LEC 278 Soil Science Lec 1-5

Eh

measure of degree of oxygenation. Redox. Can use to plot chemical equilibria in different __ pH conditions. Measured in millivolts (mV, or milliV), or volts (V) and like specific conductance. ___ pH Diagrams can provide information on the potential fixation of elements in the soil.

Erosion (Soil threats)

mismanagement of forests, farms and rangeland that causes widespread degredation of soil quality through removal of topsoil, little by little. Mudslides

aerobic conditions

molecular oxygen is part of the environment, growing in the presence of molecular oxygen as ___ organisms, certain chemical or biochemical processes occur only in presence of molecular oxygen, such as __ decomposition

anions

negatively charged particles

Fixation (and mobility)

of elements in the soil depends on the Eh and pH of the soil.

10-11

pH only attained by alkalai mineral soil

C Horizon

parent rock: Layer of large unbroken rocks.

Sealing (Soil threats

paving over soils removes air, water infiltration, removes from hydrological cycle. Carbon and Nitrogen cycles also impacted. More people in cities, more artificial areas,

rhizosphere

portion of the soil in the immediate vicinity of plant roots in which the abundance and composition of the microbial population are influenced by the presence of roots. Area influenced by roots. Zone around roots. plants can modify nutrient availabilty

Parent material

primary material from which the soil is formed. could be bedrock, organic material, an old soil surface, or a deposit from water, wind, glaciers, volcanoes, or material moving down a slope

soil quality 2

reflects how well a soil performs the functions of maintaining biodiversity and productivity, partitioning water and solute flow, filtering and buffering, nutrient cycling, and providing support for plants and other structures. Soil management has a major impact

Plant nutrients such as potassium (why CAE important)

released to plants from exchangeable sites via cation exchange.

Bioturbation

reworking of soils and sediments by animals or plants. changing texture of sediments (diagenetic), bioirrigation and displacement of microorganisms and non-living particles.

loam (clay loam, silt loam)

roughly equal concentration of sand, silt, and clay, and lends to the naming of even more classifications. Best for crop growing.

pedogenesis

soil formation

Jenkinson, 1977

soil microbial biomass has been described as 'the eye of the needle through which all the organic materials must pass'

platy (types of soil structure)

soil peds are thin, flat, and plate-like. They are oriented in a horizontal direction. This structure is commonly found in compacted soil

Soil size separates

specific range of particle sizes. Smallest particles are clay, classified as having diameters of less than .002mm. Silt is next smallest between .002 and .05mm. Sand is the largest particles and are larger than .05. Large particles course, intermediate medium, small as fine. USDA

complex

structure consisting of a central atom or ion (usually metallic), bonded to a surrounding array of molecules or anions (ligands, complexing agents).

E horizon

subsurface soil horizon apparent at the base of the A horizon when eluvation is pronounced in A.

reduction

supply of oxygen is low but the biological demand is high, the ferric ion is reduced to the ferrous ion, which being more mobile , may leach downwards. Often occurs in water-logged soils while aerated soils are under oxidizing conditions.

illuviation

the accumulation in one layer of soil of materials that have been leached out of another layer

Soil Health

the change in Soil Quality over time due to human use and management or to natural events.

Precipitation

the formation of a solid in a solution or inside another solid during a chemical reaction or by diffusion in a solid When the reaction occurs in a liquid, the solid formed is called the precipitate. Solution phase will be more mobile in soil than precipitate. Salts will form and stick in pore spaces and won't move.

sorption

the removal from the soil solution of an ion or molecule by adsorption and absorption. often used when exact mechanism unknown

Cation exchange capacity

the sum total of exchangeable cations that a soil can absorb. propensity for adsorbing cations

soil biomass

the total mass of a living matter within a the soil

Soils

those portions of the Earth's crust whose properties vary with soil forming factors

Contamination (Soil threats)

toix substances from industrial processses or chemical spills degrades capacity to provide habitat for soil organisms, plants that are safe to eat, or to safely recharge ground and surface waters. Fukushima Nuclear Power Plant accident, soil in pennines lead

crumb (types of soil structure)

very porous. Each individual particle does not fit together with each surrounding ped because the shape of each individual ped is roughly spherical.

tilth

when texture is mixed well, has humus in dead material through soil-really becomes soil

anoxic conditions

without molecular oxygen, living or functioning in the absence of air or free oxygen

Polydentate

(multiple bonded) ligands can form a chelate complex. A ligand donates at least one pair of electrons to the central atom/ion.

