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Topic: Soil structure

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	SSM - Chapter Three (Part 7 of 9) \| NRCS Soils
		The term "structural unit" is used for any repetitive soil body that is commonly bounded by planes or zones of weakness that are not an apparent consequence of compositional differences.
		In soils that have structure, the shape, size, and grade (distinctness) of the units are described.
		They extend upward to the soil surface unless there is a relatively thick overlying horizon that is very weakly compacted (loose or very friable) and does not permit the propagation of cracks (mechanically bulked subzones (fig.
	soils.usda.gov /technical/manual/contents/chapter3g.html (0 words)

	Soil structure - Wikipedia, the free encyclopedia
		Soil structure is a sub-discipline of Soil Science concerned with the description of how particles in a given soil adhere - how they stick together.
		Soil structure describes the size and shape of these individual peds, and attempts to both interpret the causative factors behind the structure, and evaluate the most productive and healthy structural characteristics of soil.
		A major focus of study in the area of soil conservation, from at least the Dust Bowl era in the United States, is the effect of agricultural tillage methods on soil structure.
	en.wikipedia.org /wiki/Soil_structure (382 words)

	Soil - Wikipedia, the free encyclopedia
		Soil is unconsolidated rock particles on the surface of the earth, mixed with organic matter from plant decay.
		Soil is vital to all life on earth because it supports the growth of plants, which supply food and oxygen and absorb carbon dioxide and nitrogen.
		Soils can be divided into two general layers or strata: topsoil, the topmost layer, where most plant roots, microorganisms, and other animal life are located, and subsoil, which is deeper and often more dense and less rich in organic matter.
	en.wikipedia.org /wiki/Soil (953 words)

	AllRefer.com - soil : Components and Structure (Agriculture, General) - Encyclopedia
		The inorganic fraction of soil may include various sizes and shapes of rocks and minerals; in order of increasing size these are termed clay, silt, sand, gravel, and stone.
		Besides organic matter, soil is largely composed of elements and compounds of silicon, aluminum, iron, oxygen, and, in smaller quantities, calcium, magnesium, sodium, and potassium.
		Acidic soils occur in humid regions because alkaline minerals are leached downward: alkaline soils occur in dry regions because alkaline salts remain concentrated near the surface.
	reference.allrefer.com /encyclopedia/S/soil-components-and-structure.html (459 words)

	10(t) Introduction to Soils
		Soil pH is generally related to the concentration of free hydrogen ions in the soil matrix.
		Soils with a relatively large concentration of hydrogen ions tend to be acidic.
		Soils of the humid tropics are generally red or yellow because of the oxidation of iron or aluminum, respectively.
	www.physicalgeography.net /fundamentals/10t.html (1201 words)

	Soil Structure (Site not responding. Last check: 2007-10-26)
		The arrangement of soil particles into groups or aggregates determines the "structure." A single mass or cluster of soil consisting of many soil particles held together in a particular way imparts particular physical characteristics to the soil, such as a clod, prism, crumb or granule.
		Soil structure is often more important than the texture to the farmer.
		Soil structure can be changed to produce improved soil conditions for maximum yield and profits.
	www.agcentral.com /imcdemo/03Soil/03-06.htm (84 words)

	6.2 Soil Structure and Friability
		Soil consists of five major components: mineral matter and organic matter that will generally bind together to form aggregates, air and water that will be held in the soil pores and soil organisms.
		Soil structure describes how the basic soil materials (sand and clay) are arranged into soil aggregates and the pore spaces between them (see Figure 1).
		Structural quality of a particular soil type can be assessed by measuring soil strength, the size and stability of aggregates and by looking at pore density and root growth.
	www.bettersoils.com.au /module6/6_2.htm (639 words)

	Soil structure
		Good soil structure is critical for maintaining the long-term capacity of agricultural land to produce crops.
		Soil compaction(as indicated by bulk density), soil carbon and soil carbon saturation deficit (a measure of the decline in soil organic matter relative to a calculated reference) are key to maintaining soil structure.
		Adequate soil cover is important for protecting the soil against the direct impact of raindrops and full sunlight.
	www.asb.cgiar.org /data/dataset/IDAUBSCE.htm (363 words)

	Soil Structure Interaction
		If a lightweight flexible structure is built on a very stiff rock foundation, a valid assumption is that the input motion at the base of the structure is the same as the free-field earthquake motion.
		However, if the structure is very massive and stiff, such as a concrete gravity dam, and the foundation is relatively soft, the motion at the base of the structure may be significantly different than the free-field surface motion.
		For large structures such as bridges and arch dams the free-field motion, at all points where the structure is in contact with the foundation, is not constant.
	www.csiberkeley.com /Tech_Info/soilStructInter.htm (2803 words)

