ENVS2060 soil science midterm

soil

a part and product of the environment, a productive resource

how many compositions are there in soils?

4

compositions of soil

1. minerals

2. water

3. air

4. organic matter

3 things colour tell us about soil

1. organic matter content

2. redox potential

3. mineralogy of soil

texture

defined on basis of relative proportion of mineral particles of different size

measurement of sand particles

2.0 - 0.05 mm

measurement of silt particles

0.05 - 0.002mm

measurement of clay particles

<0.002mm

structure?

arrangement of individual (primary) soil particles into recognizable secondary structures (aggregates or reds)

number of structures

6

types of structures

1. single grain

2. granular

3. columnar

4. platy

5. massive

6. blocky

consistency

how sticky or plastic a wet soil is or how friable or firm a dry soil is

why might the pH in a soil be high?

may be the result of carbonate presence

mineral soil horizon names

1. surface Horizon

2. Subsurface horizon

3. unaffected horizon

description of a surface horizon

is at or near the surface; eluviated and may have an accumulation of organic matter

description of a subsurface horizon

illuviated; accumulates something from the top

description of an unaffected horizon

this is relatively unaffected by pedological processes such as salts, carbonates, gleying and parent material

criteria for an organic soil

>17% organic carbon (30% organic matter)

names of the organic soil horizons

LFH, Of, OM, Oh

LFH layer

stands for forest humus layer (has various stages of decomposition)

Of layer

is largely fabric material, little change due to decomposition

OM layer

means largely Mesic material, intermediate stage of decomposition

Oh layer

means largely Humic material, advanced stage of decomposition

number of major mineral surface horizons

4

the major mineral surface horizons

Ah: dark coloured horizon enriched in organic matter

Ap: similar to Ah only subjected to cultivation

Ae: a light coloured horizon eluviated in clay, Fe, Al, or C

4 major mineral subsurface horizons

Bf: enriched in Fe and Al

Bt: enriched in clay

Bn: enriched with Na

Bm: a horizon slightly altered by pedological processes

number of horizon suffixes used for A, B, and C horizons

7

g horizon

a horizon with evidence of reduced conditions

k horizon

a horizon containing calcium salts

s horizon

a horizon containing soluble salts (Bn designation is only sodium, s refers to salts in general)

ss horizon

means slickensides (polished surface), wedge shaped peds

v horizon

is a vertical crack

y horizon

a horizon affected by cryoturbation (mixing of materials due to freezing and thawing)

z horizon

a layer of permafrost

5 soil forming factors

1. parent material

2. climate

3. topography

4. organisms

5. time

bedrock determines chemical composition of soils, glaciation determines?

texture

parent material can be found in southern Ontario

sedimentary

parent material can be found in northern Ontario

igneous and metamorphic

morainal glacial landform

an accumulation of dirt and rocks that have fallen onto glacier surface or have been pushed along by the glacier as it moves

end moraine

ridges of unconsolidated debris deposited at the snout or end of the glacier, usually reflect the shape of glaciers terminus

recessional moraine

a series of transverse ridges running across a valley behind a terminal moraine - created during temporary halts in a glaciers retreat

ground moraine

till covered areas with irregular topography and no ridges, often forming gently rolling hills or plains - accumulated at base of ice as lodgement till, but may also be deposited as the glacier retreats

drumlin

an elongated hill in the shape of an inverted spoon or half buried egg formed by glacial acting on underlying unconsolidated till or ground moraine

esker

long, winding ridge of stratified sand and gravel - frequently several km long, somewhat like railway embankments

deltas

landforms that form from deposition of sediment carried by a river as the flow leaves its mouth and enters slower moving or staring water

lacustrine silt and clay

lacustrine deposits are sedimentary rock formations which formed on the bottom of ancient lakes

what is the order of the Canadian System of soil classification, going form least to most specific?

orders (least specific)

great groups

subgroups

families

series (most specific)

cryosolic

affected by permafrost

chernozemic soil order

black and light brown chernozems, grassland soil, diagnostic horizon is formed by high levels of organic matter additions from the roots of grasses, organisms, climate

soil order of solenetzic

grassland soil with high Na levels in the B horizon, usually associated with a clay rich B horizon and often with saline

vertisolic soil order

deep vertical cracks in soil

where can you find Regosolic soils?

in any areas that have recently been disturbed

soil that has no B horizon

Regosolic

what soil is a forest soil with a minimally developed B horizon?