Water Storage and Regulation (Soil Functions)

66% of this is stored in soils for use by plants • Only 10% of this reaches rivers and lakes Every drop of water in rivers. lakes, estuaries and aquifers has either traveled through soil or flowed over its surface.

Biomantle

A horizon can also be a result of a combination of soil bioturbation and surface processes that winnow fine particles from biologically mounded topsoil.

Invertebrates

A key role at the plant-soil interface Creating flow pathways in soil Plant effects on soil food webs under different managements Transfer of plant material to detrital pools, influence on decomposer pathways Clover root weevil and sustainability of red clover

general idea of soil charge

All of the nutrients in the soil need to be held there somehow, or they will just wash away when you water the garden or get a good rainstorm

Time

All other factors assert themselves over time, often hundreds or thousands of years. Soil profiles continually change from weakly developed to well developed over time.

Organisms

All plants and animals living in or on the soil (including micro-organisms and humans). The amount of water and nutrients plants need affects the way soil forms. Humans use soils affects formation. Animals affect decomposition of waste materials and how soil materials will be moved around in the soil profile. On the soil surface remains of dead plants and animals are worked by microorganisms and eventually become organic matter that is incorporated into the soil and enriches.

Macroinvertebrates

Arthropods 0-0.5 Vertebrates Earthworms (0-1.5) (less than the overall tonagge when you add them up)

Microbes

Bacteria 2-5 Actinomycetes 0-2 Fungi 2-5 Algae 0-0.5 tonnes per hectare

Soil Fertility (why CAE important)

Cation exchange is an importanct reaction in this, in buffering soil pH and altering soil physical properties. Higher CAE the more ___

atmospheric deposition, fertiliser and lime applications.

Cation inputs to soil

Mesofauna

Collembola 0-0.5 Mites Enchytraeids

7-9

Common pH for arid region

5-7

Common pH for humid region

Salinisation (Soil forming processes)

Concentration of salts within profile and at soil surface. Particularly in Arid areas, salts move to the top. Wet areas salts move down through podsolization. Alkaline salts (Na, K) Alkaline earths (Ca, Mg)

Podzol, called Spodosoils in America

Corresponding soil type to podzolisation, typical soils for humid boreal and humid temperate zones. Unattractive for farming due to sandy fraction of the soil, which means a low level of moisture and nutrient. A low pH makes it even worse. Furthermore, phosphate deficit and aluminium toxicity are other problems. Best use leave alone or grazing.

Jenkinson's fumigation

Determination of soil biomass through chloroform fumigation, incubation. Analyses carbon and nitrogen concentrations. 24 hours humid dessicator. Inoculated with .5g fresh soil and incubated 10 days. Determines soil living biomass in soil. Kill everything in soil with chloroform. Extract soil before and after can work out difference between living in dead.

Oxidation and reduction

Determine potential mobility of substances through soil. Oxygen plays key role in chemical equilibrium- very important to determine. Oxygen around=positive for mobility. Precipitates not good for mobility, reduction also not good.

Soil meso-fauna

Diverse and large population Species depend on temperature, soil water, aeration, pH, leaf litter composition Includes mites, wood louse etc Can exceed 2000 million/hectare in old grassland Active decomposers of leaf litter Hydrolysing polysaccharides (break up sugar/carbs) Depolymerising proteins and lignin

Soil macro-Fauna

Earthworms are the most common (in highly productive areas up to 10 million per hectare). Penetrate to up to 2 m depth, common at pH 4, abundant at pH 7 Casts formed by some species, partially digested plant material N&P rich: C low (CO2 loss by respiration) Channels are transmission pores (rain or irrigation water)

Soil ion exchange

Exchange (i.e. mobility) of ions in minerals with ions in solution

3

Extreme pH for Acid peat Soil

Soil pH Humus content Clay type and content of the soil

Factors Influencing CEC

Vasily Dokuchaev (Russian Geologist)

Father of soil science, first to identify factors of soil formation. Soil isn't stable, it develops and evolves undert the influence of climatic agents and vegetation that operate over time on a given geological substrate

Ferrous

Fe2+, soluble and moves, looks grey but is actually clear/has no color.