	Improving Clay Soils
		Whether your soil has more or less clay than mine, so long as you understand what you're working with and keep at it over the years, adding organic matter and treating the soil structure right, you can get the better of clay soils and enjoy a productive kitchen garden.
		Soil texture -- The textural designation of a soil is determined by its relative portions of sand, silt, and clay particles, and indicates which of the three most influence the soil's properties.
		Soil structure is defined by the manner in which soil particles are assembled as aggregates.
	www.taunton.com /finegardening/pages/g00012.asp (1059 words)

	Deterioration of soil structure - subsoils (Site not responding. Last check: 2007-10-26)
		Soil structure or pedality, refers to the arrangements of soil particles and the spaces (pores) between them.
		Soil compaction is a dynamic soil process referring to an increase in the density of a soil.
		The soils most sensitive to aggregate deterioration tend to be sandy loams, sandy clay loams and hard-setting red and yellow sodic duplex soils in the drier parts of the State.
	www.netc.net.au /enviro/fguide/detosub.html (585 words)

	Role of large-scale soil structure in organic carbon turnover: Evidence from California grassland soils
		We characterized the effect of large-scale (>20 mm) soil physical structure on the age and recalcitrance of soil organic carbon (SOC) in upper (A) and lower (B) horizons of grassland soils from California's Central Valley.
		The radiocarbon content of SOC from surfaces and interiors of large-scale soil structural units (“peds”) was measured in order to characterize the spatial distribution of soil C pools with distinct residence times.
		The radiocarbon content of CO released following sieving was used to identify the C that is readily respired upon physical disturbance of soil structure.
	www.agu.org /pubs/crossref/2006/2006JG000174.shtml (403 words)

	NO-TILL AND SOIL STRUCTURE
		A soil with good tilth or structure is one where individual soil particles are bound together in stable aggregates.
		Soil compaction reduces water infiltration and drainage, limits aeration, restricts root growth, and reduces water and nutrient uptake.
		Soil compaction increases soil strength and density, while total porosity and average pore size are reduced.
	southcenters.osu.edu /soil/compact.htm (1202 words)

	John and Bob's Improves Soil Structure
		Most soil amendments either add soluble calcium to the soil, or they create calcium within the soil by some kind of reaction with soil lime (calcium carbonate) such as soil sulfur or sulfuric acid.
		As a result, soil scientists have discovered how important the role of the active ingredient in JandB's Soil Optimizer (the soluble part of soil humus) is, in promoting better soil structure.
		John and Bob's Soil Optimizer is air dried, while most other sources of humate and leonardite are furnace dried in the cold and wet areas of North Dakota.
	www.johnandbobs.com /article3.htm (968 words)

	ARS Project: BIOGEOCHEMICAL PROCESSES INFLUENCING SOIL STRUCTURE AND ORGANIC CARBON SEQUESTRATION (404154) Annual Report
		The soil organic matter is very important because it acts as a glue to help stabilize soil structure and is a major reservoir of both plant nutrients and plant available water.
		Furthermore, soil organic matter is the largest terrestrial reservoir of organic carbon, and therefore the cycling of soil organic matter has a big influence on atmospheric levels of greenhouse gasses such as carbon dioxide and methane.
		Logsdon, NSTL, evaluated various methods for measuring changes in soil structure and demonstrated that existing methods are unable to quantify the effects of cropping system on the rate water moves through the soil, the density of the soil, the volume of large pores, or distance between large pores.
	www.ars.usda.gov /research/projects/projects.htm?ACCN_NO=404154&fy=2003 (2305 words)

	ingham.html
		Soil decomposers (bacteria, fungi and possibly certain arthropods) are responsible for nutrient retention in soil.
		Immobilization of nutrients in soil, i.e., retention of carbon, nitrogen, phosphorus, and many micronutrients in the horizons of soil from which plants obtain their nutrients, is a process performed by bacteria and fungi.
		In the case of riparian aspen and beech soils, the soils are bacterial dominated.
	www.rain.org /~sals/ingham.html (7164 words)

	Soil Pit Structure
		A lot of soil erosion happened in the 1930’s—so much soil was blowing around in the air that it became known as the Dust Bowl.
		That is because this soil has been plowed, and the structure of the soil has been destroyed.
		Soil structure is the arrangement of smaller soil particles to form larger pieces, such as these blocks.
	www.oznet.ksu.edu /fieldday/kids/soil_pit/soil_structure.htm (291 words)

	ICS's water management solutions for arid and semi-arid regions
		Among the different environmental characteristics, soil structure is often neglected, although it has a strong impact on water and nutrient access and uptake by the crop.
		Soil structure and soil texture also have an impact on water infiltration rate and thus on water management efficiency: water losses from evaporation or runoff are either reduced or increased when soil structure is modified.
		Since soil structure has a strong impact on cover functioning and water infiltration, it must be properly characterized.
	www.ics-agri.com /soil-structure.htm (653 words)

