What is Soil: Definition and 79 Discussions

Soil is a mixture of organic matter, minerals, gases, liquids, and organisms that together support life. Earth's body of soil, called the pedosphere, has four important functions:

as a medium for plant growth
as a means of water storage, supply and purification
as a modifier of Earth's atmosphere
as a habitat for organismsAll of these functions, in their turn, modify the soil and its properties.
Soil is also commonly referred to as earth or dirt; some scientific definitions distinguish dirt from soil by restricting the former term specifically to displaced soil.
The pedosphere interfaces with the lithosphere, the hydrosphere, the atmosphere, and the biosphere. The term pedolith, used commonly to refer to the soil, translates to ground stone in the sense fundamental stone, from the ancient Greek πέδον ground, earth. Soil consists of a solid phase of minerals and organic matter (the soil matrix), as well as a porous phase that holds gases (the soil atmosphere) and water (the soil solution). Accordingly, soil scientists can envisage soils as a three-state system of solids, liquids, and gases.Soil is a product of several factors: the influence of climate, relief (elevation, orientation, and slope of terrain), organisms, and the soil's parent materials (original minerals) interacting over time. It continually undergoes development by way of numerous physical, chemical and biological processes, which include weathering with associated erosion. Given its complexity and strong internal connectedness, soil ecologists regard soil as an ecosystem.Most soils have a dry bulk density (density of soil taking into account voids when dry) between 1.1 and 1.6 g/cm3, while the soil particle density is much higher, in the range of 2.6 to 2.7 g/cm3. Little of the soil of planet Earth is older than the Pleistocene and none is older than the Cenozoic, although fossilized soils are preserved from as far back as the Archean.Soil science has two basic branches of study: edaphology and pedology. Edaphology studies the influence of soils on living things. Pedology focuses on the formation, description (morphology), and classification of soils in their natural environment. In engineering terms, soil is included in the broader concept of regolith, which also includes other loose material that lies above the bedrock, as can be found on the Moon and on other celestial objects as well.

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  1. E

    Cooling Water in Hard Soil: Data and Questions

    Here’s the data is can supply. Water temperature entering ~51°C. desired water exit temperature ~38-40°C Water flow ~approx. 300L/min. Pipe Inside Dia.- 51mm Pipe Material- HDPE PN16 We would bury the pipe around 1 meter deep. Deeper is not feasible as the trenches would be hand dug in an area...
  2. byarble

    Penetration of a stake as it goes deeper into the soil

    I was quite curious when I noticed that a stake gets progressively harder to drive the deeper it goes into the soil. When I tried looking up ballistics formulas they seemed to disagree and state that there should be a force that should work to penetrate all depths. Does the force increase...
  3. Gold Dredger

    I What wavelength can penetrate soil to 15 feet?

    As my name suggests I am a gold prospector. My question is what wavelength would penetrate 15 feet of soil, sand, and clay but be stopped when it struck gold? The goal is to create a device that will allow for looking into the ground in such a fashion as to be able to create a visible display...
  4. G

    I Explain how soil is not frozen after 3 weeks of below freezing weather

    It has been below freezing for 3 weeks, 12°F at night and in mid 20s during the day. Yard and garden are frozen 2" deep hard as cement everywhere except 3 row in the garden covered with 1/2" of pine needles. Soil under pine needle is not frozen I can push my finger into the soil 3" deep. How...
  5. R

    Force required to drive a fence post into soil

    Homework Statement:: what force is required to drive a 6ft(1.8 m) 4 inch (100 mm) post 2 ft into the ground? I'm wondering how different soils affect driving ability and where I could find information on soil resistive force. A 20 ton hydraulic tractor mounted cylinder is used to press the...
  6. S

    Lawn/Garden Soil that expands when it dries?

    Is there a type of soil that expands when it dries? The reason I'm curious is that such a soil would be useful for back filling voids under concrete slabs.
  7. Jardy

    Are there any automated methods for detecting soil nutrient levels?

