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2023-05-10T18:08:14Z

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← Older revision		Revision as of 14:08, 10 May 2023
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	=== Structure ===		=== Structure ===
	The [[Soil Structures\|structure]] of the soil refers to the way in which the soil solids are organized in relation to one another. Soil particles clump together to form [[aggregate formation\|aggregates]], and the size and stability of these aggregates depend on factors such as mineral composition, texture, moisture availability, and soil management factors [7]. Aggregates clump together, and the way in which they align themselves indicates soil structure.		The [[Soil Structures\|structure]] of the soil refers to the way in which the soil solids are organized in relation to one another. Soil particles clump together to form [[aggregate formation\|aggregates]], and the size and stability of these aggregates depend on factors such as mineral composition, texture, moisture availability, and soil management factors [7]. Aggregates clump together, and the way in which they align themselves indicates soil structure.
	There are four major types of soil structure: platelike, prism-like, blocklike, and spheroidal. Platelike structures are often found in compressed soils [8], can exist at any horizon, and have horizontal layers to them, like dinner plates stacked on top of one another. Prismlike structures have vertical tube-like prisms that vary slightly and can be broken into prismatic (angular sides and tops) and columnar (rounded tops). Prismlike structures are usually found in lower horizons. [[Soil Structures\|Soil structures]] that are blocklike (blocky) can either be cubelike or subangular. These are common in humid regions. Spheroidal soils can either be granular or crumb, depending on their porosity (granular being porous while crumb being very porous) [6].		There are four major types of soil structure: platelike, prism-like, blocklike, and spheroidal. Platelike structures are often found in compressed soils [8], can exist at any horizon, and have horizontal layers to them, like dinner plates stacked on top of one another. Prismlike structures have vertical tube-like prisms that vary slightly and can be broken into prismatic (angular sides and tops) and columnar (rounded tops). Prismlike structures are usually found in lower horizons. [[Soil Structures\|Soil structures]] that are blocklike (blocky) can either be cubelike or subangular. These are common in humid regions. Spheroidal soils can either be granular or crumb, depending on their [[porosity]] (granular being porous while crumb being very porous) [6].
	Soil structure influences water infiltration rates. Due to larger pore spaces, blocky and spheroidal soils have higher infiltration rates due to the large pore spaces between particles, while platy and prismatic have moderate-slow infiltration rates. Soil with larger aggregates yields plants with coarse roots, while finer soil aggregates yield finer roots. This influences uptake of certain nutrients but not others, as nitrates move quickly through water, but phosphorous intake is higher on finer rooted plants [9].		Soil structure influences water infiltration rates. Due to larger pore spaces, blocky and spheroidal soils have higher infiltration rates due to the large pore spaces between particles, while platy and prismatic have moderate-slow infiltration rates. Soil with larger aggregates yields plants with coarse roots, while finer soil aggregates yield finer roots. This influences uptake of certain nutrients but not others, as nitrates move quickly through water, but phosphorous intake is higher on finer rooted plants [9].

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	A solution's pH is a measurement of how many hydrogen ions are present on a logarithmic scale of 1-14, where 7.0 is neutral, anything less than 7.0 is acidic, and anything over 7.0 is basic (alkaline). Calcium carbonate (CaCO3), commonly known as limestone, indicates an alkaline soil, or one with a pH > 7.3 [13]. The availability of micronutrients and nitrogen, phosphorous, and potassium are affected by [[soil pH]] levels. For example, micronutrients such as manganese, iron, copper, and zinc tend to decrease in availability as soil pH increases [14]. Nitrification is also slow in acidic soils.		A solution's pH is a measurement of how many hydrogen ions are present on a logarithmic scale of 1-14, where 7.0 is neutral, anything less than 7.0 is acidic, and anything over 7.0 is basic (alkaline). Calcium carbonate (CaCO3), commonly known as limestone, indicates an alkaline soil, or one with a pH > 7.3 [13]. The availability of micronutrients and nitrogen, phosphorous, and potassium are affected by [[soil pH]] levels. For example, micronutrients such as manganese, iron, copper, and zinc tend to decrease in availability as soil pH increases [14]. Nitrification is also slow in acidic soils.

