Are you preparing to use your land for agricultural purposes? If so, the question you should be asking is what is the soil structure on my land?
Soil management is a critical part of the groundwork (no pun intended).
When you understand the soil structure on your property, you’re able to make better decisions regarding soil health and productivity overall.
Here’s what you should know about this key concept, soil formation and the ways that different soil types impact soil health.
1. What is soil structure?
Soil structure is the arrangement of soil particles and their aggregation into larger units called aggregates.
It is not only the arrangement of the soil particles but also their pore spaces that determine the soil’s ability to store and transmit everything from water to nutrients to air.
Ultimately, it is defined by the way sand, silt, and clay particles are assembled.
2. How is soil structure formed?
Soil structure is formed through chemical and physical interactions between soil particles, organic matter, and soil organisms.
When these components interact, aggregates form.
Aggregates are the building blocks of soil structure, and their size, shape, and stability depend on factors like soil texture, organic matter content, and microorganism activity.
3. How is soil structure described?
Soil structure is described using three factors: grade, class, and types of aggregates.
Grade (degree of aggregation)
Grade expresses the differential between cohesion within aggregates and adhesion between aggregates.
These properties will vary depending on the moisture in the soil, so it’s best to determine grade when there is average moisture in the soil (not too moist nor too dry).
Here are the four major soil grades (rated 0 to 3).
0 – Structureless
In this grade, there is no observable aggregation or definite orderly arrangement.
1 – Weak Structure
This grade has indistinct aggregates that can barely be observed in place.
2 – Moderate Structure
This soil grade has well-formed aggregates that are fairly durable and evident but do not remain if the soil is disturbed.
3 – Strong Structure
This soil grade has durable and evident aggregates that remain even if the soil is removed from the profile.
Class (average size)
Class describes the average size of individual soil aggregates.
Here are the five different classes: very fine/thin, fine/thin, medium, coarse/thick, and very coarse/thick.
Types of aggregates (form)
Here are the various forms that soil aggregates can take:
Granular and crumb structures
Blocky and subangular blocky structures
Prismatic and columnar structures
Platy structures
4. What are the different types?
Soil structure has four main types:
Single-grained: No aggregates, typical of sandy soil
Massive: No pores and aggregates, difficult for water and air to move through the soil
Blocky: Has angular or rounded aggregates, moderately well-drained soil
Crumbly: Small, round aggregates, well-drained soil
5. Why is soil structure important?
It determines everything from fertility to water-holding capacity to drainage.
When you have a healthy soil structure, you improve nutrient availability, reduce soil erosion, and increase crop productivity.
These factors increase root growth and water infiltration which allows for plant growth and development.
6. How does it affect soil fertility?
Soil structure impacts fertility in a variety of ways.
For one, nutrients play a key role in whether the soil is fertile.
Nutrients must be available and the soil must be able to access it.
Additionally, the best soil structure allows a habitat for beneficial microorganisms.
They help to break down organic matter and release nutrients, which increases nutrient availability to plants.
Furthermore, good soil structure also promotes aeration and drainage which are necessary for root development and nutrient uptake.
7. How does it affect water-holding capacity?
The type of soil structure present will impact the soil’s ability to hold water.
If the soil has a good structure, then it’ll have large pore spaces that allow water to infiltrate the soil.
The soil will hold this water until a plant requires it for dry periods.
Poorly structured soils will have smaller pores and will lack in water infiltration ability as well as storage capacity.
9. How does soil structure affect drainage?
It affects the soil’s permeability which in turn influences its ability to drain.
Well-structured soils have large pores that are well-connected.
This allows the water to move freely through the soil profile.
This enhances drainage.
Conversely, if the soil is poorly structured, then it’ll have smaller pores that will impede water movement, which ultimately results in poor drainage.
9. How does soil texture influence soil structure?
There are three primary soil textures: sand, silt, and clay.
These textures help to determine soil structure.
For example, if the soil has a high clay content, then it will have a good structure due to the high surface area of clay particles.
Conversely, sandy soils do not have good structures because they lack clay particles.
10. How does organic matter impact soil structure?
Organic matter is essential to promoting healthy soil structure.
It helps to bind particles together and form stable soil aggregates.
Soil organic matter can also serve as a food source for beneficial microorganisms, which play a critical role in soil aggregation and nutrient cycling.
11. How do microorganisms affect soil structure?
Microorganisms help break down organic matter, which is necessary to form stable soil aggregates.
They produce substances like polysaccharides and proteins that act as soil binders.
Additionally, soil microorganisms help to improve the nutrient availability in the soil for plants.
12. How can soil structure influence erosion?
Soil erosion is a significant problem in various of the country.
It doesn’t have a specific cause, and actors like wind, water, and human activities all play a role in why soil erosion occurs.
That said, good soil structure can help to prevent erosion because it produces a higher capacity to hold water.
This makes their aggregates more likely to form tight bonds and less likely to be worn away and transported by natural forces like wind.
13. How can soil structure impact crop yield and plant growth?
It directly affects how plants and crops grow.
Generally speaking, a healthy soil structure promotes good root development by providing a stable environment in which plants can grow and access the necessary water and nutrients.
It also means the ground has ideal moisture levels, which is essential for plant growth.
Similarly, it can affect crop yield due to factors like nutrient availability, water-holding capacity, and drainage.
Furthermore, soils with good structure often have higher crop yields which support healthy root growth and nutrient uptake.
14. How can you assess soil structure?
If you’re interested in assessing the soil on your land, start with a visual assessment.
