Get premium membership and access revision papers with marking schemes, video lessons and live classes.

Processing. Please wait.

In this lesson we are going to discuss about soil degeneration

Answer Text:
Soil Degeneration
- Decline in the usefulness of a soil.
Types 1. Physical Degeneration
- Decline in usefulness of a soil in which texture, structure, moisture and quality of soil are affected.
Causes
a) Deforestation which leads to removal of vegetation which forms a protective cover of the soil exposing it to erosion agents.
b) Overgrazing which causes excessive loss of water from the soil causing it to become loose and fine grained and easily eroded.
c) Poor Cultivation
Techniques
i) Pulling hoe along the surface when removing weeds which loosens the soil and when it rains it’s washed away.
ii) Ploughing of land down slope which accelerates soil erosion.
iii) Cultivation of steep slopes and along river banks which encourages soil erosion.
iv) Burning which destroys vegetation covering the soil exposing it to erosion agents.
v) Growing crops on the same peace of land from season to season which sucks nutrients from the soil making it fine,
loose and easy to be eroded.
vi) Planting crops such as maize whose foliage doesn’t provide adequate soil cover encourages soil erosion.
vii) Cultivation in areas that suffer prolonged droughts which loosen the soil causing it to be exposed to erosion during dry seasons.
d) Heavy rain resulting to excessive soil erosion and thus poorly aerated.
e) Drought which deprives the soil of moisture which holds the soil together causing particles to loosen making it
to be easily brown by wind.
f) Excavation works such as quarrying, open-cast mining, building of estates and road construction which loosen and expose the soil to erosion
agents.
g) Soil erosion which robs the soil of top fertile layer.
2. Chemical Degeneration
- Decline in usefulness due to changes in mineral nutrients of the soil.
Causes
a) Leaching which makes minerals inaccessible to shallow rooted crops.
b) Excessive application of fertilizers which interferes with bacterial activity and causes the soil to become too
acidic and unable to support a variety of crops.
c) Excess water causing water logging causing acidic conditions.
d) Planting one type of crop repeatedly which makes the soil deficient of some nutrients.
e) Excessive drought which causes accumulation of salts in the top soil.
f) Burning such as in slash and burning which kills microorganisms causing nitrogen deficiency when nitrogen
fixing bacteria is killed.
3. Biological Degeneration
- Degeneration due to decline of organic content of the soil and organic matter.
a) Deforestation which deprives the soil of its organic content and moisture making it loose and more vulnerable to erosion.
b) Burning such as in slash and burning which kills micro-organisms causing low decomposition rate which robs soil of organic matter.
c) Overgrazing which causes removal of vegetation causing excessive loss of water from the soil and hence reduced
micro-organism activity resulting into shortage of humus.
d) Drought and excessive moisture which may lead to a shortage of essential organisms such as bacteria, earthworms, termites and
burrowing animals.