	Adding lime to soil increases soil pH and neutralizes acidic soils, making them more suitable for agriculture [13]. According to the US Department of Agriculture, benefits of liming acidic soils include improvement of microbial activity, soil structure, nitrogen fixation in legumes, and some nutrient availability, and reduces the possibility of Mn2+ and Al3+ toxicity. Liming also increases potassium availability [14]. However, liming soils is not always necessary, as different crops have varying tolerances and preferences to acidity in soils [13].		Adding lime to soil increases soil pH and neutralizes acidic soils, making them more suitable for [[agriculture]] [13]. According to the US Department of Agriculture, benefits of liming acidic soils include improvement of microbial activity, soil structure, nitrogen fixation in legumes, and some nutrient availability, and reduces the possibility of Mn2+ and Al3+ toxicity. Liming also increases potassium availability [14]. However, liming soils is not always necessary, as different crops have varying tolerances and preferences to acidity in soils [13].

	== References ==		== References ==

Saigemat at 16:39, 27 April 2022

2022-04-27T16:39:03Z

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	=== Color ===		=== Color ===
	[[File:Munsell.png\|200px\|thumb\|right\| The Munsell color chart used to identify soil colors.]]		[[File:Munsell.png\|200px\|thumb\|right\| The Munsell color chart used to identify soil colors.]]
	The most widely accepted color identification system is the Munsell color system [10]~~, which is a book used in several fields, from painting to soil science~~. The Munsell charts made specifically for soils focus predominantly on reds and yellows [11]. There are three parameters to soil color identification by the Munsell system. The hue indicates the general color of the sample, such as red, yellow, green, etc. A color's value is how light or dark it is. Lastly, the chroma is how weak or strong (vibrant) the color is [12].		The most widely accepted color identification system- utilized as an important tool across several fields, from painting to soil science- is the Munsell color system [10]. The Munsell charts made specifically for soils, found within the Munsell Soil Color Book, focus predominantly on reds and yellows [11]. There are three parameters to soil color identification by the Munsell system. The hue indicates the general color of the sample, such as red, yellow, green, etc. A color's value is how light or dark it is. Lastly, the chroma is how weak or strong (vibrant) the color is [12].

	The color of soil is indicative of what the soil is made up of, and what its mineral content is. For example, the soil at the A horizon is usually a dark brown, which is a result of the breakdown of [[Organic Matter\|organic matter]] and the oxidation of soil nutrients. Whiteish soils indicate a high concentration of calcium or magnesium carbonates and other soluble salts.		The color of soil is indicative of what the soil is made up of, and what its mineral content is. For example, the soil at the A horizon is usually a dark brown, which is a result of the breakdown of [[Organic Matter\|organic matter]] and the oxidation of soil nutrients. Whiteish soils indicate a high concentration of calcium or magnesium carbonates and other soluble salts.

Saigemat at 16:31, 27 April 2022

2022-04-27T16:31:46Z

← Older revision		Revision as of 12:31, 27 April 2022
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	[[File:Soil horizons.jpg\|280px\|thumb\|left\|Figure 1 [15] - Soil horizons vary in depth depending on the environment in which they are found, but in general, all soils have these basic layers.]]		[[File:Soil horizons.jpg\|280px\|thumb\|left\|Figure 1 [15] - Soil horizons vary in depth depending on the environment in which they are found, but in general, all soils have these basic layers.]]

	[[Soil Horizons\|Soil horizons]] are layers that lay parallel to the ~~earth~~'s surface, and to one another. The O horizon contains organic material and relatively undecomposed litter. Beneath is the A horizon, is a dark layer that is often referred to as topsoil and/or [[humus]]. It is within this layer where the most biological activity occurs in the form of plants, bacteria, archaea, and numerous macroinvertebrates. Following is the B layer, also known as the subsoil, where considerable amounts of soil nutrients and illuvium (material leached from one soil horizon and deposited in another, usually via rainwater) accumulate. Next is the C layer, consisting of notably unweathered parent material of soils. The final layer is the [[bedrock]], or the R layer, which is similarly composed of unweathered materials due to a lack of exposure to various pedogenetic factors (like physical weathering from rainwater and the action of most macroinvertebrates) [2]. However, up to 35% of soil bacteria are found more than 2 meters below the surface, which means that [[microorganisms]] play a role in the formation and properties of each horizon.		[[Soil Horizons\|Soil horizons]] are layers that lay parallel to the Earth's surface, and to one another. The O horizon contains organic material and relatively undecomposed litter. Beneath is the A horizon, is a dark layer that is often referred to as topsoil and/or [[humus]]. It is within this layer where the most biological activity occurs in the form of plants, bacteria, archaea, and numerous macroinvertebrates. Following is the B layer, also known as the subsoil, where considerable amounts of soil nutrients and illuvium (material leached from one soil horizon and deposited in another, usually via rainwater) accumulate. Next is the C layer, consisting of notably unweathered parent material of soils. The final layer is the [[bedrock]], or the R layer, which is similarly composed of unweathered materials due to a lack of exposure to various pedogenetic factors (like physical weathering from rainwater and the action of most macroinvertebrates) [2]. However, up to 35% of soil bacteria are found more than 2 meters below the surface, which means that [[microorganisms]] play a role in the formation and properties of each horizon.

