Soils Module 1

6 core principles of regenerative agriculture

minimize soil disturbance, keep soil covered, understand the context of your farm, maintain living root year round, maximize crop diversity, integrate livestock

ideal soil

45% minerals

5% organic matter

20-30% air

20-30% water

pedology

study of soil formation, morphology, and classification as part of the landscape

edaphology

study of soils as an influence on living things

functions of soil

recycling system

modifies atmospheres

habitat for organisms

engineering medium

H2O supply and purification

medium for plant growth

medium for plant growth

support

air

H2O

nutrients

18 plant essential nutrients

C HOPKINS CaFe MgB Mn CuZn MoCl NiNa

types of rocks

igneous

sedimentary

metamorphic

magma

molten rock from which minerals formed or stored beneath earth’s surfacel

lava

magma that reaches earth’s surface through a volcanic vent and flows as a liquid.

3 steps of lithification are

crystallization

cementation

compaction

5 soil forming factors

parent material

topography

climate

time

organisms

O horizon

loose and partly decayed organic material

A horizon

mineral matter mixed with some humus

E horizon

zone of eluviation and leaching

B horizon

accumulation of clay, Fe, Al from above

horizon C

partially altered parent material

R horizon

unweathered parent material

residual

develops in place form weathering

widely distributed on all continents

colluvial

poorly sorted rock fragments detached from above and collects at the bottom of slopes

alluvial

sediments deposited by water—rivers or streams

temperature

each 10 degrees celcius increase

biochemical reaction rates double

eluvation

material exits a zone

illuviation

material moves into a zone

pedoturbation

biological/physical mixing of soil materials

salinization

accumulation of soluble salts

alkalization

accumulation of sodium (Na)

weathering

changes caused by exposure to climatic elements

decomposition

breakdown of minerals and organic minerals

humification

organic material converted to humus

mineralization

minerals released from organic materials

synthesis

formation of new mineral or organic compound

soil texture

sand>silt>clay

3 classes of soil texture

sandy, loamy, clayey

Stoke’s law

the velocity of a settling particle in a liquid is based on the diameter of the particle and the viscosity of the liquid

spheroidal

granular, surface A horizons

platy

thin horizontal peds, E horizons

block-like

angular blocky, B horizons

prism-like

columnar/prismatic subsurface horizons

soil density particle density constant

2.65 g/cm3

factors affecting Db

pore space

organic matter

texture

depth in profile

Soil tilth

Physical condition of a soil in relation to plant growth

Properties and types of soil colloids

Overall net charge is negative

Varies with formation and pH

Cation exchange capacity

Interchange between a cation in solution and a cation on the surface of any NEGATIVELY charged material

Lyotropic series

H+=Al3+>Ca2+>Mg2+>K+=NH4+>Na+

Anion exchange capacity

Interchange between an anion in solution and an anion on the surface of any positively charged material

Strength of anion adsorption

HPO4>SO4>NO3=Cl-

Adsorption

Attraction of ions/compounds to oppositely charged surface of solid particles

Absorption

Movement into another substance

Tetrahedral layer

Silica central atom

Octahedral layer

Al3+ dioctahedral

Mg2+ trioctahedral

CEC is

20-40X greater than kaolinite

3 factors that affect pH dependent charge

Functional groups of OM

Al/Fe oxides

Broken edges of clay

Diffusion ions

Outer sphere complex

Water molecule firms a bridge between colloid and adsorbed cation

Easily exchanged, inner sphere complexes

No water molecule present between soil colloid and ion

Strongly adsorbed

pH acidic vs basic

Acidic—less CEC

Alkaline—greater CEC

Person

Smallest sampling unit that displays the full range of properties characteristic of a particular soil

Polypedon

(Soil individual) group of similar persons

Soil series

A class of soils

Alfisols

Alf

Medium loose saturation (35%)

And idols

And

Volcanic soils

Aridisols

I’d

Dry soils in arid regions

Entisols

Ent

Youngest soils, little profile development

Gelisols

El

Permafrost; crytobation

Histosols

Ist

Peat or bog >20% OM

Inceptisols

Pet

2nd youngest soils developing diagnostic horizons

Mollisols

Oll

High loose saturation (36-50%) dark soils

Oxisols

Or

Oldest soils; highly weathered, low loose saturation <20%

Spodosols

POD

Al/Fe oxides and humus accumulation

Ultisols

Ult

2nd oldest soils, low base saturation <20%

Vertisols

Ert

Shrink/swell solids, deep cracks when soil dries

Paleudults

Ultisol

Alorthods

Spodosol

Eutrodox

Oxisol

Argixerolls

Mollisol

Vermaqualfs

Alfisol

Duricrryands

Andisol

Petrocambids

Aridisol

Ustifluvents

Entisol

Aquorthels

Gelisol

Humaquepts

Inceptisol

Cryofibrists

Histosol

Natraquerts

Vertisol

Aquic

Saturated low O2 gleying or mottling

Undid

High soil moisture humid regions

Ustic

In between unicorns and aridic

Aridic

Dry for 50% of growing seasons moist less than 90 days

Torrid

Same as aridic mild winter

Xeric

Mediterranean climate

Mollic

Thick, dark color high base saturation

Umbric

Thick, dark color low base saturation (acidic)

Ochric

Light colored, low organic matter

Melanic

Thick, high OM, volcanic ash soils

Histic

Very high OM, peat

Anthropic

Plaggen, human modified

Argillic

High activity silicate clays translocated from upper horizons

Nitric

Silicate clay accumulation >15% exchangeable Na

Kandic

Al/Fe oxides, low activity clays (kaolinite)

Oxic

Highly weathered Al/Fe oxides <10% minerals