(
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