    Good day, I would just like to ask if there are certain relationships of soil nutrients to other variables so that it can be easily detected and measured. I have searched the internet for a soil nutrient sensor but i couldn't find anything. If you have any other methods for soil nutrient...
  8. akaliuseheal

    Capacitive soil moisture sensor using TLC555

    Hello everybody, I have made soil moisture sensor and it kinda works. It is a capacative sensor not resistive sensor based upon TLC555 which has a role to create square wave. Square wave is brought to a homemade capacitor. Capacitance changes with change of moisture. Output is measured voltage...
  9. A

    Help with Copper and Zinc's Effects on a Plant Experiment

    Hi, I'm in 12th grade and for my senior project I wanted to do an experiment on the effects that copper and zinc have on mung beans. I have copper sulfate pentahyde and zinc sulfate monohydrate, which I had purchased because I have seen information on other similar experiments where these were...
  10. M

    Buying farmland -- What can I expect from the soil?

    I am considering buying a 25 acre farm in Georgia. Has been used as pasture for horses for 35+ years, no amendments, no lime, no anything added but manure droppings. Plan to have tested at Clemson - but am I crazy to think if it is as exhausted as it appears, that we can take 1-2 seasons...
  11. R

    Soil Mechanics - Shear Stress in a Soil Sample

    Homework Statement Two consolidated and drained (CO) triaxial compression tests (tests A and 8) were conducted on dense dry sand at the same void ratio. Test A had a cell pressure of 150 kPa, while in test B the cell pressure was 600 kPa (u=OkPa). These stresses were held constant throughout...
  12. A

    Can we sequester methane by pumping air through soil?

    Methanotrophs already exist in most soils. If we expose them to more methane, will they eat more? A solar powered fan blowing air down a tube that ran along under soil, with lots of small holes along its length - would that reduce the methane in the air? As a second part to the question, does...
  13. T

    Pore Water Pressure and Shear Strength of Soil: Understanding the Relationship

    Homework Statement In the notes , I can't understand that why as the pore water pressure dissipated , the shear strength of soil will decrease secondly , why the excess pore water pressure is negative when unloading occur ? Homework EquationsThe Attempt at a Solution I think it's wrong , as...
  14. T

    Synthetic fibers (rope) that absorb water and shorten

    Hello. I have an engineering idea, an invention. I want to make a watering valve for plants that opens the water when the soil moisture content is too low. I am looking for a material that (1) would not rot, and (2) absorb water and contract at a significant rate to open a valve (millimeter...
  15. S

    Can I Successfully Analyze Soil for N and K Without Commercial Test Kits?

    I would like to analyse soil samples myself for N and K. Tried some commercial test kits and the results are good enough in terms of precision. No idea what reagents are used in those kits. Is this something I can make myself knowing I have access to a minimal lab?
  16. T

    Flow in Anisotropic Soil: Horizontal and Vertical Scale Calculation

    Homework Statement In this question , it's stated that the horizontal scale is sqrt(kx / kz) X vertical scale ... i think the author's is wrong for horizontal scale and vertical scale in example 8.3... Homework EquationsThe Attempt at a Solution I think the vertcal scale should be 6.1m , as...
  17. T

    Correct Calculation of Vertical Stress in Soil

    Homework Statement In this question , i suspect the total vertical stress at the center of the clay is incorrect . Homework EquationsThe Attempt at a Solution In the figure , we can see that the water table is art 2m below the sand . So , the 2m sand thick should be dry , am i right ? Only...
  18. T

    Pore pressure at different point ( seepage in soil)

    Homework Statement I am not sure how to get Nd in this question ( circled part) I am not sure the exact location of the point where the author want to find the pore pressure . Can someone help ? This notes is confusing Homework EquationsThe Attempt at a Solution I think the Nd can be only...
  19. T

    What is the value of Nd at point a in a flownet diagram?

    Homework Statement in the picture , we can see that the number of equipotential drop , Nd = 18 . I am not sure why at point a , nd = 1.75 , how to get that ? Homework EquationsThe Attempt at a Solution In my opinion , the Nd at point a can be only whole number . It falls in the 2nd...
  20. B

    How does cotton agriculture cause soil exhaustion?

    I remember reading recently that in the Antebellum American South, part of the reason that white southerners wanted to expand slavery westward is that cotton agriculture would cause soil exhaustion. After growing cotton on a given piece of land for a few years, the soil would be degraded in...
  21. sepideh

    A Simulating a Proportional Counter with Soil Sample in SRIM

    hello every one, I want to simulate a proportional counter with soil sample in Srim. but I don't know how to put the beam into my source, I mean that how can define the position of ions in soil sample. because my beam arising from my soil sample. and my source actually is soil. if you answer my...
  22. D

    Math Foundations -- Sign conventions in this soil pressure graph

    Hey guys, so I stumbled across this, and I'm kinda confused on how do they get the sign convention of the value. I've attached the figure and also the soil pressure for better reference. Take for example at C, how do they get the minus and positive sign convention? Thanks a bunch. P/S : Please...
  23. M

    What happens to the metals thrown into the soil?

