Agriculture Reference
In-Depth Information
18
CHAPTER
Classification of Soils of the Tropics:
A Reassessment of Soil Taxonomy
Friedrich H. Beinroth and Hari Eswaran
CONTENTS
Abstract ..........................................................................................................................................231
Introduction ....................................................................................................................................232
Evolution of Concepts ...................................................................................................................233
The Dawn of Soil ClassiÝcation ..........................................................................................233
A Consensus for Modern ClassiÝcation ..............................................................................234
Purpose and Principles of Soil Taxonomy ....................................................................................235
Issues of Concern...........................................................................................................................236
The Unsubstantiated Change in the DeÝnition of the ÑisoÒ Limit .....................................237
The Flawed DeÝnition of Spodic Materials ........................................................................237
The Case of Aridic Mollisols ...............................................................................................238
The Problem of Extremely Acid Vertisols ...........................................................................238
The Ambiguity of ÑPaleÒ Great Groups ..............................................................................239
The Dilemma of Paddy Soils ...............................................................................................239
The Predicament of the Kandic Horizon in Oxisols ...........................................................240
Conclusion......................................................................................................................................241
References ......................................................................................................................................242
ABSTRACT
We brieÞy review the history of soil classiÝcation in the tropics and trace the development of
Soil Taxonomy relative to tropical soils. Although signiÝcant progress has been made in this regard,
there remain several areas that need improvement. These include the following issues that are
addressed in this chapter: (1) the undocumented change in the deÝnition of the Ñiso-Ò soil temperate
regimes, which increased the delta T from 5
C; (2) the questionable criteria for the spodic
horizon, which disagree with classical concepts of pedology; (3) the case of Mollisols with an
aridic soil moisture regime, which are illogically classiÝed as Ustolls; (4) the problem of extremely
acid, wet Vertisols, some of which are now classiÝed as Aquerts, thus being recognized for their
C to 6
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