Page 17 - Soil Degradation, Conservation and Remediation

2 1 Soil Resources and Soil Degradation

nutrient, air, and heat exchange for organisms. It provides us with food, fodder,

wood, and fiber. Almost 96 % of human food is obtained from the soil (Pimental and
Hall 1989 ). A great number of antibiotics are produced by soil microorganisms.

Soil acts as a recycler of materials and as a purifier of water. Soils provide mechanical
support for living organisms and their structures, including most of our buildings

and other installations. Soils influence the hydrological processes, including

infiltration, percolation, drainage, streamflow, and surface as well as underground

water storage. Soils regulate exchange of material, energy, water, and gas within the
lithosphere–hydrosphere–biosphere–atmosphere system. Soil is a source and sink
of pollutants. Moreover, soil respiration and carbon sequestration may infl uence
climate change. Soil is, without question, critical to the world, supplying virtually
all the food and fiber that sustain the human population and providing ecosystem

services that support life (Anderson 2010 ). It is a nonrenewable natural resource in
human life time frame (Lal 2009 ).
Soil is not land itself; it is a part of the land. The total land area of the world
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is estimated to be 130,575,894 km , including rocky surfaces, deserts, ice-covered
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areas, and lands with soil. There are about 38.5 million km or 29.45 % of the
earth’s ice-free land surface which is too dry for sustainable human habitation
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(Beinroth et al. 1994 ). About 20.2 million km or (15.46 %) of the land occurs in
the cold tundra zone, which are not easily amenable to normal agriculture. There
are other constraints, which prevent the use of soils for agriculture. For example,
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saline and alkaline soils occur in 3,105,000 km or 2.4 % of the land surface,
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and soil acidity affects 18,420,100 km or 14.1 % of the total land (Eswaran
et al. 1997 ). According to Buringh ( 1989 ), between 11 and 12 % of the land
surface is generally suitable for food and fiber production, 24 % is used for grazing,

forests occupy about 31 %, and the remaining 33 % has too many constraints
for most uses.
All agricultural soils are not fertile and productive. Some soils are naturally
unproductive; some are arid and saline; some are very sandy and dry; and some are
wet and waterlogged for a part or most of the growing season. Advanced water
management techniques including irrigation and drainage have enabled some use of
the dry lands, wetlands, and peatlands. There are sloping lands, sandy soils, and
soils with low nutrient-holding capacity. Many soils in desert regions are irrigated,
but these are considered unsustainable. Lal ( 1989 ) estimates that about 0.5 ha of
cropland per capita is needed to sustain the human population at an acceptable
level. But there are many countries where the per capita land is less than 0.07 %
(Smil 1987 ). Mismanagement and misuse have degraded many productive lands
worldwide. Oldeman et al. ( 1991 ) suggest that about 17 % of the global land area is
degraded by human interventions. The consequences of land degradation not only

affect the performance of the land for food and fiber production but also have
grave consequences for the environment. Formation of an inch top soil may need
more than thousands of years; so it should not be allowed to degrade through our
careless mismanagement.