Chapter 9

Silt

.002-.05mm in diameter. Balance of adhere. Feels powdery when dry and smooth when wet. Best for plant growth.

Sand

05-2 mm in diameter. Does not stick together or adhere to one another. Porous and allow water to pass through quickly. Require frequent irrigation.

Soils ingredients:

5% organic matter, 50% mineral matter, and the rest consists of pore space taken up with air or water

Drip irrigation

: hoses drip water directly onto plants so that much less is wasted. Makes plants use 90% of water provided. Other irrigation methods use 43%

Soil Color

Black or dark brown soils are usually rich in organic matter whereas a pale color often indicates leaching or low organic content.

Shelterbelts:

AKA Windbreaks rows of trees or tall shrubs to slow wind.

Water Erosion

Areas with steep slopes, high precipitation, and little plant cover suffer from

Cation exchange capacity

Cations that don't leach are more available to plants A useful measure of soil fertility. Greatest in fine textured or richly organic soils

5 major components of soil formation

Climate, organisms, topography, parent material, and time.

Soil degradation:

Common in drier regions. Soils deteriorate in quality and decline in productivity. Results primarily from forest removal, cropland agriculture, and overgrazing livestock. Has reduced rates of food production by 13% in cropland and 4% in rangeland.

Ways to protect soil in agriculture:

Crop rotation, contour farming, terracing, intercropping, shelterbelts, conservation tillage.

$23 billion

Degraded rangeland costs over _____ worldwide

Soil texture

Determined by size of particles. Broken down into Clay, sand, silt, and loam.

E Horizon:

Eluviated (Leaching layer)

keep the plant cover in place

Farming methods to reduce erosion have one goal

Minerals commonly leached:

From e horizon include iron, aluminum, and silicate clay

Sustainable Agricultur

Healthy soil is a key component of this. Allows soil to renew its nutrients content and retain its character from one crop to the next. Also requires clean water, minimized use of fossil fuel based fertilizers and pesticides, healthy populations of pollinating insects, sustenance of genetic diversity, and genetic modification.

Positive feedback cycle:

Planting crops made people stay. People staying inspired more crops.

Healthy Soil

Provide nutrients. Have a structure that allows roots to penetrate deeply. Retain water

An ecosystem:

Soil is a/an _______ because of being composed of living and nonliving organisms that interact in complex ways.

Cation

Soil particle surfaces that are negatively charged hold _____ or positively charged ions such as those of calcium, magnesium, and potassium.

B horizon

Subsoil where leaching brings down minerals where they accumulate

Irrigation

The artificial provision of water beyond that crops receive from rainfall. I.e. rice and cotton need a lot more water and beans and wheat require very little.

Leaching

Transports minerals downward. The process whereby solid particles suspended or dissolved in liquid are transported to another location. Like coffee grinds in a drip filter.

5

U.S. farmlands lose ___ tons of soil for each ton of grain harvested

Wind erosion

Windy regions with sparse plant cover suffer from

Soil

a complex system of disintegrated rock, organic matter, water, gasses, nutrients such nitrogen and phosphorus that enable plant growth, and microorganisms.

10,000

agriculture arose _________ years ago.

Loam

an even mixture of sand, silt, and clay particle sizes. Best for plant growth. Affects how easily air and water travel through the soil. Influences how easy soil is to cultivate

Drylands

arid and semi-arid environments that cover about 40% of the earth's land surface. Much of the world's population live and farms here. Most Prone to desertification.

Soil Classification

based on properties such as color, texture, structure, and PH.

Traditional Agriculture

biologically powered form of agriculture that uses human and animal muscle power. Hand tools, simple machines. Uses Polycultures and subsistence agriculture.

No Till benefits

carbon storage, burns less gasoline. It increases organic matter and soil biota. Reduces erosion and improves soil quality. Uses less labor, saves time, causes less wear on machinery. Adds organic matter to soils that is kept from the atmosphere

Clay

consists of particles less than .002 mm in diameter. Sticky feeling when moist. Adheres very well. Make difficult for water and air to pass through because compacted together.

A, B & C horizon:

correspond respectively to topsoil(____), subsoil (_____), and weather parent material (_____)

Crop rotation:

farmers alternate the type of crop grown in a given field from one season or year to the next. Returns nutrients to the soil, minimizes erosion from letting fields lie fallow, and can break cycles of disease associated with continuous cropping. Reduces insects or pests by not letting them get used to a certain type of crop.

