SOIL DEGRADATION

 

 The nation that destroys 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.

 

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