	=== Soil Texture ===		=== Soil Texture ===

Saigemat at 16:30, 27 April 2022

2022-04-27T16:30:43Z

← Older revision		Revision as of 12:30, 27 April 2022
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	[[File:Soil horizons.jpg\|280px\|thumb\|left\|Figure 1 [15] - Soil horizons vary in depth depending on the environment in which they are found, but in general, all soils have these basic layers.]]		[[File:Soil horizons.jpg\|280px\|thumb\|left\|Figure 1 [15] - Soil horizons vary in depth depending on the environment in which they are found, but in general, all soils have these basic layers.]]

	[[Soil Horizons\|Soil horizons]] are layers that lay parallel to the earth's surface, and to one another. The O horizon contains organic material and relatively undecomposed litter. Beneath is the A horizon, is a dark layer that is often referred to as topsoil and/or [[humus]]. It is within this layer where the most biological activity occurs in the form of plants, bacteria, archaea, and numerous macroinvertebrates. Following is the B layer, also known as the subsoil, where ~~large~~ amounts of soil nutrients and illuvium (material leached from one soil horizon and deposited in another, usually via rainwater) accumulate. Next is the C layer, consisting of notably unweathered parent material of soils. The final layer is the [[bedrock]], or the R layer, which is ~~again, left~~ unweathered due to ~~its~~ lack of exposure to ~~many~~ pedogenetic factors (like physical weathering from rainwater and the action of most macroinvertebrates) [2]. However, up to 35% of soil bacteria are found more than 2 meters below the surface, which means that [[microorganisms]] play a role in the formation and properties of each horizon.		[[Soil Horizons\|Soil horizons]] are layers that lay parallel to the earth's surface, and to one another. The O horizon contains organic material and relatively undecomposed litter. Beneath is the A horizon, is a dark layer that is often referred to as topsoil and/or [[humus]]. It is within this layer where the most biological activity occurs in the form of plants, bacteria, archaea, and numerous macroinvertebrates. Following is the B layer, also known as the subsoil, where considerable amounts of soil nutrients and illuvium (material leached from one soil horizon and deposited in another, usually via rainwater) accumulate. Next is the C layer, consisting of notably unweathered parent material of soils. The final layer is the [[bedrock]], or the R layer, which is similarly composed of unweathered materials due to a lack of exposure to various pedogenetic factors (like physical weathering from rainwater and the action of most macroinvertebrates) [2]. However, up to 35% of soil bacteria are found more than 2 meters below the surface, which means that [[microorganisms]] play a role in the formation and properties of each horizon.

	=== Soil Texture ===		=== Soil Texture ===

Saigemat at 16:27, 27 April 2022

2022-04-27T16:27:55Z

← Older revision		Revision as of 12:27, 27 April 2022
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	[[File:Soil horizons.jpg\|280px\|thumb\|left\|Figure 1 [15] - Soil horizons vary in depth depending on the environment in which they are found, but in general, all soils have these basic layers.]]		[[File:Soil horizons.jpg\|280px\|thumb\|left\|Figure 1 [15] - Soil horizons vary in depth depending on the environment in which they are found, but in general, all soils have these basic layers.]]

