frst 201 midterm soil

a naturally occurring, unconsolidated mineral or organic material at least 10cm thick that occurs at the earth's surface and is capable of supporting plant growth

a forest soil is any soil that has developed primarily under the influence of a forest cover

• - medium of plant growth
• - influences plant species composition and productivity
• - regulator of water supplies
• - recycler of raw material/nutrient cycling
• - soil contaminant reduction
• - carbon sequestration
• - habitat for soil organisms
• - engineering medium
• - protection of archaeological heritage
• - source of biochemicals and pharmaceuticals

• Mineral particles
• air
• water
• organic matter (humus, roots, organisms)

primary minerals: has not been altered chemically since its deposition and crystallization

secondary minerals:resulting from the weathering of a primary mineral

primary mimerals

secondary minerals

• - physical impacts:
• - chemical impacts
• - biological impacts

• - enhances structure       
• - enhances water holding capacity       
• - reduces erosion

• - improves soil's CEC       
• - accelerates decomposition of the soil minerals overtime
• - enhances carbon sequestration
• - enhances pesticides, heavy metals and other pollutants absorption

• - provides habitat for microorganisms
• - enhances soil microbial biodiversity and activity which can help in the suppression of diseases and pests

• - soup of many dissolved chemicals available for plants and soil organisms
• - composition varies with time and depth
• - its acidity or alkalinity determines soil pH which is a master variable of soils

• - higher humidity (near 100%)
• - composition changes within local pockets
• - CO₂ is much higher and O₂ is lower

• - texture (sand, clay, silt)
• - structure
• - porosity

influences site productivity through its effects on pore size distribution

• - water infiltration
• - water retention
• - soil aeration

voids between soil particles

soil texture and structure

• - sandy, soils have larger pores, but less total pore space
• - rapid water infiltration, low moisture retaining capacity, well aerated

• - clayey, soils have small pores, but more total pore space
• - slow water infiltration, high moisture holding capacity, tend to waterlog

root penetration

a measure of how fast air and water can move through a soil

• granular, single grain --> rapid
• prismatic, blocky -->moderate
• massive, platy --> slow

• - pH
• - CEC

• - levels of H⁺ and OH^- in the soil influence the solubility of several essential nutrients elements to plants
• - chemical and biological reactions in the soil

• pH 10-11: alkali mineral soils
• pH 6.7-9: arid region mineral soils
• pH 5-7.5: humid region mineral soils
• pH 2.5-3.5: peat soils

• - refers to the number of exchangeable cations that soil solids can adsorb
• - ability of the soil to hold onto nutrient and prevent them from leaching beyond the roots

soil fertility, quality and productivity

• - climate
• - organisms
• - topography/relief
• - parent material
• - time

water retention full, permeability drops

amount of water soil can hold after gravitational water has drained out

minimum amount of water in soil needed to make a plant wilt

• - cummulative
• - residual - saprolite
• - transported

glacier, water, wind, gravity

glacier moraine(till)

- as temperature increases from 0 to 20^oC,  clay content % increases exponentially and nitrogen content % decreases exponentially

- as precipitation increases from 0 to 125cm, clay content % increases

• - mor (L,F,H horizons prominent)
• - moder (L,F,H horizons prominent)
• - mull (Ah horizon prominent)

• Organic
• Mineral

• 1. accumulation of parent material
• 2. differentiation of horizons

• L - litter
• F - fermented
• H - humus

• L/F
• H
• Ae
• B

• L/F
• H
• Ae
• B

• L
• Ah
• B

near the soil surface, characterized by processes such as eluviation and/or accumulation of organic matter

• – Ah – enrichment with organic matter
• – Ae – eluvial horizon
• – Ap – mechanically disturbed horizon
• – Ahe - enriched with organic matter but eluviated
• – Aej – thin eluvial horizon, weakly developed

characterized by processes such as illuviation of organic matter, clay, Fe/Al oxides

• – Bh – enrichment with organic matter
• – Bf – enrichment with Fe/Al oxides
• – Bhf – characteristics from both h and f
• – Bt – enrichment with clay
• – Bn – presence of high % of Na ions. Distinctprismatic structure
• – Bm – slightly modified by hydrolysis, oxidation, or solution. Has different color, structure or both
• – Bca – enrichment with secondary carbonates from horizonsabove
• – Bss – Presence of slickensides (smooth clay coating caused bystress in high clay soils)
• – Bmk – Slight development and Ca-carbonates present
• – Bg – gleyed horizon. Gray color and/or mottles
• – Bx – horizon with fragipan character. Fragipan is loamy withhigh bulk density and low O.M.; when dry seems cemented

limited (or no) alteration through soil forming processes operative in A and B horizons

• – Ck – presence of Ca-carbonates
• – Cs – presence of soluble salts
• – Cg – gleyed horizon. Gray color and/or mottles

• W - water layer
• R - consolidated bedrock

dominant soil process

Based on the properties that reflect strengths of dominant processes (Humo-ferric Podzol) or a major contribution of a process in addition to the dominant one (Organic Cryosol)

differentiation on basis of kind and arrangement of horizons that indicate:

• • conformity to the central concept of the Great group (Orthic Humo-ferric Podzol)
• • intergrading toward soils of another order (Luvisolic Humo-ferric Podzol)
• • additional special features (Gleyed SombricHumo-ferric Podzol)

differentiated based on parent material characteristics

E.g. Gleyed Sombric Humo-ferric Podzol loamy clay, mixte, slightly alkaline

based on detailed features of a pedon. Usually from the same area

E.g. Penticton Orthic Brown Chernozem

• - chernozemic A
• - podzolic B
• - solonetzic B

• • Ah >10 cm thick,
• • 1-17% org. C,
• • C/N <17,
• • b.s. >80%, and
• • Ca2+is dominant cation

Bf, Bhf, Bh >=10 cm thick

• • Have both Bn and Bnt horizons
• • Ca exchangeable/Na exchangeable ≤10

• - Cryosolic order
• - organic order
• - vertisolic order
• - podzolic order
• - gleyslic order
• - solonetzic order
• - chernozemic order
• - luvisolic order
• - brunisolic order
• - regosolic order