© 2011 Pearson Education, Inc. CHAPTER 11 Soil: The Foundation for Land Ecosystems.

© 2011 Pearson Education, Inc. An introduction to soil and agriculture Some farmers follow the five golden rules of the tropics Keep soil covered Use minimal or no tillage Use mulch to provide nutrients to the soil Maximize biomass production Maximize biodiversity Harvests have increased dramatically Farmer experimenters experiment and educate others, leading to sustainable agriculture

© 2011 Pearson Education, Inc. The Russian desert Southeastern Russia has undergone severe desertification Stable rolling grasslands have become drifting sands Deserts are growing by thousands of acres annually Failed communist agricultural policies Plowing the thin soil for crops Grazing sheep with sharp hooves that broke the soil The sand has buried over 25 towns Building barriers and planting vegetation help limit moving sand and reclaim degraded land

© 2011 Pearson Education, Inc. Past neglect 90% of all food comes from land-based agriculture Oceans and natural systems are being depleted Protecting and nurturing soil is the cornerstone of food production and sustainability But it has been overlooked repeatedly The Greek, Roman, and Mayan empires collapsed The result of decreased agricultural productivity Brought on by soil erosion Plowing the prairie and drought caused the U.S. Dust Bowl

© 2011 Pearson Education, Inc. Asking more of the land Increased population pressures croplands and grazing lands to increase production 15% of Earth’s land was degraded in 1991 Now, land degradation is even worse 20% of cultivated land, 30% of forests, 10% of grasslands were degraded between 1981 and 2003 Soils are degraded by erosion, salt buildup, and other problems Future productivity is undermined

© 2011 Pearson Education, Inc. A rich soil is much more than dirt Soil: solid material of geological and biological origin Chemical, biological, and physical processes change soil Giving it the ability to support plant growth In productive soil, detritus feeders and decomposers constitute a biotic community Facilitating the transfer of nutrients Creating a soil environment favorable to root growth Productive topsoil involves dynamic interactions among organisms, detritus, and mineral particles of the soil

© 2011 Pearson Education, Inc. Soil characteristics Most soils are hundreds of years old They change very slowly Soil science is at the heart of agriculture and forestry Soil is classified by profile, structure, and type Soil texture: relative proportions of each soil type Parent material: mineral material of the soil Soil has its origin in the geological history of an area Weathering: gradual physical and chemical breakdown of parent material It may be impossible to tell what the parent material was

© 2011 Pearson Education, Inc. Classification of soil Soil separates: small fragments smaller than stones Sand: particles from 2.0 to 0.063 mm Silt: particles range from 0.063 to 0.004 mm Clay: anything finer than 0.004 mm Gravel, cobbles, boulders: particles larger than sand You can see the individual rock particles in sand Clay particles become suspended in water Clay is “gooey” because particles slide around each other on a film of water

© 2011 Pearson Education, Inc. Proportions Sand, silt, and clay constitute the mineral part of soil If one type of particle predominates, the soil is sandy, silty, or clayey Loam: a soil with 40% sand, 40% silt, and 20% clay To determine a soil’s texture: Add soil and water to a test tube and let the soil settle Sand particles settle first, then silt, then clay Scientists classify soil texture with a triangle It shows relative proportions of sand, silt, and clay

© 2011 Pearson Education, Inc. Properties Soil properties are influenced by its texture Larger particles have larger spaces separating them Small particles have more surface area relative to their volume Nutrient ions and water molecules cling to surfaces These properties profoundly affect soil properties Infiltration, nutrient- and water-holding capacity, aeration Workability: the ease with which soil can be cultivated Clay soils are hard to work with: too sticky or too hard Sandy soils are easy to work with

© 2011 Pearson Education, Inc. Soil profiles Horizons: horizontal layers of soil from soil formation Can be quite distinct Soil profile: a vertical slice through the soil horizons Reveals the interacting factors in soil formation O horizon: topmost layer of soil Dead organic matter (detritus) deposited by plants High in organic content Primary source of energy for the soil community Humus: decomposed dark material at the bottom of the O horizon

© 2011 Pearson Education, Inc. Subsurface layers A horizon (topsoil): below the O horizon A mixture of mineral soil and humus Permeated by fine roots Usually dark May be shallow or thick Vital to plant growth Grows an inch or two every hundred years E horizon: pale-colored layer below the A horizon Eluviation: process of leaching (dissolving) minerals due to downward movement of water

