Soil Processes include additions, losses, translocations and transformations. Additions include water as precipitation and runoff, deposited sediments, oxygen and carbon dioxide from the atmosphere, nitrogen from legumes and salts in the groundwater. Losses include loss of soil by erosion, water by transpiration,nitrogen by enitrification, carbon from organic matter, water, nutrients and elements by leaching. Translocations by clay, organic matter and sesquioxides leachates, nutrients circulated by plants, soluble alts in water and mass movementby soil animals. Transformations include reduced partixle size by physical weathering, mineral decomposition, structure development, clay and organic matter changes and humus from organic matter.
Some of the soil processes have an integral role in the formation of soils. Water infiltration and addition of organic matter occur at the soil surface. Weathering and trasnformations of rock-forming minerals ocur in the soil parent material. Movement of clays, oxides and carbonates accumulate lower in the soil profile. The soil profile then eventually suffers from elaching and loss of soluble salts from the soil profile. In summary, inert geological materials are turned into soil profiles b weathering, accumulation of organic matter and live organisms.
There are two main layered properties of soils; soil horizons and soil profiles. Soil horizons are layers aproximately parallel with the earths surface and are interrelated by processe of formation and degradation. Soil profiles are a complete vertical succession of soil horizons and continu own to prent material, othe consolidated substrate material to a selected depth in unconsolidated materials. Soil differences are marked by differences in the nature and distribution of soil horizons down the soil profile. The main soil horizons include topsoil (A horizon), subsoil (B horizon) and deep subsoil (C horizon).
In many farming and erosion ontrol situations, we need to know about the nature and properties of only two soil layers, the opsoil and the subsoil. THe topsoil is the organically enriched surfacehorizon that contains the bulk of the plant roots and is the major entry point into the soil of air and water and provides the chief nutrient reservoir in the soil. The subsoil is the horizon below the topsoil and above the parent material. Subsoils are important as much of the water and some of the nutrients needed by plants are stored in the subsoil. However, subsoils are also impermeable, strongly acidic or alkaline, havepoor drainage and tend to swell and shrink.
Soil pits are a cheap and effeective means of exposing the changes in the horizons down a soil profile. A hand-auger may be used routinely to describe and collect samples from soil profiles where no exposures occur. The soil materials should be laid out systematically in 30cm increments down the borehole. He properties ofeach soil horizon should then be described usin th standard terminology.
There are many properties of each soil horizon that need to be considered. These include upper and lower depths of each horizon, horizon colour, field texture, coarse fragments, structure, consistency, field pH and boundaries between horizons.
Soil Organic Mater (SOM) is the msot important of all soil properties. The living tissues ad dead remains of plants and animals are in various stages of growth and decomposition. Living soil microbes and their residues are also present in the soil. Organic substances such as humus, which occurs from decompositional products of dead organisms are also very important in soil.
Soil Organic Carbon (SOC) is also very important. It can by converted to SOM by multiplying by a factor of 1.72. SOC forms aggregates and stabilises water-movement pathways in soils and may be up to 10-12% weight of highly organic, peaty topsoils. SOC should be at least 1.8 % in a good soil (SOM> 3%) and it is commonly less than 0.9% in poorly managed soils. SOC content and composition defines the quality and health of a soil.
Decomposition of soil organic matter occurs when soil microbes break complx components of organic residues down, releasing carbon dioxide into the air. One year after incorporation into the soil, more than 2/3 of the carbon wlbe ost from the soil as carbon dioxide. Decomposition rates are very high in the humid tropics. More organic matter put into the soil means that evn more carbon dioxide will be produced by the microbes.
Despite rapid turnover in organic matter, very long periods of time (much longer than human or hisoric time spans) are required to producea soil profile. Organic matter-enriched topsoil horizons require at least 100 to several thousands of years. Clay-rich subsoils require at least 1000 years and possibly as much as 10000 years. Deep subsoil features require at least 10000 years and may be of the order of 100000 years. Many soil management practices overlook the time required to form a soil proile and the inherent fragility of the soil. Because of the vast time period required, eroded soils cannot 're-form' within human or historical time spans.
Soil colour can be determined using the munsell colour system. The colour chips are arranged by hu, value and chroma. While munsell colour notations define exact points in colourspaces, the system itself is a continuum allowing the selection of any colour that exists. Soil colour may be used as an indicator of soil moisture status, organic matter content, oxidation state of iron and seasonal waterlogging. Dark soil colours indicate the soil is wet or has a high soil organic mater content. But note, topsoils of eucalypt forest soils are much arker than those of rainforest soils. Red soils contain hematite (an oxidised iron oxide) for good drainage and aeration, yellow soils contain geothite (a hydrated iorn oxyhydroxide) which is generally poorly drained. Grey soils have iron leached out of the soil matrix and may be deposited as ironsone gravel in the soil resulting in very poor dranage and/or seasonal water login. Mottled soils have strong iron redistribution as a result of prolonged waterlogging. Bleached A2 horixons have impeded drainage in the subsoil.
Field texture can also indicate the composition of soils. Light textured soils are sandy while heavy textured soils are clayey. Loamy soils are an equal mix of sand, silt and clay. Field texture gives an estimate of particle-size distribution, water entry and water holding capacity, ease of cultivation and susceptibility to erosion.
