Marginality Principle - Principles of Sustainable Soil Management in Agroecosystems - page 19

2 Marginality Principle
Jerry L. Hatfield and Lois Wright Morton
CONTENTS
2.1 Introduction .................................................................................................... 19
2.2 Dimensions of Marginality ............................................................................. 23
2.3 Soil Degradation and Loss of Soil Function ................................................... 23
2.3.1 Biological Degradation ....................................................................... 24
2.3.2 Chemical Degradation ........................................................................ 26
2.4 Extent of Soil Degradation ............................................................................. 27
2.4.1 Soil Management Practices ................................................................ 28
2.5 Scales of Variation .......................................................................................... 30
2.5.1 Water Availability ............................................................................... 30
2.5.2 Crop Productivity................................................................................ 30
2.5.3 Environmental Quality ....................................................................... 33
2.6 Multifunctionality: Optimum Performance of Soil Resource ........................ 35
2.6.1 Soil Management to Reduce Marginality ........................................... 35
2.6.2 Agroforestry ........................................................................................ 37
2.7 Social Values of Soil Functions: Definitions and Meanings of Marginality ........ 38
2.7.1 Social Definitions of Marginality ....................................................... 40
2.7.2 Willingness and Capacity to Protect Soil Resource ........................... 42
2.7.3 Capacity to Act: Whose Responsibility Is It to Protect the Soil? ....... 45
2.8 Conclusions ..................................................................................................... 47
Abbreviations ........................................................................................................... 48
References ................................................................................................................ 48
2.1 INTRODUCTION
There are 12 different soil orders in the United States representing a wide variation
among soils both horizontally and vertically with a range of economic, social, and
environmental functions (Hamdar 1999). The distinct traits of these soil orders have
been used to create a classification system similar to the way in which we divide
animals or plants into genus and species. The names of these soil orders provide
us with a general description of the soils: Alfisol (moderately weathered); Andisol
(volcanic ash); Aridisol (very dry); Entisol (newly formed); Gelisol (frozen); Histosol
(organic, wet); Inceptisol (slightly developed, young); Mollisol (deep, fertile); Oxisol
(very weathered); Spodosol (sandy, acidic); Utisol (weathered); and Vertisol (shrinks
and swells). Soil classification allows for a comparison of different soil series and
their aggregation into soil associations, which describe how different series are posi-
tioned adjacent to each other across a landscape. A county soil map provides a visual
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