The secondary particles arrangement of the building blocks called (peds) within the soil mass together within the pore size distribution.
CHARACTERISTICS OF SOIL STRUCTURE
Same experience and researches have rise to multitude of descriptions in soil structure. The term soil tithe is often used to describe the quality of soil structure for crop growth. A soil considered to posse’s good tilt is one that readily fractures whether the stress arise from tillage, emerging seedlings or growing root and plants or micro-organisms.
1. Description of the aggregate: This refers how the shape, stability, size, and durability in the water, but in this Aggregates description are four basic areas in this.
(a) Rounded aggregates and spherical: This is the circles arrangements of particles in soil they are of two types; Crumb and Granular structure
(i) The crumb arrangement this has large gravels, pore space between the aggregates which has same shape with angular but are more porous because there are found in topsoil.
(ii) Spheroidal arrangement: (granular arrangement/the particles are lamented or bound together in circular form with lots of air spaces it is found in topsoil.
(c) Aggregate arrangement: This is clay soil containing > 15% tend to form structural aggregate in both physical and biological processes, it may very in size from crumbs (2 mm) to polyhedorons or sub-angular <0.005-0.02m to prism columns > 1.0m,
This primary individual particles form aggregate and are arranged in the profile, like (loamy) this arrangement is desirable for agriculture license it has good air, and water movement for plant growth. E.g are
(2) block-like and
(CI) Plate like aggregate arrangement: The primary soil particles are arranged in horizontally and flat resembling plates or leaflets on top of each other. Whish is found in the sub-soil.
Plate-like aggregate arrangement
(iii) Prismatic arrangement: Is the vertical axis is long than the horizontal axis with air spaces
Prismatic arrangement: The vertical axis is long than the horizontal axis with air spaces, when the top ones are round columnar but they are flat found in the sub-soil.
(iv) Block like arrangement: The arrangement of particles whose edges are irregular and may either shape or round, it is found in rich clay soil at the sub-soil.
2. Description of pore size distribution
Here the wide range of soil are the pore space exist in inevitable gaps in packing of soil particles the disturbances is due to roots, tillage, swelling, soil animal, which allow soil to act as a medium for air and water transport can be grouped into some categories.
(a) Large pores (macro-pores) this pores are large mainly used for air and water conduction which is active in drainage with Demeter of range 5.000-0.1 micron.
(b) Litho spores (mesopores) this used to condition and to a limited extent for water retention, it has size range of 0.1 -0.005 microns in diameter cylindrical range and it is intermediate between macro and Micro-pores
© Micro- pores (capillary or very small pores
It is mostly used for storage and retention of water, while the size range are <0.005-microns.
3. Quantifying the pore volume-are the formation of soil structure aggregates, they are formed in two ways processes.
1. Cementation: Of soil material: Is the binding of micro-aggregate with other primary soil particle like (sand, clay and silt) which has same cementing or building agents, it has headiness, brittleness caused by the building or cementing agent than clay with the following cementing or building agent are e.g clay organic matter, sesquoxides (like Fe and AL oxide) and calcite.
2. Flocculation : This is getting together of clay particles to form clay domains, tactoids or floccules, micro-aggregate forms the factoids, while foclutation occur when the soil is witty or flocculation can be encourage through the following ways.
(i) High concentration of salt in soils. This encourage flocculation equal discourages it when it dilute concentration.
(ii) Polyvalent cations: This are di and all trivalent cation as mg2+, Fe2+, Ca2+ AL3+, Fe3+ this will improve flocculation:
The persent of monovalent cations in dilute amound discourage flocculation and encourage detoloccuation or dispersion e.g are Na+,L1+, K+.
Management of soil structure
1. It ensuring optimal porosity in crop growth for maximum yield under good conditions.
2. It help in decourased transportation and detachability by water and wind in soil conservation, erosion and runoff reduced while infiltration and percolation rate increased) it can be improved by the
3. Crop rotation
4. Proper tillage
5. Addition of organic matter
6. Quality irrigation water
7. Soil amendments
Before we go on there are some agent that can destroyed soil structure both physical and chemical properties.
Physical compaction of soil is (tillage, trampling by animal, practices)
1. Irrigating with high sodium
2. High salt content
Tillage and it effect on soil structure
The word tillage can be defined as the mechanical method of the soil manipulation for any purpose in crop production. Tillage particles can be reducing it operation on land for e.g.
(i) Plow and plant
(ii) Plow – plant
(iii) Strip cropping
All this type can reduce tillage in the land while weeds are controlled by using chemical.
Importance of soil structure
1. It support aeration for roots and micro-organism
2. Adequate water
3. It eases root penetration, permitting through exploitation of soil for water and nutrients.
4. Seed germination in rapid and uniform.
5. It resistance of soil slaking surface sealing and acceleration erosion by water and wind.
In this are two most useful indices of soil structure
(1) Bulk density
(2) Aggregates stability
(a) Bulk density is: Is the measurements which relevant to conditions of (i) (ii) and (iii) above this increase with high value sandy texture while
(2) Aggregates stability is the coherence of soil from iv and v above while aggregate decreases with declining organic matter and silty fine sandy loam.
Aeration and water support depend on soil pre size distribution in air capacity and available water capacity, water logging is susceptibility in others.