soil & agriculture - coach anderson's blog -...
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Soil & Agriculture
Who cares? You do!
• In India, one child dies every minute from severe acute malnutrition.
Case Study: The Dust Bowl
• In the “dirty thirties” a large area of cropland was abandoned due to soil erosion caused by poor farming practices and drought.
• Spurred one of the largest internal migrations in U.S. history.
But that was a long time ago, right? Wrong!• Modern Dust Bowl
Why is soil important?
•Our lives depend on it!
• It’s a habitat for other organisms
•Cleans and Stores Water
What is Soil?
• Thin layer on the Earth’s surface made of: rock, mineral nutrients, decaying organic matter, water, air, many organisms
• 4 Parts
• Mineral Particles (45%)
• Organic Matter (5%)
• Water (25%)
• Air (25%)
Structure of Soil
• Soil Horizons:
• O Horizon: surface litter, i.e. freshly fallen undecomposed or partially decomposed organic matter. Normally brown or black.
• A Horizon: topsoil layer of partially decomposed organic material (humus) and inorganic mineral particles.
•B Horizon: subsoil, mixture of sand, silt, clay, and gravel.
• Gravel—coarse to very coarse particles
• Sand—medium sized particles
• Silt—fine particles
• Clay—very fine particles
•C Horizon: parent material, often unweathered bedrock.
How is it formed?
•Weathering
• Chemical—minerals in rock react with other substances to form new materials
• Physical—cracking and breaking rock apart to form smaller particles
• Biological—plant roots can crack and break rocks apart
•Decomposition—complex organic matter is broken down into simpler forms of matter
What does this describe?
•A plant’s roots or animal cells undergo cell respiration and the CO2
produced diffuses into soil, reacts with H2O & forms carbonic acid (H2CO3). This eats parts of the rock away.
Properties of Soil
• Soil Texture
• Determined by type and relative amount of soil particles
• Soil texture can be described as:
• Gritty—sandy
• Sticky—lots of clay
• Smooth—silty (feels like flour)
•Porosity
• Volume of space per unit of soil
•Permeability
• Rate at which water and air move through the soil
Infiltration & Leeching
•As water moves down through the soil it dissolves minerals and organic matter. These dissolved materials are carried from the upper layers to the lower layers.
Is soil renewable? Are we using it sustainably? • It takes from fifteen years to
hundreds of years to form 1cm (.4 in) of soil.
• “Soil is being swept and washed away 10-40 times faster than it is being replenished”• According to David Pimentel in his study "Soil Erosion: A Food
and Environmental Threat"
• Erosion
• Materials are moved from one place to another. Caused primarily by water and wind.
Global Soil Stats
• Soil on 38% of the world’s cropland is eroding faster than it forms.
• Food production has decreased on 16% of the world’s croplands.
U.S. Soil Stats
•6.4 billion tons of soils are eroded from the U.S. each year
•On farmed land, soil is eroding 16 times faster than it is being formed.
Types of Soil Degradation
• Desertification
• A decrease in the productivity of arid or semiarid land by 10% or more.
• Moderate
• Severe
• Very Severe
• Salinization
• An accumulation of salts in soil due to repeated irrigation
What are we doing about it?
• Agriculture Adjustment Act (AAA)
• Subsidized farmers taking erodible land out of production and planting it with soil saving plants for 10-15 years
• Killed excess livestock
• Cut soil losses by 66%
• Agricultural Act of 2014
• Farm Bill
Soil Conservation
• Conservation-tillage (Used on 45% of U.S. farms in 2003)
• Minimum tillage farming—soil is undisturbed over the winter, special tillers break subsurface soil without turning over topsoil, crop residue, or cover crop.
• No-till farming—seeds, fertilizer, pesticide are injected into thin slits made in unplowed soil.
Terracing—converting slopes into flat terraces that run across the lands contour.
