Land Formation and Usage

Layers of the Earth Many geologists believe that as the Earth cooled the heavier, denser materials sank to the center and the lighter materials rose to the top.

Four Layers of the Earth 1: crust is made of the lightest materials - consists of numerous plates Chemical makeup of the crust: 1: crust is made of the lightest materials - consists of numerous plates Chemical makeup of the crust: Oxygen46.6% Silicon27.7 Aluminum8.1 Iron5.0 Calcium3.6 Sodium2.8 Potassium2.6 Magnesium2.1 All Others1.5 KNOW !

Four Layers of the Earth 2. mantle is much hotter and has the ability to flow (consistency of flowing asphalt) - lava 3&4. Outer and Inner Cores – made of heavy metals such as Iron and Nickel (speculated) 2. mantle is much hotter and has the ability to flow (consistency of flowing asphalt) - lava 3&4. Outer and Inner Cores – made of heavy metals such as Iron and Nickel (speculated)

Layers of the Earth

Geologic Processes Shifting of the Crust: Pg 110 and crust is broken up into large plates - location of the boundaries is the site of geologic activity such as earthquakes (when the plates shift – greater shift = larger earthquake ) Shifting of the Crust: Pg 110 and crust is broken up into large plates - location of the boundaries is the site of geologic activity such as earthquakes (when the plates shift – greater shift = larger earthquake )

Plate Boundaries 1. Divergent : move away from each other – create a ridge or trench that may allow magma from the mantle to flow upward

Plate Boundaries 2. Convergent : plates ram into one another - may push each other up and form mountains - one plate may be forced under the other in a process called subduction – plate being forced under will eventually hit the mantle and begin to melt the excess magma may rise through the crust of the overriding plate and form volcanoes 2. Convergent : plates ram into one another - may push each other up and form mountains - one plate may be forced under the other in a process called subduction – plate being forced under will eventually hit the mantle and begin to melt the excess magma may rise through the crust of the overriding plate and form volcanoes

Plate Tectonics

3. Transform Plates: plates slide past one another = earthquakes produce seismic waves – energy of the vibrations of the shifting plates moving through the land 3. Transform Plates: plates slide past one another = earthquakes produce seismic waves – energy of the vibrations of the shifting plates moving through the land

Plate Tectonics Transform Plates

Earthquakes begins far below the surface at the focus which is directly beneath the epicenter – the point at the top of the earth ’ s crust above the focus – severity is measured on the Richter scale – each point on the scale is 30 times more powerful than the point below it begins far below the surface at the focus which is directly beneath the epicenter – the point at the top of the earth ’ s crust above the focus – severity is measured on the Richter scale – each point on the scale is 30 times more powerful than the point below it

Measured on a Seismograph

Secondary Effects of Earthquakes 1.property damage 2.deaths 3.landslides – massive erosion 4.tsunamistsunamis 5.pollution from destruction of property, etc 1.property damage 2.deaths 3.landslides – massive erosion 4.tsunamistsunamis 5.pollution from destruction of property, etc

Volcano Formation 1.Subduction 2.Thin spots in crust  Hot spots in mantle Volcano Video Ring of Fire Video – 10 min Impact of Volcanoes on the Climate (8:00 – 13:00) 1.Subduction 2.Thin spots in crust  Hot spots in mantle Volcano Video Ring of Fire Video – 10 min Impact of Volcanoes on the Climate (8:00 – 13:00)

Types of Rock 1.Igneous – from the cooling of magma (lava) Ex: obsidian, granite, pumice 1.Igneous – from the cooling of magma (lava) Ex: obsidian, granite, pumice

Igneous Rock

Types of Rock 2.Sedimentary – form by the compaction of smaller bits of eroded rock or deposited material Ex: limestone, diatomecious earth 2.Sedimentary – form by the compaction of smaller bits of eroded rock or deposited material Ex: limestone, diatomecious earth

Sedimentary Rock

Types of Rock 3. Metamorphic – rock that is changed because it is in a new environment usually due to subduction – becomes exposed to heat and pressure and rearranges the way the rock is organized Ex: Limestone  Marble 3. Metamorphic – rock that is changed because it is in a new environment usually due to subduction – becomes exposed to heat and pressure and rearranges the way the rock is organized Ex: Limestone  Marble

