World’s Soil Resources

In several Asian countries, a blend of engineering, reclamation and biological approaches has been adopted
to address salinity and waterlogging problems. In Pakistan, engineering solutions included large-scale Salinity
Control and Reclamation Projects (SCARPs), which covered 8 million ha at an estimated cost of US$2 billion
(Qureshi et al., 2008). Two big drainage water disposal projects were also undertaken. Measures to address the
saline soil problem included leaching of salts by excess irrigation, use of chemicals (such as gypsum and acids),
the addition of organic matter, and biological measures such as salt-tolerant plants, grasses, and shrubs.
Improvements in on-farm water and crop management have also been practiced. In North America,
changes in land use and management practices have reduced the risk of salinization and helped to improve
soil health and agri-environmental sustainability.
In Iraq and Egypt, surface and subsurface drainage systems have been installed to control rising water
tables and arrest soil salinity. In Iran, Syria and other Gulf countries, crop-based management, and fertilizers
are used to combat salinization (Qadir, Qureshi and Cheraghi, 2007). In Iran, Haloxylon aphyllum, Haloxylon
persicum, Petropyrum euphratica and Tamarix aphylla are potential species for saline environments
(Djavanshir, Dasmalchi and Emararty, 1996). Also in Iran, Atriplex has been shown to be a potential fodder
shrub in the arid lands which could bring annual income as high as US$ 200 ha -1 (Koocheki, 2000; Nejad and
Koocheki, 2000). Breeding of salt tolerant crop varieties (e.g. wheat, barley, alfalfa, sorghum etc.) is also a
recognized management response for saline environments. However, most results have been obtained in
controlled environments, with few real field results so far.
The use of organic amendments in Egypt showed that the mixed application of farmyard manure and gypsum
(1:1) significantly reduces soil salinity and sodicity (Abd Elrahman et al., 2012). Recently, phytoremediation or
plant based reclamation has been introduced in the Near East region. In Sudan good responses for control
of sodicity have been obtained through phytoremediation. The production of H+ proton in the rhizosphere
during N-fixation from legumes such as the hyacinth bean (Dolichos lablab L.) removed as much Na+ as
gypsum application. This indicates the importance of this technology in calcite dissolution of calcareous salt
affected soils (Mubarak and Nortcliff, 2010).
6.6 | Soil biodiversity status and trends
6.6.1 | Introduction
Over the last few decades the importance of soil biota for terrestrial functioning and ecosystem services has
emerged as an important focus for soil science research. Current evidence shows that soil biota constitute an
important living community in the soil system, providing a wide range of essential services for the sustainable
functioning of global terrestrial ecosystems and thereby impacting human wellbeing, directly and indirectly
(van der Putten et al., 2004). Soil organisms (e.g. bacteria, fungi, protozoa, insects, worms, other invertebrates
and mammals) shape the metabolic capacity of terrestrial ecosystems and many soil functions. Below-ground
biodiversity represents one of the largest reservoirs of biodiversity on earth (Bardgett and van der Putten,
2014). Essential services provided by soil biota include: regulating nutrient cycles; controlling the dynamics of
soil organic matter; supporting soil carbon sequestration; regulating greenhouse gas emissions; modifying
soil physical structure and soil water regimes; enhancing the amount and efficiency of nutrient acquisition
by vegetation through symbiotic associations and nitrogen fixation by bacteria; and influencing plant and
animal health through the interaction of pathogens and pests with their natural predators and parasites.
Fungi and bacteria are important decomposers in the soil. They are remarkably efficient. The smaller the
pieces to be decomposed, the faster these microorganisms are able to do their job. Organic waste such as
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