HOW WATER MOVES THROUGH SOIL - In the basic water cycle, water falls on the land in some type of precipitation (rain or snow). It either is soaked into the ground or runs off into a body of water – stormwater or natural. Eventually, it returns to the atmosphere. After a large rain event, even a good soil mixture can get saturated. Excess water runs over the soil – or city streets – and into retention ponds. Cities have learned to create these ponds to hold the water until it can soak through the soil at the bottom of the pond. This helps the water flow naturally back into the groundwater table, instead of surface waters like streams and lakes. But, the part of the story about water movement in soil is complex. Soil scientists call this topic “soil hydrology.” Soil texture, soil structure, and gravity influence water movement. Each of these factors is critical in how we understand soil hydrology concepts. Once we understand them, we can then use them for agriculture, construction, and environmental sustainability purposes. Soil particles are either sand, silt, or clay. Sand-sized particles are the largest of the three and are typically held loosely together. Clay-sized particles are the smallest particles and tightly bound together. Silt-sized particles are sized in between sand and clay. The relative amount of sand, silt and clay in a given area makes up the “soil texture.” “Soil porosity” describes the amount of macro- and micropores in the soil. These pores exist in gaps where soils particles come together.

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 How does water move through soil?

James Hartsig

 

In the basic water cycle, water falls on the land in some type of precipitation (rain or snow).

It either is soaked into the ground or runs off into a body of water – storm water or natural.

Eventually, it returns to the atmosphere.

After a large rain event, even a good soil mixture can get saturated.
Excess water runs over the soil – or city streets – and into retention ponds.
Cities have learned to create these ponds to hold the water until it can soak
 through the soil at the bottom of the pond. This helps the water flow naturally back
into the groundwater table, instead of surface waters like streams and lakes.

But, the part of the story about water movement in soil is complex.

Soil scientists call this topic “soil hydrology.” Let’s cover some basics first.

Soil texture, soil structure, and gravity influence water movement.

Each of these factors is critical in how we understand soil hydrology concepts.

Once we understand them, we can then use them for agriculture, construction, and environmental sustainability purposes.

Soil particles are either sand, silt, or clay.

Sand-sized particles are the largest of the three and are typically held loosely together.

Clay-sized particles are the smallest particles and tightly bound together. Silt-sized particles are sized in between sand and clay.

The relative amount of sand, silt and clay in a given area makes up the “soil texture.”

“Soil porosity” describes the amount of macro- and micropores in the soil. These pores exist in gaps where soils particles come together.

The macropore space in a sand-dominated soil, where the particles are larger, would be much more than the micropore space in a clay-dominated soil, where particles are smaller and held together tightly.

Water will move in and out of these pores if they are connected to one another.

These pores also allow water to enter the soil surface through infiltration, where it starts moving both laterally and vertically.

The term soil scientists use for the connectivity of soil macro- and micropores and how quickly water moves through them is “soil permeability”.

High soil permeability means that the pore space in the soil is well-connected and that the pores are found throughout the soil. Beach sand is highly permeable.

Soils with low permeability may have several pores but those pores may not be connected. Or there may be very few pores.

However, once water reaches pores in low-permeability soils, it has to move down the soil profile via gravity or laterally via capillary action.

Water will move laterally in the soil profile if there is enough pore space in that soil. This movement is aided by the capillary action of water in small spaces.

The water will bind to the edges of the pores and slowly move laterally and even upward if the voids are small enough. You might see a puddle of water in this instance.

Soil particles clump together – in what soil scientists call aggregates.
These structures can also affect water’s ability to move in soil.
This is a close up of aggregated soil particles with both
 subangular blocky and granular soil structures. 

There are several types of “soil structures” in the soil environment, and they affect the rate at which water moves through soil profiles.

Soil structures that allow water to move easily through the soil profile are granular or crumb shaped.

These types of soil structures form clumps in a way that allows for abundant connected void space.

