Chapter 9

Irrigation

The artificial provision of water to support agriculture.

Parent Material

The base geologic material in a particular location.

Overgrazing

The consumption by too many animals of plant cover, impeding plant regrowth and the replacement of biomass. Overgrazing can worsen damage to soils, natural communities, and the land's productivity for further grazing.

Bedrock

The continuous mass of solid rock that makes up Earth's crust.

Terracing

The cutting of level platforms, sometimes with raised edges, into steep hillsides to contain water from irrigation and precipitation. Terracing transforms slopes into series of steps like a staircase, enabling farmers to cultivate hilly land while minimizing their loss of soil to water erosion.

How did the US government respond to the Dust Bowl?

The government increased support for research into soil conservation

Clear-cutting

the removal of all trees from an area at once...leads to soil erosion, especially on steep slopes.

How do farming and grazing practices and policies contribute to soil erosion?

-Overcultivating fields through poor planning or excessive tilling (plowing) -Grazing rangeland with more livestock than the land can support -Clearing forests on steep slopes or with large clear-cuts

What are the forms of nitrogen available to plants?

1. Ammonium (NH4+) 2. Nitrate (N03-)

What are the five factors that influence soil formation?

1. Climate= soil forms faster in warm, wet climates 2. Organisms= earthworms and other burrowing animals mix and aerate soil, add organic matter, and facilitate microbial decomposition. Plants add organic matter and affect a soil's composition and structure. 3. Topography= hills and valleys affect exposure to soil (sun, wind, and water effect how soil moves). steeper slopes promote runoff and erosion and hinder leaching, accumulation of organic matter, and differentiation of soil layers 4. Parent Material= chemical and physical attributes of the parent material influence properties of the resulting soil 5. Time= soil formation can take decades, centuries, or millennia

What are the four ways to classify soils?

1. Color= indicate composition and fertility 2. Texture= determined by the size of particles 3. Structure= clumpiness of soil 4. PH= plants can die in soils that are too acidic or too alkaline

What are 6 methods farmers can employ to conserve soil?

1. Crop Rotation 2. Contour Farming 3. Terracing 4. Intercropping 5. Shelterbelts 6. Conservation Tillage

What are the different causes of soil degradation by agriculture?

1. Deforestation 2. Cropland Agriculture 3. Other Exploitation 4. Industrialization 5. Overgrazing

What are the primary plant nutrients?

1. Nitrogen (N)= most important nutrient besides water; determines rate of growth (chlorophyll, proteins, nucleic acids) 2. Phosphorus (P)= required during germination and fruit/seed formation 3. Potassium (K)= regulatory and root growth

Distinguish between physical, chemical, and biological weathering

1. Physical= results from wind, rain, freezing, thawing 2. Chemical= occurs as water or gases chemically alter rock (acid rain, oxidation) 3. Biological= involves living things (tree roots and lichens)

What is the path of movement of water in the drainage basin?

1. Precipitation 2. Interception 3. Infiltration 4. Percolation 5. Groundwater flow 6. River 7. Evapotranspiration

Soil

A complex plant-supporting system consisting of disintegrated rock, organic matter, air, water, nutrients, and microorganisms.

Humus

A dark, spongy, crumbly mass of material made up of complex organic compounds, resulting from the partial decomposition of organic matter.

Soil Degradation

A deterioration of soil quality and decline in soil productivity, resulting primarily from forest removal, cropland agriculture, and overgrazing of livestock.

Inorganic Fertilizers

A fertilizer that consists of mined or synthetically manufactured mineral supplements. Inorganic fertilizers are generally more susceptible than organic fertilizers to leaching and runoff and may be more likely to cause unintended off-site impacts.

Desertification

A form of land degradation in which more than 10% of a land's productivity is lost due to erosion, soil compaction, forest removal, overgrazing, drought, salinization, climate change, water depletion, or other factors. Severe desertification can result in the expansion of desert areas or creation of new ones. (in Middle East and arid and semiarid lands)

Land Degradation

A general deterioration of land that diminishes its productivity and biodiversity, impairs the functioning of its ecosystems, and reduces the ecosystem services the land can offer us.

Compost

A mixture produced when decomposers break down organic matter, such as food and crop waste, in a controlled environment.

Slash-and-burn

A mode of agriculture frequently used in the tropics in which natural vegetation is cut and then burned, adding nutrition to the soil, before farming begins. Generally farmers move on to another plot once the soil fertility is depleted.

Pollination

A plant-animal interaction in which one organism (for example, a bee or a hummingbird) transfers pollen (containing male sex cells) from flower to flower, fertilizing ovaries (containing female sex cells) that grow into fruits with seeds.

