CHAPTER 13

Question 1

perform functions that contribute to
the soil’s development,structure and productivity.

Answer 1

Soil biota

Question 2

_____ act on the soil environment by aiding in
structure and porosity.

Answer 2

Plants (soil flora)

Question 3

act to stabilize soil through aggregation
and intact root systems can decrease soil loss.

Answer 3

Roots

Question 4

the narrow zone of soil directly
surrounding plant roots, is the most biologically active
region of the soil.

Answer 4

Rhizosphere

Question 5

It contains sloughed root cells and secreted
chemicals (i.e., sugars, organic acids) that provide
organisms with food

Answer 5

Rhizosphere

Question 6

______ work as soil engineers, initiating the
breakdown of dead plant and animal material, ingesting
and processing large amounts of soil, burrowing
‘biopores’ for water and air movement, mixing soil
layers, and increasing aggregation.

Answer 6

Soil fauna

Question 7

Important soil fauna include (5)

Answer 7

earthworms, insects,
nematodes, arthropods and rodents.

Question 8

considered one of the most important soil
fauna.

Answer 8

Earthworms

Question 9

Through the process of _______, earthworms provide channels
that increase the soil’s porosity, and water infiltration.

Answer 9

burrowing

Question 10

earthworms are
able to build soil by moving
between ________ tons of subsoil
per ______ to the surface,
possibly helping offset losses by
erosion.

Answer 10

1 to 100

acre per year

Question 11

This shows
what a healthy soil needs in
the way of soil life

Answer 11

Soil food web

Question 12

Soil food web ranges from (5)

Answer 12

worms,
springtails, moles to fungi
and bacteria.

Question 13

If concentrated on
nutrition for the plant, the
______ & ______ in
particular are responsible for
releasing and dissolving the
absorbable minerals for the
plant.

Answer 13

bacteria and fungi

Question 14

are an important fraction of the soil.

Answer 14

Living organisms

Question 15

True or false

In a healthy soil, the domestic animal weight above the
ground surface is substantially exceeded by the weight of
the organisms living in the soil.

Answer 15

True

Question 16

are invisible to the naked eye.

Answer 16

Microorganisms ( microbes)

Question 17

Microbes aid soil structure by physically surrounding
particles and ‘gluing’ them together through the
secretion of organic compounds, mainly ____.

Answer 17

sugars

Question 18

Soil microbes includes (5)

Answer 18

bacteria, protozoa, algae,
fungi and actinomycetes.

Question 19

are the smallest and most diverse soil microbes.

Answer 19

Bacteria

Question 20

the nitrogen-fixing bacteria associated with
legume roots.

Answer 20

Rhizobia

Question 21

are mobile
organisms that feed on other microbes and OM.

Answer 21

Protozoa

Question 22

A soil microbe, like plants, photosynthesize and are found near the
soil surface.

Answer 22

Algae

Question 23

are a diverse group of microbes that are extremely
important in the breakdown of OM and large aggregate
stability.

Answer 23

Fungi

Question 24

An important relationship found in almost all soils
and plants, including many crop species, are ___

Answer 24

Mycorrhizae

Question 25

are a plant-fungal symbiosis (a
relationship between two interacting species) in which
fungi infect and live in, or on, a plant root.

Answer 25

Mycorrhizae

Question 26

is anything that is living or the remains
of a living thing.

Answer 26

Organic matter

Question 27

is a build-up in the soil of decayed plant and
animal residues.

Answer 27

Organic matter

Question 28

contain from 20% to as
much as 95% organic matter.

Answer 28

Peats

Question 29

contain anywhere from a trace to 15% or
20% organic matter.

Answer 29

Mineral soils

Question 30

is composed of about 57% organic
carbon.

Answer 30

Organic matter

Question 31

Organic matter is composed of about ____ organic
carbon.

Answer 31

57%

Question 32

The benefits of organic matter in the soil include
….

Answer 32

improving soil structure and increasing the nutrient and
water holding capacity of the soil.

Question 33

Soils with ______ ____ _____ can have ‘poor’ structure,
hold little water, and erode or leach nutrients easily

Answer 33

low organic matter

Question 34

Soils with ____ levels have ‘good’
structure, good water-holding capacity, and reduced
erosion and nutrient leaching.

Answer 34

high organic matter

Question 35

ꞝWhen the organic matter is fully broken down, one of
the things that is left is ___.

Answer 35

humus

Question 36

True or false

Humus has some useful qualities in that it adsorbs
nutrients, adsorbs much higher quantities of water than
clay pan, and improves soil structure due to its low
plasticity and good cohesion.

Answer 36

True

Question 37

is one of the companies that develops
products that do not harm soil life

Answer 37

N-xt Fertilizers

Question 38

Everything in nature has a ___ ratio

Answer 38

carbon-nitrogen

Question 39

Carbon-nitrogen ratio
which ensures that the ___&___

Answer 39

soil food web continuously
cycles and releases nitrogen.

Question 40

, are major limiting factors for soil organism
activity.

Answer 40

Residue and OM quantity and quality, primarily nitrogen
(N) content

Question 41

Management practices can affect soil organism activity
through changes in ___&____, cropping
systems, and inputs.

Answer 41

aeration and structure

Question 42

____ also tend to increase with
practices that increase OM levels and minimize soil
disturbances.

Answer 42

Earthworm populations

Question 43

_____ may support more organism
diversity and activity than monoculture systems due to
increased and more diverse residues and specific
interactions occurring between certain plants and
organisms

Answer 43

Crop rotation systems

Question 44

can also influence soil
organism populations and activity.

Answer 44

Fertilizer application

Question 45

___ activity in soils with low fertility or OM
content will likely increase with the addition of
fertilizers, particularly those containing N; populations
will eventually stabilize as N is consumed.

Answer 45

Biotic