Granular soil structures are an ideal surface soil (topsoil) structure as it allows for both the vertical and lateral movement of water immediately upon infiltration.

Granular soil structures have plenty of space for water to flow around the soil, which will then begin to move downward once the topsoil horizon becomes saturated.

Soil structures that inhibit the vertical movement of water down the soil profile are “plate-like” and “massive” (in this case, we don’t mean large, we just mean the structure has no form!)

As clays accumulate and bind together, they tend to form hard subsurface layers.

Water will have difficulty moving past these layers and can result in standing water – puddles, ponding, even swampy areas.

It is often recommend that soils with low water permeability be aerated to allow surface flow.

If the soil has trouble moving water down the soil profile, it will then move laterally or above the soil surface.

If water can successfully move down the soil profile, it will eventually reach the groundwater table.

The pathway to get to the groundwater table is often very complex and incorporates several soil physical characteristics.

Healthy soils tend to be those with moderate soil porosity, a mixture of clayey and sandy soil textures, well-aggregated soil structures like granular and blocky, and active gravimetric forces.

Soils with poor hydrology typically have hardened, clayey soil textures with little to no porosity.

These types of soils exhibit issues (surface ponding, perched water tables) for agriculture, construction, and environmental sustainability.

By identifying and evaluating the soil physical characteristics of a given soil profile, soil scientists can determine the rate of water movement and if measures need to be taken to improve it.

By James Hartsig, Soil Scientist, Duraroot Environmental Consulting, LLC

To receive notices about future blogs, be sure to subscribe to Soils Matter by clicking on the Follow button on the upper right! Explore more on our webpage About Soils. There you will find more information about Soil Basics, Community Gardens, Green Infrastructure, Green Roofs, Soil Contaminants, materials for Teachers and more.

Thanks for visiting “Soils Matter, Get the Scoop!”, published by the Soil Science Society of America (SSSA).

SSSA is the premier organization devoted to soil science. Our goal for “Soils Matter, Get the Scoop!” is to help preserve soil – a  valuable natural resource – by educating the public about sustainable practices.

Soils play a role in every part of our lives: the food we eat, the water we drink, the clothes we wear…even the beds we sleep in! Without soil we could not grow forests or food, or build houses. Soils even help clean the air we breathe.

https://soilsmatter.wordpress.com/2016/05/15/how-does-water-move-through-soil/

What is

groundwater

CLICK HERE . . . to view . . . 

https://puricare.blogspot.com/2016/06/groundwater-there-is-immense-amount-of.html

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Springs 

The Water Cycle

CLICK HERE . . . to view . . . 

https://puricare.blogspot.com/2016/06/springs-spring-is-result-of-aquifer.html

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https://puricare.blogspot.com/2019/12/aquifers-underground-stores-of.html

https://puricare.blogspot.com/2020/01/quicksand-quicksand-is-denser-than.html

AGGREGATES - Aggregates are coarse particulate rock-like material consisting of a collection of particles ranging in size from < 0.1 mm to > 50 mm. It includes gravel, crushed rock, sand, recycled concrete, slag, and synthetic aggregate. Aggregate is a granular material, such as sand, gravel, crushed stone, crushed hydraulic-cement concrete, or iron blast-furnace slag, used with a hydraulic cementing medium to produce either concrete or mortar. Types of aggregates include Coarse aggregate and fine aggregate. The aggregate of each type is further sub-divided into many types and classification based on its size. The technique of Sieve Analysis is used for gradation of aggregate for use in concrete and for other applications. Aggregate is called bound material when it is mixed with cement or binding materials and referred to as unbound material when used without cement or binding materials. Aggregates are commonly obtained by crushing naturally occurring rock. The properties of aggregates depend on the parent rock which can be igneous, sedimentary, or metamorphic. Aggregates are evaluated through tests to determine their suitability for various applications. Mineralogy, grain size and texture, and petrographic description of rock samples are also used to evaluate suitability. Coarse-grained aggregates will not pass through a sieve with 4.75 mm openings (No. 4).

