Soil, Agriculture, and HungerSoil, Agriculture, and Hunger
Things we’ll talk aboutThings we’ll talk about
Soil formation, characteristicsSoil formation, characteristics
Soil erosionSoil erosion
Hunger and malnutritionHunger and malnutrition
Agricultural practicesAgricultural practices
Feeding the world’s hungryFeeding the world’s hungry
Soils: FormationSoils: Formation
Soil horizonsSoil horizons Soil profile Soil profile Humus Humus
O horizonLeaf litter
A horizonTopsoil
B horizonSubsoil
C horizonParent
material
Mature soil
Young soil
Immature soil
E horizonLeaching zone
R horizonbedrock
Weak humus-mineral mixture
Mosaicof closelypackedpebbles,boulders
Dry, brown toreddish-brown, with variable accumulationsof clay, calciumcarbonate, andsoluble salts
Desert Soil(hot, dry climate)
Grassland Soil(semiarid climate)
Alkaline,dark,and richin humus
Clay,calciumcompounds
mollisol
Soil Types
Acidiclight-coloredhumus
Iron andaluminumcompoundsmixed withclay
Forest litterleaf mold
Humus-mineralmixture
Light, grayish-brown, silt loam
Dark brownFirm clay
Tropical Rain Forest Soil(humid, tropical climate)
Deciduous Forest Soil(humid, mild climate)
oxisol alfisol
Laterite (a clay) - ironstone
Soil Components-What is dirt?Soil Components-What is dirt?
Inorganic mineralsInorganic minerals
Organic matterOrganic matter
Water and airWater and air
Living organismsLiving organisms
Inorganic mineralsInorganic minerals
45% of volume45% of volume
Macronutrients-nitrogen, phosphorus, potassium (NPK)-calcium, magnesium, sulfur
Macronutrients-nitrogen, phosphorus, potassium (NPK)-calcium, magnesium, sulfur
Micronutrients (trace elements)-iron, copper, zinc
Micronutrients (trace elements)-iron, copper, zinc
Limiting factorsLimiting factors
Organic MatterOrganic Matter
1-7% of volume1-7% of volume
Humus - helps retain water- helps retain water-soluble nutrients
- potassium, magnesium, ammonia- serves as food for soil organisms- provides future soil nutrients
Humus - helps retain water- helps retain water-soluble nutrients
- potassium, magnesium, ammonia- serves as food for soil organisms- provides future soil nutrients
Water and AirWater and Air
~ 50% of volume~ 50% of volume
Fills pore spacesFills pore spaces
Different soils have different pore size- sand - large- silt - medium- clay - small
Different soils have different pore size- sand - large- silt - medium- clay - small
Water for photosynthesis, air forrespiration
Water for photosynthesis, air forrespiration
Water Water
High permeability Low permeability
Living OrganismsLiving Organisms
~0.1% of volume~0.1% of volume
Bacteria, fungi, molds, nematodes,earthworms, insects, mammals
Bacteria, fungi, molds, nematodes,earthworms, insects, mammals
Actions contribute to soil fertility, porosity Actions contribute to soil fertility, porosity
Burrowing, feces, slime, secretions, death Burrowing, feces, slime, secretions, death
Soil: Determining FactorsSoil: Determining Factors
1) Parent material2) Climate3) Abrasion4) Organisms5) Topography6) Time
1) Parent material2) Climate3) Abrasion4) Organisms5) Topography6) Time
Parent MaterialParent Material
Rocks>>weathering>>inorganic minerals Rocks>>weathering>>inorganic minerals
Residual soils - develop on bare rockduring primary succession
Residual soils - develop on bare rockduring primary succession
Transported soils - deposited in areasby actions of wind, water, glaciers,humans
Transported soils - deposited in areasby actions of wind, water, glaciers,humans
Floodplain soils (1/3 of croplands)Floodplain soils (1/3 of croplands)
ClimateClimate
Weathering of parent materialWeathering of parent material
Heating, cooling, ice, rain (acidic)Heating, cooling, ice, rain (acidic)
AbrasionAbrasion
Physical breakdownPhysical breakdown
Rub rocks togetherRub rocks together
Wind, water, glaciersWind, water, glaciers
OrganismsOrganisms
Plant roots enlarge cracksPlant roots enlarge cracks
Burrowing helps aerateBurrowing helps aerate
Feces, death build up organic matterFeces, death build up organic matter
TopographyTopography
Steep areas subject to moreweathering, but reducedaccumulation
Steep areas subject to moreweathering, but reducedaccumulation
Flat areas subject to less weathering,but higher accumulation- deposits of transported soils
Flat areas subject to less weathering,but higher accumulation- deposits of transported soils
TimeTime
Period of weatheringPeriod of weathering
Soil Properties - PhysicalSoil Properties - Physical
Infiltration Infiltration
Leaching Leaching
Porosity/permeability Porosity/permeability
Texture Texture
Loam Loam
100%clay
Increasingpercentage silt
Increasingpercentage clay
0
20
40
60
80
80
60
40
20
