Historical and Sociocultural Aspects of Soil Organic Matter and Soil Organic Carbon Benefits - Soil Carbon: Science, Management and Policy for Multiple Benefits - page 171

complex, but integrated system of analysis
for the diagnosis and prediction of fertility
(Feller et al ., 2003). This was certainly the
first example of real concern with farming
sustainability, and what is more, it was
based on organic practices. In terms of plant
production, this period certainly marked
the golden age of 'soil OM benefits' until the
emergence of the mineral theory of plant
nutrition.

early 20th century. The mineralist approach
reached its peak in the 30- year period fol-
lowing World War II, with the development
of high-input, heavily subsidized agriculture
in Europe and North America. During the
first half of the 20th century, the generaliza-
tion of agricultural practices without any re-
turn of SOM to the soil led to intense land
degradation. The clearest examples are the
spectacular water and wind erosions of the
Dust Bowl and Black Sunday in the USA
( 14 April 1935).

The mineralist period (1840-1940)

From agronomy to ecology (1940-1992)

Although Liebig takes many of his ideas
from the work of Sprengel (1838; cf. van der
Ploeg et al ., 1999), his authoritative text, Die
organische Chemie in ihrer Anwendung auf
Agrikultur und Physiologie (1840), is often
considered as the first reflection on the ori-
gin of plant dry matter from mineral com-
pounds based on scientific experiments. It
was the birth of the 'mineral theory' of plant
nutrition and the beginning of the 'NPK
era'. Carbon was considered to be derived
from carbon dioxide, hydrogen from water
and other nutrients from the soluble salts
present in soil and water. Since Liebig's
synthesis accounted rather satisfactorily
for the fertilizing effect of mineral inputs, it
provided the basis for modern agricultural
sciences. Liebig promoted the use of min-
eral fertilizers to compensate for soil min-
eral depletion, and his work paved the way
for recommendations on the massive use of
chemical fertilizers in cropping patterns
and the abandonment of organic or organo-
mineral fertilization. None the less, Liebig, as
'one of the last “complete” men among the
Great Europeans' (Hyams, 1976), was him-
self an advocate of mixed fertilization. As a
result, until World War I, organic or organo-
mineral inputs to soils were no longer con-
sidered to benefit plant production, even if
scientific investigations had demonstrated
the indirect importance of SOM for proper-
ties playing a role in soil fertility.
The potential of chemical fertilization to
increase crop yield was widely recognized at
the end of the 19th century, the industrial
synthesis of nitrogen (N) and the processing
of phosphorus (P) being mastered by the

Societal and scientific doubts concerning
the sustainability of intensive farming arose
as early as in the 1930s, when a connection
was suspected between the decline in soil
fertility, the quality of the human diet and
human health (Balfour, 1944). This pro-
moted the definition of the 'healthy' func-
tion of SOM and the creation of the organic
farming movement.
Steiner (1924) provided the incentive
for the first organic farming movement, the
so-called 'biodynamic agriculture'. Steiner's
scientific bases and that of his followers
(e.g. Pfeiffer, 1938) were shallow, and they
referred to both holistic and cosmogonic
concepts (i.e. interrelationships between
the stars, soil and geochemical elements,
plants, animals and humans) to propose a
new kind of agriculture that excluded the
use of any chemical input. The most influ-
ential and rational approaches to modern
organic farming were those by Howard
(1940, 1952), Balfour (1944) and Rodale
(1945); for detailed reviews of the history of
organic farming see Scofield (1986) and
Lotter (2003). They shared one main object-
ive, which was to improve soil, plant, animal
and human health by biologically managing
soil fertility. Two fundamental aspects of or-
ganic farming philosophy put SOM at the
heart of cropping sustainability: the holistic
paradigm and the Law of Return.
The philosophy of organic farming is
fundamentally holistic and considers 'all life,
all creation as being inextricably interrelated,
such that something done or not done to