8 Difference Between Soil Structure And Soil Texture (With Pictures)

What Is Soil Structure?

Soil structure is the overall arrangement of soil particles into clusters or aggregates of various sizes and shapes. Aggregates that occur naturally in the soil are referred to as peds, while clumps of soil caused by tillage are referred to as clods. In other words, Soil structure is determined by how individual soil granules clump, bind together and aggregate, resulting in the arrangement of soil pores between them.

Soil particles (sand, silt, clay or even organic matter) binds together to form peds. Depending on the composition and on the conditions in which the peds formed, the ped has a specific shape. They could be granular (like garden soil), blocky, columnar, platy, massive (like modeling clay) or single-grained (like beach sand). Structure correlates to the pore space in the soil which influences root growth and air and water movement.

Soil structure is inherently a dynamic and complex system that is affected by different factors such as tillage events, wind erosion, shrinking, swelling, freezing and thawing. In turn, reciprocally, soil structure interacts and affects the root growth and function, soil fauna and biota, water and soluble transport processes, gaseous exchange, thermal conductivity and electrical conductivity, traffic bearing capacity and many other aspects in relation with soil.

Soil structure can be modified and improved by inputs of organic matter such as mulches, composts or cover crops. This helps stabilize aggregate macro-structure and prevents clay dispersion.  Excessive tillage can break down both the macro and micro structure of aggregates leading to hardsetting and crusting of surface soil.

Soil Structural Categories

There are eight primary types of soil structure, including blocky, columnar, crumb, granular, massive, platy, prismatic, and single grain.

• Blocky—The units are block-like. They consist of six or more flat or slightly rounded surfaces.
• Columnar—The units are similar to prisms and are bounded by flat or slightly rounded vertical faces. The tops of columns are very distinct and normally rounded.
• Crumb—The aggregates are small, porous, and weakly held together.
• Granular—The units are approximately spherical or polyhedral. The aggregates are small, non-porous, and held together strongly.
• Massive—There is no apparent structure. Soil particles cling together in large uniform masses.
• Platy—The units are flat and plate-like. They are generally oriented horizontally. Plates overlap, usually causing slow permeability.
• Prismatic—The individual units are bounded by flat to rounded vertical faces. Units are distinctly longer vertically. The tops of the prisms are somewhat indistinct and normally flat.
• Single grain—There is no apparent structure. Soil particles exist as individuals and do not form aggregates.

Facts About Soil Structure

• Soil structure is the arrangement and organization of the particles and substances that constitute soil.
• There are a range of methods of measuring soil structure that have been used for a long time, they include: aggregate water stability, bulk density, drainable porosity and penetration resistance.
• Soil structure can be modified for better or worse in a relatively short period of time.
• Soil structure has a major influence on water and air movement, biological activity, root growth and seedling emergency.
• Soil structure is classified based on the arrangement and organization of the particles and substances that constitute soil.
• Soil structure can be classified into the following types: Platy, Prismatic, Columnar, Blocky, Granular, Wedge and Lenticular.
• Soil structure has agricultural, biological and geological application such as determination of soil properties, solute transport processes, soil management etc.
• Factors that influence soil structure include: Tillage, wheel traffic, roots biological activities in the soil, rainfall, wind erosion, shrinking, swelling, freezing and thawing.

What Is Soil Texture?

Soil texture (such as loamy, sandy or clay) refers to the proportion of sand, silt and clay sized particles that make up the mineral fraction of the soil. Sand particles are the coarser or largest, silt, the medium sized whereas clay particles the finest or smallest.

In other words, the relative percentages of sand, silt and clay are what give soil its texture. Soil texture is interrelated with the soil fertility and quality in the long term.  The soil texture is associated with soil porosity, which in turn regulates the water holding capacity, gaseous diffusion and water movement that determines the soil health.

Texture is important because it influences:

• The amount of water the soil can hold
• The rate of water movement through the soil
• How workable and fertile the soil is.

For example, sand is well aerated but does not hold much water and is low in nutrients. Clay soils generally hold more water and are better at supplying nutrients. Texture often changes with depth; therefore roots have to cope with different conditions as they penetrate the soil.

Soil texture has agricultural applications such as determining crop suitability and to predict the response of the soil to environmental and management conditions such as drought or calcium (lime) requirements.

Soil texture has 12 main classifications, according to the United States Department of Agriculture. Soil textures are classified by the fractions of each soil separate (sand, silt, and clay) present in a soil. Classifications are typically named for the primary constituent particle size or a combination of the most abundant particles sizes, e.g. “sandy clay” or “silty clay”. A fourth term, loam, is used to describe equal properties of sand, silt, and clay in a soil sample, and lends to the naming of even more classifications, e.g. “clay loam” or “silt loam”.

The twelve classifications are:

• Sand
• Loamy sand
• Sandy loam
• Loam
• Silt loam
• Silt sandy clay loam
• Clay loam
• Silty clay loam
• Sandy clay
• Silty clay
• Clay

Soil Textural Triangle

Facts About Soil Texture

• Soil texture (such as loamy, sandy or clay) refers to the proportion of sand, silt and clay sized particles that make up the mineral fraction of the soil.
• Soil texture can be determined through the following methods: Texture by Feel, Hydrometer, Pipette method, the particulate organic matter method (POM) and the rapid method.
• Soil texture is generally considered a fixed property that cannot be changed.
• Soil texture and its clay content influence the amount of air in the soil and its water-holding capacity.
• Soil texture is classified based on the percentage of sand, silt and clay in the soil.
• Soil texture has agricultural applications such as determining crop suitability and to predict the response of the soil to environmental and management conditions such as drought or calcium requirement.
• Soil texture is influenced by the relative percentages of sand, silt and clay in the soil.
• The twelve classifications of soil texture are sand, loamy sand, sandy loam, loam, silt loam, silt, sandy clay loam, clay loam, silty clay loam, sandy clay, silty clay, and clay.

Difference Between Soil Structure And Soil Texture In Tabular Form