b.sc. agri sem ii agricultural microbiology unit 3 soil profile

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Agricultural Microbiology Unit 3 Soil Profile B.Sc Agriculture II

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Page 1: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Agricultural Microbiology

Unit 3

Soil Profile

B.Sc Agriculture II

Page 2: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

• Bedrock Weathering and Formation of Parent Material• Bedrock is not considered soil parent material because soil layers

do not form in it. Rather, the unconsolidated debris produced fromthe weathering of bedrock is soil parent material.

• When bedrock occurs at or near the land surface, the weathering ofbedrock and the formation of parent material may occursimultaneously with the evolution of soil layers.

• Single soil horizon, the topsoil layer, overlies the R layer, or bedrock.The topsoil layer is about 12 inches (30 cm) thick and has evolvedslowly at a rate controlled by the rate of rock weathering.

• The formation of a centimeter of soil in hundreds of years isaccurate for this example of soil formation. Rates of parent materialformation from the direct weathering of bedrock are highlyvariable.

• A weakly cemented sandstone in a humid environment mightdisintegrate at the rate of a centimeter in 10 years and leave 1centimeter of soil.

Page 3: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

• Con-versely, quartzite (metamorphosedsandstone) nearby might weather so slowly thatany weathered material might be removed bywater or wind erosion.

• Soluble materials are removed during limestoneweathering, leaving a residue of insolublematerials. Estimates indicate that it takes 100,000years to form a foot of residue from theweathering of limestone in a humid region.

• Where soils are underlain at shallow depths bybedrock, loss of the soil by erosion producesserious consequences for the future managementof the land.

Page 4: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

• SOIL FORMATION

• Soil layers are approximately parallel to the landsurface and several layers may evolvesimultaneouslyover a period of time. The layers ina soil are genetically related; however, the layersdiffer from each other in their physical, chemical,and biological properties. In soil terminology, thelayers are called horizons.

• Because soils as natural bodies are characterizedby genetically developed horizons, soil formationconsists of the evolution of soil horizons.

• A vertical exposure of a soil consisting of thehorizons is a soil profile.

Page 5: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

• Soil-Forming Processes

• Horizonation (the formation of soil horizons) resultsfrom the differential gains, losses, transformations,and translocations that occur over time within variousparts of a vertical section of the parent material.

• Examples of the major kinds of changes that occur toproduce horizons are:

• (1) addition of organic matter from plant growth,mainly to the topsoil; (2) transformation representedby the weathering of rocks and minerals and thedecomposition of organic matter; (3) loss of solublecomponents by water moving downward through soilcarrying out soluble salts; and, (4) translocationrepresented by the movement of suspended mineraland organic particles from the topsoil to the subsoil.

Page 6: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

• Formation of A and C Horizons

• Many events, such as the deposition ofvolcanic ash, formation of spoil banks duringrailroad construction, melting of glaciers andformation of glacial sediments, or catastrophicflooding and formation of sediments havebeen dated quite accurately.

• By studying soils of varying age, soil scientistshave reconstructed the kinds and thesequence of changes that occurred to producesoils.

Page 7: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

• Glacial sediments produced by continental and alpineglaciation are widespread in the northern hemisphere, andthe approximate dates of the

• formation of glacial parent materials are known.• After sediments have been produced near a retreating ice

front, the temperature may become favorable for theinvasion of plants.

• Their growth results in the addition of organic matter,especially the addition of organic matter at or near the soilsurface. Animals, bacteria, and fungi feed on the organicmaterials produced by the plants, resulting in the loss ofmuch carbon as carbon dioxide.

• During digestion or decomposition of fresh organic matter,however, a residual organic fraction is produced that isresistant to further alteration and accumulates in the soil.

• The resistant organic matter is called humus and theprocess is humification.

Page 8: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

• The microorganisms and animals feeding on theorganic debris eventually die and thus contribute to theformation of humus.

• Humus has a black or dark-brown color, which greatlyaffects the color of A horizons. In areas in which thereis abundant plant growth, only a few decades arerequired for a surface layer to acquire a dark color, dueto the humification and accumulation of organicmatter, forming an A horizon.

• The A horizon was converted into a plow layer byfrequent plowing and tillage. Such A horizons are calledAp horizons, the p indicating plowing or otherdisturbance of the surface layer by cultivation,pasturing, or similar uses.

• For practical purposes, the topsoil in agricultural fieldsand gardens is synonymous with Ap horizon.

Page 9: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

• At this stage in soil evolution, it is likely that theupper part of the underlying parent material hasbeen slightly altered.

• This slightly altered upper part of the parentmaterial is the C horizon. The soil at this stage ofevolution has two horizonsthe A horizon and theunderlying C horizon.