0100%sand 80 60 40 20 100%silt
Increasing percentage sand
Water Water
High permeability Low permeability
Texture: effects on soil characteristicsTexture: effects on soil characteristics
Texture Nutrient Infiltration Water-Holding Aeration TilthCapacity Capacity
Clay Good Poor Good Poor Poor
Silt Medium Medium Medium Medium Medium
Sand Poor Good Poor Good Good
Loam Medium Medium Medium Medium Medium
Soil Properties - ChemicalSoil Properties - Chemical
pH - acidity, alkalinity1-6 acidic 7 neutral 8-14 alkaline- acidity produced by rain (pH 5.5), organic matter
breakdown, some fertilizers
pH - acidity, alkalinity1-6 acidic 7 neutral 8-14 alkaline- acidity produced by rain (pH 5.5), organic matter
breakdown, some fertilizers
Crops have pH preferencesneutral - alfalfa; acidic - corn, wheat;very acidic - potatoes
Crops have pH preferencesneutral - alfalfa; acidic - corn, wheat;very acidic - potatoes
Soil pH adjustment - lime (up), water (down)Soil pH adjustment - lime (up), water (down)
Soil ErosionSoil Erosion
Loss of soil by actions of wind, waterLoss of soil by actions of wind, water
Worldwide net loss - 23 billion tons/yr- eroding faster than it forms on 38% of croplands- 200-1000 years to produce 1 inch of soil
Worldwide net loss - 23 billion tons/yr- eroding faster than it forms on 38% of croplands- 200-1000 years to produce 1 inch of soil
U.S. losses - 18 tons/hectare/year- 0.7% per year- eroding 16 X faster than it is forming
U.S. losses - 18 tons/hectare/year- 0.7% per year- eroding 16 X faster than it is forming
Areas of serious concern
Areas of some concern
Stable or nonvegetative areas
Global Soil ErosionGlobal Soil Erosion
Soil Erosion: ContributorsSoil Erosion: Contributors
AgricultureAgriculture
Logging Logging
MiningMining
ConstructionConstruction
Poor Agricultural PracticesPoor Agricultural Practices
Farming steep slopesFarming steep slopesRemoving fence rowsRemoving fence rowsMoldboard plowing (in fall)Moldboard plowing (in fall)Overgrazing Overgrazing Farming natural waterwaysFarming natural waterwaysCompacting soil with large machinesCompacting soil with large machines
Lack of crop rotationLack of crop rotation
Dust Bowl - U.S. Great PlainsDust Bowl - U.S. Great Plains
Early 1930sEarly 1930s
Intensive agriculture & droughtIntensive agriculture & drought
Destroyed/damaged 90 million acresDestroyed/damaged 90 million acres
Led to Soil Conservation ServiceLed to Soil Conservation Service
Soil Conservation ServiceSoil Conservation Service
Natural Resources Conservation Service Natural Resources Conservation Service
Goal: encourage proper land usepractices to
1) maintain soil fertility2) control erosion
Goal: encourage proper land usepractices to
1) maintain soil fertility2) control erosion
Maintaining Soil FertilityMaintaining Soil Fertility
Organic (Natural) FertilizersOrganic (Natural) Fertilizers
Stimulate growth of decomposersStimulate growth of decomposers
Animal and plant wastesAnimal and plant wastes
More difficult to handle, applyMore difficult to handle, apply
Maintaining Soil FertilityMaintaining Soil Fertility
Inorganic Fertilizers (most U.S. soils)Inorganic Fertilizers (most U.S. soils)
NPK - may harm soil (sustained use)-low or no micronutrients- decrease soil oxygen- lower soil’s ability to produce useable N forms
NPK - may harm soil (sustained use)-low or no micronutrients- decrease soil oxygen- lower soil’s ability to produce useable N forms
May wash into water suppliesMay wash into water supplies- more readily dissolved than manure- more readily dissolved than manure
Soil Erosion ControlSoil Erosion Control
Conservation tillage- low-till or no-till
Conservation tillage- low-till or no-till
Soil Erosion ControlSoil Erosion Control
Strip cropping and contour farmingStrip cropping and contour farming
Soil Erosion ControlSoil Erosion Control
Crop rotationCrop rotation
Soil Erosion ControlSoil Erosion Control
Windbreaks and shelterbeltsWindbreaks and shelterbelts
Soil Erosion ControlSoil Erosion Control
Terracing Terracing
Soil Erosion ControlSoil Erosion Control
Not planting marginal landsNot planting marginal lands
Soil Erosion ControlSoil Erosion Control
Grass waterwaysGrass waterways
Soil Erosion ControlSoil Erosion Control
Rotational grazingRotational grazing
AgricultureAgriculture
Industrialized agriculture- mechanized- energy supplement from fossil fuels
Industrialized agriculture- mechanized- energy supplement from fossil fuels
Non-industrialized agriculture- unmechanized- energy supplement from
humans and animals
Non-industrialized agriculture- unmechanized- energy supplement from
humans and animals
Industrialized Agriculture in U.S.Industrialized Agriculture in U.S.
