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What is Soil structure?
The structure of a soil refers to the arrangement of the soil particles and the adhesion of smaller particles to form large ones or aggregates
According to Marshall and Holmes, It is the arrangement of the solid parts of the soil and of the pore spaces located between them
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Soil structure is associated with the tilth of the soil since tillage largely affects the aggregation of soil particles through rearrangement, floculation or cementation
What are different types of Soil structures?
Following are the different types of soil structures
1. Platy
The units are flat and platelike.
They are generally oriented horizontally
2. Prismatic
The individual units are bounded by flat to rounded vertical faces
Units are distinctly longer vertically, and the faces are typically casts or molds of adjoining units
3. Columnar
The units are similar to prisms and bounded by flat or slightly rounded vertical faces
The tops of columns, in contrast to those of prisms, are very distinct and normally rounded
4. Blocky
The units are blocklike or polyhedral
They are bounded by flat or slightly rounded surfaces that are casts of the faces of surrounding peds
Typically, blocky structural units are nearly equidimensional but grade to prisms and plates
5. Granular
The units are approximately spherical or polyhedral
They are bounded by curved or very irregular faces that are not casts of adjoining peds
6. Wedge
The units are approximately elliptical with interlocking lenses that terminate in acute angles
7. Lenticular
The units are overlapping lenses parallel to the soil surface
They are thickest in the middle and thin towards the edges
Lenticular structure is commonly associated with moist soils, texture classes high in silt or very fine sand (e.g., silt loam)
How does Soil structure affect soil?
The soil structure influences primarily
a) Permeability for air and water
b) Total porosity and in turn water storage capacity in a given volume of soil
c) Root penetration and proliferation
Soils without definite structure may be single grain types, sands or massive types such as heavy clays
A structure-less soil allows water to percolate either too rapidly or too slowly while Platy structure restricts the downward movement of water
Which is the best soil structure for normal crop growth?
Crumbly, granular and prismatic structural types are most desirable for efficient irrigation water management and normal crop growth
Further readings and references
Handbook of Agriculture