Shelterbelts

A row of trees or other tall perennial plants that are planted along the edges of farm fields to break the wind and thereby minimize wind erosion.

Cation Exchange Capacity

A soil's ability to hold cations- making them available to plants and reducing leaching -measure of soil fertility -greatest in fine soils -reduced as pH drops

Fertilizer

A substance that promotes plant growth by supplying essential nutrients such as nitrogen or phosphorus.

Traditional Agriculture

Agriculture in which human and animal muscle power, along with hand tools and simple machines, performs the work of cultivating, harvesting, storing, and distributing crops.

Sustainable Agriculture

Agriculture that can be practiced in the same way and in the same place far into the future. Sustainable agriculture does not deplete soils faster than they form, nor reduce the clean water, genetic diversity, pollinators, and other resources essential to long-term crop and livestock production.

No-till Farming

Agriculture that does not involve tilling (plowing, disking, harrowing, or chiseling) the soil. The most intensive form of conservation tillage.

Conservation (or reduced) Tillage

Agriculture that limits the amount of tilling (plowing, disking, harrowing, or chiseling) of soil. Furrows are cut in the soil, a seed is dropped in and the furrow is closed.

Industrial Agriculture

Agriculture that uses large-scale mechanization and fossil fuel combustion, enabling farmers to replace horses and oxen with faster and more powerful means of cultivating, harvesting, transporting, and processing crops. Other aspects include large-scale irrigation and the use of inorganic fertilizers. Use of chemical herbicides and pesticides reduces competition from weeds and herbivory by insects.

Organic Fertilizers

Agriculture that uses no synthetic fertilizers or pesticides but instead relies on the remains or wastes of organisms (manure, crop residues, fresh vegetation)

Dust Bowl

An area that loses huge amounts of topsoil to wind erosion as a result of drought and/or human impact. First used to name the region in the North American Great Plains severely affected by drought and topsoil loss in the 1930s.

How does soil form?

Begins when the lithosphere is parent material is exposed to the effects of the atmosphere, hydrosphere, and biosphere. It may be hardened lava or volcanic ash; rock or sediment deposited by glaciers; etc. Parent material is broken down by weathering. Then biological activity contributes to soil formation through deposition, decomposition, and accumulation of organic matter.

What are the underpinning factors of agriculture?

Crops require soil, sunlight, water, nutrients, and mechanisms for pollination. Livestock require food and water

Soil Profile

Cross-section of a soil as a whole, including all soil horizons from the surface to the bedrock

Cropland

Land that people use to raise plants for food and fiber.

E Horizon

Eluviated (leaching layer)= minerals and organic matter tend to leach out of this horizon

How has the evolution of conventional (industrial) agriculture degraded soil?

Erosion rates from conventional (industrial) agriculture are high. They greatly exceed rates in fields farmed under conservation tillage, rates in areas covered by native vegetation, and rates averaged over the geological record.

Rangeland

Land used for grazing livestock.

Soil Conservation Act 1935 (Now named Natural Resources Conservation Service)

Established the soil conservation service which was an agency that worked closely with farmers to develop conservation plans for individual farms, using science to assess the land's resources and to ensure that the plans harmonized with land owners' objectives

Farm Bill

Funded 15 programs that encourage the conservation of soil, grasslands, wetlands, wildlife habitat, and other natural resources on agricultural lands

What region are soils currently being degraded the fastest? Why is this occurring?

In tropical areas because there is a large amount of rain that falls in tropical regions which leaches minerals and nutrients out of the topsoil. The warm temperatures also speed up the decomposition of leaf litter and the uptake of nutrients by plants.

Case Study

Kennesaw State University has 3 local farms and opened the Commons, a dining hall that feeds more than 5000 students. The Farm-to-Campus program uses organic fertilizer and serve them at the university. They re-use the waste and put it back into the farm. This minimizes energy use, water consumption, and waste generation

What soil type is the most desireable for agriculture?

Loam= relatively even mixture of clay, silt and sand sized particles. Black or dark brown soils are best because they are rich in organic material. An intermediate degree of clumpiness is best for plant growth, as well as intermediate PH values.

Cation Exchange in Soil

Negatively charged soils hold cations

O Horizon

Organic (litter layer)= organic matter deposited by organisms

Why is overapplication of fertilizer a problem?

Over-application of fertilizers is a problem because nutrients not taken up by plants end up elsewhere. Nitrates can leak into aquifers and contaminate ground water and drinking water, runoff of phosphorus and nitrogen can cause eutrophication, and pollute the air.

Sand

Particles are .05-2 mm in diameter. Sand grains are large enough to see individually and do not adhere to one another.