Soil structure relates the arrangement of primary soil particles into natural aggregates called peds. Soils structure is described in terms of shap, size and grade o the peds. THe main ped types are granular, lenticular, platy, angular, subangular blocky, polyhedral, prismatic and columnar. Soil structure describes the manner in which soil constituents are agregated together into peds and the nature of the system of pores and channels in the soil. Apedal materials lack epds and are either massive or single grain.
learn more
Makemegenius: Types of soil
Smart Learning for All: Layers of Soil
Bodhaguru: Soil Formation and Soil Layers
Questions
Some of the soil processes have an integral role in the formation of soils. Water infiltration and addition of organic matter occur at the soil surface. Weathering and trasnformations of rock-forming minerals ocur in the soil parent material. Movement of clays, oxides and carbonates accumulate lower in the soil profile. The soil profile then eventually suffers from elaching and loss of soluble salts from the soil profile. In summary, inert geological materials are turned into soil profiles b weathering, accumulation of organic matter and live organisms.
There are two main layered properties of soils; soil horizons and soil profiles. Soil horizons are layers aproximately parallel with the earths surface and are interrelated by processe of formation and degradation. Soil profiles are a complete vertical succession of soil horizons and continu own to prent material, othe consolidated substrate material to a selected depth in unconsolidated materials. Soil differences are marked by differences in the nature and distribution of soil horizons down the soil profile. The main soil horizons include topsoil (A horizon), subsoil (B horizon) and deep subsoil (C horizon).
In many farming and erosion ontrol situations, we need to know about the nature and properties of only two soil layers, the opsoil and the subsoil. THe topsoil is the organically enriched surfacehorizon that contains the bulk of the plant roots and is the major entry point into the soil of air and water and provides the chief nutrient reservoir in the soil. The subsoil is the horizon below the topsoil and above the parent material. Subsoils are important as much of the water and some of the nutrients needed by plants are stored in the subsoil. However, subsoils are also impermeable, strongly acidic or alkaline, havepoor drainage and tend to swell and shrink.
Soil pits are a cheap and effeective means of exposing the changes in the horizons down a soil profile. A hand-auger may be used routinely to describe and collect samples from soil profiles where no exposures occur. The soil materials should be laid out systematically in 30cm increments down the borehole. He properties ofeach soil horizon should then be described usin th standard terminology.
There are many properties of each soil horizon that need to be considered. These include upper and lower depths of each horizon, horizon colour, field texture, coarse fragments, structure, consistency, field pH and boundaries between horizons.
Soil Organic Mater (SOM) is the msot important of all soil properties. The living tissues ad dead remains of plants and animals are in various stages of growth and decomposition. Living soil microbes and their residues are also present in the soil. Organic substances such as humus, which occurs from decompositional products of dead organisms are also very important in soil.
Soil Organic Carbon (SOC) is also very important. It can by converted to SOM by multiplying by a factor of 1.72. SOC forms aggregates and stabilises water-movement pathways in soils and may be up to 10-12% weight of highly organic, peaty topsoils. SOC should be at least 1.8 % in a good soil (SOM> 3%) and it is commonly less than 0.9% in poorly managed soils. SOC content and composition defines the quality and health of a soil.
Decomposition of soil organic matter occurs when soil microbes break complx components of organic residues down, releasing carbon dioxide into the air. One year after incorporation into the soil, more than 2/3 of the carbon wlbe ost from the soil as carbon dioxide. Decomposition rates are very high in the humid tropics. More organic matter put into the soil means that evn more carbon dioxide will be produced by the microbes.
Despite rapid turnover in organic matter, very long periods of time (much longer than human or hisoric time spans) are required to producea soil profile. Organic matter-enriched topsoil horizons require at least 100 to several thousands of years. Clay-rich subsoils require at least 1000 years and possibly as much as 10000 years. Deep subsoil features require at least 10000 years and may be of the order of 100000 years. Many soil management practices overlook the time required to form a soil proile and the inherent fragility of the soil. Because of the vast time period required, eroded soils cannot 're-form' within human or historical time spans.
Soil colour can be determined using the munsell colour system. The colour chips are arranged by hu, value and chroma. While munsell colour notations define exact points in colourspaces, the system itself is a continuum allowing the selection of any colour that exists. Soil colour may be used as an indicator of soil moisture status, organic matter content, oxidation state of iron and seasonal waterlogging. Dark soil colours indicate the soil is wet or has a high soil organic mater content. But note, topsoils of eucalypt forest soils are much arker than those of rainforest soils. Red soils contain hematite (an oxidised iron oxide) for good drainage and aeration, yellow soils contain geothite (a hydrated iorn oxyhydroxide) which is generally poorly drained. Grey soils have iron leached out of the soil matrix and may be deposited as ironsone gravel in the soil resulting in very poor dranage and/or seasonal water login. Mottled soils have strong iron redistribution as a result of prolonged waterlogging. Bleached A2 horixons have impeded drainage in the subsoil.
Field texture can also indicate the composition of soils. Light textured soils are sandy while heavy textured soils are clayey. Loamy soils are an equal mix of sand, silt and clay. Field texture gives an estimate of particle-size distribution, water entry and water holding capacity, ease of cultivation and susceptibility to erosion.
Soil structure relates the arrangement of primary soil particles into natural aggregates called peds. Soils structure is described in terms of shap, size and grade o the peds. THe main ped types are granular, lenticular, platy, angular, subangular blocky, polyhedral, prismatic and columnar. Soil structure describes the manner in which soil constituents are agregated together into peds and the nature of the system of pores and channels in the soil. Apedal materials lack epds and are either massive or single grain.
learn more
Makemegenius: Types of soil
Smart Learning for All: Layers of Soil
Bodhaguru: Soil Formation and Soil Layers
Questions
- describe the munsell colour system.
- what are the main ped types?
- what are the main soil forming processes?
- What are the 4 soil processes?
- what chemicals do different soil colours indicate and what does that mean for the soil quality?