Soil Structure - How Soils Aggregate Together

Table of Contents:

Why Is Soil Structure Important?
How Does Soil Structure Differ From Soil Texture?
1. Soil Structure Distinctions
2. Soil Texture Distinctions
How Is Soil Structure Classified?
How to Assess Soil Structure
How to Improve Soil Structure

When we talk about soil structure, we're referring to the way that it aggregates together. These conglomerates and the pores which they contain define the overall structure of our soil.

seedling pepper in soil block with roots in hand 2 inch — Soil blocking (like this jalapeño pepper) is a great way to learn about what types of soils will hold together, and which will crumble apart.

Why Is Soil Structure Important?

Microbiome Health

Erosion Reduction

Soil erosion from wind and rain represents a substantial portion of nutrient outflows from agricultural systems.

This means that mitigating erosion is crucial for keeping nutrients in your soil.

Well-structured soil is far less susceptible to erosion than soils with poor structure. Let's look at how soil structure affects the rate and severity of soil erosion:

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Increased Water Infiltration Rate

Pore space in the soil aggregates are what allow for water absorbtion, and affect the rate at which that water can infiltrate.

With enough pore space in well-structured soil, large rainfall events can rapidly infiltrate soil, and absorbtion capacity is high. This prevents topsoil erosion due to runoff.

Compacted soils without adequate structure and pore spacing have low infiltration rates and low absorbtion capacity. Rainfall events are not easily handled by poorly-structured soils, and runoff readily occurs. Large-scale nutrient loss is common in these soils, which can perpetuate a cycle of further soil structure issues.

Improved Drought Tolerance

Increased Water Holding Capacity

How Does Soil Structure Differ From Soil Texture?

At first glance, soil structure may seem similar to soil texture, which we've discussed here.

Though these are related and tangential to one another, there are some distinct differences between soil structure and soil texture that are worth understanding

Let's talk about how these two differ:

Soil Structure Distinctions

Refers to the way in which soil particles and air / water space (pores) aggregate together to form soil conglomerates
Assessed visually, in the field

Soil Texture Distinctions

Refers to the relative proportions of the various particle sizes (sand, silt, and clay) which comprise soil
Assessed via soil composition test or other particle size analysis