	[[Soil Horizons\|Soil horizons]] are layers that lay parallel to the earth's surface, and to one another. The O horizon contains organic material and relatively undecomposed litter. Beneath is the A horizon, is a dark layer that is often referred to as topsoil and/or [[humus]]. It is within this layer where the most biological activity occurs in the form of plants, bacteria, archaea, and numerous macroinvertebrates. Following is the B layer, also ~~referred to~~ as the subsoil, where large amounts of soil nutrients and illuvium (material leached from one soil horizon and deposited in another, usually via rainwater) accumulate. Next is the C layer, consisting of notably unweathered parent material of soils. The final layer is the [[bedrock]], or the R layer, which is again, left unweathered due to its lack of exposure to many pedogenetic factors (like physical weathering from rainwater and the action of most macroinvertebrates) [2]. However, up to 35% of soil bacteria are found more than 2 meters below the surface, which means that [[microorganisms]] play a role in the formation and properties of each horizon.		[[Soil Horizons\|Soil horizons]] are layers that lay parallel to the earth's surface, and to one another. The O horizon contains organic material and relatively undecomposed litter. Beneath is the A horizon, is a dark layer that is often referred to as topsoil and/or [[humus]]. It is within this layer where the most biological activity occurs in the form of plants, bacteria, archaea, and numerous macroinvertebrates. Following is the B layer, also known as the subsoil, where large amounts of soil nutrients and illuvium (material leached from one soil horizon and deposited in another, usually via rainwater) accumulate. Next is the C layer, consisting of notably unweathered parent material of soils. The final layer is the [[bedrock]], or the R layer, which is again, left unweathered due to its lack of exposure to many pedogenetic factors (like physical weathering from rainwater and the action of most macroinvertebrates) [2]. However, up to 35% of soil bacteria are found more than 2 meters below the surface, which means that [[microorganisms]] play a role in the formation and properties of each horizon.

	=== Soil Texture ===		=== Soil Texture ===

Saigemat at 16:27, 27 April 2022

2022-04-27T16:27:27Z

← Older revision		Revision as of 12:27, 27 April 2022
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	[[File:Soil horizons.jpg\|280px\|thumb\|left\|Figure 1 [15] - Soil horizons vary in depth depending on the environment in which they are found, but in general, all soils have these basic layers.]]		[[File:Soil horizons.jpg\|280px\|thumb\|left\|Figure 1 [15] - Soil horizons vary in depth depending on the environment in which they are found, but in general, all soils have these basic layers.]]

	[[Soil Horizons\|Soil horizons]] are layers that lay parallel to the earth's surface, and to one another. The O horizon contains organic material and relatively undecomposed litter. Beneath is the A horizon, is a dark layer that is often referred to as topsoil and/or [[humus]]. It is within this layer where the most biological activity occurs in the form of plants, bacteria, archaea, and numerous macroinvertebrates. ~~Below this~~ is the B layer, or subsoil, where ~~many~~ soil nutrients and illuvium (material leached from one soil horizon and deposited in another, usually via rainwater) accumulate. Next is the C layer, consisting of notably unweathered parent material of soils. The final layer is the [[bedrock]], or the R layer, which is again, left unweathered due to its lack of exposure to many pedogenetic factors (like physical weathering from rainwater and the action of most macroinvertebrates) [2]. However, up to 35% of soil bacteria are found more than 2 meters below the surface, which means that [[microorganisms]] play a role in the formation and properties of each horizon.		[[Soil Horizons\|Soil horizons]] are layers that lay parallel to the earth's surface, and to one another. The O horizon contains organic material and relatively undecomposed litter. Beneath is the A horizon, is a dark layer that is often referred to as topsoil and/or [[humus]]. It is within this layer where the most biological activity occurs in the form of plants, bacteria, archaea, and numerous macroinvertebrates. Following is the B layer, also referred to as the subsoil, where large amounts of soil nutrients and illuvium (material leached from one soil horizon and deposited in another, usually via rainwater) accumulate. Next is the C layer, consisting of notably unweathered parent material of soils. The final layer is the [[bedrock]], or the R layer, which is again, left unweathered due to its lack of exposure to many pedogenetic factors (like physical weathering from rainwater and the action of most macroinvertebrates) [2]. However, up to 35% of soil bacteria are found more than 2 meters below the surface, which means that [[microorganisms]] play a role in the formation and properties of each horizon.

	=== Soil Texture ===		=== Soil Texture ===

Saigemat at 16:25, 27 April 2022

2022-04-27T16:25:06Z

← Older revision		Revision as of 12:25, 27 April 2022
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	[[File:Soil horizons.jpg\|280px\|thumb\|left\|Figure 1 [15] - Soil horizons vary in depth depending on the environment in which they are found, but in general, all soils have these basic layers.]]		[[File:Soil horizons.jpg\|280px\|thumb\|left\|Figure 1 [15] - Soil horizons vary in depth depending on the environment in which they are found, but in general, all soils have these basic layers.]]