Metamorphic Rock

Land Uses World Land Use: 33% : Rock, ice, tundra, desert, roads, and urban areas 26% : Forests 26% : Permanent Pastures 12% : Cropland 3% : Wetlands and Lakes World Land Use: 33% : Rock, ice, tundra, desert, roads, and urban areas 26% : Forests 26% : Permanent Pastures 12% : Cropland 3% : Wetlands and Lakes

Uses of Land - living - agriculture - grazing - logging - preservation - recreation - living - agriculture - grazing - logging - preservation - recreation

Managing Public and Private Lands in USA 35% is owned by the federal government Overseen by: U.S. Department of the Interior: - Bureau of Land Management - Fish and Wildlife Services - National Park Services U.S. Department of Agriculture - U.S. Forest Service 35% is owned by the federal government Overseen by: U.S. Department of the Interior: - Bureau of Land Management - Fish and Wildlife Services - National Park Services U.S. Department of Agriculture - U.S. Forest Service

Issues of Land Use Overuse, pollution, preservation of biodiversity Overgrazing  erosion, desertification Over harvesting of timber  erosion, loss of habitat for native species Mining  acid mine drainage, destruction of habitat Tourism  disruption of native habitats, traffic, pollution Overuse, pollution, preservation of biodiversity Overgrazing  erosion, desertification Over harvesting of timber  erosion, loss of habitat for native species Mining  acid mine drainage, destruction of habitat Tourism  disruption of native habitats, traffic, pollution

Land Management Techniques in US - Land Use Planning and Zoning : what types of development can go where - Taxing : changing areas can raise the taxes on that land and thus prevent or encourage development - Federal Designations : - prescribes what can and cannot be done in specific areas - Land Use Planning and Zoning : what types of development can go where - Taxing : changing areas can raise the taxes on that land and thus prevent or encourage development - Federal Designations : - prescribes what can and cannot be done in specific areas

Federal Designations 1. Wilderness areas : lands set aside to preserve their primeval character and prevents permanent improvements or human habitation - these areas may be managed to prevent overuse issues Ex: Build outhouse and camping sites to limit damage done by people visiting the areas 1. Wilderness areas : lands set aside to preserve their primeval character and prevents permanent improvements or human habitation - these areas may be managed to prevent overuse issues Ex: Build outhouse and camping sites to limit damage done by people visiting the areas

Federal Designations 2. National Parks : Yellowstone – first NP - preserve lands to teach people about the natural environment, management of natural resources and knowledge of national history Problems: OVERUSE 2. National Parks : Yellowstone – first NP - preserve lands to teach people about the natural environment, management of natural resources and knowledge of national history Problems: OVERUSE

National Parks Glacier national Park

National Parks Yellowstone

National Parks Grand Teton

National Parks Bad Lands

Federal Designations 3. Wildlife Refuges : to preserve lands and waters for the conservation of fishes, wildlife, and plants of the US - allows for hunting, fishing and observation as long as they fit with fish and wildlife management techniques 3. Wildlife Refuges : to preserve lands and waters for the conservation of fishes, wildlife, and plants of the US - allows for hunting, fishing and observation as long as they fit with fish and wildlife management techniques

Federal Designations 4. National Forests : intended for multiple uses – hunting, fishing, logging, water use, outdoor recreation – all activities are regulated to maintain the health of the area

Soil

Components of Soil 1. Mineral Particles (about 45%) from weathering of rock (parent rock) Influences on Erosion: Type of rock Size of particles Topography – steep areas erode faster Climate – freeze/thaw cycles crack rock Acid Deposition 1. Mineral Particles (about 45%) from weathering of rock (parent rock) Influences on Erosion: Type of rock Size of particles Topography – steep areas erode faster Climate – freeze/thaw cycles crack rock Acid Deposition

 determines the basic chemical nature of the soil Ex: soil eroded from limestone (C a CO 3 ) will be high in calcium and have a basic pH Soil eroded from granite will be higher in aluminum or sodium and have a neutral or acidic pH  can take 200 to 1000 years to produce 1 inch of soil  depends on lichens, plants, weather  determines the basic chemical nature of the soil Ex: soil eroded from limestone (C a CO 3 ) will be high in calcium and have a basic pH Soil eroded from granite will be higher in aluminum or sodium and have a neutral or acidic pH  can take 200 to 1000 years to produce 1 inch of soil  depends on lichens, plants, weather