Contour farming—crops are planted across slopes instead of up and down the slope
Strip Cropping—alternating row (corn) and cover (legume) crop
Agroforestry—crops planted between rows of trees
Soil Restoration
• Fertilizers
• Organic
• Compost (animal manure, plant material), bone meal, peat
• Inorganic
• Includes fertilizers produced by factories, which are composed primarily of N, P, K.
Agriculture
•Croplands—77% of the world’s food, mostly grains
•Rangelands—16% of the world’s food, mostly livestock
•Ocean Fisheries—7% of the world’s food
•Production has increased significantly since the 1930’s due to: technological advances, machinery, selective breeding, genetic engineering.
Industrialized-High Input-Agriculture
•Uses large amounts of: fossil fuel, water, fertilizer, pesticides
•Crops grown in monocultures
Fig. 13-21, p. 289
Trade-Offs
Animal Feedlots
Advantages Disadvantages
Increased meat
production
Need large inputs
of grain, fish
meal, water, and
fossil fuelsHigher profits
Concentrate
animal wastes
that can pollute
water
Less land use
Reduced overgrazing
Reduced soil
erosionAntibiotics can
increase genetic
resistance to
microbes in
humans
Help protect
biodiversity
Fig. 13-18, p. 285
Biodiversity Loss Soil Water Air Pollution Human Health
Loss and
degradation of
grasslands,
forests, and
wetlands
Erosion Water waste Greenhouse gas emissions from fossil fuel use
Nitrates in drinking water
Loss of fertility Aquifer depletion
Pesticide residues in drinking water, food, and air
Salinization Increased runoff and flooding from cleared land
Other air pollutants from fossil fuel use
Fish kills from
pesticide runoff
Waterlogging
Sediment pollution from erosion Greenhouse gas
emissions of nitrous oxide from use of inorganic fertilizers
Contamination of drinking and swimming water with disease organisms from livestock wastes
Desertification
Killing wild predators to
protect livestock
Fish kills from pesticide runoff
Surface and groundwater pollution from pesticides and fertilizers Belching of the
greenhouse gas methane by cattle
Loss of genetic diversity of
wild crop strains replaced
by monoculture strains
Bacterial contamination of meat
Overfertilization of lakes and rivers from runoff of fertilizers, livestock wastes, and food processing wastes
Pollution from pesticide sprays
Traditional-Low Input-Agriculture•Uses less: water, fertilizer, pesticide,
etc.
•Depends on human labor, draft animals
Aquaculture
• Fish farming—fish are raised and harvested in enclosed ponds
• Fish ranching—fish are raised, released, and then harvested when they return to spawn.
Fig. 13-24, p. 292
Trade-Offs
Aquaculture
Advantages Disadvantages
High efficiency Needs large inputs
of land, feed, and
waterHigh yield in
small volume
of waterLarge waste
output
Destroys
mangrove forests
and estuaries
Can reduce
overharvesting
of conventional
fisheries Uses grain to feed
some species
Low fuel use Dense populations
vulnerable to
disease
Tanks too
contaminated to
use after about 5
years
High profits
Profits not tied
to price of oil
Livestock & their Products•Chickens, pigs, sheep, cattle
• Eggs, meat, leather, wool, manure
Factory Farming
•High density livestock operations
Free Range Farming
• Lower density livestock operations
SOLUTIONS: MOVING TOWARD GLOBAL FOOD SECURITY
• People in urban areas could save money by growing more of their food.
• Urban gardens provide about 15% of the world’s food supply.
• Decrease food waste!
• Up to 90% of the world’s food is wasted.
Figure 13-26
Solutions: Steps Toward A More Sustainable Food System
•We will have to address production, processing, distribution, consumption and waste to achieve a sustainable food system
What can you do? Think About Your Own Consumption
• Diet & Ecological Footprint
• More energy, water and land is required to produce meat products than to produce plant products
• Therefore, high meat diets have larger ecological footprints than high plant diets
• Eating more chicken and fish and less beef and pork reduces the harmful impacts of meat production on the environment
• Eat a whole food, plant based diet and change the types of meat that you eat.
What can you do?