• Such soils are AC soils; the evolution of an AC soil.

• Formation of B Horizons

• The subsoil in an AC soil consists of the C horizonand, perhaps, the upper part of the parentmaterial.

• Under favorable conditions, this subsoil layer

Page 10: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

• eventually develops a distinctive color and some otherproperties that distinguish it from the A horizon andunderlying parent material, commonly at a depth ofabout 60 to 75 centimeters.

• This altered subsoil zone becomes a B horizon anddevelops as a layer sandwiched between the A and anew deeper C horizon. At this point in soil evolution,insufficient time has elapsed for the B horizon to havebeen significantly enriched with fine-sized (colloidal)particles, which have been translocated downwardfrom the A horizon by percolating water.

• Such a weakly developed B horizon is given the symbolw (as in Bw), to indicate its weakly developedcharacter. A Bw horizon can be distinguished from Aand C horizons primarily by color, arrangement of soilparticles, and an intermediate content of organicmatter. A soil with A, B, and C horizons

Page 11: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

• The Bt Horizon Soil parent materials frequently contain calciumcarbonate (CaCO 3), or lime, and are alkaline. In the case of glacial parentmaterials, lime was incorporated into the ice when glaciers overrodelimestone rocks.

• The subsequent melting of the ice left a sediment that contains limestoneparticles. In humid regions, the lime dissolves in percolating water and isremoved from the soil, a process called leaching.

• Leaching effects are progressive from the surface downward. The surfacesoil first becomes acid, and subsequently leaching produces an acidsubsoil.

• An acid soil environment greatly stimulates mineral weathering or thedissolution of minerals with the formation of many ions. The reaction oforthoclase feldspar (KAISiO 3 ) with water and H+ is as follows:

• 2 KAISiO3 + 9H2O + 2H +• (orthoclase)• = H4AI 2 Si 2 09 + 2K+ + 4H4 Si04• (kaolinite)

• (silicic acid)

Page 12: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

• The weathering reaction illustrates threeimportant results of mineral weathering. First,clay particles (fine-sized mineral particles) areformed-in the example, kaolinite.

• In effect, soils are "clay factories. Second, ions arereleased into the soil solution, including nutrientions such as K + . Third, other compounds (silicicacid) of varying solubility are formed and aresubject to leaching and removal from the soil.

• Clay formation results mainly from chemicalweathering. Time estimates for the formation of1 percent clay inn rock parent material rangefrom 500 to 10,000 years. Some weathered rockswith small areas in which minerals are beingconverted into clay

Page 13: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

• Many soil parent materials commonly containsome clay. Some of this clay, together withclay produced by weathering during soilformation, tends to be slowly translocateddownward from the A horizon to the B horizonby percolating water.

• When a significant increase in the clay contentof a Bw horizon occurs due to claytranslocation, a Bw horizon becomes a Bthorizon

Page 14: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

• The Bhs Horizon Many sand parent materials• contain very little clay, and almost no clay forms in them via

weathering. As a consequence, clay illuviation is insignificant and Bthorizons do not evolve. Humus, however, reacts with oxides ofaluminum and/or iron to form complexes in the upper part of thesoil.

• Where much water for leaching (percolation) is present, as in humidregions, these complexes are translocated downward in percolatingwater to form illuvial accumulations in the B horizon.

• The illuvial accumulation of humus and oxides of aluminum and/oriron in the B horizon produces Bhs horizons. The h indicates thepresence of an illuvial accumulation of humus and the s indicatesthe presence of illuvial oxides of aluminum and/or iron.

• The symbol s is derived from sesquioxides (such as Fe 2O3 and A12O3). Bhs horizons are common in very sandy soils that are found inthe forested areas of the eastern United States from Maine toFlorida. The high content of sand results in soils with low fertilityand low water-retention capacity (droughtiness).

Page 15: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

• Formation of E Horizons• The downward translocation of colloids from the A horizon

may result in the concentration of sand and silt-sizedparticles (particles larger than clay size) of quartz and otherresistant minerals in the upper part of many soils.

• In soils with thin A horizons, a light-colored horizon maydevelop at

• the boundary of the A and B horizons.• This horizon, commonly grayish in color, is the E horizon.

The symbol E is derived from eluviation, meaning, "washed-out." Both the A and E horizons are eluvial in a given soil.

• The main feature of the A horizon, however, is the presenceof organic matter and a dark color, whereas that of the Ehorizon is a light-gray color and having low organic mattercontent and a concentration of silt and sand-sized particlesof quartz and other resistant minerals.

Page 16: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

• Formation of 0 Horizons

• Vegetation produced in the shallow waters of lakes andponds may accumulate as sediments of peat and muckbecause of a lack of oxygen in the water for theirdecomposition.