Clay

Particles are less than .002 mm in diameter. Clay particles readily adhere to one another and give clay a sticky feeling when moist.

Drip Irrigation

Pipes or hoses that have holes in them that drips directly on the plants that need it. This helps prevent salinization.

Justus Von Liebig's Law of Minimum

Plant production can be no greater than that level allowed by the growth factor present in the lowest amount relative to the optimum amount for that factor

Intercropping

Planting different types of crops in alternating bands or other spatially mixed arrangements.

Why do farmers use fertilizers?

Plants require nitrogen, phosphorus, and potassium. Plants remove these nutrients from soil as they grow. If farmland soil is depleted of nutrients, crops yields decline

What is Porosity? What the difference between finer particles and larger particles?

Porosity is Percent of pore space -Finer Particles: Lower porosity, low oxygen, and water infiltration -Larger Particles: Water passes too quickly

What are the pros and cons of irrigation?

Pros: boost productivity, can farm in arid regions, high yields in times of drought Cons: depletes groundwater, dries up rivers and lakes, water logging, salinization

C Horizon

Regolith= Weathered parent material (initial step in soil formation)

What is Salinization? What is salinization prevention?

Salinization= The buildup of salts in surface soil layers. Salinization Prevention= crop selection, low-salt water, irrigation efficiency

Silt

Silt particles are .002-.05 mm in diameter. Silt is intermediate= it is powdery when dry and smooth when wet.

Loam

Soil with a relatively even mixture of clay-, silt-, and sand-sized particles.

How does modern agriculture rely on pollination?

Stable grain crops, such as wheat and corn, are derived from grasses and are wind pollinated, but many fruit, vegetable, and nut crops depend on insects for pollination.

B Horizon

Subsoil= minerals and clay and organic matter accumulate here

Topsoil

That portion of the soil that is most nutritive for plants and is thus of the most direct importance to ecosystems and to agriculture. A soil horizon also known as the A horizon.

What US Federal Department is the largest owner of land in the nation? What does the department do?

The Bureau of Land Management (BLM) assesses the carrying capacity of rangelands and informs livestock owners of those limits, so that herds are rotated from site to site as needed. They establish and enforce limits on grazing on publicly owned land; ranchers can be granted rights to graze livestock on BLM lands for inexpensive fees.

Deposition

The arrival of eroded soil at a new location.

Polycultures

The planting of multiple crops in a mixed arrangement or in close proximity. An example is some traditional Native American farming that mixed maize, beans, squash, and peppers

Crop Rotation

The practice of alternating the kind of crop grown in a particular field from one season or year to the next. Cover crops protect soil when main crops aren't planted (wheat, corn, or soybeans)

Agriculture

The practice of cultivating soil, producing crops, and raising livestock for human use and consumption.

Contour Farming

The practice of plowing furrows sideways across a hillside, perpendicular to its slope, to help prevent the formation of rills and gullies.

Leaching

The process by which minerals dissolved in a liquid (usually water) are transported to another location (generally downward through soil horizons).

Weathering

The process by which rocks and minerals are broken down, turning large particles into smaller particles. Weathering may proceed by physical, chemical, or biological means.

Erosion

The removal of material from one place and its transport to another by the action of wind or water.

Waterlogging

The saturation of soil by water, in which the water table is raised to the point that water bathes plant roots. Waterlogging deprives roots of access to gases, essentially suffocating them and damaging or killing the plants.

Monocultures

The uniform planting of a single crop over a large area. Characterizes industrial agriculture.

Precision Agriculture

The use of technology to precisely monitor crop conditions, crop needs, and resource use to maximize production while minimizing waste of resources.

What are the key current issues regarding pollination?

Today, many pollinating insects are in trouble as a result of pesticide use and habitat loss

A Horizon

Topsoil= some organic material mixed with mineral components and humus. Plant roots grow in this dark-colored layer.

Conservation Reserve Program

U.S. policy in farm bills since 1985 that pays farmers to stop cultivating highly erodible cropland and instead place it in conservation reserves planted with grasses and trees.

R Horizon

Unweathered Rock (bedrock) layer that is beneath all the other layers (parent material= bedrock, lava, etc.)

Capillary Action

Very narrow tubes (capillaries) can cause Capillary action (capillarity) which can pull water upwards against gravity (smaller pores, more capillary action)

How does grazing affect soil quality? Why is it considered a positive feedback loop?

When livestock remove too much plant cover or churn up the soil with their hooves, soil is exposed and made vulnerable to erosion. In a positive feedback loop, soil erosion makes it difficult for vegetation to regrow, a problem that perpetuates the lack of cover, and gives rise to more erosion.