134
R. R. Shahin
decade’s changes in land use and management have already led to a significant
decline in organic matter levels in many soils which increases the susceptibility to soil
erosion [113]. The water stability was significantly correlated with a carbon content of
the aggregates. Arable soils of low SOM content are susceptible to slumping when
wetted due to aggregate instability, leading to less infiltration and greater surface
runoff [130]. Specific decreases in the aggregate stability of 10–40% with a 1%
decrease in SOM content have been recorded in the UK and similar locations [131],
as well as a decrease in the resilience of soil to physical stresses, such as compaction
[132].
Soil compaction is the compression of soil due to outside pressure. The effect of
soil compaction is an increase in the density of soil and a corresponding reduction
in the amount of air present in the spaces between soil particles. This process can be
caused mainly by the depletion of SOM and may be harmful or beneficial depending
on the circumstances:
1. Causes nutrient deficiencies
2. Restricts root development
3. Reduces soil aeration
4. Decreases soil available water
5. Reduces infiltration rate
6. Increases bulk density
7. Increases sediment and nutrient losses
8. Increases surface runoff
9. Damages soil structure, through reroute the traffic
10. Break up the hard layers
11. Reduces crop productivity.
(b) Surface Sealing and Crusting
Soil crusting refers to the formation of a compact, thin layer having high bulk density
and high penetration resistance at the surface of the soil when dries after the dispersion
of fine particles clogging of pores due to the beating action of raindrop and slaking
of irrigation water. Soil crust is formed in two phases. (1) Surface sealing: The
initial or wetting phase. (2) Surface crusting: The hardening of the surface seal in the
subsequent dry phase [133]. When a seal layer exists, the chance of runoff occurrence
can dramatically increase. On a vegetated surface, the seal layer can enhance the
effects of heterogeneous soil properties and surface features and lead to a highly
heterogeneous pattern of runoff and soil moisture distribution [134, 135]. Therefore,
higher organic matter levels tend to reduce the risk of soil capping particularly on
fine-textured soils through an improved soil structure.
R. R. Shahin
decade’s changes in land use and management have already led to a significant
decline in organic matter levels in many soils which increases the susceptibility to soil
erosion [113]. The water stability was significantly correlated with a carbon content of
the aggregates. Arable soils of low SOM content are susceptible to slumping when
wetted due to aggregate instability, leading to less infiltration and greater surface
runoff [130]. Specific decreases in the aggregate stability of 10–40% with a 1%
decrease in SOM content have been recorded in the UK and similar locations [131],
as well as a decrease in the resilience of soil to physical stresses, such as compaction
[132].
Soil compaction is the compression of soil due to outside pressure. The effect of
soil compaction is an increase in the density of soil and a corresponding reduction
in the amount of air present in the spaces between soil particles. This process can be
caused mainly by the depletion of SOM and may be harmful or beneficial depending
on the circumstances:
1. Causes nutrient deficiencies
2. Restricts root development
3. Reduces soil aeration
4. Decreases soil available water
5. Reduces infiltration rate
6. Increases bulk density
7. Increases sediment and nutrient losses
8. Increases surface runoff
9. Damages soil structure, through reroute the traffic
10. Break up the hard layers
11. Reduces crop productivity.
(b) Surface Sealing and Crusting
Soil crusting refers to the formation of a compact, thin layer having high bulk density
and high penetration resistance at the surface of the soil when dries after the dispersion
of fine particles clogging of pores due to the beating action of raindrop and slaking
of irrigation water. Soil crust is formed in two phases. (1) Surface sealing: The
initial or wetting phase. (2) Surface crusting: The hardening of the surface seal in the
subsequent dry phase [133]. When a seal layer exists, the chance of runoff occurrence
can dramatically increase. On a vegetated surface, the seal layer can enhance the
effects of heterogeneous soil properties and surface features and lead to a highly
heterogeneous pattern of runoff and soil moisture distribution [134, 135]. Therefore,
higher organic matter levels tend to reduce the risk of soil capping particularly on
fine-textured soils through an improved soil structure.