• These sediments are the parent material for organicsoils. Organic soils have 0 horizons; the O refers to soillayers dominated by organic material.

• In some cases, extreme wetness and acidity at thesurface of the soil produce conditions unfavorable fordecomposition of organic matter.

• The result is the formation of O horizons on the top ofmineral soil horizons. Although a very small proportionof the world's soils have O horizons, these soils arewidely scattered throughout the world.

Page 17: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Ecological pyramids

Page 18: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

An ecological pyramid is a graphical

representation designed to show…….

the number of organisms,

energy relationships, and

biomass of an ecosystem.

They are also called Eltonian pyramids after Charles Elton, who developed the concept of ecological pyramids.

Charles Elton (1927) developed the concept of ecological pyramids who noted that "…the animals at the base of a food chain are relatively abundant while those at the end are relatively few in number…"

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Page 19: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Producer organisms (usually green plants) form the base

of the pyramid,

With succeeding levels above representing the different

trophic levels (respective position of the organisms

within ecological food chains).

Succeeding levels in the pyramid represent the

dependence of the organisms at a given level on the

organisms at lower level.

Page 20: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

There are three types of pyramids:

of numbers, of biomass, and of energy.

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Fig 1

Page 21: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Pyramid of Biomass

Biomass is (is the mass of living biological organisms in a given area or ecosystem at a given time) renewable organic (living) material.

A pyramid of biomass is a representation of the amount of energy contained in biomass, at different trophic levels for a particular time.

It is measured in grams per meter2, or calories per meter2. This demonstrates the amount of matter lost between trophic levels.

Each level is dependent on its lower level for energy, hence the lower level determines how much energy will be available to the upper level. Also, energy is lost in transfer so the amount of energy is less higher up the pyramid.

Page 22: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

There are two types of biomass pyramids: upright and inverted.

An upright pyramid is one where the combined weight of producers is larger than the combined weight of consumers. An example is a forest ecosystem.

An inverted pyramid is one where the combined weight of producers is smaller than the combined weight of consumers. An example is an aquatic ecosystem.

Page 23: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

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Fig 2

Page 24: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Pyramid of Numbers The pyramid of numbers represents the number of organisms in each trophic level.

This pyramid consists of a plot of relationships between the number herbivores

(primary consumers), first level carnivore (secondary consumers), second level

carnivore (tertiary consumers) and so forth. This shape varies from ecosystem to

ecosystem because the number of organisms at each level is variable

Upright, partly upright and inverted are the three types of pyramids of numbers.

An aquatic ecosystem is an example of upright pyramid where the number of

organisms becomes fewer and fewer higher up in the pyramid.

A forest ecosystem is an example of a partially upright pyramid, as fewer

producers support more primary consumers, but there are less secondary and

tertiary consumers.

An inverted pyramid of numbers is one where the number of organisms depending

on the lower levels grows closer toward the apex. A parasitic food chain is an

example.

Page 25: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

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Fig 3

Page 26: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

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Fig 4

Page 27: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Pyramid of EnergyThe pyramid of energy represents the total amount of energy

consumed by each trophic level. An energy pyramid is always

upright as the total amount of energy available for utilization

in the layers above is less than the energy available in the lower

levels. This happens because during energy transfer from lower

to higher levels, some energy is always lost.

Page 28: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Ecosystem

Ecosystem

Natural Ecosystem

Artificial Ecosystem

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Page 29: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Functions of Natural Ecosystem

Air pollution are tapped by leaves of tree and convert into harmless compounds

Waste water gets filtrated through the natural soil and make drinkable

Page 30: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Types Of Ecosystems

Forest Ecosystem

Grassland Ecosystem

Desert Ecosystem

Aquatic Ecosystem

Estuarine Ecosystem

Page 31: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Forest Ecosystem

A forest ecosystem is a

terrestrial unit of living

organisms.

All interacting among

themselves and with the

environment (soil, climate,

water and light) in which

they live.14

Fig 5

Page 32: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Types Of Forest Ecosystems

Tropical Rain Forest( Average rain fall: <150cm/year)

Temp: 18oC

Warmed , humid, high diversity of animal, plant, insects

Tropical Deciduous Forest (Rain fall: 100-120cm/yr)

Climate is not evenly distributed

Page 33: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Temperate Deciduous

(cold climate, annual temp: 7-15oC)Summer is very hot and winter is very cold

Tall decidous tree

Boreal Forest/TIAGA/CONIFEROUS

Climate is very cold

Rainfall: 100mm to 350 mm

Temperate Rain forest

Very cold

Winter rain fall

Summer is very hot and Dry

Page 34: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Functions Forest Ecosystems