© 2011 Pearson Education, Inc. Subsurface layers B horizon (subsoil): below the E horizon Contains minerals leached from the A and E horizons High in iron, aluminum, calcium, other minerals, clay Reddish or yellow colored from oxidized metals C horizon: parent mineral material Weathered rock, glacial deposits, volcanic ash Reveals geologic process that created the landscape Not affected by biological or chemical processes

© 2011 Pearson Education, Inc. Soil classification Soil comes in an almost infinite variety of structures and textures Soils are classified by: Order: the most inclusive group Suborder, groups, subgroups, families Class: best corresponds to the soil in question Four major soil orders most important for agriculture, animal husbandry and forestry: Mollisols, oxisols, alfisols, aridisols

© 2011 Pearson Education, Inc. Important soil orders Mollisols: fertile, dark soils of temperate grasslands The world’s best agricultural soils Midwest U.S., Ukraine, Mongolia, Argentinian pampas Deep A horizon; rich in humus and minerals With less precipitation, minerals don’t leach downward Oxisols: soils of tropical and subtropical rain forests The B horizon has a layer of iron and aluminum oxides Little O horizon: rapid decomposition of vegetation Limited agriculture: minerals are in living plant matter Leached minerals form a hardpan, resisting cultivation

© 2011 Pearson Education, Inc. Two more important soil orders Alfisols: widespread, moderately weathered forest soils Well-developed O, A, E, and B horizons Typical of moist, temperate forests Suitable for agriculture if they are fertilized Aridisols: soils of drylands (arid, semiarid, and seasonally dry areas) and deserts Unstructured due to lack of vegetation and precipitation Thin, light colored Some areas may support rangeland animal husbandry Irrigation leads to salinization

© 2011 Pearson Education, Inc. Soil and plant growth For best growth, plants need a root environment that supplies Mineral nutrients, water, oxygen The proper pH and salinity Soil fertility: the soil’s ability to support plant growth The presence of proper amounts of nutrients and all other needs Farmers refer to a soil’s ability to support plant growth as tilth

© 2011 Pearson Education, Inc. Mineral nutrients Initially become available through rock weathering Phosphate, potassium, calcium, etc. Much too slow to support normal plant growth Breakdown and release (recycling) of detritus provides most nutrients Leaching: nutrients are washed from the soil by water Decreases soil fertility Contributes to water pollution Nutrient-holding capacity: the soil’s capacity to bind and hold nutrient ions until they are absorbed by roots

© 2011 Pearson Education, Inc. Fertilizer Agriculture removes nutrients from the soil Fertilizer: nutrients added to replace those that are lost Organic fertilizer: plant or animal wastes or both Manure, compost (rotted organic material) Leguminous fallow crops (alfalfa, clover) Food crops (lentils, peas) Inorganic fertilizer: chemical formulations of nutrients Lacks organic matter Much more prone to leaching

© 2011 Pearson Education, Inc. Water is crucial for plants Transpiration: water is absorbed by roots and exits as water vapor through pores (stomata; singular = stoma) in the leaves Oxygen enters, and carbon dioxide exits, through stomata Loss of water through stomata can be dramatic Wilting: a plant’s response to lack of water Conserves water Shuts off photosynthesis by closing stomata Severe or prolonged wilting can kill plants

© 2011 Pearson Education, Inc. Water and water-holding capacity Water is resupplied to the soil by rainfall or irrigation Infiltration: water soaks into the soil Water runoff is useless to plants and may cause erosion Water-holding capacity: soil’s ability to hold water after it infiltrates Poor holding capacity: water percolates below root level Plants must depend on rains or irrigation Sandy soils Evaporative water loss depletes soil of water The O horizon reduces water loss by covering the soil

© 2011 Pearson Education, Inc. Aeration Novice gardeners kill plants by overwatering (drowning) Roots must breathe to obtain oxygen for energy Land plants depend on loose, porous soil Soil aeration: allows diffusion of oxygen into, and carbon dioxide out of, the soil Overwatering fills air spaces Compaction: packing of the soil Due to excessive foot or vehicular traffic Reduces infiltration and runoff Strongly influenced by soil texture

