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Basic training: CEC
Christoph KesselOPVG – District 1 Tomato Day
February 17, 2011
Soil test report
What is cation exchange capacity (CEC)?
• relative reflection of the total ability of soil to hold (adsorb) cation nutrients
What is cation exchange capacity?
IPNI Soil Fertility Manual 2006
Soil test report
potassium + magnesium + calcium + sodium = CEC cmol/kgK + Mg + Ca + Na = CEC cmol/kg
Basic cations: • potassium (K)• magnesium ( Mg)• calcium (Ca)
CEC calculated using
Reported ppm K, Mg, Ca, Na
Converted to meq/100g soil
Added together
% base saturation calculated using:
meq/100g soil of K, Mg, Ca, Na
divide by CEC meq/100 g soil
X 100
2-5% K, 6-12% Mg, 65-85% Ca
Soil test report
A BpH 7.5 7.6
ppmpotassium 80 66
magnesium 250 195calcium 4086 2650
CEC cmol/kg 24 15
2 soil reports
Same soil, different labs
A BpH 7.5 7.6
ppmpotassium 80 66
magnesium 250 195calcium 4086 2650
CEC cmol/kg 24 15
Same soil, different labs
A BpH 7.5 7.6
ppmpotassium 80 66
magnesium 250 195calcium 4086 2650
CEC cmol/kg 24 15CEC = potassium (K) + magnesium (Mg) + calcium (Ca) cmol/kg
A BpH 7.7 7.7
ppmpotassium 85 85
magnesium 373 373calcium 4416 4416
CEC cmol/kg 27 17
2 soil reports
Same soil, CEC effective , CEC actual
A BpH 7.7 7.7
ppmpotassium 85 85
magnesium 373 373calcium 4416 4416
CEC cmol/kg 27 17effective actual
Soil test report
What is cation exchange capacity (CEC)?• relative reflection of the total ability of soil to
hold cation nutrients– CEC calculated number– Differs between lab analyses– CEC effective– CEC actual
Effect on soil fertility recommendations
RecommendationsFeed the plantSufficiency approach
Feed the soilBuild-up maintenance/base
cations saturation ratio approach
Feed the plant: sufficiency recommendations
OMAFRA Pub 611 Soil Fertility Handbook
Crop value & fertilizer
cost
Fertilizer application rate
Maximum yield
Feed the plant: sufficiency recommendations
Crop value & fertilizer
cost
Fertilizer application rate
Maximum yieldHR - high response
MR -medium response
LR – low response
RR – rare response
NR – no response
OMAFRA Pub 611 Soil Fertility Handbook
Feed the soil: BM-BCSR RecommendationsCritical level Maintenance level
Build up range
Maintenance range
Draw-down range
Soil test level
Fertilizer
level
OMAFRA Pub 611 Soil Fertility Handbook
Feed the soil: BM-BCSR RecommendationsCritical level Maintenance level
Build up range
Maintenance range
Draw-down range
Soil test level
Fertilizer
level
2-5 % K
6-12 % Mg
65-85 % Ca
Desired K at a certain CEC
Soil test K
Crop removal K2 O
Amount K2 O to be applied
OMAFRA Pub 611 Soil Fertility Handbook
recommended kg K2 O/haCEC
cmol/kgppm
KOMAFRA Build
maintenance
same soil different
labs
Lab A
24 80 480 737
Lab B
15 66 480 603
recommended kg K2 O/haCEC
cmol/kgppm
KOMAFRA Build
maintenancesame soil
different CEC
CEC eff
27 85 400 804
CEC act
17 85 400 583
Soil test reported CEC: • effective CEC• calculated• differs between lab analyses• affect on soil fertility recommendations
Soil test report
Basic training: CEC
CEC = relative reflection of the total ability of soil to hold (adsorb) cation nutrients