This will allow you to evaluate the soil’s physical properties such as texture, color, and aggregate stability.
Begin by digging a hole and observing the soil’s form and texture.
If you need more information after you do this, you can use testing tools like the slake test — which demonstrates the stability of soil aggregates in water — or the water stability test.
See below to learn more about how you can test your soil structure.
15. How can you test your soil?
Testing the soil structure of the soil on your land is often a necessary step to identify problems and determine appropriate management tactics.
Here are the methods we recommend:
Visual assessment
As noted above, you can do a visual assessment to see signs of compaction, crusting, and aggregate formation.
Penetration resistance
This type of test helps to measure the force required to penetrate the soil surface with a penetrometer.
If there is high penetration resistance from the soil, then it indicates that the ground is highly compact and has poor structure.
Permeability
Permeability measures how quickly water moves through the soil.
You want a high degree of permeability because it indicates that the soil is not highly compact, which is a sign of good soil structure.
Water infiltration
Water infiltration measures how quickly water moves into the soil.
If there is poor water infiltration, then this indicates soil compaction or poor soil structure as well.
16. How can you improve soil structure?
If you’re not impressed with the soil that is currently on your land, don’t give up yet!
There are a few different things you can do to address and improve soil structure and stability.
Here’s how you can improve soil structure on your land.
Incorporate organic matter
By adding organic matter (compost, manure, cover crops, etc.). to the soil, you can help to promote the growth of beneficial microorganisms and increase soil carbon content.
Both will help to improve the soil structure overall.
Avoid soil compaction
When you compact the soil, you reduce pore space and disrupt soil aggregates.
So, you should prevent any actions that lead to compaction.
One common example includes driving heavy machinery over wet soil.
Additionally, you can consider using no-till farming practices to minimize soil disturbance.
Use appropriate tillage practices
Tillage can be used to improve soil structure by breaking up compacted soil and promoting aggregate formation.
This is a helpful practice, but it can be overdone.
Be careful to avoid excessive tillage, which can cause damage.
Maintain proper soil pH
The pH of your soil is influenced by a variety of factors including the activity of microorganisms and the availability of nutrients.
We recommend maintaining a neutral pH (around 7) to ensure your soil structure remains healthy.
17. How can you maintain good structure?
Perhaps you’re just starting on your land, and based on your evaluation, you’re in good shape so far.
However, you know that you can do damage to your land as a landowner if you’re not careful.
The power to maintain good soil structure is in your hands.
So, now you may be wondering how you can maintain the great condition of your land for the long term.
Here are some ideas.
Practice crop rotation
When you rotate your crops, you integrate different root systems and promote varying nutrient requirements.
This is good for the soil and can help you maintain a good soil structure.
Avoid overuse of synthetic fertilizers
Synthetic fertilizers contain chemicals, which can alter the soil’s pH.
We know that the soil’s pH should stay around 7, and when this is changed, it can affect the soil’s healthy structure.
Additionally, synthetic fertilizers can affect present organic matter which would otherwise help.
Reduce soil disturbances
When the soil is disturbed, the soil aggregates and pore space are impacted.
This will impact the soil’s structure.
So, if possible, you want to use no-till farming practices and reduce any other soil disturbances.
Incorporate cover crops
Cover crops allow you to maintain good soil structure by adding organic matter, promoting beneficial microorganisms, and reducing erosion.
Manage soil moisture
You want an appropriate amount of moisture present.
As a landowner, you’ll want to manage this moisture by not overwatering or underwatering.
Monitoring soil moisture levels is necessary, so you can adjust irrigation accordingly.
18. What are some common soil structure problems?
The top problems include:
Soil compaction
This can occur due to excessive tillage, heavy machinery use, or livestock grazing.
Poor drainage
This can occur due to soil compaction or high clay content.
Low organic matter content
This can result from overuse of synthetic fertilizers or poor management practices.
19. What are the best ways to correct these issues?
If you want to fix these issues, then you’ll need to address the underlying factors that cause the problem.
Above, we highlighted the three most common problems: compaction, poor drainage, and low organic matter.
Here are some strategies that can help you fix each of these.
Soil compaction – Use appropriate tillage practices, reduce soil disturbances, and add organic matter to the soil.
Poor drainage – Add organic matter to the soil and reduce compaction.
Low organic matter – Add organic matter like compost or manure to the soil and reduce or cease the use of synthetic fertilizers.
Final Thoughts
So, what is soil structure?
It’s a critical factor in soil health, plant growth, and crop yield.
If you want to use your land for agriculture, then it’s important to understand how to effectively manage the soil.
By understanding and promoting the factors that influence soil structure, you as a landowner can maintain healthy soil and promote sustainable agricultural practices.
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Disclaimer: we are not lawyers, accountants or financial advisors and the information in this article is for informational purposes only. This article is based on our own research and experience and we do our best to keep it accurate and up-to-date, but it may contain errors. Please be sure to consult a legal or financial professional before making any investment decisions.
Prior to starting Gokce Capital, Erika received a Bachelor of Architecture from the University of Southern California and a graduate degree in Urban Policy from Columbia University. She worked as both an architectural designer and engineer in New York before joining the New York City Department of Housing Preservation and Development.
Erika currently lives in the New York Metropolitan area with her spouse, daughter and cat. She is originally from Chicago and still considers herself a midwesterner at heart.
Erika also loves to read, write and travel (fun fact, she has visited all 50 states and more than 30 countries!). Her new book, Land Investing Mistakes: 11 True Stories You Need To Know Before Buying Land, is now available on Amazon.