Who cares? You do! In India, one child dies every minute from severe acute malnutrition.

Transcription

1 Soil & Agriculture

2 Who cares? You do! In India, one child dies every minute from severe acute malnutrition.

3 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.

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7 But that was a long time ago, right? Wrong! Modern Dust Bowl

8 Why is soil important? Our lives depend on it! It s a habitat for other organisms Cleans and Stores Water

9 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%)

10 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.

11 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.

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14 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

15 Decomposition complex organic matter is broken down into simpler forms of matter

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19 What does this describe? A plant s roots or animal cells undergo cell respiration and the CO 2 produced diffuses into soil, reacts with H 2 O & forms carbonic acid (H 2 CO 3 ). This eats parts of the rock away.

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21 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)

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23 Porosity Volume of space per unit of soil Permeability Rate at which water and air move through the soil

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25 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.

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27 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 times faster than it is being replenished According to David Pimentel in his study "Soil Erosion: A Food and Environmental Threat"

28 Erosion Materials are moved from one place to another. Caused primarily by water and wind.

29 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.

30 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.

31 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

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34 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 years Killed excess livestock Cut soil losses by 66% Agricultural Act of 2014 Farm Bill

35 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.

36 Terracing converting slopes into flat terraces that run across the lands contour.

37 Contour farming crops are planted across slopes instead of up and down the slope

38 Strip Cropping alternating row (corn) and cover (legume) crop

39 Agroforestry crops planted between rows of trees

40 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.

41 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

42 Production has increased significantly since the 1930 s due to: technological advances, machinery, selective breeding, genetic engineering.

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45 Industrialized-High Input- Agriculture Uses large amounts of: fossil fuel, water, fertilizer, pesticides Crops grown in monocultures

46 Trade-Offs Animal Feedlots Advantages Disadvantages Increased meat production Higher profits Less land use Reduced overgrazing Reduced soil erosion Help protect biodiversity Need large inputs of grain, fish meal, water, and fossil fuels Concentrate animal wastes that can pollute water Antibiotics can increase genetic resistance to microbes in humans Fig , p. 289

47 Biodiversity Loss Soil Water Air Pollution Human Health Loss and Erosion Water waste Greenhouse gas Nitrates in degradation of emissions from drinking water Loss of fertility Aquifer depletion grasslands, fossil fuel use forests, and Salinization Increased runoff and Pesticide residues in drinking water, wetlands flooding from cleared Other air pollutants Waterlogging land from fossil fuel use food, and air Fish kills from pesticide runoff Killing wild predators to protect livestock Loss of genetic diversity of wild crop strains replaced by monoculture strains Desertification Sediment pollution from erosion Fish kills from pesticide runoff Surface and groundwater pollution from pesticides and fertilizers Overfertilization of lakes and rivers from runoff of fertilizers, livestock wastes, and food processing wastes Greenhouse gas emissions of nitrous oxide from use of inorganic fertilizers Belching of the greenhouse gas methane by cattle Pollution from pesticide sprays Contamination of drinking and swimming water with disease organisms from livestock wastes Bacterial contamination of meat Fig , p. 285

48 Traditional-Low Input- Agriculture Uses less: water, fertilizer, pesticide, etc. Depends on human labor, draft animals

49 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.

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51 Trade-Offs Advantages Aquaculture Disadvantages High efficiency High yield in small volume of water Can reduce overharvesting of conventional fisheries Low fuel use High profits Profits not tied to price of oil Needs large inputs of land, feed, and water Large waste output Destroys mangrove forests and estuaries Uses grain to feed some species Dense populations vulnerable to disease Tanks too contaminated to use after about 5 years Fig , p. 292

52 Livestock & their Products Chickens, pigs, sheep, cattle Eggs, meat, leather, wool, manure

53 Factory Farming High density livestock operations

54 Free Range Farming Lower density livestock operations

55 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

56 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

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58 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

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60 Eating more chicken and fish and less beef and pork reduces the harmful impacts of meat production on the environment

61 What can you do? Eat a whole food, plant based diet and change the types of meat that you eat.