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Aggregates

By: Haseeb Jamal

 

Aggregates Definition:

Aggregates are coarse particulate rock-like material consisting of a collection of particles ranging in size from < 0.1 mm to > 50 mm.

It includes gravel, crushed rock, sand, recycled concrete, slag, and synthetic aggregate.

Aggregate is a granular material, such as sand, gravel, crushed stone, crushed hydraulic-cement concrete, or iron blast-furnace slag, used with a hydraulic cementing medium to produce either concrete or mortar.

Types of aggregates include Coarse aggregate and fine aggregate.

The aggregate of each type is further sub-divided into many types and classification based on its size.

The technique of Sieve Analysis is used for gradation of aggregate for use in concrete and for other applications.

Aggregate is called bound material when it is mixed with cement or binding materials and referred to as unbound material when used without cement or binding materials.

Aggregate Origin and Geology

Aggregates are commonly obtained by crushing naturally occurring rock.

The properties of aggregates depend on the parent rock which can be igneous, sedimentary, or metamorphic.

Aggregates are evaluated through tests to determine their suitability for various applications.

Mineralogy, grain size and texture, and petrographic description of rock samples are also used to evaluate suitability.

Types of Aggregates

Coarse Aggregate

Coarse-grained aggregates will not pass through a sieve with 4.75 mm openings (No. 4).

Those particles that are predominantly retained on the 4.75 mm (No. 4) sieve and will pass through 3 inch screen, are called coarse aggregate. 

The coarser the aggregate, the more economical the mix.

Larger pieces offer less surface area of the particles than an equivalent volume of small pieces.

Use of the largest permissible maximum size of coarse aggregate permits a reduction in cement and water requirements.

Using aggregates larger than the maximum size of coarse aggregates permitted can result in interlock and form arches or obstructions within a concrete form.

That allows the area below to become a void, or at best, to become filled with finer particles of sand and cement only and results in a weakened area.

For Coarse Aggregates in Roads following properties are desirable:

1.        Strength

2.        Hardness

3.        Toughness

4.        Durability

5.        Shape of aggregates

6.        Adhesion with bitumen

Fine Aggregate

The other type of aggregates are those particles passing the 9.5 mm (3/8 in.) sieve, almost entirely passing the 4.75 mm (No. 4) sieve, and predominantly retained on the 75 µm (No. 200) sieve are called fine aggregate.

For increased workability and for economy as reflected by use of less cement, the fine aggregate should have a rounded shape.

The purpose of the fine aggregate is to fill the voids in the coarse aggregate and to act as a workability agent.

Properties of Aggregates also has effect on resulting concrete. e.g. variation in size, grading, texture, shape and strength of aggregates means variation in the properties of resulting concrete. 

Purpose & Uses of Aggregates

In concrete, an aggregate is used for its economy factor, to reduce any cracks and most importantly to provide strength to the structure.

1.    Aggregates are used as the base, subbase, and/or surface of roads in several forms

2.    In roads and railway ballast, it is used to help distribute the load and assist in ground water running off the road.

3.    Increases the volume of concrete, thus reduces the cost. Aggregates account for 60-75% of the volume of concrete and 79-85% weight of PCC

4.    Provide dimensional stability

5.    Influence hardness, abrasion resistance, elastic modulus and other properties of concrete to make it more durable, strong and cheaper.

6.    Other uses include fills, backfills, and drainage and filtration applications.

Haseeb Jamal

I am a Civil Engineer, graduated from University of Engineering and Technology, Peshawar, Pakistan in 2010. I also have a PG-Diploma in Disaster Management and MS in Urban Infrastructure Engineering (In Progress). My expertise include civil related softwares like AutoCAD, SAP2000, MS Project, Primavera, MS Office and GIS. My technical skills include project management, monitoring and evaluation, structural assessment, disaster risk management, Quantity survey, land survey, material testing, site management and technical writing. I am trained in writing project progress reports as well as proposals and concept papers. I have also received advanced training on surveying, proposal writing, Monitoring and Evaluation of projects as well as organizations.

