Plant Science: Chp. 5

Front 1

Soils differ around the world, but they are basically composed of ___

Back 1

Weathered rock, air, water, decomposed organic material, and various organisms

Front 2

Soils consists of 4 components. List each component and define/describe each.

Back 2

1. A solid fraction; that is, rock fragments and minerals

2. An organic fraction; the decayed and decaying residues of plants, microbes, and soil animals

3. A liquid fraction; including water and dissolved minerals

4. A soil atmosphere or soil air

Front 3

___ is the open (nonsolid) portion of soil that holds air or water

Back 3

Pore space

Front 4

A productive soil has ___

Back 4

50% pores that will drain water quickly after a thorough watering and 50% that hold water through capillary forces

Front 5

___ is the percentage of water remaining in a soil two or three days after having been saturated and after free drainage due to gravity has practically ceased

Back 5

Field capacity

Front 6

List, describe, and give examples of the three types of rocks

___- firmed from the hardening of various kinds of molten rock material and are composed of minerals such as quartz and feldspar

___-unconsolidated and composed of rock fragments that have been transported and deposited by wind, water, or glaciers. Limestone, sandstone, and shale are examples

___-from from igneous or sedimentary rocks that have been subjected to sufficiently high pressures and temperatures to change their structure and composition. Slate, gneiss, schist, and marble are examples

Back 6

Igneous rocks

Sedimentary rocks

Metamorphic rocks

Front 7

Soil is derived from ___

Back 7

Rocks, minerals, and decaying organic matter

Front 8

Physical weathering is also caused by moving water, as in ___

Back 8

Stream erosion, sheet erosion, rill erosion, or wave action

Front 9

Give an example of how plant roots can physically break down parent rocks?

Back 9

A tree root growing into a crack in a rock can ultimately fracture the rock

Front 10

Chemical weathering entails four distinct processes. What are they?

Back 10

Dissolution

Hydration

Hydrolysis

Oxidation

Front 11

Dissolution is the process by which the constituents of parent material dissolve in __ or weak, naturally occurring __ and are leached away

Back 11

Water

Acids

Front 12

Hydration adds molecular water to another compound to form a hydrated material more vulnerable to ___

Back 12

Pulverization

Front 13

Hydrolysis is the reaction between a compound and water to form a more ___

Back 13

Soluble product

Front 14

Oxidation reactions form ___ by reaction with oxygen

Back 14

Parent material

Front 15

Land can be desalinated by flooding with water and ___ downward through the soil profile

Back 15

Leaching the salts

Front 16

What are the three functions of roots?

Back 16

They support and anchor the plant stem

They absorb water and nutrients

They provide storage for food reserves

Front 17

What is the most abundant soil organism?

Back 17

Bacteria

Front 18

The two major processes in soil formation are ___

Back 18

Accumulation

Transformation of the parent material

Front 19

Many soil organisms are involved in ___ in soil organic matter

Back 19

Decomposition and recycling of nutrients

Front 20

The roots of nearly all plants in the wild are associated with mycorrhiza which are ___

Back 20

Fungi that assist in plant uptake of nutrients and water

Front 21

Soil animals include ___

Back 21

Nematodes, mollusks (slugs and snails), annelids (including earthworms), and arthropods (mites, insects, millipedes, spiders)

Front 22

The nonliving organic components of the soil are ___

Back 22

Residues of plants and animals

Front 23

Vegetation aids soil formation by supplying organic matter in the form of ___ and ___

Back 23

Dying and decomposing plants

Front 24

____ is caused by interactions between biological and chemical agents reacting with parent material over long periods of time differentiate the soil into horizons

Back 24

Soil horizons

Front 25

Soils without well-developed horizons are classified as ___, even though the parent material ___

Back 25

Young soils

May have been present for a great many centuries

Front 26

Name and describe the three soil horizons:

___ Zone of greatest biological activity. Varies in depth and contains most of the plant roots. This leached zone often lacks some important mineral nutrients, but it does contain the largest amount of organic matter

___ Zone of accumulation. Plant nutrients, salts, clays, and other materials from the upper layer are leached into and accumulate in this horizon

___ Consists of unweathered to slightly weathered material from which the A and B horizons are formed. Can also include accumulated calcium carbonates or other salts

Back 26

A horizon

B horizon

C horizon

Front 27

___ is a soil component derived from the natural breakdown of rocks by physical and chemical forces

Back 27

Parent material

Front 28

A ___ is a distinct layer of soil having ___ differences resulting from soil-forming processes as seen in vertical cross-section

Back 28

Horizon

Physical and/or chemical

Front 29

___ are distinct layers of soil that develop over time from the weathering of parent material, biological activity, and other factors

Back 29

Soil profile

Front 30

What factors are responsible for soil formation?

Back 30

Parent material

Climate

Biology

Topography

Time

Front 31

The first step in the development of soil is the formation and accumulation of material by chemical and physical weathering of ___

Back 31

Parent rocks

Front 32

___ is the physical breakdown of large pieces of rock into smaller and smaller pieces

Back 32

Physical weathering

Front 33

___ is the peeling of the outer layers of rocks caused by differential rates of contraction and expansion that in turn are caused by temperature changes

Back 33

Exfoliation

Front 34

___ is a product of glacial weathering in which rock particles varying in size from clay to boulders are deposited by the glacier on the land surface as it melts and recedes

Back 34

Glacial till

Front 35

___ is defined as the percentage of sand, silt, and clay particles in a soil

Back 35

Soil texture

Front 36

A relationship between two dissimilar organisms living together for mutual benefit is called ___

Back 36

Symbiosis

Front 37

___ is a Genus of bacteria that live symbiotically in the roots of legumes and fix nitrogen that is used by plants

Back 37

Rhizobium

Front 38

___ is the more or less stable fraction of the soil organic matter remaining after the major portion of plant and animal residues have decomposed

Back 38

Humus

Front 39

The ___ ratio is nearly constant at about ___ of Carbon to ___ nitrogen, worldwide

Back 39

Carbon:nitrogen (C:N)

12 parts

One part

Front 40

Accelerated erosion removes soil ___ reducing the depth of the ___

Back 40

Faster than new soil can be formed

Productive topsoil

Front 41

Soil fragments vary in size from course rock fragments ___ to those so small ___ that an electron microscope is needed to observe them

Back 41

(>2 mm)

0.002 mm

Front 42

The distribution of different particle sizes determines the ability of soils to ____

Back 42

Hold and transmit water

Front 43

Soil with a high percentage of sand ___ retaining little for plant use

Back 43

Loses water quickly

Front 44

In soils largely composed of very fine clay particles, movement of both air and water can be ___

Back 44

Limited

Front 45

What soil mixture produces a loam soil?

Back 45

40% sand, 40% silt, 20% clay

Front 46

Loams are usually excellent soils for ___

Back 46

Crop production

Front 47

Most plants do not grow well in ___ or ___ soils

Back 47

Highly acidic

Highly alkaline

Front 48

Most plants will grow in the pH range of ___

Back 48

5 to 7

Front 49

___ is the ability of some soil components to resist a change in soil pH

Back 49

Buffering