Environmental ScienceEnvironmental Science

Chapter 9Chapter 9

Notes #2Notes #2

Agriculture and SoilAgriculture and Soil

Arable Land –Arable Land –• Fertile land that can grow crops wellFertile land that can grow crops well• Amount decreases every yearAmount decreases every year

Population growth, erosion, poor farming Population growth, erosion, poor farming methodsmethods

• World wide 1/5World wide 1/5thth was lost in just 15 years was lost in just 15 years 1985 To 20001985 To 2000 In comparison to 10,000 years of farmingIn comparison to 10,000 years of farming Houses, roads, mines, farms left bareHouses, roads, mines, farms left bare

Agriculture and SoilAgriculture and Soil Ancient Methods of FarmingAncient Methods of Farming

• PlowingPlowing People/animals, cutting through/turning over)People/animals, cutting through/turning over)

• FertilizationFertilization manuremanure

• IrrigationIrrigation Digging ditches for water to flow throughDigging ditches for water to flow through

• Pest controlPest control Pulling weeds, covering plants, etc)Pulling weeds, covering plants, etc)

• Technology has made it easier, increases erosionTechnology has made it easier, increases erosion

Machinery

Synthetic fertilizers

Sprinklers, advanced water systems

Chemicals that kill pests

Agriculture and SoilAgriculture and Soil

Fertile SoilFertile Soil• Supports rapid growth of healthy plantsSupports rapid growth of healthy plants• Plants grow in topsoilPlants grow in topsoil

Loose surface layerLoose surface layer Fertile- consists of rock, water, air, organic matterFertile- consists of rock, water, air, organic matter Living Things Living Things

• Fungi/bacteria/microorganisms – decomposeFungi/bacteria/microorganisms – decompose• Bacteria “fix” nitrogenBacteria “fix” nitrogen• Worms/insects/break up soil, letting in air (aeration) & Worms/insects/break up soil, letting in air (aeration) &

water water

• Bottom = bedrockBottom = bedrock

Agriculture and SoilAgriculture and Soil Takes 1000’s of years Takes 1000’s of years

to form a few cm of soilto form a few cm of soil Bedrock breaks up due Bedrock breaks up due

to temp changes and to temp changes and moisture (causing moisture (causing breaking/cracking)breaking/cracking)

Mixes with organic Mixes with organic decaying matter, water decaying matter, water and airand air

Voila! Soil has formed!Voila! Soil has formed!

Agriculture and SoilAgriculture and Soil Topsoil erosionTopsoil erosion

• Wearing away of topsoil by wind and waterWearing away of topsoil by wind and water• In US 50% of topsoil has been lost in the In US 50% of topsoil has been lost in the

last 200 yearslast 200 years One of top ecological problems we face todayOne of top ecological problems we face today

• Plowing and harvesting contribute to Plowing and harvesting contribute to erosionerosion

Produces loose surface area that can Produces loose surface area that can blow/wash awayblow/wash away

Removes roots that hold soil in placeRemoves roots that hold soil in place

• Clearing of trees increases amt of water Clearing of trees increases amt of water flowing over the groundflowing over the ground

Trees absorb tons of waterTrees absorb tons of water

Agriculture and SoilAgriculture and Soil

DesertificationDesertification• Loss of topsoil that destroys fertilityLoss of topsoil that destroys fertility• Result of too many crops grown in the Result of too many crops grown in the

land (no fallow time)land (no fallow time)• Overgrazing (no fallow time)Overgrazing (no fallow time)• Especially severe in dry areas – no water Especially severe in dry areas – no water

holding soil togetherholding soil together• Results in erosion Results in erosion

Agriculture and SoilAgriculture and Soil

Soil ConservationSoil Conservation• 1. Contour plowing1. Contour plowing

Strips of vegetation in between plowed Strips of vegetation in between plowed areasareas

• 2. No Till Farming2. No Till Farming Slits to plant new crop among the remains of Slits to plant new crop among the remains of

the old cropthe old crop

• 3. Organic v. Inorganic Fertilizer3. Organic v. Inorganic Fertilizer Organic helps replenish the soilOrganic helps replenish the soil

Agriculture and SoilAgriculture and Soil

Sustainable agricultureSustainable agriculture Low in Put FarmingLow in Put Farming

• Without lots of energy or pesticides & Without lots of energy or pesticides & fertilizersfertilizers

Example:Example:• Organic FarmingOrganic Farming• No syntheticsNo synthetics

Agriculture and SoilAgriculture and Soil

SalinizationSalinization• Accumulation of salts in soilAccumulation of salts in soil• Caused by irrigationCaused by irrigation

Ground Water has more salt than rainwaterGround Water has more salt than rainwater Most irrigation comes from ground and Most irrigation comes from ground and

riversrivers When it evaporates, leaves behind salt, kills When it evaporates, leaves behind salt, kills

seedlingsseedlings Irrigation also causes groundwater levels to Irrigation also causes groundwater levels to

rise, resulting in the same effectrise, resulting in the same effect

Agriculture and SoilAgriculture and Soil

Old and New FoodsOld and New Foods Researchers are looking at ancient Researchers are looking at ancient

and new plants for 2 purposesand new plants for 2 purposes• To find foods that grow easily and have To find foods that grow easily and have

a high percent yielda high percent yield• Plants that improve soil conditions so Plants that improve soil conditions so

the area can again be used for the area can again be used for agricultural purposesagricultural purposes

Agriculture and SoilAgriculture and Soil Old and New Foods – AquacultureOld and New Foods – Aquaculture

• ““Fish Farming”Fish Farming” Many ponds, raising fish of different ages, to be Many ponds, raising fish of different ages, to be

harvestedharvested Water circulates through bring in oxygen and removing Water circulates through bring in oxygen and removing

wastewaste

• Fish RanchFish Ranch Example- salmon, raised and releasedExample- salmon, raised and released No fishing zones to reduce over harvestingNo fishing zones to reduce over harvesting

• 23% of seafood comes from aquaculture23% of seafood comes from aquaculture• DrawbacksDrawbacks

Uses local water supply/wetlands are sometimes Uses local water supply/wetlands are sometimes damageddamaged