Tony O’Neill, gardener and author of the popular “Composting Masterclass” and “Your First Vegetable Garden,” combines lifelong passion and expert knowledge to simplify the art of gardening. His mission? Helping you cultivate a thriving garden.
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Almost all of global food production depends on soil. Also, it is home to a quarter of all terrestrial species on earth. Soil also plays a vital role in storing carbon and water that, helps mitigate climate change and avoids flooding. It is undoubtedly one of the most important natural resources available to humankind. Besides soil, its structure also plays a major role in plant growth.
The soil structure affects its ability to retain and transmit air, water, and organic and inorganic substances that support root growth and development. It also plays an important role in improving soil productiveness, enhancing permeability, and preventing erosion.
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A healthy garden needs healthy soil. So, ensuring that your garden’s soil has a good structure supporting plant growth is essential. There are quite a few things that will help you understand, improve, and maintain the structure of your garden soil.
What is Soil Structure?
Soil structure is how soil particles (sand, silt, and clay) are arranged. Soil that has a good structure would empty spaces between these particles. This allows air, water, roots, and other organisms to move around easily.
Soil structure can influence its capability to sustain life and perform important functions like carbon, water, and nutrient cycling. Maintaining a good soil structure will allow air and water into the soil, which is essential for the healthy growth of plants. A healthy soil structure promotes germination, emergence, crop yields, and grain quality.
The soil will suffer from waterlogging, anaerobic, and nutrient lock-up without a proper structure. This can eventually lead to stunted growth and even death of the plant.
A decline in the structure of the soil is usually associated with land use and crop management practices. However, changes in climate and biological activity can also impact the soil structure.
How Does Soil Structure Support Plant Growth?
Soil offers the following to plants to ensure their proper growth:
Anchorage
Soil offers a home to the root systems of the plants that extend outward and downward, thus, stabilizing plants.
Oxygen
The spaces between the soil particles contain air from which the plants acquire oxygen. Since living cells use oxygen to break down sugars and release energy, these spaces are essential for proper growth.
Water
Other than air, the spaces between the soil particles also contain water that moves upward through the plants. Water helps the plant in cooling down while also carrying essential nutrients. Water also helps maintain the size of cells and ensures that the plants don’t wilt. And most importantly, water serves as a raw material for the process of photosynthesis.
Temperature Modification
While water can help the plant cool down, the soil is a much better insulator that protects the roots from drastic fluctuations in temperature. This is important, especially during excessively hot or cold months times of the year.
Nutrients
One of the most important ways soil supports plant growth is by supplying nutrients. Other than this, it can also hold the nutrients added to it in the form of fertilizers.
Types of Soil Structures
Some of the most basic types of aggregate arrangements in soil are:
Platy
In this type of soil structure, the units are flat and plate-like. Usually oriented horizontally, the plates are generally thickest in the middle and become thinner towards the edges. This structure is usually found in the soil’s subsurface, subjected to leaching or compaction by heavy machinery or animals. This structure obstructs the downward movement of water and plant roots through the soil.
Prismatic
A prismatic soil structure is where the individual units are confined by flat to rounded vertical faces. These units are usually recognized by their distinctive vertical length, while the tops are generally flat. In this structure, water movement in the soil is mostly vertical. Thus, the supply of water to the roots, as well as drainage, is generally quite poor.
Columnar
The columnar structure is somewhat similar to prisms. Flat or slightly rounded vertical faces also bound them. However, the tops are usually very distinct and rounded compared to the prismatic structure. Since this structure is extremely dense, plant roots cannot penetrate these layers. One can consider using techniques like deep plowing to help restore some fertility in columnar soil structures.
Blocky
As the name suggests, the units are blocklike or polyhedral in a blocky structure. Flat or slightly rounded surfaces bound the units. The soil particles cling together in almost square or angular blocks and relatively sharp edges.
Blocky soil structures can be further divided into angular blocky and subangular blocky structures (based on their sharp or rounded edges). Large blocks indicate difficulty in the penetration and movement of water.
Granular
Units that are almost spherical or polyhedral form a granular soil structure. Rounded or uneven faces bound them. In layman’s terms, they may look like cookie crumbs. This structure is commonly found in the surface soils of nutrient-rich and highly amended garden soils.
