CHAPTER 13 Flashcards
perform functions that contribute to
the soil’s development,structure and productivity.
Soil biota
_____ act on the soil environment by aiding in
structure and porosity.
Plants (soil flora)
act to stabilize soil through aggregation
and intact root systems can decrease soil loss.
Roots
the narrow zone of soil directly
surrounding plant roots, is the most biologically active
region of the soil.
Rhizosphere
It contains sloughed root cells and secreted
chemicals (i.e., sugars, organic acids) that provide
organisms with food
Rhizosphere
______ 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.
Soil fauna
Important soil fauna include (5)
earthworms, insects,
nematodes, arthropods and rodents.
considered one of the most important soil
fauna.
Earthworms
Through the process of _______, earthworms provide channels
that increase the soil’s porosity, and water infiltration.
burrowing
earthworms are
able to build soil by moving
between ________ tons of subsoil
per ______ to the surface,
possibly helping offset losses by
erosion.
1 to 100
acre per year
This shows
what a healthy soil needs in
the way of soil life
Soil food web
Soil food web ranges from (5)
worms,
springtails, moles to fungi
and bacteria.
If concentrated on
nutrition for the plant, the
______ & ______ in
particular are responsible for
releasing and dissolving the
absorbable minerals for the
plant.
bacteria and fungi
are an important fraction of the soil.
Living organisms
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.
True
are invisible to the naked eye.
Microorganisms ( microbes)
Microbes aid soil structure by physically surrounding
particles and ‘gluing’ them together through the
secretion of organic compounds, mainly ____.
sugars
Soil microbes includes (5)
bacteria, protozoa, algae,
fungi and actinomycetes.
are the smallest and most diverse soil microbes.
Bacteria
the nitrogen-fixing bacteria associated with
legume roots.
Rhizobia
are mobile
organisms that feed on other microbes and OM.
Protozoa
A soil microbe, like plants, photosynthesize and are found near the
soil surface.
Algae
are a diverse group of microbes that are extremely
important in the breakdown of OM and large aggregate
stability.
Fungi
An important relationship found in almost all soils
and plants, including many crop species, are ___
Mycorrhizae
are a plant-fungal symbiosis (a
relationship between two interacting species) in which
fungi infect and live in, or on, a plant root.
Mycorrhizae
is anything that is living or the remains
of a living thing.
Organic matter
is a build-up in the soil of decayed plant and
animal residues.
Organic matter
contain from 20% to as
much as 95% organic matter.
Peats
contain anywhere from a trace to 15% or
20% organic matter.
Mineral soils
is composed of about 57% organic
carbon.
Organic matter
Organic matter is composed of about ____ organic
carbon.
57%
The benefits of organic matter in the soil include
….
improving soil structure and increasing the nutrient and
water holding capacity of the soil.
Soils with ______ ____ _____ can have ‘poor’ structure,
hold little water, and erode or leach nutrients easily
low organic matter
Soils with ____ levels have ‘good’
structure, good water-holding capacity, and reduced
erosion and nutrient leaching.
high organic matter
ꞝWhen the organic matter is fully broken down, one of
the things that is left is ___.
humus
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.
True
is one of the companies that develops
products that do not harm soil life
N-xt Fertilizers
Everything in nature has a ___ ratio
carbon-nitrogen
Carbon-nitrogen ratio
which ensures that the ___&___
soil food web continuously
cycles and releases nitrogen.
, are major limiting factors for soil organism
activity.
Residue and OM quantity and quality, primarily nitrogen
(N) content
Management practices can affect soil organism activity
through changes in ___&____, cropping
systems, and inputs.
aeration and structure
____ also tend to increase with
practices that increase OM levels and minimize soil
disturbances.
Earthworm populations
_____ 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
Crop rotation systems
can also influence soil
organism populations and activity.
Fertilizer application
___ 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.
Biotic