Nation’s largest industry
- 20% of labor force- 1 person feeds 77- reduces labor by 99%- yield 4 X higher- doubled food production in 150 years
Nation’s largest industry
- 20% of labor force- 1 person feeds 77- reduces labor by 99%- yield 4 X higher- doubled food production in 150 years
Industrialized Agriculture in U.S.Industrialized Agriculture in U.S.
Major problem- energy intensive- may require up to 9 units of
supplemental energy to produce 1 unit of food energy
- non-mechanized ag yields 3 units offood energy for each unit ofsupplemental energy (27 X better)
Major problem- energy intensive- may require up to 9 units of
supplemental energy to produce 1 unit of food energy
- non-mechanized ag yields 3 units offood energy for each unit ofsupplemental energy (27 X better)
Combating Hunger and MalnutritionCombating Hunger and Malnutrition
Producing more foodProducing more food
1) Cultivate more land1) Cultivate more land
2) Improve crop yields2) Improve crop yields
3) Catch, raise more fish & seafood3) Catch, raise more fish & seafood
Cultivating More LandCultivating More Land
Problems with 56% of potential croplands Problems with 56% of potential croplands
Remote locationRemote location
Insect infestationInsect infestation
Poor soils, lack of waterPoor soils, lack of water
High costs, no economic incentivesHigh costs, no economic incentives
Competition for other usesCompetition for other uses
Improving Crop YieldsImproving Crop Yields
Develop higher-yield varieties Develop higher-yield varieties Quickest and cheapest way
- better adapted to climate, soil conditions- wheat, rice
Quickest and cheapest way- better adapted to climate, soil conditions- wheat, rice
Problem: require more fertilizer, water,pesticides- weaker plants- seeds more costly for farmers in
developing nations
Problem: require more fertilizer, water,pesticides- weaker plants- seeds more costly for farmers in
developing nations
Catching, Raising More FishCatching, Raising More Fish
Supplies 25% of animal proteinSupplies 25% of animal protein
Increasing demand, level or decliningcatches- reached or exceeded MSY- fish not abundant, higher trophic levels- shrimp 1:75 energy ratio
Increasing demand, level or decliningcatches- reached or exceeded MSY- fish not abundant, higher trophic levels- shrimp 1:75 energy ratio
Alternatives?- krill, aquaculture
Alternatives?- krill, aquaculture
Can simply producing more foodsolve the world’s hunger andmalnutrition problem?
Can simply producing more foodsolve the world’s hunger andmalnutrition problem?
1) Poverty is chief cause of hunger, malnutrition
1) Poverty is chief cause of hunger, malnutrition
2) Inadequate distribution system2) Inadequate distribution system
Can simply producing more foodsolve the world’s hunger andmalnutrition problem?
Can simply producing more foodsolve the world’s hunger andmalnutrition problem?
3) Livestock gets most of the crops- enough to feed 16 billion people
3) Livestock gets most of the crops- enough to feed 16 billion people
Can simply producing more foodsolve the world’s hunger andmalnutrition problem?
Can simply producing more foodsolve the world’s hunger andmalnutrition problem?
