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Chapter 8
Edaphic adaptability and suitability (continued)

TABLE 9.1
Relationships between topsoil loss and yield loss

Soil susceptibility rankingLevels of inputsEquation
Least susceptibleLowY = 1.0 X
IntermediateY = 0.6 X
HighY = 0.2 X
 
Intermediate susceptibleLowY = 2.0 X
IntermediateY = 1.2 X
HighY = 0.4 X
 
Most susceptibleLowY = 7.0 X
IntermediateY = 5.0 X
HighY = 3.0 X

Y = productivity loss in percent;
X = soil loss in cm.

TABLE 9.2
Ranking of soils (Kenya Soil Survey) according to their susceptibility to productivity loss per unit of topsoil loss

Most susceptibleIntermediate susceptibleLeast susceptible
Acrisols, except Humic AcrisolsArenosolsChernozems
Ferralic CambisolsCambisols, except Ferralic CambisolsFluvisols
Ferralsols, except humic FerralsolsGleysolsHistosols
Ironstone soilsGreyzemsHumic Andosols
LithosolsHumic AcrisolsMollic Andosols
PlanosolsHumic FerralsolsVertisols
RendzinasKastanozems 
SolonchaksLuvisols 
SolonetzNitisols 
 Phaeozems 
 Regosols 
 Vitric Andosols 
 Xerosols 
 Yermosols 

TABLE 9.3
Regeneration capacity of topsoil (mm/year) by length of growing period (LGP) and thermal zone
(derived from Hammer (1981)

LGP
(days)
Thermal zone
 T1T2T3T4T5T6T7T8T9
< 750.50.50.50.50.50.250.250.250.25
75–1791.01.01.00.50.50.250.250.250.25
180–2691.51.51.50.750.750.50.50.50.5
> 2702.02.02.01.01.00.50.50.50.5

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