I have worked as Project Engineer at National Research and Development Foundation, Peshawar and CENCON Associates. I also worked with Spectra Engineering Solutions as Senior Civil Engineer in monitoring of World Bank and UNDP funded projects all over Khyber Pakhtunkhwa and FATA. Currently, I am working as Deputy Manager Development at NayaTel, Peshawar.

https://www.aboutcivil.org/aggregates-types-uses-definition.html

SOIL AGGREGATES - Poorly aggregated soils disintegrate easily when exposed to erosive forces. They tend to break down faster, leading to soil degradation. Poor stability can lead to pore spaces being filled in and can ultimately result in the formation of soil crusts. This can lead to reduced infiltration and gaseous exchange. Poorly aggregated soils can reduce crop productivity. Soil management often influences aggregate size, shape, and stability. The ground beneath your feet might seem like a uniform material, but it’s really a mixture of soil particles, organic matter, and other mineral/organic components. For a soil to be healthy, it must have good structure. Soil is made up of a combination of primary particles – sand, silt and clay. These particles can be bound together into what soil scientists call “aggregates.” Soil aggregates retained on a 4.75 mm sieve after wet sieving experiment. These aggregates are clumps of soil that range from the micro level (less than 0.25mm in diameter) to the macro level (greater than 0.25mm in diameter). Furthermore, they can resemble various shapes: granular, blocky, etc. These varied shapes allow for healthy soil to have pores spaces for air and water, needed for healthy plant growth. Aggregate formation is a complex process. Soil aggregates are formed through physical, chemical and biological activity below ground. They are even influenced by human factors, like tilling, walking on the surface, or even how you fertilize your garden.

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Soil  Aggregates

What are soil aggregates?

Soil is made up of a combination of primary particles – sand, silt and clay.These particles can be bound together into what soil scientists call “aggregates.”

.

Poorly aggregated soils disintegrate easily when exposed to erosive forces. They tend to break down faster, leading to soil degradation. Poor stability can lead to pore spaces being filled in and can ultimately result in the formation of soil crusts. This can lead to reduced infiltration and gaseous exchange. Poorly aggregated soils can reduce crop productivity. Soil management often influences aggregate size, shape, and stability.

Soil Science Society of America

by Nall I. Moonilall, Ohio State University

 

The ground beneath your feet might seem like a uniform material, but it’s really a mixture of soil particles, organic matter, and other mineral/organic components.

For a soil to be healthy, it must have good structure.

Soil is made up of a combination of primary particles – sand, silt and clay.

Soil aggregates retained on a 4.75 mm sieve after wet sieving experiment.

These particles can be bound together into what soil scientists call “aggregates.”

These aggregates are clumps of soil that range from the micro level (less than 0.25mm in diameter) to the macro level (greater than 0.25mm in diameter).

Furthermore, they can resemble various shapes: granular, blocky, etc.

These varied shapes allow for healthy soil to have pores spaces for air and water, needed for healthy plant growth.

Aggregate formation is a complex process.

Soil aggregates are formed through physical, chemical and biological activity below ground.

They are even influenced by human factors, like tilling, walking on the surface, or even how you fertilize your garden.

Formation of aggregates begins with finer soil primary particles binding together.

You may know that clay particles have a negative charge.

And, the fertilizers you use include salts that have positively charged cations (things like potassium nitrate, etc.)

The positively charged cations allow the negatively charged clay particles to bind together creating “floccules.”

Soil crust formation on a soil exposed to simulated rainfall.  You can see

 the crust formation on the surface of the soil as well as how deep

 the crust extends. (This really is soil – not cement!)

The type and amount of clay minerals in the soil often plays an influential role in aggregation formation.

The second part of aggregate formation deals with cementation.

Here, the clay floccules and other soil particles are bonded together by some type of cementing agent. (Here we mean “binding” – not cement like in concrete!)