4) Food must be of proper quality and quantity- marasmus - skinny, bloated belly
- diet low in calories and protein- kwashiorkor - entire body bloated
- diet high in calories, low in protein
4) Food must be of proper quality and quantity- marasmus - skinny, bloated belly
- diet low in calories and protein- kwashiorkor - entire body bloated
- diet high in calories, low in protein
Can simply producing more foodsolve the world’s hunger andmalnutrition problem?
Can simply producing more foodsolve the world’s hunger andmalnutrition problem?
5) Food must be culturally acceptable5) Food must be culturally acceptable
Alternatives to producing more foodAlternatives to producing more food
1) Simplifying diets2) Use and waste less food, fertilizer3) Use new, unconventional, enriched,
and fabricated foods4) Reduce crop losses from pests,
diseases
1) Simplifying diets2) Use and waste less food, fertilizer3) Use new, unconventional, enriched,
and fabricated foods4) Reduce crop losses from pests,
diseases
Simplifying DietsSimplifying Diets
Eating lower on the food webEating lower on the food web 1/3 of world grain production used to support
meat diets of people in developed nations
1/3 of world grain production used to support meat diets of people in developed nations
U.S. citizens eat 25 X more meat than people in developing nations
U.S. citizens eat 25 X more meat than people in developing nations
75% of N. Amer. grain goes to cattle (<5% in developing nations)
75% of N. Amer. grain goes to cattle (<5% in developing nations)
Eliminate U.S. feedlots - food for 400 million people
Eliminate U.S. feedlots - food for 400 million people
10% meat reduction - 60 million people 10% meat reduction - 60 million people
Use, Waste Less FoodUse, Waste Less Food
Wasted food - cafeterias, homes, etc.Wasted food - cafeterias, homes, etc.
Overnutrition - 30-50% of adults, 10% of children
Overnutrition - 30-50% of adults, 10% of children
Fertilizer use on non-ag land- food for 65 million
Fertilizer use on non-ag land- food for 65 million
Pets - food for 21 million
Pets - food for 21 million
New, Unconventional, Enriched, Fabricated FoodsNew, Unconventional, Enriched, Fabricated Foods
80,000 edible plants, 175 cultivated,- 16 important, 3 “biggies”
- corn, wheat, rice
80,000 edible plants, 175 cultivated,- 16 important, 3 “biggies”
- corn, wheat, rice
New crop plants - winged bean, ye-edNew crop plants - winged bean, ye-ed
Unconventional foods - insects!- high protein
Unconventional foods - insects!- high protein
New, Unconventional, Enriched, Fabricated FoodsNew, Unconventional, Enriched, Fabricated Foods
Enriched foods- combat malnutrition, disease, by
adding vitamins, minerals- salt with iodine - goiter- rice with vitamin B1 - beriberi
Enriched foods- combat malnutrition, disease, by
adding vitamins, minerals- salt with iodine - goiter- rice with vitamin B1 - beriberi
Problem: added during processing,may be unavailable to those whogrow your own
Problem: added during processing,may be unavailable to those whogrow your own
New, Unconventional, Enriched, Fabricated FoodsNew, Unconventional, Enriched, Fabricated Foods
Fabricated foods- substitute plant products for animal
- margarine for butter- veg. oil for lard- imitation bacon (soybeans, wheat)- soy burgers (soybeans, edible mold)
- high protein
Fabricated foods- substitute plant products for animal
- margarine for butter- veg. oil for lard- imitation bacon (soybeans, wheat)- soy burgers (soybeans, edible mold)
- high protein
Reduce Crop Losses from Pests, DiseasesReduce Crop Losses from Pests, Diseases
45% of potential crops destroyed each year- 33% before harvest- 12% during storage
45% of potential crops destroyed each year- 33% before harvest- 12% during storage
More use of pesticides needed?- similar losses in U.S. where pesticide
use is high and other countries whereuse is low
More use of pesticides needed?- similar losses in U.S. where pesticide
use is high and other countries whereuse is low
Pesticide ProblemsPesticide Problems
Persistence Persistence
Bioaccumulation/biomagnification- DDT and the bald eagle
Bioaccumulation/biomagnification- DDT and the bald eagle
Nonspecificity Nonspecificity
Development of resistanceDevelopment of resistance
Biological Controls: AlternativesBiological Controls: Alternatives
Predators or parasitesPredators or parasites
Attractants (pheromones = sex hormones)Attractants (pheromones = sex hormones)
Sterilization Sterilization
Resistant crops (genetic)Resistant crops (genetic)
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