© 2011 Pearson Education, Inc. Relative acidity (pH) pH refers to the acidity or alkalinity of any solution The pH scale runs from 1 to 14 7 is neutral (neither acidic or alkaline) Different plants are adapted to different pH ranges Most do best with a pH near neutral Many plants do better with acidic or alkaline soils Blueberries do best in acidic soils

© 2011 Pearson Education, Inc. Salt and water uptake Buildup of salt in the soil makes it impossible for roots to take in water High enough salt levels can draw water out of a plant By osmosis Dehydrates and kills plants Only specially adapted plants grow in saline soils None of them are crops Irrigation can lead to salt buildup in soil (salinization)

© 2011 Pearson Education, Inc. The soil community To support plants, soils must Have nutrients and good nutrient-holding capacity Allow infiltration and have good water-holding capacity Resist evaporative water loss Have a porous structure that allows aeration Have a near-neutral pH Have low salt content According to the principle of limiting factors, the poorest attribute is the limiting factor

© 2011 Pearson Education, Inc. Limiting factors in plant growth Sandy soils dry out too quickly to be good for agriculture They have poor water-holding capacity Clay soils do not allow infiltration or aeration The best soils are silts and loams They moderate limiting factors Soil texture limitations are improved by the organic parts of the soil ecosystem Detritus Soil organisms

© 2011 Pearson Education, Inc. Organisms and organic matter in the soil Dead leaves, roots, other detritus on and in the soil Support a complex food web Bacteria, fungi, mites, insects, millipedes, spiders, earthworms, snails, slugs, moles, etc. Millions of bacteria are in a gram of soil Humus: residue of partly decomposed organic matter In high concentrations at the bottom of the O layer Extraordinary capacity for holding water and nutrients Composting: fosters decay of organic wastes Is essentially humus

© 2011 Pearson Education, Inc. Soil structure and topsoil Animals feeding on detritus also ingest mineral soil particles Castings: earthworm excrement of stable clumps of “glued” inorganic particles plus humus Burrowing of animals keeps clumps loose Soil structure: refers to the arrangement of soil particles Soil texture: refers to the size of soil particles A loose soil structure: best for infiltration, aeration, and workability Topsoil: clumpy, loose, humus-rich soil Loss of topsoil reduces crop yield by 85–90%

© 2011 Pearson Education, Inc. Interactions between plants and soil biota Mycorrhizae: a symbiotic relationship between the roots of some plants and certain fungi Fungi draw nourishment from the roots Fungi penetrate the detritus, absorb nutrients, and pass them to the plant Nutrients are not lost to leaching Bacteria add nitrogen to the soil Nematodes: small worms that feed on roots Detrimental to plants May be controlled by other soil organisms (e.g., fungi)

© 2011 Pearson Education, Inc. Soil enrichment Most detritus comes from green plants So green plants support soil organisms Soil organisms create the chemical and physical soil environment beneficial to plants Green plants further protect the soil by reducing erosion and evaporative water loss So keep an organic mulch around garden vegetables The mutually supportive relationship between plants and soil is easily broken Keeping topsoil depends on addition of detritus

© 2011 Pearson Education, Inc. Mineralization If detritus is lost, soil organisms starve Soil will no longer be kept loose and nutrient-rich Humus decomposes, breaking down the clumpy aggregate structure of glued soil particles Water- and nutrient-holding capacities, infiltration, and aeration decline Mineralization: loss of humus and collapse of topsoil All that remains are the minerals (sand, silt, clay) Topsoil results from balancing detritus and humus additions and breakdown

© 2011 Pearson Education, Inc. Soil degradation Turnover of plant material produces detritus When humans cut forests, graze livestock, or plant crops, the soil is managed or mismanaged Soil degradation: occurs when key soil attributes required for plant growth or other ecosystem services deteriorate Some reports on soil degradation are incorrect or outdated 75% of the land in Burkina Faso was said to be degraded But agricultural yields have increased due to soil and water conservation

© 2011 Pearson Education, Inc. LADA The Land Degradation Assessment in Drylands Part of the UN’s Food and Agricultural Organization Land degradation: a reduction in the capacity of land to perform ecosystem functions and services that support society and development Hot spots: regions that are worsening 24% of global land area worsened between 1981 and 2003 South Africa: 29% of land is degraded Poor management Bright spots: regions that are improving (16% of land area)

