Chapter 20 APES

The U.S. Department of Agriculture divides soil textures into ______ large layers: ________, __________, and __________.

3; clay; silt; sand.

What is soil?

A complex mixture of eroded rock, mineral nutrients, decaying organic matter, water, air, and billions of living organisms, most of them microscopic decomposers.

Discuss the benefits of alley cropping.

A form of intercropping; Several crops are planted together in strips or alleys between trees and shrubs that can provide fruit or fuelwood; trees provide shade which reduces water loss (usually inflicted by evaporation) and helps slowly release and retain soil moisture; tree and shrub trimmings can be used as mulch, aka green manure for the crops or as fodder for livestock.

Differentiate between conservation and preservation.

Able to use in the future/maximizes long-term usage with conservation; Traps so it it doesn't change, maximizes use in preservation.

What are the benefits and drawbacks of windbreaks? How are they used?

Aka shelterbelts; reduce wind erosion by fostering long rows of trees planted to partially block the wind. Effective so long as land is kept uncovered with vegetation; beneficial because they help retain soil moisture, supply some wood for fuel, and habitats.

What does porosity do for soil?

Allows permeability for water to pass through or be held on to.

Why is strip-cropping beneficial?

Allows water catering and timing of different plants harvest at different times; instead of having full and then fully empty it can be more regeneration and allow for restoring the soil.

Identify and describe the R horizon.

Bedrock. Below all other layers of soil.

Which soil layer is the Parent material? Subsoil? B horizon? Which layer is the organic layer? Elluvial?

C horizon; B horizon; Topsoil; O layer; E horizon;

Identify the various methods of soil conservation and preserving soil fertility.

Conventional tillage farming, conservation tillage farming, terracing, contour farming, strip cropping, alley cropping, wind breaks, organic fertilizers, animal manure, green manure and crop rotation.

What are consequences of soil erosion?

Exposes subsoil, clogged/polluted water ways, habitat destruction, decreased soil fertility, increased acidity, decreased water storage in soil, increased nutrients in water, decreased soil for plants, decreased food production=lower yields.

What happens when soil pH is too acidic?

Ions of heavy metals such as mercury or Aluminum can leach into the groundwater through the process of acid deposition. Such ions can even travel into streams and harm both plants and aquatic life.

Why is soil acidity an important component of soil?

It affects the solubility of nutrients, which in turn determines the extent to which nutrients are available for absorption by plant roots. When soil is too acidic or basic certain soil nutrients will not be able to be used by the regional plants.

Describe crop rotation and discuss the benefits.

Just like rotating students so different students take different patience levels; different plants take different nutrients out of the soil; prevents soil depletion, maintains soil fertility, reduces soil erosion, controls insect/mite pests, reduces reliance on chemical/synthetic fertilizers, prevents diseases, helps control weeds.

What is conventional tillage farming? What is one drawback to this method?

Land is plowed and then soil is broken up and smoothed to make a planting surface. One drawback is that it is ineffective since crop-fields are usually plowed in the fall, so soil is left bare during the winter and early spring months and bare soil is more susceptible to erosion.

How is heavily salinated soil replenished?

Land is taken out of production for 2-5 years, and underground networks of perforated drainage pipes can be installed, and soil can be flushed with large quantities of low-salt water.

What is the general idea of conservation tillage farming?

Leaves pieces of root structure, turns over soil, limits how much it gets disturbed;

Why is erosion dangerous?

Losing topsoil makes soil less fertile and less able to hold water, which causes resulting sediment to clog irrigation ditches, boat channels, reservoirs, and lakes. Also, if topsoils erodes faster than it forms on a piece of land, the soil there becomes a nonrenewable resource. It also poses a problem to farmers because farmers need arable land for crop yield success.

What contributes to soil erosion?

Natural forces of nature, such as the longterm wearing down of mountains and building up of plains of deltas due to the combined action of physical, chemical and biological factors; however, farming, logging, construction, overgrazing by livestock, off-road vehicles, deliberate burning of vegetation can also leave soil more vulnerable to erosion. Other human-inflicted causes of soil erosion include: slash and burn agriculture, urbanization, over-cultivation of agricultural fields.

What pH range does soil fall under?

Neutral to slightly acidic--4-8 (0-14 scale).

Identify the soil layers in order from uppermost to bottommost.

O horizon, A horizon, E horizon, B horizon, C horizon, and R horizon. (Only Ants Eat Bread Crumbs, Right)

Identify and describe the O horizon.

Organic layer; Primarily made of organic material such as waste from organisms, the bodies of decomposing organisms and live organisms. This layer also includes "humus," or dark, crumbly material that results from the decomposition of organic material forms.