 Fundamental unit is silicate (S i O 4 4- )  - negative charge is occupied by cations ( H +, N a +, K +, M g 2+, C a 2+ and F e 2+ )  Fundamental unit is silicate (S i O 4 4- )  - negative charge is occupied by cations ( H +, N a +, K +, M g 2+, C a 2+ and F e 2+ )

 determines plant communities based on minerals available EX: Aluminum rich soils = acidic Magnesium and Iron Silicate soils = C a 2+, NO 3 - and PO 4 3- deficient  determines plant communities based on minerals available EX: Aluminum rich soils = acidic Magnesium and Iron Silicate soils = C a 2+, NO 3 - and PO 4 3- deficient

 mineral content determines POROSITY of soil  amount of space between soil particles  Filled with water and Air – air is necessary for the respiration of plant roots and animals in the soil  large particles = very porous = drains well, does not hold water EX: Sandy soils  medium particles = silt  small particles = not porous = drains poorly – holds water EX: clay  mineral content determines POROSITY of soil  amount of space between soil particles  Filled with water and Air – air is necessary for the respiration of plant roots and animals in the soil  large particles = very porous = drains well, does not hold water EX: Sandy soils  medium particles = silt  small particles = not porous = drains poorly – holds water EX: clay

 Size of particles Sand > Silt > Clay – page 333  Soil texture is based on the amount of sand, silt and clay  Loamy soil = 40% sand, 40% silt, 20% clay  Size of particles Sand > Silt > Clay – page 333  Soil texture is based on the amount of sand, silt and clay  Loamy soil = 40% sand, 40% silt, 20% clay

 water moving through soil by percolation is called leachate and is a solution of nutrients and minerals  if soil is too porous then the nutrients and minerals can leach too quickly and the soil become nutrient poor  leaching of nutrients into lower soil levels is called illuviation  water moving through soil by percolation is called leachate and is a solution of nutrients and minerals  if soil is too porous then the nutrients and minerals can leach too quickly and the soil become nutrient poor  leaching of nutrients into lower soil levels is called illuviation

2) Organic Matter (about 5%)  dead and decaying materials – return nutrients to soil for plant uptake  broken down by bacteria, fungi and animals (worms, insects such as beetle larva, beetles, ants, termites)  helps retain water and nutrients  increases air space  particularly beneficial for helping soils of low porosity  broken down or partially broken down materials are called humus (hew-mus) 2) Organic Matter (about 5%)  dead and decaying materials – return nutrients to soil for plant uptake  broken down by bacteria, fungi and animals (worms, insects such as beetle larva, beetles, ants, termites)  helps retain water and nutrients  increases air space  particularly beneficial for helping soils of low porosity  broken down or partially broken down materials are called humus (hew-mus)

3) Water (about 25%) 4) Air (about 25%) 5) Other: Plants, animals, bacteria, fungi, mycorrhizae, protozoans 3) Water (about 25%) 4) Air (about 25%) 5) Other: Plants, animals, bacteria, fungi, mycorrhizae, protozoans

 Can alter the soil by:  adding organic materials  breaking down and decompose materials  aerate soil – tunnels – earthworms – their poop is called Castings  Worm Farming Worm Farming  disrupt soil integrity and increase erosion – burrows and holes (larger animals)  Page 331  Can alter the soil by:  adding organic materials  breaking down and decompose materials  aerate soil – tunnels – earthworms – their poop is called Castings  Worm Farming Worm Farming  disrupt soil integrity and increase erosion – burrows and holes (larger animals)  Page 331

 Changes in Soil:  continued weathering of parent material – adds more sediment  erosion of soil – loss of materials  deposition of organic materials  acid rain – changes pH – alters nutrient uptake by plants  Changes in Soil:  continued weathering of parent material – adds more sediment  erosion of soil – loss of materials  deposition of organic materials  acid rain – changes pH – alters nutrient uptake by plants

Soil Horizons Layers of Soil from Surface Down: - denoted by the letters O, A, B, C, and E. - Not all soils will have these horizons, with some immature soils having none. Most have at least three of these (A, B and C). Layers of Soil from Surface Down: - denoted by the letters O, A, B, C, and E. - Not all soils will have these horizons, with some immature soils having none. Most have at least three of these (A, B and C).

1) O-horizon: top horizon - may not be present - comprised of organic matter - normally found in forest soils, where dead leaves and other detritus can build up on a yearly basis. 1) O-horizon: top horizon - may not be present - comprised of organic matter - normally found in forest soils, where dead leaves and other detritus can build up on a yearly basis.