© 2011 Pearson Education, Inc. Erosion Erosion: the process of soil and humus particles being picked up and carried away by water and wind Occurs any time soil is bared and exposed Soil removal may be slow and gradual (e.g., by wind) or dramatic (e.g., gullies formed by a single storm) Vegetative cover prevents erosion from water Reducing the energy of raindrops Allowing slow infiltration Grass is excellent for erosion control Vegetation also slows wind velocity

© 2011 Pearson Education, Inc. Splash, sheet, and gully erosion Splash erosion: begins the process of erosion Raindrops break up the clumpy structure of topsoil Dislodged particles wash between other aggregates Decreases infiltration and aeration Sheet erosion: the result of decreased infiltration More water runs off, carrying away fine particles Gully erosion: water converges into rivulets and streams Water’s greater volume, velocity, energy remove soil Once started, erosion can turn into a vicious cycle Less vegetation exposes soil to more erosion

© 2011 Pearson Education, Inc. Desert pavement Another devastating feature of wind and water erosion: differential removal of soil particles Lighter humus and clay are the first to be carried away Rocks, stones, coarse sand remain The remaining soil becomes coarser Deserts are sandy because wind removes fine material Desert pavement: occurs in some deserts Removal of fine material leaves a thin surface layer of stones and gravel This protective layer is easily damaged (e.g., by vehicles)

© 2011 Pearson Education, Inc. Cryptogamic crusts Water erosion can change soil composition Rainfall clogs soil Soil hardens when it dries Cryptograms (algae, lichens, mosses) grow Growth of these plants causes a cryptogamic crust It stabilizes soil It adds nutrients through nitrogen fixation It can inhibit infiltration and seed germination These crusts are easily broken up by livestock, etc. Loosened soil is subject to wind and water erosion

© 2011 Pearson Education, Inc. Drylands and desertification Clay and humus are the most important parts of soil For nutrient- and water-holding capacity Their removal results in nutrients being removed Regions with sparse rainfall or long dry seasons support grasses, scrub trees, and crops only if soils have good water- and nutrient-holding capacity Erosion causes these areas to become deserts Desertification: a permanent reduction in the productivity of arid, semiarid, and seasonally dry areas (drylands) Does not mean advancing deserts

© 2011 Pearson Education, Inc. Drylands Desertification is a process of land degradation Due to droughts, overgrazing, erosion, deforestation, overcultivation It is extremely serious because it is permanent Dryland ecosystems cover 41% of Earth’s surface They are defined by precipitation, not temperature They receive minimal rainfall Droughts are common—they can last for years Rainfall causes vegetation to return so drylands are not desertified

© 2011 Pearson Education, Inc. Drylands in danger 10–20% of drylands suffer some form of degradation Inhabited by some of the world’s poorest The UN Convention to Combat Desertification (UNCCD) Addresses funding projects to reverse degradation “Bottom-up” programs so people can help themselves Gathering and dissemination of traditional knowledge TerrAfrica: UNCCD alliance to coordinate efforts to arrest degradation and promote sustainable management Humans pose the greatest threat to dryland ecosystems

© 2011 Pearson Education, Inc. Causes of erosion: overcultivation Plowing to grow crops exposes soil to wind and water erosion Soil remains bare before planting and after harvest Plowing causes splash erosion Destroying soil’s aggregate structure Decreasing aeration and infiltration Tractors compact soil Reducing aeration and infiltration Increasing evaporative water loss and humus oxidation Rotating cash crops with hay and clover is sustainable

© 2011 Pearson Education, Inc. No-till planting No-till agriculture: a technique allowing continuous cropping while minimizing erosion Routinely practiced in the U.S. After spraying a field with herbicide to kill weeds A planting apparatus cuts a furrow through the mulch Drops seeds and fertilizer Closes the furrow The waste from the previous crop becomes detritus So the soil is never exposed Low-till farming uses one pass (not 6–12) over a field

© 2011 Pearson Education, Inc. Inorganic fertilizer Can provide optimal amounts of nutrients efficiently But it lacks organic matter to support organisms and build soil structure It can keep nutrient content high under intensive cultivation (two or more cash crops/year) But mineralization and soil degradation proceed Additional fertilizer leaches into waterways Chemical fertilizers have a valuable place in agriculture Organic fertilizers may not have enough nutrients Growers must use each fertilizer as necessary