Ferric

Fe3+, oxidized and red iron in soil

Peat formation (Soil forming processes)

Formed where upper horizons remain saturated for much of the year and organic matter is not decomposed and accumulates. Found in swamps, uplands, low lying areas.

Abiotic Constituents

From weathered primary bedrock; secondary material transported from other locations, e.g. colluvium and alluvium Some soils are directly from the breakdown of the underlying rocks they develop on. Sometimes materials that have been transported from other locations by wind, water and gravity. Windblown material called loess is common in the Midwest of North America and in Central Asia and other locations.

Indiana

Has 82% of Endangered soils

Microbial biomass P and organic P released to water (Turner and Haygarth, Nature, 2001)

Higher microbial phosphorus, high extractable water.

Calcification (Soil forming processes)

In areas less arid than where Salinisation occurs. Rainfall surplus, Soluble salts leach. Less soluble Calcium compound precipitated lower in profile.

A Horizon

Layer of mineral soil with most organic matter accumulation and soil life. This layer eluviates iron, clay, aluminum, organic compounds, and other soluble constituents.

cations/humus

More humus, the more cations in can hold. More cations can hold better crops can be produced

7

Neutral pH

Descriptive terms for Soil Health

Organic Matter - high Crop appearance = green, healthy,lush erosion - Soil will not erode earthworms - numerous infiltration - fast, no ponding Compaction - minimal

O horizon

Organic matter: Litter layer of plant residues in relatively undecomposed form.

Soil bulk density

Oven dried mass/volume of soil, depends greatly on the mineral make up of soil and the degree of compaction The density of quartz is around 2.65g/cm³ but of a mineral soil is normally about half that density, between 1.0 and 1.6g/cm³

Medium for Plant Growth (Soil Functions)

Physical support, air (root respiration, water, temperature moderation, protection from toxins, nutrient elements.

Decomposing Organic Matter

Plant material is transformed from one organic compound to another, mainly by organisms in the soil Organisms create by-products, wastes, and cell tissue Compounds released as waste by one organisms can often be used as food by another. Organic acids mixed up with decomposing material

Biotic constituents

Plants, animals, fungi, bacteria Animals and micro-organisms mix soils to form burrows and pores Plant roots open channels in the soils Some plants with fibrous roots are easily decomposed, adding organic matter Dead plants and dropped leaves and stems fall to the surface of the soil and decompose Organisms feed on them and mix the organic material with the upper soil layers; these added organic compounds become part of the soil formation process....

cations

Positively charged particles

Microfauna

Protozoa 0-0.2 Nematodes 0-0.2

Semi-arid Climate huge Mechanisation (demand for wheat war) drought and winds crops couldn't hold like natural prarie grass

Reasons for dust bowl 1930s

Compaction (Soil threats)

Reduces pore sizes, store less water, less permeable, more runoff,more erosion. Average weight of tractor increases as depth of compacted layer deeper and deeper.

Elluviation

Refers to the downward movement of dissolved or suspended material within soil by leaching. Found in the E layer below the A layer and B layer in soils.

Key reactions and processes

Soil bulk density and measurement pH Ion exchange and adsorption/desorption Cation (and anion) exchange Precipitation & dissolution Complexation Oxidation/reduction

clay, silt, and sand

Soil separates types

what the soil developed from; the environmental conditions under which the soil formed; the clay present, the organic materials present; and the recent history of management. Structure declines under most forms of cultivation- returns of organic matter helps retain structure

Soil structure is dependent on

water and air movement, biological activity, root growth and seedling emergence

Soil stucture is a major influence on

the fractions of each soil separate (sand, silt, and clay) present in a soil. (Normally named by most abundant combination)

Soil textures are classified by

Loss of Organic Matter (Soil threats)

Soils thaw and warm, microorganisms warm and previously stored carbon is lost. High organic soils where forest is cleared for agriculture. When soils are cultivated but don't return organic matter-sub-Saharan Africa

soils, biodiversity and medicine

Streptomyces are found predominantly in soil and decaying vegetation Isolates used to produce over two-thirds of the clinically useful antibiotics of natural origin (e.g., neomycin, chloramphenicol) Soil organisms may harbour as yet untapped biological and medical resources Kieser et al., 2000

B Horizon

Subsoil: This layer accumulates iron, clay, aluminum and organic compounds, a process referred to as illuviation.