Enhance the water resources in both quality

and quantity

Hydrological cycle depend on the forest

ecosystem

Forest gives shelter to wildlife and fish

Considered as a pathway for exchange and

regulation of atmospheric gases, water and trace

elements

Page 35: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Coniferous forest of Alaska Tropical rain forest

Deciduous Forest15

Fig 6

Page 36: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Grassland Ecosystem

Grasslands are areas where the vegetation is dominated by grasses

Page 37: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Types Of Grassland

Ecosystem

Tropical and Savannas grasslands Tropical and subtropical grasslands,

savannas, and shrublands are a grassland terrestrial biome located in semi-arid to semi-humid climate regions of subtropical and tropical latitudes.

Tropical grasslands include the savanna usually associated with Africa, and savanna-type grasslands found in India, Australia, Nepal and the Americas.

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Page 38: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Temperate grasslands Temperature: warm to hot season (often with a cold to

freezing season in winter) Soil: fertile with rich nutrients and minerals Plants: grass; trees or shrubs in savanna and shrubland Animals: large, grazing mammals; birds; reptiles Rain fall: 25-60cm/yr Although large areas have now been converted to

agriculture, in the past temperate grasslands were home to herds of large grazing animals such as bison, deer or kangaroos.

North America, the steppes of Russia and the pampas of Argentina.

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Page 39: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Flooded Grass land

Flooded grasslands and savannas is a terrestrial biome.

Its component ecoregions are generally located at subtropical and tropical latitudes, which are flooded seasonally or year-round.

A common term is swamp.

CharacteristicsFlooded grasslands are characterized by:

very wet to saturated soil moisture content in nutrient rich soils.

in temperate—warm to tropical—hot climates.

They are found as grasslands, savannas, and wetlands.

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Page 40: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Tundra Biome

Tundra is the coldest of all the biomes. Tundra comes from the Spanish word tunturia, meaning treeless plain.It is noted for its frost-molded landscapes, extremely low temperatures, little precipitation, poor nutrients, and short growing seasons. The two major nutrients are nitrogen and phosphorus. Nitrogen is created by biological fixation, and phosphorus is created by precipitation. Tundra is separated into two types: arctic tundra and alpine tundra.

characteristics Extremely cold climate Low biotic diversity Simple vegetation structure Short season of growth and reproductionEnergy and nutrients in the form of deadorganic material

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Page 41: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Arctic

Arctic tundra is located in the northern hemisphere, encircling the north pole and extending south to the coniferous forests of the taiga.

The arctic is known for its cold, desert-like conditions.

The growing season ranges from 50 to 60 days.

The average winter temperature is -34° C (-30° F), but the average summer temperature is 3-12° C (37-54° F) which enables this biome to sustain life.

Rainfall may vary in different regions of the arctic. Yearly precipitation, including melting snow, is 15 to 25 cm (6 to 10 inches). Soil is formed slowly.

Alpine

Alpine tundra is located on mountains throughout the world at high altitude where trees cannot grow. The growing season is approximately 180 days

Mammals: pikas, marmots, mountain goats, sheep, elk

Birds: grouselike birds

Insects: springtails, beetles, grasshoppers, butterflies

Page 42: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Montane

High-altitude grasslands located on high mountain ranges around the world, like the Páramoof the Andes Mountains. They are part of the montane

grasslands and shrublands biome and also constitute tundra.

Desert and xericAlso called desert grasslands, this is composed of sparse grassland ecoregions located in the deserts and xeric shrublands biome

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Page 43: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Desert Ecosystem

A desert ecosystem exists where

there is little rainfall and the

climate is extreme in harshness.

It occupies about 17% of the

earth’s surface.

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Page 44: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Types Of Desert Ecosystem

Temperate Deserts: Sahara in Africa, Thar

in Rajasthan

Tropical Deserts: Mojave in south

California

Cold Deserts: Gobi desert in China

Page 45: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Components of desert Ecosystem

A biotic components: Nutrition's present in the soil and aerial environment

Biotic Components:

Producers: There are shrubs, Grasses and few trees. Some time few cacti

Consumers: Reptiles, Insects, Birds mammals and camels

Decomposers: There are very few, as due to poor vegetation the amount of dead organic matter is less.

There are few fungi and most of them are thermophlic

Page 46: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

Thar DesertSahara Desert

Mojave in south CaliforniaGobi desert in China

22Fig 7

Page 47: B.sc. agri sem ii agricultural microbiology unit 3 soil profile

• References:

• Fig 1 to 7 Soil Microbiology SELMAN A. WAKSMAN

• Soil Microbiology SELMAN A. WAKSMAN