Agriculture Reference
In-Depth Information
Stage I: Decline in soil productivity
and carbon
for 40% of the total population of India.
However, reports of the land use and soils of
the Indo-Gangetic Plains indicate a general
decline in soil fertility, and long-term soil
fertility studies have shown a reduction in
soil organic matter and essential nutrients
(Abrol and Gupta, 1998; Bhandari et al .,
2002). The levelling off of crop yield in the
Indo-Gangetic Plains following the Green
Revolution started in the 1980s. This trend
was linked to soil quality, and specifically
to a decline in soil organic carbon, with
levels dropping as low as 0.02% (Abrol and
Gupta, 1998; Abrol et al ., 2002) (for more
detail see Chapter 28, this volume).
Conversion from native ecosystems to
intensive agricultural cultivation has caused
documented carbon losses in China as well.
The changes in soil organic carbon content
over time in the fertile black soil region in
north-eastern China provide direct evidence
for Stage I (Wang et al ., 2002) (Fig. 3.3 ). The
soil organic carbon content of the non-culti-
vated black soils (native grass-covered black
soils) in the area is as high as 87.3 g kg 1 .
However, within the first 20 years of agriculture,
values dropped dramatically to levels in the
order of 45 g kg 1 for areas under agriculture.
Ultimately, after 100 years of cultivation, the
soil carbon content had been reduced sys-
tematically to 30 g kg 1 .
Rangelands have also seen the effects of
human intervention. Cattle grazing, population
A decline in agricultural productivity has
been documented historically in different
parts of the world. One striking example
comes from the Mediterranean region, where
the philosopher Plato (427- 347 bc ) recog-
nized loss of soil fertility in Greece as the
effect of human action: 'The rich, soft soil
has all gone away leaving the land nothing
but skin and bone' (Plato, Critias 3. III). Agri-
cultural decline in ancient Greece and Rome
is characterized extensively by Huges (1994),
who documented loss of soil fertility through
concurrent accounts of the problem. Geo-
archaeological surveys confirm the severity
of the soil degradation Plato lamented about
(Fuchs et al ., 2004).
More contemporary accounts of re-
gional Stage I soil productivity decline has
been documented in, for example, India.
Both the Indo-Gangetic Plains and the black
soil region of India were brought to cultiva-
tion after removing forests. Between 1860-
1920 and 1920-1978, nearly 49.1 and
59.6 million ha (Mha) of land was brought
under cultivation (Richards et al ., 1993).
Conversion of land was completed by the
time the Green Revolution began in 1965-
1966 (Abrol et al ., 2002). The Indo-Gangetic
Plains, covering about 13% of the country,
produce today nearly half of the food grains
95
85
75
65
55
45
35
25
0
5
10
20
40
60
100
Years of cultivation
Fig. 3.3. Changes in soil organic carbon (SOC) content with the years of agricultural cultivation in the
black soil region in the Beian area, north-eastern China. (From Wang et al ., 2002.)
 
 
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