Sweden Agriculture

farmers cultivate plat for one to a few years and then moves on to clear another plot leaving the first to grow back to forest. (done in tropical rainforest due to low soil fertility)

subsistence agriculture.

form of agriculture in which families produce only enough food for themselves

Industrial Agriculture

form of agriculture that uses large-scale mechanization and fossil fuels to boost yields. (dominates today) Also uses pesticides, irrigation, and fertilizers and monoculture.

Topography

hills and valleys affect exposure to sun, wind, and water

Organic matter ingredients

includes living and dead microorganisms as well as decaying material derived of plants and animals.

soil structure and texture

influence root penetration and growth

Parent material

influences properties of resulting soil

Top soil horizon A

inorganic and organic material most nutritive for plants Vital for agriculture

Selective Breeding

intentionally planting seeds from plants whose produce was most desirable. Artificial made from wild plants or animals. Started by our ancestors and has produced many hundreds of crops we enjoy today.

Soil Structure

is a measure of soil's "clumpiness". A medium amount of clumpiness is best for plants. Repeated tilling compacts soil, decreasing its water-absorbing capabilities

Green Revolution

new technology, crop varieties, and farming practices were introduced to developing countries Increased yields and decreased starvation Degraded the integrity of the soil

Deposition:

occurs when eroded material is deposited at a new location. Flowing water deposits nutrient-rich sediment in river valleys and deltas. Floodplains are excellent for farming

Time

soil can take decades to millennia to form

Positive feedback loop

soil erosion makes it difficult for vegetation to regrow the problem continues because of lack of cover and gives rise to more erosion.

Teams formed by SCS

soil scientists, forestry experts, engineers, economists, and biologists

Climate

soils form faster in warm, wet climates

H20 and soil

soils that retain the right amount of this but drain excess make the perfect amount for plants to grow.

Humus

spongy material formed by partial decomposition of organic matter; holds moisture. Provides nutrients. holds micro organisms that break down plant waste.

Meta-Analysis:

statistical analysis of numerous studies.

Monoculture

uniform planting of a single crop

70%

:_____ of fresh water that people withdraw is used for irrigation. Which has depleted aquifers and dried up rivers and lakes.

Bacteria & fungi algae and protists:

A teaspoon of soil can contain millions of _____ and thousands of ____, _____, & ______.

Cropland

Land used to raise plants for human use feed most of human population Covers 12% of earth's surface.

No till difficulties

Needs for more chemical herbicides due to less weed removal, and synthetic fertilizer.

Conservation Measures

No Till farming, Cover Crops, taking soil sample to determine fertilizer usage, growing grass borders to keep soil and nutrients in, installing a bioreactor an underground container full of carbon rich woodchips to filter out excess nitrogen so it does not pollute ground water.

Rangeland:

Pasture of land used for grazing livestock. Covers 26% of earth's surface

Soil erosion

Physical barriers to capture soil can prevent it. Plants slow wind and water flow. Roots hold soil in place No-till agriculture leaves plant residue on fields Cover crops protect soil between crop plantings

Cover Crops

crops planted to hold the soil in place between times that main food crops are growing. I.e. Rye grass seeds that prevent erosion when corn and soy beans are not growing and makes planting easier by loosening the soil structure. Recycle nutrients and may reduce fertilizer use.

Terracing

cutting level platforms into steep hillsides The steps of this "staircase" hold water

Green manure:

dead plants as fertilizer.

Desertification

describes a form of land degradation in which more than 10% of productivity is lost as a result of erosion (most due to this), soil compaction, forest removal, overgrazing, drought, salinization, climate change, water depletion, and other factors. Made worse by climate change.

Conservation tillage

describes an array of approaches that reduce the amount of tilling relative to farming. One way is leaving 30% of crop residue covering soil after harvest.

Land degradation:

deterioration of land that diminishes productivity and biodiversity, impairs the functioning of its ecosystems, and reduces the ecosystem services it offers us. Caused by unsustainable agriculture, deforestation, and urban development. Soil erosion, nutrient depletion, water scarcity, salinization.

Polycultures

different crops are planted in one field

Conservation Districts

districts that promote soil conservation practices at the county level. Operate with federal direction, authorization, and funding and are organized by the states

Horizon

each different layer of soil. IN ORDER: o, a, e, b, c, r. Degree of weathering and concentration of organic matter decrease as you move down this ______.

Soil conservation act of 1935:

established Soil Conservation Service (SCS) an agency that worked closely with farmers to develop conservation plans for individual farms using science to assess the land's resources and problems, and collaboration with landowners.

