Aggregate stability this refers to the ability of soils
aggregates to resist disintegration
,when disruptive forces associated to with tillage and water or wind erosion
are applied wet aggregate stability suggest how well a soil can resist raindrop
impact and water erosion, while size distribution of dry aggregates can be used
to predict resistance to abrasion and wind erosion.
PROBLEM
ASSOCIATED TO POOR AGGREGATE STABILITY
Aggregate stability is critical for infiltration, root growth, and resistance to
water and wind erosion, unstable aggregate disintegrates during rainstorm,
dispersed soil particles fill surface
pores and a hard physical crust development which dries to reduce infiltration and
increase run off surface and water and wind erosion,
it reduced water available for plant and inhibits seedling emergence
Poor aggregate stability can result in:
i.
Hard setting soils
ii.
Soils
crusting impeding
iii.
Limited
water holding capacity
iv.
Compaction
due to structure collapse
v.
Water
logging
PRACTICES
CONNECTED TO POOR AGGREGATE STABILITY
1.
tillage methods and soil disturbance
activities that breaks down plant
organic matter, prevents accumulation of
soil organic matter, and disrupts existing
aggregates
2.
Cropping, grazing, and other production systems
that leaves soil bare and exposed to the
physical impacts of raindrops or winds
3.
Removing sources of organic matter and surface roughness by burning, harvesting or other
wise removing crop residues
4.
Using pesticides harmful to beneficial soil
micro organism
ASSESSING
AGGREGATE STABILITY
one of the simplest way of assessing
aggregate stability is to measure how well individual aggregates hold in the
presence of water; when a fragment of soil is immersed in fresh water’ there
are four that can happen
1
it
can remain unchanged
2
it can swell
3
it
can fall apart into smaller fragments [slaking]
4
it
can disperse into a fine milky
suspension [dispersion]
soils
with poor aggregate stability can often
disperse or slake
Slaking : On wetting
porous aggregates rapidly absorbs water becoming soft and rapping air internally, with further wetting weak
aggregates collapse and breaks into smaller particles, this process is
know as slaking, this is due to low soil organic
matter and is often associated with intense rainfall hitting dry bare soil and
occurs within minutes. It can lead to
blocking of soil pores normally associated
with gas exchange and water movement slaking leads to dispersion
Dispersion: Dispersion
causes micro aggregates to collapse and relies clay, Silt, and sand particles, smaller particles move to block soil pores,
which slows internal drainage and contributes
to an increased risk of water logging, soil which disperse in
water, reduce soil strength, making them
more prone to erosion.
METHODS OF
IMPROVING AGGREGATE STABILITY
Improving aggregate stability on crop
land, typically involves some
conservation practice such as
1.
the use of cover crops and green manure crops
2.
Pest
management and crop residue management
3.
Prescribed
gazing
4.
Decreased
tillage and soil disturbance
5.
Salinity
and sodic soil management
6.
Surface
rougbening
7.
Raised
beds, in areas where water logging is a problem, raised beds can alleviate
pressure on soil structure by draining
excess water away