	[[Soil Horizons\|Soil horizons]] are layers that lay parallel to the earth's surface, and to one another. The O horizon contains organic material and relatively undecomposed litter. ~~Following,~~ the A horizon is a dark layer, often referred to as topsoil and/or [[humus]]~~, which~~ is where most biological activity occurs in the form of plants, bacteria, archaea, and numerous macroinvertebrates. Below this is the B layer, or subsoil, where many soil nutrients and illuvium (material leached from one soil horizon and deposited in another, usually via rainwater) accumulate. Next is the C layer, consisting of notably unweathered parent material of soils. The final layer is the [[bedrock]], or the R layer, which is again, left unweathered due to its lack of exposure to many pedogenetic factors (like physical weathering from rainwater and the action of most macroinvertebrates) [2]. However, up to 35% of soil bacteria are found more than 2 meters below the surface, which means that [[microorganisms]] play a role in the formation and properties of each horizon.		[[Soil Horizons\|Soil horizons]] are layers that lay parallel to the earth's surface, and to one another. The O horizon contains organic material and relatively undecomposed litter. Beneath is the A horizon, is a dark layer that is often referred to as topsoil and/or [[humus]]. It is within this layer where the most biological activity occurs in the form of plants, bacteria, archaea, and numerous macroinvertebrates. Below this is the B layer, or subsoil, where many soil nutrients and illuvium (material leached from one soil horizon and deposited in another, usually via rainwater) accumulate. Next is the C layer, consisting of notably unweathered parent material of soils. The final layer is the [[bedrock]], or the R layer, which is again, left unweathered due to its lack of exposure to many pedogenetic factors (like physical weathering from rainwater and the action of most macroinvertebrates) [2]. However, up to 35% of soil bacteria are found more than 2 meters below the surface, which means that [[microorganisms]] play a role in the formation and properties of each horizon.

	=== Soil Texture ===		=== Soil Texture ===

Saigemat at 16:23, 27 April 2022

2022-04-27T16:23:45Z

← Older revision		Revision as of 12:23, 27 April 2022
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	[[File:Soil horizons.jpg\|280px\|thumb\|left\|Figure 1 [15] - Soil horizons vary in depth depending on the environment in which they are found, but in general, all soils have these basic layers.]]		[[File:Soil horizons.jpg\|280px\|thumb\|left\|Figure 1 [15] - Soil horizons vary in depth depending on the environment in which they are found, but in general, all soils have these basic layers.]]

	[[Soil Horizons\|Soil horizons]] are layers that lay parallel to the earth's surface, and to one another. The O horizon contains organic material and relatively undecomposed litter. Following, the A ~~layer~~ is a dark layer, often referred to as topsoil and/or [[humus]], which is where most biological activity occurs in the form of plants, bacteria, archaea, and numerous macroinvertebrates. Below this is the B layer, or subsoil, where many soil nutrients and illuvium (material leached from one soil horizon and deposited in another, usually via rainwater) accumulate. Next is the C layer, consisting of notably unweathered parent material of soils. The final layer is the [[bedrock]], or the R layer, which is again, left unweathered due to its lack of exposure to many pedogenetic factors (like physical weathering from rainwater and the action of most macroinvertebrates) [2]. However, up to 35% of soil bacteria are found more than 2 meters below the surface, which means that [[microorganisms]] play a role in the formation and properties of each horizon.		[[Soil Horizons\|Soil horizons]] are layers that lay parallel to the earth's surface, and to one another. The O horizon contains organic material and relatively undecomposed litter. Following, the A horizon is a dark layer, often referred to as topsoil and/or [[humus]], which is where most biological activity occurs in the form of plants, bacteria, archaea, and numerous macroinvertebrates. Below this is the B layer, or subsoil, where many soil nutrients and illuvium (material leached from one soil horizon and deposited in another, usually via rainwater) accumulate. Next is the C layer, consisting of notably unweathered parent material of soils. The final layer is the [[bedrock]], or the R layer, which is again, left unweathered due to its lack of exposure to many pedogenetic factors (like physical weathering from rainwater and the action of most macroinvertebrates) [2]. However, up to 35% of soil bacteria are found more than 2 meters below the surface, which means that [[microorganisms]] play a role in the formation and properties of each horizon.

	=== Soil Texture ===		=== Soil Texture ===

Saigemat at 16:22, 27 April 2022

2022-04-27T16:22:39Z

← Older revision		Revision as of 12:22, 27 April 2022
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	[[File:Soil horizons.jpg\|280px\|thumb\|left\|Figure 1 [15] - Soil horizons vary in depth depending on the environment in which they are found, but in general, all soils have these basic layers.]]		[[File:Soil horizons.jpg\|280px\|thumb\|left\|Figure 1 [15] - Soil horizons vary in depth depending on the environment in which they are found, but in general, all soils have these basic layers.]]