Agriculture extension agents:

experts who assist farmers by providing information on new research and by helping them apply this knowledge with new techniques. Provided by state universities.

Cation exchange capacity:

expresses soils ability to hold cations ad prevent them from leaching (thus making them available for the plants.) Useful measure of soil fertility.Decreases with lower pH High ____________= soils with fine textures and rich in organic matter. Lower PH (more acidic) = Lower ___________.

Parent Material:

is the base of geologic material in a particular location. I.E. Hardened lava or organic ash, rock or sediment deposited by glaciers, wind-blown dunes, sediments deposited by river, or bedrock.

Erosion:

is the removal of material from one place and its transport toward another by action of wind or water. Tends to happen more quickly than soil is formed. Removes topsoil

C Horizon:

is weathered parent material. Most nutritious for plants and takes its loose texture, dark coloration, an strong water holding capacity from humus.

Waterlogging:

occurs with overirrigated soils saturated with water. When water table rises to the point that water drowns plant roots depriving them access to gases and suffocating them.

Fertile Crescent

one of five independent areas that started raising and domesticating plants and animals. Located in the Middle East. Possibly earliest found area 10,500 years ago. Wheat, barley, rye, peas, lentils, onions, garlic, carrots, grapes, and other crops originated here. As did goats and sheep. Earliest.

O Horizon:

organic material or leaf litter.

Biological Weathering

organisms produce soil through physical or chemical means

Peoples negative impacts on erosion:

over cultivating fields through poor planning and excessive tilling, grazing rangeland with more livestock than the land can support, and clearing forest on steep slopes or with large clear cuts.

Chemical Weathering

parent material is chemically changed

Intercropping:

planting different crops in alternating bands or other spatially mixed arrangements. Helps slow erosion by providing more ground cover that does a single crop. Increases ground cover, preventing erosion. Decreases pests and disease. Replenishes soil

Organisms

plants and decomposers add organic matter

Soil PH

plants can die in soils that are too acidic or too alkaline. Intermediate values best for plant growth. 8, 7, & .influences the availability of nutrients for plants I.e during leaching acids from organic matter may remove nutrients from the site of exchange.

Cation Exchange

plants gain many nutrients through this process. Plant roots donate hydrogen ions to the soil in exchange for nutrient ions which the soil particles then replenish by exchange with water.

Contour Farming

plowing furrows sideways across a hillside perpendicular to its slope. Sides of furrows trap water and prevent erosion.

Tilling:

plowing, disking, harrowing, or chiseling the soil. Aerates soil and works weeds and old crop residue into the soil to nourish it, but leaves the soil bare allowing wind and water to erode away topsoil.

Weathering

processes that break large rock particles down into smaller ones Physical, chemical, or biological

Organic matter

provides nutrients and helps with structure and water retention.

No-till farming

rather than plowing after each harvest you leave crop residues atop of fields keeping the soil covered in plant material at all times. To plant next crop you cut a thin shallow groove into the soils surface, drop in seeds, and cover them. Less soil erodes, organic material accumulates, and soil soaks up more water all of which encourages better plant growth. Saves fuel, time, effort, and wear and tear on the equipment.

Terrestrial primary succession:

succession of plant life, occurring in an environment in which new substrate devoid of vegetation and other organisms usually lacking soil, such as a lava flow or area left from retreated glacier, is deposited. Begins with lithosphere being exposed to the effects of the atmosphere, hydrosphere, and biosphere.

Soil Profile

the cross-section of soil as a whole. Degree of weathering and amount of organic matter decrease in lower horizons. composed of 6 horizons that create distinct layers based on their composition from surface to bedrock.

Agriculture:

the practice of raising crops and livestock for human use and consumption. (Most food and fiber comes from cropland and rangeland) Land devoted to _______ covers 38% of Earth's land

"Tragedy of the commons":

traditionally ranchers have had no incentive to conserve rangelands because most grazing has taken place on public lands leased by the government and tax payers have heavily subsidized grazing.

Farming or grazing on unsuitable lands:

turns grass land into deserts, remove forests, diminish biodiversity, encourage invasive species, pollute soil/air/ water with toxic chemicals, and allow fertile soil to be blown away.

Natural resources conservation service (NRCS):

what SCS changed to. Responsibilities added to include protection of water quality and pollution control.

Physical (mechanical) weathering

wind and rain; no chemical changes in the parent material