2) A horizon: where the organic material is mixed in with the inorganic material -usually darker in color - generally be fertile for plant life 2) A horizon: where the organic material is mixed in with the inorganic material -usually darker in color - generally be fertile for plant life

3) E horizon: below the A in forest communities - a result of water becoming acidic as it passes through the O and A horizons and then leaching minerals out of the soil 3) E horizon: below the A in forest communities - a result of water becoming acidic as it passes through the O and A horizons and then leaching minerals out of the soil

4) B horizon: where the minerals and clay grains accumulate - can be very thick and tightly pored, resulting in hardpan that can very effectively impede the flow of water through it. 5) C horizon: contains the parent inorganic material for the soil. 4) B horizon: where the minerals and clay grains accumulate - can be very thick and tightly pored, resulting in hardpan that can very effectively impede the flow of water through it. 5) C horizon: contains the parent inorganic material for the soil.

Types of Soil 1. Spodosols: colder climates, lots of precipitation, good drainage, evergreen forests, layer of acidic litter (Acid Duff) in O- horizon, no A horizon, low fertility

2. Mollisols: found in grassland areas - have a relatively rich, dark- colored A horizon zone as a result of the organic matter from the being added from the grass. - fertile nature of these soils makes them excellent media for growing grain crops. The Great Plains 2. Mollisols: found in grassland areas - have a relatively rich, dark- colored A horizon zone as a result of the organic matter from the being added from the grass. - fertile nature of these soils makes them excellent media for growing grain crops. The Great Plains

3. Aridisols – dry for very long periods of time - deserts, hot dry climates, layer of pebbles on surface, thin A horizon - high calcium carbonate concentration, with layers of clay, silica, salt, and gypsum in the subsurface regions 3. Aridisols – dry for very long periods of time - deserts, hot dry climates, layer of pebbles on surface, thin A horizon - high calcium carbonate concentration, with layers of clay, silica, salt, and gypsum in the subsurface regions

4) Oxisols - heavily oxidized soils found in tropical and subtropical rainforest - soils have undergone heavy amounts of weathering and are very low in fertility because water has leached most of the other minerals out of the soil -very thin layer of organic material on the surface – rapid decomposition and nutrient uptake by plants due to temperature and rainfall 4) Oxisols - heavily oxidized soils found in tropical and subtropical rainforest - soils have undergone heavy amounts of weathering and are very low in fertility because water has leached most of the other minerals out of the soil -very thin layer of organic material on the surface – rapid decomposition and nutrient uptake by plants due to temperature and rainfall

5) Alfisol – temperate deciduous forests – hot summer, cold winter - leaves and detritus litter O-horizon - A-horizon rich with humic materials – decomposition is slower due to colder seasons 5) Alfisol – temperate deciduous forests – hot summer, cold winter - leaves and detritus litter O-horizon - A-horizon rich with humic materials – decomposition is slower due to colder seasons

Soil Chemistry, Conservation Agricultural Practices

Soil Chemistry Soil particles are negatively charged  bind to positive ions  repel negative ions  high leachability of nitrates and phosphates Soil particles are negatively charged  bind to positive ions  repel negative ions  high leachability of nitrates and phosphates

Cation Exchange Capacity - plants may not be able to absorb the positive ions if they are strongly attracted to the soil particles  - in order to obtain the cations, plants release CO 2 from cellular respiration CO 2 + H 2 O  H 2 CO 3 (carbonic acid)  HCO H + - plants may not be able to absorb the positive ions if they are strongly attracted to the soil particles  - in order to obtain the cations, plants release CO 2 from cellular respiration CO 2 + H 2 O  H 2 CO 3 (carbonic acid)  HCO H + Makes soil acidic

Cation Exchange (cont.)  The resulting H+ bind to the soil particles and cause the cations to be released into the water solution and can then be absorbed by the plant.