    I wonder about what will happen to the metals and alloys such as iron, lead, argent, gold, mercury, cambium, steel, nickel, bronze when thrown into the soil. Can bacteria decompose them such as organic components? They were already under the soil before men picked them out. This is a very hard...
  24. F

    Hydraulic conductivity in soil

    Homework Statement why there's no horizontal conductivity in this question ? Homework EquationsThe Attempt at a Solution IMO , there's also horizontal conducitivity in this question because of the water can also flow horizontally across layer A , B and also C . [/B]
  25. F

    Pressure in Seepage: Why Is It (H1 + z + (h/H2)(z))(y_w)?

    Homework Statement Can anyone explain why the pore pressure at C is given by( H1 + z + (h/ H2)(z) ) (y_w) ? Homework EquationsThe Attempt at a Solution Shouldnt it be ( H1 + z + ) (y_w) only ? [/B]
  26. S

    Desai Yield Surface, Parameters

    Hey guys, Desai Yield Surface: I have a hard time understanding the parameters of the model for soils. If I have three principle stresses, σ1, σ2, σ3. And R is defined as the Tri-axial strength in tension, how would I define R. Lastly can I just say that I1 = σ1+σ2+σ3 J2= 1/6 * ((σ1-σ2)2...
  27. Astronuc

    Agronomy, Soil Science, and just plain Dirt

    Agronomy and soil science are about dirt. The two used to be synonymous, but agronomy has evolved to so much more, and soil science is subtopic or subset. According to the Wikipedia article - "Agronomy (Ancient Greek ἀγρός agrós 'field' + νόμος nómos 'law') is the science and technology of...
  28. emma69

    Why do fruit trees generally prefer more acidic soil than vegetable plants?

    Hello guys, I have been wracking my little brain with this one. Why do fruit trees generally prefer a more acidic soil than vegetable plants. Veg plants like 6-7ph (except potatoes - why again !) Fruit around 5-6pH. Thanks in advance :)
  29. C

    How long does soil take to heat up

    Im trying to work out how long it would take me to heat up soil. If I had a 300mm diameter and 1200 long ss pipe filled with soil threw the centre of an 800 deg c oven, the soil would be preheated to 50 deg c how long would it take to heat up to 400 deg c. If anyone could help or know of a...
  30. emma69

    How does lime flocculate clay soil

    Hello guys, I have another question for you that I am stressing myself over, I would value your insights. Thanks in advance. When you add lime (Calcium carbonate) to clay soil it flocculates it and improves the structure, how does this happen ?
  31. emma69

    Why can't you change soil texture

    Hi, there appears to be a consensus in the literature that you can't change soil texture (not structure!). Many texts state this but they don't say why. If I have half a bucket of clay soil and mix in the correct proportion of sand, why isn't this a sandy loam ? I am having trouble with this...
  32. P

    Carnivorous plants need nitrogenous soil?

    The Venus Flytrap, like most carnivorous plants, meets its nitrogen requirements by trapping insects and digesting them. What will happen if this plant grows in nitrogenous soil? Will it even grow in such soil? If it grows will it stop trapping insects? Thank you
  33. R

    An integral relation in soil physics

    Hi every one, Here is my question: In soil physics, knowing the relation between suction head, h, and the soil water content, S, one can derive the hydraulic conductivity, K, of that soil using a formula like: (ignore the superscripts "cap") where in my problem, τ=0.5, κ=1, β=2...
  34. M

    Pipe excavation in silt clay soil and pipe safety

    Problem: Excessive settlement I was considering adding new material under the pipe to avoid settlement. But I ran into another problem which has to do which the pipe's edges. How to avoid shears there in silt clay soil? pipe depth is 4m. Thanks
  35. E

    Calculating Mass of Soil Scooped in 0.009 m3

    Homework Statement Hi, I really need help with a problem. I have a plate and need to calculate how much soil it can dig. Homework Equations [b]3. The Attempt at a Solution [/b I first calculated the volume of the scoop (a square scoop) and after that I'm stuck. Anyone have an...
  36. J

