Page 71 - Soil Degradation, Conservation and Remediation

2.3 Waterlogging 57

allowing the 3 m tracks to be centrally spaced at the same distance. The advantages
are the tractor can be less powerful because the wheels run on packed soil
while only minimum or no tilling is required on the non-compacted beds in
between; nor is there any need to subsoil every few years. In CFT, water penetra-
tion is better, there are no ruts or ridges left over from previous operations, the
fuel saved is substantial, and the crops yield much better because of zero
compaction.
Building Up of Organic Matter : Organic matter improves soil structure, decreases
soil bulk density, and increases porosity. Organic matter resists compression
and consolidation of soil. For building up of soil organic matter and keeping the
soil loose, generous additions of farmyard manures, poultry manures, composts
and municipal biosolids, and adopting green manuring and crop rotations are
needed.
Mulching : Mulching increases infiltration and decreases runoff and evaporation.

Mulching conserves soil moisture. Several materials are used as mulch. Types of
organic mulches are compost, composted manure, grass clippings, newspaper,
straw, shredded leaves, straw, etc. Types of inorganic mulches are gravels, peb-
bles and crushed stones, plastic sheets, woven ground cloth, aluminum-coated
plastic foil, and ground rubber tires. Organic mulches are natural and cheap
materials, and along with reducing compaction, they improve soil fertility.
Mulches protect soils, increase infiltration, improve water-holding capacity,

reduce weed growth, and prevent soil compaction. Organic mulches are gradu-
ally decomposed and release plant nutrients. Mulched plants have more roots
than plants that are not mulched.

2.3 Waterlogging

Waterlogging is a state of saturation of soil with water for a prolonged period.
Soils may, sometimes, be saturated with water for a very short time, say some
hours, as during fl ash floods in piedmont areas. This temporary stagnation is not

regarded as waterlogging. This water drains away easily. Waterlogging is a condi-
tion of soil when draining excess water is difficult and requires time, labor, plan-

ning, and energy. Waterlogging develops due to many different causes, including
natural conditions and human activities. Natural conditions include heavy rains,

low lands, clay soils, flooding, and presence of impervious subsoil. Human activi-
ties include faulty irrigation, inadequate drainage, surface sealing, and deep soil
compaction by tillage implements. Wetlands are permanently waterlogged.
Waterlogging also occurs when the groundwater table rises to the root zone and
remains there for a considerable period of the year (Michael and Ojha 2006 ).
Waterlogging may also occur as a form of standing water in the farm, which does
not lower with time (Murty 1985 ). Worldwide, about 10 % of all irrigated land
suffers from waterlogging. As a result, productivity has fallen about 20 % in these
croplands.