© 2011 Pearson Education, Inc. Reducing soil erosion Contour strip cropping: plowing and cultivating at right angles to contour slopes Shelterbelts: protective belts of trees and shrubs planted along plowed fields The U.S. Natural Resource Conservation Service (NRCS) Established in response to the Dust Bowl Regional offices provide information to farmers and others regarding soil and water conservation practices U.S. soil erosion has decreased through conservation Windbreaks, grassed waterways, vegetation to filter runoff

© 2011 Pearson Education, Inc. Overgrazing Livestock graze on grasslands and cleared forest slopes 65% of drylands are grasslands Land is often overgrazed Barren land is eroded and degraded In the 1800s American buffalo (bison) were slaughtered Rangelands stocked with cattle were overgrazed Leading to erosion and growth of unpalatable plants U.S. western rangelands produce less than 50% of the forage they produced before commercial grazing Yet 20% of rangelands remain overstocked

© 2011 Pearson Education, Inc. Degraded rangelands The National Public Lands Grazing Campaign documents harmful effects of livestock grazing Competition of livestock with native animals for food One-third of endangered species are in danger due to cattle-raising practices (predator control, fire suppression) Wooded zones along streams are trampled and polluted Polluted streams make fish species the fastest- disappearing wildlife group Desertification impacts 85% of North America’s drylands The most widespread cause is livestock grazing

© 2011 Pearson Education, Inc. Public lands Overgrazing occurs because rangelands are public lands Tragedy of the commons: the incentive is for all to keep grazing, even though the range is being overgrazed The U.S. Bureau of Land Management (BLM) and Forest Service leases grazing rights on 2 million km 2 of land Federal land is owned by taxpayers Animal unit = one cow-calf pair or five sheep The grazing fee ($1.35/animal unit/month) is 10% what would be paid on private land

© 2011 Pearson Education, Inc. Why are rangelands overgrazed? The 1934 Taylor Grazing Act prohibits reducing grazing levels or keeps grazing fees below market level The U.S. government lost $115 million in 2004 $500 million more was lost in ecological costs (to watersheds, streams, wildlife, endangered species) When Congress and the BLM try to raise fees, western congressmen threaten to cut the BLM budget

© 2011 Pearson Education, Inc. Solutions to overgrazing Better management could restore rangelands Benefiting wildlife and cattle production Conservation Stewardship Program (NRCS) Provides information and support to land-owning ranchers to burn woody plants, reseed land, rotate cattle The government could buy up some of the 26,000 permits Retire rangelands Generously pay ranchers for their permits Use the land for wildlife, recreation, watershed protection

© 2011 Pearson Education, Inc. Deforestation Porous, humus-rich forest soil efficiently holds and recycles nutrients Also absorbs and holds water Converting a forested hillside to grassland doubles the amount of runoff and increases nutrient leaching When forests are cut and soils are left exposed Topsoil becomes saturated with water and slides off the slope Subsoil continues to erode

© 2011 Pearson Education, Inc. Forests are cut at alarming rates 13 million hectares (32 million acres) are cut per year Mostly in developing countries Cutting tropical rain forests causes acute problems Heavy rains have leached soils of minerals Parent material is already maximally weathered So tropical soils (oxisols) lack nutrients Clearing rain forests washes away the thin layer of humus Leaving only the nutrient-poor subsoil Very poor for agriculture

© 2011 Pearson Education, Inc. The other end of the erosion problem Water that does not infiltrate enters streams and rivers Causing flooding Sediment: eroded soil carried into streams and rivers Clogs channels, intensifies floods, fills reservoirs Kills fish and coral reefs Damages streams, rivers, bays, estuaries Excess sediments and nutrients from erosion are the greatest pollution problem in many areas Groundwater is depleted Rainfall runs off and does not refill soil or ground water

© 2011 Pearson Education, Inc. Irrigation Irrigation: supplying water to croplands artificially Dramatically increases production Is a major contributor to land degradation Flood irrigation: river water flows into canals to flood fields Center-pivot irrigation: water is pumped from a well into a giant pivoting sprinkler The U.S. Bureau of Reclamation is involved with supplying irrigation water to the western states Irrigating 4 million hectares (10 million acres) Worldwide irrigation is huge and is still rising