Soil Erosion and Degradation Erosion: movement of soil components from one place to another  Natural: wind, rain, snow, ice  Most soil erosion is caused by moving water:  Sheet erosion – wide flow  Rill erosion – fast flowing little rivulets  Gully erosion – rivulets joining together cutting deeper and wider channels (gullies) Erosion: movement of soil components from one place to another  Natural: wind, rain, snow, ice  Most soil erosion is caused by moving water:  Sheet erosion – wide flow  Rill erosion – fast flowing little rivulets  Gully erosion – rivulets joining together cutting deeper and wider channels (gullies)

Wind Erosion

Erosion Gullies

Erosion in a Pasture

Increasing Rate of Erosion  lack of plants – roots hold soil in place  flooding  lack of plants – roots hold soil in place  flooding

Human Impact - removal of plants - construction - overgrazing by cows - logging - land overuse – “off roading”, poor hiking techniques - removal of plants - construction - overgrazing by cows - logging - land overuse – “off roading”, poor hiking techniques

Impact of Soil Erosion - loss of soil and nutrients for plant growth - sediment clogs ditches, boat channels, reservoirs, and lakes. - Sediment laden water is cloudy, tastes bad and it can kill aquatic life - loss of soil and nutrients for plant growth - sediment clogs ditches, boat channels, reservoirs, and lakes. - Sediment laden water is cloudy, tastes bad and it can kill aquatic life

Soil Erosion in the U.S.  About 1/3 of nation's original prime topsoil has been washed or blown into streams, lakes and oceans – mostly as the result of over cultivation, overgrazing and deforestation.  Soil on cultivated land is eroding 16 times faster than it can form. Erosion rate is even faster in heavily farmed areas (Great Plains)  About 1/3 of nation's original prime topsoil has been washed or blown into streams, lakes and oceans – mostly as the result of over cultivation, overgrazing and deforestation.  Soil on cultivated land is eroding 16 times faster than it can form. Erosion rate is even faster in heavily farmed areas (Great Plains)

Desertification  process whereby productive potential or arid or semiarid land falls by 10% or more – and results primarily from human activities.

Practices that leave topsoil vulnerable to desertification 1.overgrazing 2.deforestation without reforestation 3.surface mining without land reclamation 4.irrigation techniques 5.salinization 6.farming on land that has unsuitable terrain or soil 7.soil compaction by farm machinery and cattle hooves 1.overgrazing 2.deforestation without reforestation 3.surface mining without land reclamation 4.irrigation techniques 5.salinization 6.farming on land that has unsuitable terrain or soil 7.soil compaction by farm machinery and cattle hooves

Slowing Desertification Plant trees, grasses to anchor soil and hold water

Solutions: Soil Conservation  involves reducing soil erosion and restoring soil fertility  keep the soil covered with vegetation  involves reducing soil erosion and restoring soil fertility  keep the soil covered with vegetation

Conventional-tillage farming land is plowed and the soil broken up and smoothed to make a planting surface. land is usually plowed in the fall, left bare during the winter and early spring exposes soil to the climate which increases run-off and wind erosion land is plowed and the soil broken up and smoothed to make a planting surface. land is usually plowed in the fall, left bare during the winter and early spring exposes soil to the climate which increases run-off and wind erosion

Conventional Tilling

Conservation-tillage farming (minimum-tillage or no-till farming)  special tillers break up and loosen the subsurface soil without turning over the topsoil, previous crop residues and any cover vegetation

 special planting machines inject seeds, fertilizers and weed killers into slits made in the unplowed soil.  Main Benefit: Preserves soil cover which lowers erosion  special planting machines inject seeds, fertilizers and weed killers into slits made in the unplowed soil.  Main Benefit: Preserves soil cover which lowers erosion

Added Benefits of No-Till Farming  saves fuel  cuts costs  holds more water in the soil  Prevents compaction of soil  saves fuel  cuts costs  holds more water in the soil  Prevents compaction of soil

Conservation or No-till Farming  Video Video  Video Video

Terracing  reduces erosion on steep slopes (converted into a series of broad nearly-level terraces that run across the land contour  Retains water and reduces erosion by controlling runoff  Good choice for mountainous areas  reduces erosion on steep slopes (converted into a series of broad nearly-level terraces that run across the land contour  Retains water and reduces erosion by controlling runoff  Good choice for mountainous areas

Terracing

Contour Farming  on gently sloping land  plowing and planting crops in rows across rather than up and down the sloped contour of the land.  on gently sloping land  plowing and planting crops in rows across rather than up and down the sloped contour of the land.

Contour Farming

Strip Cropping A row crop (corn) alternates with another crop (a grass or grass-legume mixture).  The cover crop traps soil that erodes from the row crop.  They catch and reduce water runoff and help prevent the spread of pests and plant diseases. Soybeans and alfalfa help restore soil fertility. A row crop (corn) alternates with another crop (a grass or grass-legume mixture).  The cover crop traps soil that erodes from the row crop.  They catch and reduce water runoff and help prevent the spread of pests and plant diseases. Soybeans and alfalfa help restore soil fertility.