	Soil structure and its quantitative parameter (Site not responding. Last check: 2007-10-26)
		If the soil structure potential is defined as a comprehensive potential ability from the arrangement and linkage features of soil particles, then it includes the ability to maintain soil-self (stability of soil structure) in one hand and the ability to change soil-self (variability of soil structure) in the other.
		The soil structure potential is higher if the linkage is stronger in the sense of soil structure stability, and the deformation after structure destruction is larger in the sense of soil structure variability.
		This soil structure parameter can be calculated on the basis of only three compression test conducted for the soil specimens of original structural condition, its saturated condition and its remolded condition respectively.
	www.ins.itu.edu.tr /2001/abstract/1129.htm (600 words)

	Quantification of soil structure (Site not responding. Last check: 2007-10-26)
		Structure, the arrangement of particles in a soil or other porous medium, is a major influence on the hydraulic properties of the medium.
		Soil structure has mostly been investigated in qualitative terms, for example, concerning the characteristic shape and cohesiveness of soil aggregates, clods, or peds.
		A related problem is the artificial modification of soil structure, as happens when soil is disturbed for purposes of farming, waste disposal, mining, construction, or other activities.
	wwwrcamnl.wr.usgs.gov /uzf/theory.struc.html (301 words)

	SOIL PHYSICAL PROPERTIES
		soil structure type - A classification of soil structure based on the shape of the aggregates or peds in the profile.
		Assumption: The particle density of this soil is 2.65 g/cm³.
		Determination of Soil Texture in the Field: booklet from the University of Florida by R.B. Brown to assist in the determination of soil texture in the field using the touch test.
	www.cst.cmich.edu /users/Franc1m/esc334/lectures/physical.htm (1639 words)

	Building Healthy Soil
		Improving the soil structure is one of the most important aspects of soil care, and adding organic matter is the most effective way to accomplish this.
		As the structure of a soil is made more granular and crumbly by decomposing organic matter, the soil absorbs moisture that would otherwise run off, causing erosion and a loss of nutrients in the process.
		For soil that is primarily clay or sand, or that has a hard surface crust (water runs off), or is compacted, incorporate 2 to 3 inches of organic matter in the top few inches of soil and mulch liberally for several years.
	www.ext.vt.edu /pubs/envirohort/426-711/426-711.html (0 words)

	CHAPTER ONE: SOIL TEXTURE, STRUCTURE AND COLOR (Site not responding. Last check: 2007-10-26)
		When manipulating a moist soil sample, you observe noticeable grittiness yet you are able to form a ribbon of 4 inches consistently.
		In addition, good soil structure is often associated with strong cohesion of soil particles, decreasing the potential for erosion.
		Mottles present near the soil surface suggest the soil exhibits poor drainage and poor aeration.
	soils.ag.uidaho.edu /Soils206/Manual/one.htm (314 words)

	Soil Structure revisited
		What we’ve seen of soil structure so far has involved structure of the solid phase.
		This preferential interconnection of the largest pores is what I would call soil pore structure (to distinguish it from soil solid structure – cementation, aggregation, and the like).
		Unfortunately, the structure of the largest pores (the so-called “structural pores”) is the single greatest determinant of the saturated hydraulic conductivity.
	www.agron.iastate.edu /soilphysics/a577struct2.html (384 words)

	Step-by-step guide: Structure (Site not responding. Last check: 2007-10-26)
		oil structure is the shape that the soil takes based on its physical and chemical properties.
		Massive: Soil has no visible structure, is hard to break apart and appears in very large clods.
		Below are some images of the different soil structures.
	ltpwww.gsfc.nasa.gov /globe/pvg/prop1.htm (189 words)

	Corn and the Environment- Corn, Soil Structure and Erosion
		Good soil structure is important in allowing crop plants to yield well, and in helping resist erosion caused by the action of rainfall, melting snow in early spring, and wind.
		The control of soil erosion and the use of soil tests which ensure that excessive phosphate fertilizer is not applied are means of reducing water contamination by phosphates.
		While this helps to improve the structure of deeper soil layers, it is less effective in stabilizing surface soil than are the fine, shallow roots of crops such as perennial grass species and winter cereals.
	www.ontariocorn.org /envt/enverosion.htm (376 words)

	Defining the "ideal" soil structure in surface soil of a typic fluvaquent in the Netherlands -- Bouma et al. 63 (2): ... (Site not responding. Last check: 2007-10-26)
		Defining the "ideal" soil structure in surface soil of a typic fluvaquent in the Netherlands -- Bouma et al.
		Defining the "ideal" soil structure in surface soil of a typic fluvaquent in the Netherlands
		Traditional soil structure descriptions are static and qualitative.
	soil.scijournals.org /cgi/content/abstract/63/2/343 (353 words)

	Help4diy.com®>Improving Soil Structure
		Fertile soil will make gardening a pleasure, plants will flourish and be more resistant to pest and disease attack, worms and natural soil organisms will help to make the soil easier to work and improve drainage naturally.
		Dry areas of soil are usually found under large trees which draw the moisture out of the ground.
		Acid soils can be corrected by adding lime or better calcified seaweed which also adds valuable nutrients and minerals to the soil.
	www.btinternet.com /~kappacel/improvin.htm (801 words)

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