Brunisolic

soil that has a Bt horizon

Luvisolic soils

soil order of Podzolic

forest soil with a Bf (enriched in Fe and Al) horizon

soil that has been impacted by water logging

Gleysolic

what are some ways we can determine the texture of soil?

-Seives for sand size particles

-Pipette method

-Hydrometer method

stokes law

determining texture by measuring the amount of time it will take for certain sized particles to fall out of suspension

a soil that has a high organic matter content will have/be:

unlikely to slake

no turbidity

no crusting

not likely to erode

factors that influence BD and PSR

-texture and structure

-organic matter content

-water content

-traffic

-tillage

clay usually has..

lower BD and higher PSR

List the following from least likely for bulk specific volume to be impacted by water content to most likely: clay, sand

Sand - least likely for water content to have impact on bulk specific volume

clay - most likely for water content to have impact on bulk specific volume

how big are macropores?

>30 micrometers

how big are mesopores?

0.2 - 30 micrometers

how big are micropores?

<0.2 micrometers

problem for plant growth with too many micropores

pores may be too small that the plants cannot physical extract the water

when soil is compacted, there is..

an increase in BD due to the loss of large pores and aggregates are reoriented and over time with more and more compaction the large pores continue to be lost

how can we straighten out the leaning tower of Pisa?

drill large holes on side of tower to allow micropores to be formed

implications of conventional tillage:

change in BD and PSR over a matter of several years. may get better pore inter connectivity and allows for good drainage, BD tends to be a bit higher

implications for conventional tillage:

there are changes in profile in tillage zone and below tillage zone

For high BD, how does it influence the structure on plant growth?

leads to shorter, thicker roots caused by high soil resistance to penetration. Short roots can only extract water from storage in shallow amount of soil

For low BD, how does it influence the structure on plant growth?

leads to longer, narrower roots so plants will be able to extract water from a larger depth of soil

does management have an impact on soil structure or texture?

impact is primarily on soil structure, has minimal direct effects on texture

practices that improve or sustain soil structure

-reduce tillage

-maintain increased crop residue on soil surface

-increase OM content by rotating crops that include cereals, forages

- increase OM by the addition of manure, organic wastes

-reduce incidents of serious compaction

min amount of clay a soil must contain to be considered clay soil

40%

soil that is likely to be the most resistant to compaction

a delta deposit

a delta deposit is most suitable for?

a sports field

the element most often involved in classifying soils based on oxidation/reduction reactions

Iron

category of soil taxonomy provides the greatest specificity of soil properties

series

soil structure is typically found in wet structured A horizons

granular

soil order that is most likely to have a columnar structure

vertisol

soil that has reduced iron in it

Gleysol

this soil is most likely to be found on the Canadian shield

Podzol

soil that has a high salt concentration

solonetz

soil that is poorly drained

gleysol

this soil is likely to have been formed with coniferous trees on it

Podzol

soil texture is most likely to have the greatest shrink-swell potential

silty clay

diagnostic horizon of a Luvisolic soil

Bt horizon

the change in great groups is related to...

a change in climate and vegetation

why do we find igneous and metamorphic rocks in SO when bedrock of the area is sedimentary rock?

centre of ice accumulation impacting southern Ontario is mainly in mid northern Quebec. there is igneous & metamorphic rock in this area that the glaciers could pick up and some of it was carried far enough to be deposited in SO where the typical bedrock is sedimentary

True or false: BD and PSR are good predictors for plant growth

false

reduced bulk density and greater PSR indicates..

more pore space that would enable better water drainage and aeration as well as improved root growth for plants

why does the Ck horizon have a higher pH than the soil horizons above it?

Ck horizon has not been impacted by soil forming. Above the Ck horizon, it is likely that much if not all of the carbonate has weathered out. The carbonate in the ck horizon will neutralize hydrogen = maintain high pH

has negative charge and acts as a stabilizer

clay

German word for clay

Ton

chroma

describes strength or purity of colour

value

describes the degree of darkness of a colour

loam

a mixture of sand, silt, and clay particles

single grain

individual sand grain in Air C horizon not held together by OM or clay. It has a rapid infiltration rate