	[[Soil Horizons\|Soil horizons]] are layers that lay parallel to the earth's surface, ~~as well as~~ one another. The O horizon contains organic material and relatively undecomposed litter. Following, the A layer is a dark layer, often referred to as topsoil and/or [[humus]], which is where most biological activity occurs in the form of plants, bacteria, archaea, and numerous macroinvertebrates. Below this is the B layer, or subsoil, where many soil nutrients and illuvium (material leached from one soil horizon and deposited in another, usually via rainwater) accumulate. Next is the C layer, consisting of notably unweathered parent material of soils. The final layer is the [[bedrock]], or the R layer, which is again, left unweathered due to its lack of exposure to many pedogenetic factors (like physical weathering from rainwater and the action of most macroinvertebrates) [2]. However, up to 35% of soil bacteria are found more than 2 meters below the surface, which means that [[microorganisms]] play a role in the formation and properties of each horizon.		[[Soil Horizons\|Soil horizons]] are layers that lay parallel to the earth's surface, and to one another. The O horizon contains organic material and relatively undecomposed litter. Following, the A layer is a dark layer, often referred to as topsoil and/or [[humus]], which is where most biological activity occurs in the form of plants, bacteria, archaea, and numerous macroinvertebrates. Below this is the B layer, or subsoil, where many soil nutrients and illuvium (material leached from one soil horizon and deposited in another, usually via rainwater) accumulate. Next is the C layer, consisting of notably unweathered parent material of soils. The final layer is the [[bedrock]], or the R layer, which is again, left unweathered due to its lack of exposure to many pedogenetic factors (like physical weathering from rainwater and the action of most macroinvertebrates) [2]. However, up to 35% of soil bacteria are found more than 2 meters below the surface, which means that [[microorganisms]] play a role in the formation and properties of each horizon.

	=== Soil Texture ===		=== Soil Texture ===

Saigemat at 16:22, 27 April 2022

2022-04-27T16:22:20Z

← Older revision		Revision as of 12:22, 27 April 2022
Line 6:		Line 6:
	[[File:Soil horizons.jpg\|280px\|thumb\|left\|Figure 1 [15] - Soil horizons vary in depth depending on the environment in which they are found, but in general, all soils have these basic layers.]]		[[File:Soil horizons.jpg\|280px\|thumb\|left\|Figure 1 [15] - Soil horizons vary in depth depending on the environment in which they are found, but in general, all soils have these basic layers.]]

	[[Soil Horizons\|Soil horizons]] lay parallel to the earth's surface ~~and~~ one another. The O horizon contains organic material and relatively undecomposed litter. Following, the A layer is a dark layer, often referred to as topsoil and/or [[humus]], which is where most biological activity occurs in the form of plants, bacteria, archaea, and numerous macroinvertebrates. Below this is the B layer, or subsoil, where many soil nutrients and illuvium (material leached from one soil horizon and deposited in another, usually via rainwater) accumulate. Next is the C layer, consisting of notably unweathered parent material of soils. The final layer is the [[bedrock]], or the R layer, which is again, left unweathered due to its lack of exposure to many pedogenetic factors (like physical weathering from rainwater and the action of most macroinvertebrates) [2]. However, up to 35% of soil bacteria are found more than 2 meters below the surface, which means that [[microorganisms]] play a role in the formation and properties of each horizon.		[[Soil Horizons\|Soil horizons]] are layers that lay parallel to the earth's surface, as well as one another. The O horizon contains organic material and relatively undecomposed litter. Following, the A layer is a dark layer, often referred to as topsoil and/or [[humus]], which is where most biological activity occurs in the form of plants, bacteria, archaea, and numerous macroinvertebrates. Below this is the B layer, or subsoil, where many soil nutrients and illuvium (material leached from one soil horizon and deposited in another, usually via rainwater) accumulate. Next is the C layer, consisting of notably unweathered parent material of soils. The final layer is the [[bedrock]], or the R layer, which is again, left unweathered due to its lack of exposure to many pedogenetic factors (like physical weathering from rainwater and the action of most macroinvertebrates) [2]. However, up to 35% of soil bacteria are found more than 2 meters below the surface, which means that [[microorganisms]] play a role in the formation and properties of each horizon.

	=== Soil Texture ===		=== Soil Texture ===