its soil, destroys itself
~ Franklin D. Roosevelt
What is soil degradation-
Soil degradation is the decline in soil condition caused
by its improper use or poor management, usually for agricultural, industrial or
urban purposes.
Causes of
soil degradation-
The
loss of farm land has been caused by a number of factors,
many or most of which
are tied to human development. The primary causes are:
·
Deforestation
·
Overgrazing
·
Overexploitation for
fuel wood
·
Agricultural
activities
·
Increased flooding
·
Industrialization.
The following figure illustrates the relative sizes of the causal mechanism as
a function of region
On the global basis, the soil degradation is caused primarily by
overgrazing (35%), agricultural activities (28%), deforestation (30%), over
exploitation of land to produce fuel wood (7%), and industrialization (4%).
The main reasons for unproductiveness or degradation of soils are
as follows:
1.
Nutrient disorder
2.
Water-logging
3.
Salinity
4.
Erosion
5.
Biological degradation
6.
Other causes
Impact of Soil Degradation:
The following are the impacts of soil degradation:
1.
Degradation leads to reduction in crop yield in the affected lands and a
possible decline in cropping intensity.
2. In
extreme cases, soil becomes unfit for cultivation.
3.
Silting of drainage, canals, rivers and reservoirs results in increased floods
and droughts.
4. In
some cases farmers use more fertilizer inputs to compensate reduced soil
productivity while in other cases, they use excess fertilizers.
5. The
rate of siltation in many water reservoirs are significantly high. According to
Central Water Commission (1991), nearly 11 per cent of the total capacity of
water reservoirs has been silted.
6. Soil
degradation has several adverse impacts on the environment. It affects global
climate through alterations in water cycle and energy balances and disruptions
of carbon, nitrogen and sulfur cycles.
The
estimated annual loss of different crops due to soil degradation ranges from
Rs. 89 billion to 232 billion which represent a loss of 11 to 26 per cent
yield.
Control
of erosion-
(Adapted
from ACS Distance Education 2009)
As erosion
is caused by the effects of wind and water, control methods are generally aimed
at modifying these effects. The following list describes some of the most
common control methods:
·
Prevention of soil detachment by the use of cover materials such
as plants.
·
Crop production techniques (e.g. fertilizing with organic fertilizer), to improve soil characteristics and promote plant growth and hence
surface cover.
·
Ploughing to destroy rills and contour planting to create small
dams across a field, to retard or impound water flow.
·
Filling small gullies with mechanical equipment or conversion
into a protected or grassed waterway.
·
Terracing of slopes to reduce rates of runoff.
·
Prevention of erosion in the first place by careful selection of
land use practices.
·
Conservation tillage methods.
· Armoring of channels with rocks, tires, concrete and timber to
prevent bank erosion.
·
The use of wind breaks to modify wind action.
·
Ploughing into clod sizes too big to be eroded, or ploughing
into ridges.
Conclusion-
People can be a major asset in reversing a trend towards
degradation. However, they need to be healthy and politically and economically
motivated to care for the land as subsistence agriculture, poverty, and
illiteracy can lead important causes of land and environmental degradation
especially in Zambia which has inadequate laws and policies aimed directly at
preventing land degradation.