Strip Cropping

Alley Cropping (agroforestry) is a form of intercropping  several crops are planted together in strips or alleys between trees or shrubs that provide fruit or fuel wood.  The trees provide shade (helps to retain moisture).  Trimmings from the trees and shrubs provide mulch (green manure) for the crops. is a form of intercropping  several crops are planted together in strips or alleys between trees or shrubs that provide fruit or fuel wood.  The trees provide shade (helps to retain moisture).  Trimmings from the trees and shrubs provide mulch (green manure) for the crops.

Alley Cropping

Gully Reclamation  restore sloping bare land on which water runoff quickly creates gullies  plant fast growing plants, shrubs, vines and trees to stabilize soil  cover the soil with netting, fibers or hydromulch to hold soil in place until plants can be established  restore sloping bare land on which water runoff quickly creates gullies  plant fast growing plants, shrubs, vines and trees to stabilize soil  cover the soil with netting, fibers or hydromulch to hold soil in place until plants can be established

Erosion Control

Erosion Netting

Hydromulch

Windbreaks (shelterbelts)  reduce wind erosion  long rows of trees  reduce wind erosion  long rows of trees

Windbreaks

PAM – Polyacrylamide  used to sharply reduce erosion of some irrigated fields  can reduce erosion by 70-99%  increases cohesiveness of surface soil particles  used to sharply reduce erosion of some irrigated fields  can reduce erosion by 70-99%  increases cohesiveness of surface soil particles

Fertilizers  – partially restore plant nutrients lost by erosion, crop harvesting and leaching.  organic fertilizer – from plant and animal materials  commercial inorganic fertilizer -produced from various minerals  – partially restore plant nutrients lost by erosion, crop harvesting and leaching.  organic fertilizer – from plant and animal materials  commercial inorganic fertilizer -produced from various minerals

Three basic types of organic fertilizer 1. Animal Manure  Dung and urine of cattle, horses, poultry and other farm animals  improves soil texture, adds organic nitrogen, stimulates beneficial soil bacteria and fungi 1. Animal Manure  Dung and urine of cattle, horses, poultry and other farm animals  improves soil texture, adds organic nitrogen, stimulates beneficial soil bacteria and fungi

Three basic types of organic fertilizer 2. Green Manure  fresh or growing green vegetation plowed into the soil to increase organic matter and humus available to the next crop  weeds, grasses, clover, legumes, alfalfa, soybeans 2. Green Manure  fresh or growing green vegetation plowed into the soil to increase organic matter and humus available to the next crop  weeds, grasses, clover, legumes, alfalfa, soybeans

Three basic types of organic fertilizer 3. Compost  rich natural fertilizer and soil conditioner  aerates soil  improves its ability to retain water and nutrients  helps prevent erosion  prevents nutrients from being wasted in landfills 3. Compost  rich natural fertilizer and soil conditioner  aerates soil  improves its ability to retain water and nutrients  helps prevent erosion  prevents nutrients from being wasted in landfills

Natural Fertilizer

Crop Rotation Plant corn, tobacco or cotton one year.  following year plant legumes to add nitrogen to the soil (soybeans, oats, rye, barley, sorghum).  Also helps reduce crop losses to insects by presenting them with a changing target.  Video Video Plant corn, tobacco or cotton one year.  following year plant legumes to add nitrogen to the soil (soybeans, oats, rye, barley, sorghum).  Also helps reduce crop losses to insects by presenting them with a changing target.  Video Video

Inorganic Fertilizers  Advantages: Easy to transport, store, apply

Inorganic Fertilizers Disadvantages  Do not add humus to the soil (so organic content of soil will decrease) and soil will become compacted.  Decreased soil porosity leads to reduced oxygen content and prevent added fertilizer from being taken up efficiently.  Usually supply only two or three of the needed 20 or so nutrients  Cause water pollution especially on sloped land near streams.  Rainwater leaches nitrates into the groundwater. Disadvantages  Do not add humus to the soil (so organic content of soil will decrease) and soil will become compacted.  Decreased soil porosity leads to reduced oxygen content and prevent added fertilizer from being taken up efficiently.  Usually supply only two or three of the needed 20 or so nutrients  Cause water pollution especially on sloped land near streams.  Rainwater leaches nitrates into the groundwater.