Agriculture Reference
In-Depth Information
Table 2.5.
Soil classi
fi
cation and main characteristics of tropical soils and orders.
Order
Characteristic
Agricultural productivity
Entisol
Recent alluvium, also on barren
sands and near deserts. Lacks
signi
fi
cant pro
fi
le
Some very productive alluvial soils
Vertisol
Swelling clay. Cracks in dry
weather
Productive, dif
fi
cult to till
Inceptisol
Horizons forming, little accumu-
lation of Al or Fe oxides. Tropic
with long, wet season,
acid
Very prone to erosion, good if well
drained
Aridisol
Deserts, little organic matter,
CaCO
3
, CaSO
4
and soluble
salts
Need irrigation to be agriculturally
productive
Mollisols
Granular or crumbly soils. High
in silt and organic matter
Most productive worldwide
Al
fi
sol
Humid regions soil with grey or
brown upper horizon and silicate
clay below
Good soils, prone to erosion, easily
compacted
Ultisol
Highly weathered, acidic in moist,
warm tropical areas, moderate
fertility
Very productive, easily compacted,
prone to erosion, needs fertilizer
Oxisol
Highly weathered, in hot, heavy
rainfall areas, deep clay of
hydrous oxides of Al and Fe, can
be very acidic, leached
Needs nutrients to be productive,
susceptible to erosion if left bare
Andisols
Surface deposits of volcanic ash,
free draining, low bulk density
Erosion serious problem, high P
fi
xation, high Al and Fe
fi
xation,
excellent structure, productive
provided other factors are favourable. In some cases considerable management
skill is required to maintain the crops in good growth and production. Soil pH
can be corrected by liming during fi eld preparation, with most trees preferring
pH 5.5-6.5. Papaya is one of the few fruit crops that is adapted to a wide
range of soil pH, growing and producing well in soil pH ranging from 5.0
to well into the alkaline range. Defi ciencies in phosphorus associated with
adsorption and excess aluminium need to be addressed in the oxisols, ultisols
and some inceptisols. Soil organic matter can be maintained by use of manure,
ground cover crops and mulches to preserve soil moisture and structure, and
improve the rhizosphere. Magnesium, zinc and boron defi ciencies may also be
encountered in some tropical soils, but these are relatively easy to correct in a
management programme. Saline and alkaline soils, along with deep peat soils,
should be avoided for fruit production because of their dii cult nature. Acid