© 2011 Pearson Education, Inc. Salinization Salinization: the accumulation of salts in and on the soil Suppresses plant growth Even the freshest irrigation water has some salt Watering dryland soils dissolves minerals in the soil Evaporation or transpiration leaves salts behind Salinization is considered a form of desertification 1.5 million hectares (3.7 million acres) are lost each year to salinization and waterlogging 160,000 hectares (400,000 acres) in California are unproductive, costing $30 million/year

© 2011 Pearson Education, Inc. Salinization can be avoided or reversed Enough water must be used to leach salts downward Insufficient drainage results in waterlogged soils Installing drainage pipes is expensive Kesterson National Wildlife Refuge received drainage from selenium-enriched soils Killing birds, fish, insects, and plants It was declared a toxic waste dump It has been drained and capped with soil Over 14 other U.S. locations have toxic irrigation water The “Kesterson Effect”

© 2011 Pearson Education, Inc. Soil conservation Healthy soils are essential for agricultural production Human activities (overcultivation, overgrazing, deforestation) cause erosion Sustainability means doing all we can to reduce erosion Soil conservation must be practiced at two levels Individual landholders can best preserve soil through traditional knowledge and practices Public policies can lead to conservation or disaster

© 2011 Pearson Education, Inc. Helping individual landholders Individual landholders, farmers, and herders hold the key to sustainable soil stewardship They must be convinced that conservation will work That it is affordable and will help them in the long run Small, realistic steps must be taken Microloans, advice, and encouragement Sustainable Agriculture and Rural Development Initiative (SARD) coordinates efforts to reach small farmers Farmers organize and adopt sustainable practices These practices can be used in other similar situations

© 2011 Pearson Education, Inc. The Keita Project Niger is one of the hottest countries in the world Part is in the Sahel, a semiarid grassland In 1982 the Italian government started an antierosion project in the Keita district, which has 230,000 people Dams were built to catch summer rains 18 million trees were planted Rock dams stopped sheet erosion Local people (especially women) worked The Keita district is now a flourishing place for crops Desertification has been halted

© 2011 Pearson Education, Inc. Two paradigms Desertification is happening in many areas Leading to permanent damage, poverty, and misery Human factors: population growth, immigration, unjust land tenure, cash crops Erosion from overgrazing and overcultivation is made worse by drought and climate change Desertification is not inevitable: another option is to recognize degradation and take corrective measures Better management, soil and water conservation, diversifying income to relieve pressure on the land

© 2011 Pearson Education, Inc. Public policy and soils Original U.S. farm policy: increasing production This goal was achieved The federal government supports agriculture through subsidies Farm policy emphasizes income and farm commodities Farmers are guaranteed price levels for grains, cotton, sugar, peanuts, dairy products, soybeans, etc. Subsidies cost taxpayers $11 billion in 2009 Crop insurance and loans added $10 billion more Subsidies occurred in spite of record income

© 2011 Pearson Education, Inc. Subsidies hurt the environment They encourage excessive use of pesticides and fertilizers They reduce crop rotation by locking farmers into annual crop support subsidies They encourage aquifer drawdown For irrigation Subsidies undercut objectives of soil conservation

© 2011 Pearson Education, Inc. Goals of sustainable agriculture Maintain productive topsoil Keep food safe and wholesome Reduce chemical fertilizers and pesticides Keep farms economically viable Sustainable options mimic past practices Contouring, crop rotation, terracing, little or no chemicals The U.S. Sustainable Agriculture Research and Education program (SARE) (1988) Provides $5–12 million/year for building and disseminating knowledge about sustainable agriculture

© 2011 Pearson Education, Inc. Farm legislation Federal Agricultural Improvement and Reform Act (FAIR) (1996) reduced subsidies and controls Farmers had greater flexibility over what to plant Declining prices prompted farm aid packages, which maintained subsidies and controls 2002 Farm Security and Rural Investment Act subsidized farm products and kept price supports and farm income The Food, Conservation and Energy Act of 2008 kept high subsidies and encouraged farmers to plow grasslands But it does have programs to conserve soil and wetlands

© 2011 Pearson Education, Inc. Conservation programs The Conservation Reserve Program (CRP; 1985) Farmers are paid $125/hectare ($50/acre) per year Highly erodible land is put into forest or grass In 2008, 14 million hectares (34.7 million acres) were enrolled, saving 454 million tons of topsoil from erosion/year The 2009 acreage was reduced to 32 million acres Conservation activities now receive $5 billion/year Wildlife Habitat Incentives Program (WHIP) Environmental Quality Incentives Program (EQIP)