Anion exchange capacity

Sum total of exchangeable ions that a soil can absorb. Propensity for adsorbing anions

Soil texture

Term used to describe the grains and mineral particle sizes in a sediment. Particles are grouped according to their size into what are called soil separates, and classification is based on the fractions of soil separates present in a soil

pore distribution

The distribution of organisms in soils is influenced by this (and influences this)

Relief or Topography

The location of a soil on a landscape can affect how climatic processes impact it. At bottom of a hill will get more water than on slopes.Slopes that directly face the sun will be drier than soils on slopes that do not. Mineral accumulations, plant nutrients, type of vegetation, vegetation growth, erosion, and water drainage are dependent on this.

Soil Structure

The physical makeup of the soil. Once soil is formed and settled, forms different types of .Determined by how individual soil granules clump or bind together and aggregate, and therefore, the arrangement of soil pores between them. the arrangement of the solid parts of the soil and of the pore space located between them

reduces weed competition, creates seedbed that promotes uniform efficient crop establishment, buries residue decreases disease innoculum, promotes water infiltration, reduces extreme surface roughness for more efficient tool usage, stimulates organic matter mineralization and nutrient release, more rapid warming in spring, breaks up surface soil crusts, reduces compaction,mixes fertilizer nutrients throughout rooting depth, disrupts pest life cycle,

Tillage Advantages

Reduces soil structure & disrupts aggregates, exposes soil to raindrop impact, promotes erosion, greater extremes in soil temps, destroys macropores, destroys cracking patterns in soils with vertic characteristics, increased drying & reduced water efficiency, compaction and tillage pan formation, disrupts beneficial life cycles-earthworms, decreases store of organic nutrients in soil, fragment fungal hyphae, increased fertilizer immobilization/fixation, greater inputs of fuel and energy, requires greater investment in equipment, accelerates oxidization of labile organic matter and interferes with soil carbon sequestration

Tillage Disadvantages

Fresh Residues

Up to 15% of organic matter. Comprised mainly of litter fall. Much can be recognized as plant residue

Climate

Weathering forces such as heat, rain, ice, snow, wind, sunshine, and other environmental forces, break down parent material and affect how fast or slow soil formation processes go. Ex: Heat and thaw, breaks up rock. Moisture makes a real difference. Presence/absence of water. Wind erosion.

Bulk Density

Weight of the solid particles in a standard volume of field soil. Solids plus pore space occupied by air and water.

Gleying (Soil forming processes)

When soil is water saturated, there is movement of water within soil that changes iron oxidation state into negative form. Becomes very grey. When oxidized becomes very red. Changes in Iron Oxidation State from Fe3+ to Fe2+ due to reducing conditions, Results in mottled profile

Glacial till

a component of many soils in the northern and southern latitudes and those formed near large mountains. (process turns abiotic constituents into soil)

A high CEC value (>25)

a good indicator that a soil has a high clay and/organic matter content and can hold a lot of cations.

Humus

a)combination of resistant materials from the original plant tissue, b) compounds synthesized as part of the microorganisms' tissue, which remain as the organisms die. (Fulvic and Humic Acid)

buffering capacity

ability of soil to resist changes in pH. Determined by presence of clay, humus and other colloidal materials.

Salinization (Soil threats)

accumulation of salts in improperly irrigated soils in arid regions of the world. Salts move to surface.

alluvium

all detrital material deposited or in transit by streams, including gravel, sand, silt, clay and various forms or mixtures of these. unconsolidated.

Clay Particles

almost always have a negative (-) charge, so they attract and hold positively (+) charged nutrients and non-nutrients

oxidation

an important reaction in well-aerated soil material where oxygen supply is high and biological demand is low. Aerated soils

soil solution

aqueous liquid phase of soil and its solutes, consisting of ions dissociated from the surfaces of the soil particles and other soluble materials. Plants can't take nutrients directly out of soil particles, must be from this.