    Modeling soil temperature at a depth of 5ft

    Hello everyone, This isn't really my area of expertise, so I am looking for a bit of guidance. I wish to estimate the temperature underground at a depth of 5ft. The climate is Saskatchewan (Canada) so it is covered with snow in the winter, and fairly hot in the summer. There is no tree...
  37. M

    Evidence of water found in Martian soil

    http://www.nasa.gov/content/goddard/curiositys-sam-instrument-finds-water-and-more-in-surface-sample/#.UkTyTz8pnjK Curiosity has found evidence of water in the martian soil – with its very first scoop. "One of the most exciting results from this very first solid sample ingested by...
  38. D

    What Are the Effective and Total Deviator Stresses in Saturated Silty Clay?

    Urgent Question Soil Mechanics -- Please Help Homework Statement A saturated over-consolidated silty clay is estimated to have the effective strength parameters c'=5 kPa ∅'=25 kPa A specimen of the silty is mounted into a triaxial cell and full consolidated to 400 kPa with a cell...
  39. P

    What Affects Soil Magnetization and Susceptibility?

    Hi everyone I'd like to know what will happen to the magnetization and susceptibility of a given soil sample when it is denatured by heating.
  40. P

    Correlation between Magnetic susceptibility of soil and it's fertility

    Hi everyone I'm about to undertake my final year project and i will be researching and writing on THE EFFFCT OF HEAT ON THE MAGNETIC SUSCEPTIBILITY OF TOPSOIL and how it relates to SOIL FERTILITY.. I really need help on how to go about it and i'll also need links on contemporary...
  41. Z

    Water drainage rate through soil.

    Hi, I'm designing the attached aquaponic system and am trying to estimate the speed at which water will drain through the pipes. Basically, water enters the top of the pipe, then drains through roughly 5 feet of soil before it exits the pipe. Is there a way to estimate the speed at which the...
  42. R

    Broken Concrete as Fill versus Soil

    Hi, Supposed the ground floor of a building needs to be raised 2 feet higher with respect to street level. How good is using broken concrete as fill versus putting soil? I heard one needs to compact the broken concrete. What do they exactly do when they compact it? Would the overall cost be...
  43. B

    Material that has characteristics of soil

    Hello :) I am a student searching for a way to preserve raw food without a fridge for an assignment. Thinking about the method in which you wrap your food and bury it to keep it fresh, I wondered if there is some material that resembles the characteristics of soil. Have you came across...
  44. C

    Gravity retaining wall with back slope and cohesive soil

    Homework Statement I have a gravity retaining wall with a backslope and an inlcined prestressed anchor. The soil properties are c'=5 kPa, phi`=15 degrees, gamma=16 kN/m3. The water table is well below the bottom of the retaining wall. I have been told to assume the wall adhesion is 80% of...
  45. S

    Resistor which reacts to moisture in soil or water.

    my friend and i are doing a DP lab, we are trying to find a resister which reacts to water/ moisture in soil. a resistor that is directly proportional to the moisture in the soil thank you.
  46. D

    Soil displaced and depth of a pile

    When i hit a pile with a hammer and a certain kinetic energy is transferred to the pile. How can i calculate how deep it will go in relation to the force applied? It seems to me that the Earth must have some sort of resistance and that the force applied must overcome the earthreisitance on...
  47. A

    Relationship between soil suction and angle of repose

    I am writing a report for my civil engineering subject. and i have few questions. is there any relationship between angle of repose and total soil suction. is there any relationship between angle of repose and particle size distribution. is there any relationship between angle of repose and...
  48. M

    Soil Mechanics: Relationship between pH of seawater and sand

    Is there any relationship between the pH of seawater and any properties of the sand at the beach? If so, what/ why/ how? Context: I am writing a report for my Soil Mechanics course, for which we analysed some sand we collected at the beach, as well as some seawater. One of the key properties...
  49. B

    Need help rigging something to chill soil.

    I have some indoor plants that I didn't realize needed to be cooled in order to bloom. SInce it's too late to get cold air from outside, I'm trying to rig something to make it happen indoors (as cheaply as possible). The stem of the plant where it meets the soil is supposed to be kept around...
  50. R

    Contain radioactive fallout in soil

    I read about neutralizing radioactivity in soil by using paramagnetic clays or ashes because it may chelate the radioactive particles and bind them tightly so they cannot be absorbed by the plant. How true is that?