Page 59 - Soil Degradation, Conservation and Remediation

Chapter 2
Physical Deterioration of Soil

Physical deterioration of soil involves the destruction of soil structure, dispersion of
soil particles, sealing of pores, compression and increasing density, consolidation,

compaction and reduced root penetration, low infiltration, waterlogging and runoff,
and accelerated erosion. Along with denudation, these processes lead to desertifi ca-
tion in the arid and semiarid regions. The ultimate result is the loss of the capacity
to support ecosystems. There are about 68.3 M ha compacted soil globally which
accounts for 4 % of human-induced soil degradation. Soil compaction is a global
problem associated with mechanized agriculture. It has caused yield reductions of
25–50 % in some regions of Europe and North America and between 40 and 90 %
in West African countries. Planned and integrated management involving reduced,
conservation and timely tillage, generous addition of organic matter, mulching, crop

rotation, subsoiling, and controlled trafficking are recommended for sustainable use

of compacted soils. Desertification is a process of land degradation occurring mainly
in the arid and semiarid regions due to human actions on ecosystems combined with
adverse climatic conditions. The United Nations estimates that desertifi cation
affects 70 % of arid lands, amounting to about 30 % of the world cultivable land.

2.1 Processes and Types of Physical Deterioration of Soil
Important physical properties of soils related to soil fertility, productivity, and soil
quality are texture, structure, bulk density, porosity, soil water, air, and temperature.
Of these properties, only soil texture is a permanent property that cannot be easily
altered. The other properties may be readily changed by soil management practices.

Soil structure may be modified by tillage and addition of manures. Tillage opera-
tions break the clods and peds and modify the size of pores and the proportion of
large and small pores. Consequently, the bulk density, water holding capacity, and
aeration status are modified. Often, tillage operations destroy soil structure, reduce

porosity, and make the soil compact. Thus, physical deterioration of the soil may

K.T. Osman, Soil Degradation, Conservation and Remediation, 45
DOI 10.1007/978-94-007-7590-9_2, © Springer Science+Business Media Dordrecht 2014