1
Question
Humus is formed in
Humus is formed in
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Solution
The correct option is C O-horizon
Introduction to humus :
Humus is a cellulose and lignin-rich dark coloured, amorphous organic matter obtained by the action of degradative enzymes of saprophytic decomposers (bacteria, fungi, etc) on dead and decaying organic matter (detritus). The process of humus formation is known as humification.
Soil profile :
Cross section of a well developed soil shows more or less distinct layers called horizons. The sequence of horizons from surface to downwards is known as the soil profile and shows 5 distinct horizons - O, A, B, C and R.
O-horizon :
O - horizon is the topmost layer of organic matter that lies above the true soil. Humus is formed in this horizon.
A-horizon :
A - horizon is the topmost horizon of soil known as topsoil. It contains minerals and humus but humification does not occur in this layer.
B-horizon :
B - horizon or the subsoil lying beneath the topsoil. It is coarse textured and is rich in minerals, clay and water but poor in aeration.
C-horizon :
The C - horizon lies beneath the subsoil and consists of unweathered rock fragments. It is devoid of any biological activity.
Final answer :
(A) O-horizon
Introduction to humus :
Humus is a cellulose and lignin-rich dark coloured, amorphous organic matter obtained by the action of degradative enzymes of saprophytic decomposers (bacteria, fungi, etc) on dead and decaying organic matter (detritus). The process of humus formation is known as humification.
Soil profile :
Cross section of a well developed soil shows more or less distinct layers called horizons. The sequence of horizons from surface to downwards is known as the soil profile and shows 5 distinct horizons - O, A, B, C and R.
O-horizon :
O - horizon is the topmost layer of organic matter that lies above the true soil. Humus is formed in this horizon.
A-horizon :
A - horizon is the topmost horizon of soil known as topsoil. It contains minerals and humus but humification does not occur in this layer.
B-horizon :
B - horizon or the subsoil lying beneath the topsoil. It is coarse textured and is rich in minerals, clay and water but poor in aeration.
C-horizon :
The C - horizon lies beneath the subsoil and consists of unweathered rock fragments. It is devoid of any biological activity.
Final answer :
(A) O-horizon
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