report soil mech vl.doc

7/26/2019 report soil mech vl.doc

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FACTORS THAT AFFECT THE BEHAVIORAL PROPERTIES OF SOIL

REPORTER:

VINCENT LOUIE “POGI” A. ABIN

BSCE 4B

What is SoilMineral-Sand,Silt,ClayOrganic Matter-Decomposed Plants-DecomposedMicroorganisms-Decomposed Animal

Factors

Involved

In SoilFormatio



n

Climate

Parent Material

Ecology (plant and animal life)

SlopeTime

emperature

Temperature directly affects the activity of the soil biota bydetermining the rate of physiological activity such as enzyme activity

and indirectly by affecting physico-chemical properties such asdiffusion & solubility of nutrients, mineral weathering and evaporationrates



Soil pH

(In a similar manner to temperature, organisms have a range of pH atwhich they are active !ithin certain limits, organisms can toleratee"tremes but this normally re#uires the cell to use energy inmaintaining the correct internal cellular pH (pH $% ' few organisms(bacteria & archaea can tolerate very e"treme pH values such as pH orpH but these are e"treme conditions are not found in agricultural

soils )arger soil animals may be more sensitive to pH thanmicroorganisms

Soil mineralogy

Soil minerals are weathered by bacteria and fungi either as a directsource of energy for the soil biota (chemoautotrophs or a conse#uenceof the production of acids such as sulphuric acid (*roz et al, +%%



's well as weathering minerals, bacteria have been shown to formminerals (arraga et al, . /epending on the pH, some nutrientsparticularly ammonium may become bound up with the clay an unavailable

Soil

Micro

organi

sms

N fixation in legume crops

(Rhizoium)!ecompose organic materialsCrop residues

"rganic chemicals

!iseasesMineralize and immoilize

nutrients



)ight

In soil, light directly affects those organisms on or 0ust below thesurface and indirectly by heating the soil surface hototrophs, such asplants, algae and cyanobacteria, use the energy from sunlight tosynthesis carbohydrates In plants, some of this material (thephotosynthate finds its way into the soil biota via the roots and fromleaf fall !ith algae and cyanobacteria, the organic matter is directlyinputted into soil either from release of material from the cell or whenthe cell dies

Soil

moisture

Soilmoistureaffects thesoil biotain twoways

1iologically water is essential for life and for enzyme activity andmetabolism and, is a solvent for biological nutrients and otherchemicals hysically, soil moisture affects soil temperature (water isgood conductor of heat and soil aeration The degree at which soilpores are filled affects the movement and predation of microorganisms insoil In very dry soil, plants may not be able to e"tract sufficientwater through the roots because of the energy it ta2es to remove waterfrom the small pores This is 2nown as the permanent wilting point,

beyond which the plant cannot recover 3onversely, under wet conditions,o"ygen does not diffuse through the soil as readily so the levelsavailable to organism may become depleted leading to anaerobicconditions



Soil Po!osit" a#$

P%!&%a'ilit"•Porosity is the total



amount of pore space in the soil (30 to 60%) –Affects the storage of air and water –Affects the

rate of movement of air and water •Permeability

is the ease in which water, air, and plantroots move through the soil –ase of air, water and root movement –Affects rate of water inta!e

and drainage•Porosity and permeability areaffected by soil te"ture, structure, organicmatter andcompaction

report soil mech vl.doc

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