Cultural Heritage (Soil Functions)

archeological sites

Sorptive properties

arise from the electrical charges and large surface area of the clay minerals and humus Soils contain clay minerals and organic matter, which adsorb ions, molecules and gases Hence soils act as a buffer zone between atmosphere and groundwater (provide plants with a steady state of nutrients)

Soil quality

capacity of a specific kind of soil to function, within natural or managed ecosystem boundaries, to sustain plant and animal productivity, maintain or enhance water and air quality, and support human health and habitation. (Toth et al 2007) measure of the condition of soil relative to the requirements of one or more biotic species and or to any human need or purpose

exterman climate, biotic potential/organisms, relief/topography, parent material, time, dots additional factors. state factors, determine state of soil system

clorpt

mobile

complex substances are less

Podzolisation (Soil forming processes)

comprehensive name for the process of mobilization and precipitation of dissolved organic matter, together with aluminum Al and iron Fe as they are leaching down from the A and E horizons to the B horizon. Through this process the overlying eluvial horizons are getting bleached. The complexes are moving to the brown, red or black horizon, which consist of cemented sesquioxides and/or organic compounds. The process occurs usually under low pH value

Hans Jenny s=f(cl,o,r,p,t...)

defined soil as a system, swiss redefined meaning of pedogenesis factors, assuming they were independent variables. Formulated now famous equation...

colluvium

deposit of rock fragments and soil material accumulated at the base of steep slopes as a result of gravitational action

Soil Organic Matter

encompasses all organic components of a soil: Fresh residues <10% Decomposing organic matter (active) 33-55% Stable organic matter (humus) 33-55% Living organisms <5%

Support for structures (Soil Functions)

engineering medium, terra firma (firm ground) to construct road beds/building formations

Colonial America

example of no replenishment, would use the soil, exhaust it and keep expanding.

Soil Acidity and Alkalinity

expressed as soil pH, a master variable. chemical and biological reactions are dependent on pH. Can be manipulated.

s=f(cl,o,r,p)t

first equation of soil formation

Importance of N and P

give basic nutrition for production of crops, animals and fiber, foundation of human existence. Plant growth highly dependent, soil provides critical veneer through which N and P cycling occurs. Greatest pools of significance of these are in soil.

Climate Regulation and Carbon Storage (Soil Functions)

global carbon cycle, once carbon enters is not lost for a long time. soils have capacity to assimilate organic waste, turn into humus, convert mineral nutrients in wastes to forms plants and animals utilize, return to atmosphere as CO2

A low CEC value (<5)

good indication that a soil is sandy with little or no organic matter, and that it cannot hold many cations.

Catena

group of soils that occur on similar parent material but in a different sequential position from the top to the bottom of a slope

Habitat for Organisms (Soil Functions)

handful of soil contains billions of organisms in thousands of species. provides variety of niches. Soils harbor much of earth's genetic diversity.

Soil Organic Matter

has both positive and negative charges, so it can hold on to both cations and anions.

Exchange sites (why CAE important)

hold cations in soil, reducing their mobility and slowing their loss by leaching. may also adsorb metals and pollutants from waste waters, purifying the water percolating into groundwater supplies

Function of Humus

holds water and nutrients sticks together & helps establish and maintain a strong crumb structure & thus reduce soil erosion it provides some nutrients (N & P) as it is slowly decayed by microbial activity buffers effects of pesticides Creates good soil " Tilth" Coates the sand, silt, clay particles making them dark; the darker the colour, the greater the amount of soil humus present.

2.5% per year

humus decomposes at the rate of

Soil Micro-organisms

including fungi and bacteria, affect chemical exchanges between roots and soil and act as a reserve of nutrients. Some soils may contain up to one million species of microbes per gram, most of those species being unknown, making soil the most abundant ecosystem on Earth

Soil pH

influences the solubility and hence availability of many plant nutrients and pollutants, particularly metals

Granular (types of soil structure)

looks like crumbs. This soil is found where roots have permeated the soil.

blocky (types of soil structure)

looks like irregularly-shaped blocks. The form of each individual ped is caused by the peds that surround it. Each ped can be broken into smaller block peds.