Identify and describe the C horizon.

Parent layer; encompasses large pieces of rock that have not undergone much weathering; bottom-most layer of soil.

Describe characteristics of silt.

Particles .002-.05 mm in diameter;

Why is overgrazing bad for soil?

Plants need to be in place to hold the soil and compaction enables it to stay in place; crops won't grow if no existing soil is there.

How do you desalinate?

Precipitation, but it takes thousands of years in arid/semiarid areas where irrigation is used. One can also flush salts out by applying much more irrigation water than needed for crop growth; however, it increases pumping, and crop production costs, and wastes enormous amounts of water.

What happens in conservation tillage farming?

Promotes disturbing the soil as little as possible while planting crops. In min-till. farming special tillers break up or loosen subsurface soil without turning over topsoil, previous crop residues or any vegetation. Non-till. farming works by having special planting machines inject seeds, fertilizers, and weed killers into slits made in the unplowed soil.

Describe contour farming, and discuss the benefits.

Reduces soil erosion by 30-50% but on gently sloping land; one plows and plants crops in rows across, rather than up and down the sloped contour of the land; Each row planted along the contour acts as a dam.

What are the benefits to terracing?

Reduces soil erosion on steep slopes; retains water for crops at each level and reduces soil erosion by controlling runoff; in areas with higher precipitation, diversion ditches have to be built behind each terrace to permit adequate drainage.

Describe strip cropping and discuss the benefits.

Reduces soil erosion; a row crop such as corn alternates in strips with another crop that completely covers the soil and thus reduces erosion; the strips that covers crops traps soil and reduces water runoff and helps prevent the spread of pests and plant diseases.

How is conservation tillage farming effective?

Saves fuel costs; cuts costs, holds more water in the soil, keeps soil from getting packed down and allows more crops to be grown during a season.

Identify and describe the three types of water erosion.

Sheet erosion, hill erosion and gully erosion; Sheet erosion happens when surface water moves down a slope or across a field in a wide flow and peels off relatively uniform sheets or layers of soil. Hill erosion occurs when the surface water forms fast-flowing little rivulets that cut small channels in the soil; Gully erosion occurs when rivulets of fast-flowing water join together and with each succeeding rain the channels get wider and deeper until they become ditches or gullies.

Identify and describe clay.

Smallest particles; particles are less than .002 mm in diameter; Can easily adhere to each other and there is little room between particles for aeration or workability.

What are the harmful effects of salinization?

Stunts crop growth, lowers crop yields, and eventually kills crop plants and ruins the land.

Identify and describe the B horizon.

Subsoil layer; receives all of the minerals that are leached out of the A horizon, also known as organic materials that are washed down from the topsoil above; Zone of illuviation (through infiltration) meaning the movement of dissolved material from higher to lower soil layers through infiltration caused by gravity.

Identify and describe the E horizon.

This is known as the elluvial layer; leached of clay, iron, aluminum oxides; minerals in this layer are sand/silt sized.

Identify and describe the A horizon.

This is the topsoil layer; made of weathered rock and some organic material that travels from the O horizon; pertinent to plant growth and is known as the zone of leaching.

Describe the benefits of green manure.

Tree and shrub trimmings can be used as mulch; green manure used for the crops, or as fodder for livestock.

How is soil produced?

Weathering of rocks, sediments deposited by erosion, and by the decomposition of organic matter in dead organisms.

How does water-logging occur? What is one effect?

When farmers apply large amounts of irrigation water to leach salts deeper into the soil; without adequate draining, water accumulates underground causing the water table to rise; saline water envelops deep roots of plant and kills them as a result. Can also lead to the increase of hydrophilic plants (water-loving plants) through the process of natural selection.

How does salinization occur?

When irrigation water not absorbed into the soil evaporates, leaving behind a thin crust of dissolved salts in the top soil, in which the accumulation of these salts over time leads to salinization.

What are the two main agents of soil erosion?

Wind and water.

Describe characteristics of sand.

coarse soil structure; particles .05-2 mm in diameter. Sand particles are too large to easily stick together, and have more porosity which allows for more permeability for water to pass through or be held onto.

What are two drawbacks to losing topsoil?

makes soil less fertile and less able to hold water which causes resulting sediment to clog reservoirs, lakes, etc.; If topsoil erodes faster than it can reform on a piece of land the soil there becomes a nonrenewable resource.

How is animal waste used as a means of soil conservation.

uses compost in the soil to increase the amount of organic matter in the soil which slows down the effects of wind and reduces the amount of damage done to the soil by tillage plowing.