Examples of cementing agents include organic matter, and liming materials like calcium carbonate.

Even types of oxides, like iron and aluminum can help cement particles together.

In the case of organic matter, it is broken down by the soil microorganisms and soil fauna (earthworms, etc.)

When breakdown occurs, these organisms secrete organic compounds that are the “glue” that makes cementation occur.

Plant roots also play a role in aggregate formation by secreting organic compounds called root exudates.

These help bind soil together near the root zone. Fungal hyphae also contribute to aggregate formation by entangling and weaving around soil particles.

As you can see, aggregate formation is the result of many interactions and feedback loops occurring below ground.

Soil aggregates play a major role in soil structure formation and soil health.

In agriculture, the stability of aggregates is critical to how well an agroecosystem will function. The pore spaces in soil influence air and water storage, and gaseous exchange.

They create habitat for soil microorganisms, and allow for plant root development and penetration.

They also assist in nutrient cycling and transport.

Soils that have high aggregate stability are less susceptible to erosion.

Keep soil covered! Crop residues on the soil surface help
 to protect soil from erosive forces.

They hold their shape when exposed to disruptive forces, like water, and do not easily break apart.

Poorly aggregated soils disintegrate easily when exposed to erosive forces. They tend to break down faster, leading to soil degradation.

Poor stability can lead to pore spaces being filled in and can ultimately result in the formation of soil crusts.

This can lead to reduced infiltration and gaseous exchange. Poorly aggregated soils can reduce crop productivity.

Soil management often influences aggregate size, shape, and stability. Favorable practices that promote and maintain greater stability include:

·      Minimizing soil disturbance, like minimal tillage. This reduces aggregate destruction because they are not physically or mechanically broken apart;

·      Adding organic matter enhances aggregate strength and stability;

·      Keeping soil covered is essential to keeping soil intact. Vegetative cover on the soil reduces the impact of erosive forces;

·      Promoting a diverse cropping system. Systems that promote perennial plants or meadows have expansive rooting systems and require no tillage. Promoting this kind of diversity within a system will ensure that soil’s function is not reduced;

·      Managing for grazing. Grasses have strong root systems, but if animals graze too long, that can be disruptive to the forage system. There are many ways to graze animals and preserve or enhance soil stability; and,

·      Managing for pest control. The choice of plants and how they are managed (e.g., annual vs. perennial, cover crops, rotation) are highly influential.

To recap – soil aggregates are the building blocks that make up soil and their stability is extremely important in the long-term.

Soils that are well aggregated exhibit greater soil health, ensure greater agronomic productivity, are less susceptible to soil erosion, and can play a role in carbon sequestration.

Answered by Nall I. Moonilall, Ohio State University

To receive notices about future blogs, be sure to subscribe to Soils Matter by clicking on the Follow button on the upper right! Explore more on our webpage About Soils. There you will find more information about Soil Basics, Community Gardens, Green Infrastructure, Green Roofs, Soil Contaminants, materials for Teachers and more.

Soil Science Society of America (SSSA)

SSSA is the premier organization devoted to soil science. Our goal for “Soils Matter, Get the Scoop!” is to help preserve soil – a  valuable natural resource – by educating the public about sustainable practices.

Soils play a role in every part of our lives: the food we eat, the water we drink, the clothes we wear…even the beds we sleep in! Without soil we could not grow forests or food, or build houses. Soils even help clean the air we breathe.

Whether you are interested in soil science in general or have a specific question about your home garden, our blog will have something to interest you. Send us your questions, either by posting to the blog or emailing us at soils-matter@soils.org.

SSSA has more soils-related information for the general public on our main website, http://www.soils.org under the About Soils tab (https://www.soils.org/about-soils). Here, we have topics like Soil Basics, Soils in the City, Food, Climate, etc. We encourage you to explore all you can about soils – because Soils Sustain Life!

https://soilsmatter.wordpress.com/2019/07/15/what-are-soil-aggregates/