Document Sample
STATE AGRICULTURE PLAN _SAP_ 1.0019 Powered By Docstoc
					                                               State Agriculture Plan – Tamil Nadu     39

6. Stabilized Dunes / Partially stabilized Dunes

   Depending on the rainfall and protection available from grazing, the bare sand
dunes gradually establishes vegetal cover thus making them to get stabilized. In
partially stabilized dunes, the erosion / deposition will be still active to some extent.
When they established a good vegetal cover either in the form of grasses, shrubs and
scrubs, they get stabilized and the erosion / deposition activity will be at minimal. By
virtue of vegetal cover and physiography, they are discernible on satellite imagery.

                              Stabilized sandune

                       Partially stabilized sanddune
                                              State Agriculture Plan – Tamil Nadu    40

7. Un-stabilized dunes

   Due to their inherent vulnerability because of lack of vegetal cover, these are quite
active during summer season. The sand starts moving and engulfing the adjoining
agricultural lands, engineering structures and demands immediate attention for their
stabilization. The unstabilized sand dunes changes their location and shape from
season to season and hence they are often called shifting dunes.

Water logging

   Water logging is considered as physical deterioration of land. It is the affected by
excessive ponding / logging of water for quite some period and affects the
productivity of land or reduces the choice of taking crops.

8. Surface Ponding

   This category addresses the water logging caused by flooding of river water,
submergence by rainwater and human intervention in natural drainage systems that
adversely affect the natural drainage, where the water stagnates for quite a long time.
Depending the number of crops it affects it has been sub-divided into two severity
classes, slight- affecting one crop and moderate – affecting more than one crop.
Flooding of paddy fields is not included as it is a unique cultural practice rather than
degradation of soil.
                                                 State Agriculture Plan – Tamil Nadu     41

   Waterlogging may be seasonal or permanent. Seasonally waterlogged areas are
those low lying or depression areas that get saturated due to heavy rains and are normal
in post-monsoon season. Permanent waterlogged areas are those areas where there is
continuous surface ponding of water or soil profile is saturated for one or more seasons.

9. Sub-surface Water logging
   If the water table is with in 2 m from the surface it adversely affects crop by virtue
of saturating the root zone due to capillary rise. These areas are potential threat to get
surface ponded in due course of time, if the water accumulation continues. The sub-
surface waterlogged areas can be reclaimed with little ease.

10. Salinization / Alkalization

   Salinization can result from improper management of canal irrigation water resulting
in the rise of water table and consequent accumulation of salts in the root zone in arid,
semi-arid and sub humid (dry) conditions and ingress of sea water in coastal regions
and/or use of high-salt containing ground water. They also become saline when soils have
developed on salt-containing parent materials or have saline ground water. The soils with
EC more than 2ds/m in vertisols and >4ds/m in non-vertisols was considered as saline in
the present project. Increase in soil pH beyond 8.5 results in sodicity or alkalization that
result in increase of exchangeable sodium percentage in soils (> 15). Based on the type of
problem, it has been divided into saline, sodic and salinesodic.

               Salinity                                                 Sodic
                                                State Agriculture Plan – Tamil Nadu    42

11. Acidification
         pH is one of the most-important soil property that affects the nutrient uptake
by plants and there by influencing the crop productivity. Any soil processes or
management practices which lead to buildup of hydrogen cations (also called protons)
in the soil will result in soil acidification. It also occurs when base cations such as
Calcium, Magnesium, Potassium and Sodium are lost from the soil leading to high
hydrogen ion concentration. This results in decrease of soil pH below 6.5. It occurs in
laterite regions, coastal regions upon drainage or oxidation of pyrite containing soils.
         If the pH is 4.5 to 5.5 then they are called moderate and if the pH is < 4.5,then
they are mapped under severe category. The soils respond to lime application, which
results in improvement of crop productivity.


         These are the areas under perpetual snow covered areas confined to
Himalayan region. The type of degradation includes frost heaving and snow covered

12. Frost Heaving
         Frost heaving is defined as a process in glacial and periglacial environment
where intense frost action and freezing of water evolves peculiar forms of rock,
regolith and soil. The water crystallizes to ice below the surface horizon leading to
micro-relief variations on the surface. This process affects the germination and root
growth of several crops there by limiting the productivity of land.

Shared By: