Soil Chemistry

soil chemistry is affected by

mineral composition, organic matter and environmental factors

soils can be

acid, alkaline or neutral

soil pH influences

nutrient absorption and plant growth

types of soil

sandy, clay, silt, peat, chalk, loam

sandy soil

• round/angular

• 2mm to 0.05mm

• light soil

• gritty

• large particles

• large spaces

• drains quickly

• fewer nutrients

• not good for growing plants

clay soil

• 0.002mm

• heavy soil

• 25% clay

• small spaces

• drains slowly

• can be molded to shape

• swells with water

• shrinks and hardens with water evaporation

silt soil

• 0.05mm to 0.02mm

• fine, medium-sized particles

• floury powder

• erosion by glaciers

• light and moisture-retentive soil

• high fertility rate

• easily compacted

• drains and holds moisture well

• prone to being washed away

peat soil

• high in organic matter

• retains a large amount of moisture

• often imported into a garden for optimum planting soil

chalk soil

• can be either light or heavy

• highly alkaline due to lime or calcium carbonate content

• does not support ericaceous plants

loam soil

• mixture of sand, silt and clay

• fertile

• easy to work with

• provides good drainage

• can be either sandy or clay

s ix layers of Soil

• O - organic

• A - top soil

• E - eluviation layer

• B - sub soil

• C - regolith

• R - bedrock

O - organic

made up mostly of decomposed organic matter; contain more than 20% organic carbon; either thin, thick or not present at all

A - top soil

where seeds germinate and roots grow; may either be darker and contain more organic matter or lighter and contain less clay

E - eluviation layer

leached of mineral and organic content, resulting in a pale layer; present in older soils

B - sub soil

consists of mineral layers altered by pedogenesis; usually brownish or reddish due to iron oxides; accumulate minerals from A and E horizons; also known as illuviated horizon

C- regolith

consists of slightly broken-up bedrock; very little organic material; the absence of pedogenesis; formed either from deposits or erosion of residual bedrock

R - bedrock

base layer of bedrock; largely comprises continuous masses of hard rock

Properties of Soil

texture, structure, porosity, chemistry and color

refers to the size of the particles that make up the soil

soil texture

soil texture

soil is made up of different-sized particles

refers to the grouping of soil particles into porous compounds (aggregates)

soil structure

soil structure

important for plant growth, regulating air and water movement, influencing root development and affecting nutrient availability

types of aggregate arrangements

granular, blocky, prismatic, massive/platy

pores within the soil

soil porosity

soil porosity

healthy soils have high porosity between aggregates, and poor quality soul have low porosity, cracks and holes

soil color

produced by minerals present and organic matter content

soil composition

soil is composed of biotic (living) and abiotic (non-living) factors

soil consists of 50% solid and 50% water and air

46% minerals, 4% organic matter, 25% water, 25% air

the most common minerals in soil for plant growth

phosphorus, potassium, nitrogen gas

the less common minerals in soil

calcium, magnesium, sulfur

soil remediation

scientific approach with the collaboration of varying fields of sciences

why remediate soil?

reduce contaminants; clean groundwater; better vegetation; clean air

what affects choice of remediation?

nature of contamination; how it will affect wildlife; expected degree of success; soil type and cost

types of soil remediation

in-situ (onsite) and ex-situ (offsite)

soil pollution

causes contamination and degradation of soil

two types of soil pollution

specific and widespread

causes of soil pollution

industrial waste; deforestation; excessive use of chemicals; garbage

effects of soil pollution

climate change; loss of soil fertility; impact on human health