© 2011 Pearson Education, Inc. Other farmland conservation programs The 2002 Conservation Security Program (CSP) Encourages stewardship of farms, forests, watersheds Renamed the Conservation Stewardship Program in the 2008 farm bill $1 billion to enroll 12 million acres of farmland Farmers and ranchers should have incentives to protect soil Productivity would increase The most significant obstacle to soil conservation A lack of knowledge about what conservation can do Particularly in developing countries

© 2011 Pearson Education, Inc. The residue of partly decomposed organic matter is called ______ and is found in high concentrations at the bottom of the O horizon. a.desertification b.decomposition c.humus d.topsoil Review Question-2

© 2011 Pearson Education, Inc. The residue of partly decomposed organic matter is called ______ and is found in high concentrations at the bottom of the O horizon. a.desertification b.decomposition c.humus d.topsoil Review Question-2 Answer

© 2011 Pearson Education, Inc. Mineralized soils can be revitalized through the addition of a.compost and other organic matter. b.materials from the C horizon. c.topsoil. d.all of the above. Review Question-3

© 2011 Pearson Education, Inc. Mineralized soils can be revitalized through the addition of a.compost and other organic matter. b.materials from the C horizon. c.topsoil. d.all of the above. Review Question-3 Answer

© 2011 Pearson Education, Inc. ______ occurs when there is an accumulation of salts in soil as a result of ______. a.The tragedy of the commons; overgrazing b.Deforestation; logging c.Salinization; irrigation d.Overcultivation; no-till farming Review Question-5

© 2011 Pearson Education, Inc. ______ occurs when there is an accumulation of salts in soil as a result of ______. a.The tragedy of the commons; overgrazing b.Deforestation; logging c.Salinization; irrigation d.Overcultivation; no-till farming Review Question-5 Answer

© 2011 Pearson Education, Inc. According to Fig. 11-3, soil with roughly 40% sand, 40% silt, and 20% clay is called a.loam. b.silt loam. c.sandy clay loam. d. loamy sand. Interpreting Graphs and Data-1

© 2011 Pearson Education, Inc. According to Fig. 11-3, soil with roughly 40% sand, 40% silt, and 20% clay is called a.loam. b.silt loam. c.sandy clay loam. d. loamy sand. Interpreting Graphs and Data-1 Answer

© 2011 Pearson Education, Inc. According to Fig. 11-2, when detritus, mineral particles, and the detritus food web interact, they form a.leaves, stems, flowers, and seeds. b.leached minerals. c.nitrogen fixation. d.topsoil. Interpreting Graphs and Data-2

© 2011 Pearson Education, Inc. According to Fig. 11-2, when detritus, mineral particles, and the detritus food web interact, they form a.leaves, stems, flowers, and seeds. b.leached minerals. c.nitrogen fixation. d.topsoil. Interpreting Graphs and Data-2 Answer

© 2011 Pearson Education, Inc. The human activities that lead to erosion and desertification are a.overcultivation, overgrazing, and deforestation. b.sustainability, stewardship, and sound science. c.pollution, overcultivation, and sustainability. d.overgrazing, sound science, and hypotheses. Thinking Environmentally-1

© 2011 Pearson Education, Inc. The human activities that lead to erosion and desertification are a.overcultivation, overgrazing, and deforestation. b.sustainability, stewardship, and sound science. c.pollution, overcultivation, and sustainability. d.overgrazing, sound science, and hypotheses. Thinking Environmentally-1 Answer

© 2011 Pearson Education, Inc. True or False: If soil conservation is to be successful, it must be practiced on the levels of both the individual landowner and public policy. a.True b.False Thinking Environmentally-2

© 2011 Pearson Education, Inc. True or False: If soil conservation is to be successful, it must be practiced on the levels of both the individual landowner and public policy. a.True b.False Thinking Environmentally-2 Answer

© 2011 Pearson Education, Inc. CHAPTER 11 Soil: The Foundation for Land Ecosystems.

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© 2011 Pearson Education, Inc. CHAPTER 11 Soil: The Foundation for Land Ecosystems.

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