They also have high organic matter content. This structure also has good absorbency and allows easier air and water movement. Thus, it is a great structure to ensure the healthy growth of plants.
Structureless
Some soils lack structure. Soils that are structureless have no definite arrangement of the soil particles. Usually, sand and sandy-loam soils are structureless that have a single-grain arrangement. Other than this, clay soils can also be referred to be structureless. This is when the particles create a massive structure with no small aggregates inside.
Factors Influencing Soil Structure
Certain elements and practices like compaction, excessive moving and handling of soil, screening, and excessive sodium can deteriorate the soil structure. Heavy machinery can compact the soil making it less permeable to water. This can increase the probability of soil erosion and even flooding. High livestock densities can also do the same and damage the soil structure.
Besides, factors like overworking the soil through tillage can also be quite harmful. This practice can also decrease the organic content and nutrients in the soil.
It is also known that a high proportion of sodium to magnesium and calcium can also cause the clay particles to repel each other when damp. This can reverse the process of soil structure formation. Excessive irrigation or salting roads can lead to high levels of sodium which can eventually cause the small organic particles to clog up and make the soil almost impermeable to water.
Other than these activities, there are also a few factors that can influence the structure of the soil in your garden:
- Organisms (like worms and bugs) present in the soil
- The amount of organic matter the soil contains
- Any freeze/thaw that occurs with the soil
- The amount of tillage performed with the soil
- The presence and size of soil colloids
- Water flow and movement
Checking Your Soil Structure
To improve the structure of your soil, it is vital to examine it first. You can dig a 30- to the 40-centimeter-deep hole while ensuring no spade marks along one side. Now, you need to examine the unmarked side of the hole by inserting a knife around a centimeter. The areas where you sense a greater resistance would indicate compacted zones.
Moreover, it would be best to look at the root development and any traces of worm activity. This will also give you an idea of whether the soil is well-structured. Restricted root growth or lack of activity usually indicates an issue with the soil structure that should be addressed.
Ways to Improve Soil Structure
With careful and proper management and certain practice, one can enhance and maintain the structure of the soil. A few interventions can prove to be extremely beneficial for soil structure. Here are some simple and easy ways in which you can improve the structure of your soil:
Balancing the amount of organic matter in your soil
While lack of organic matter in the soil is a common issue gardeners face, excessive organic matter can sometimes be an issue. Thus, it is important to maintain a proper balance of organic matter to ensure proper plant growth.
While deficiency of organic matter would result in a lack of nutrients responsible for plant growth, an excessive amount of organic matter in soil may stimulate the growth of wrong plants, such as algae.
To increase the amount of organic matter in your soil, you can add fertilizers like manure to help the soil regain its strength and even provide the plants with nitrogen which is crucial for their healthy growth. One can also grow cover crops to add organic matter to the soil.
On the other hand, if one needs to decrease the organic matter in your soil, one can try tilling and turning the soil. However, one should carefully examine the soil very closely to maintain balance.
Increase Your Soil Organisms
The bacteria and those natural critters are essential for the soil. They are significant in stabilizing the structure and holding the soil together. Other than this, fungi also play a pivotal role in decomposing particles and ensuring healthier soil. One should encourage wildlife in their soil as well, such as earthworms. They serve as ‘ecosystem engineers’ that aerate the soil as they burrow their way underneath it.
Prepare Your Soil for Extreme Weather Conditions
Regarding weather, there is very little that one can do. However, one can prepare the soil for the upcoming drought, flood, frost, or scorching sun and ensure it is well-conditioned to face the adversities ahead.
For this, one can try growing cover crops, rotating fields, working with more fertilizer, or improving irrigation or drainage.
Conclusion on Is Soil Structure Important for Plant Growth
Good soil structure is crucial for sustainable agriculture. And with the proper knowledge of your soil structure, you will be able to maintain and enhance your soil’s health, which will significantly impact water movement, regulating soil temperature and nutrient cycling, thus ensuring proper plant growth.
We hope these tips will help you improve the structure of your soil and grow healthy plants in your garden.
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