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Level 154

Organics IV

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All components affect soil structure & properties but the least chemically complex molecules contribute
most to the soil community in terms of available energy & nutrients because they are most accessible and easily decomposed
varies over time (days to centuries)
Breakdown, retention & release of nutrients from SOM types and components
Particulate Organic Matter
pom thought to be
themost available portion of SOM
pom represents
10 % of active SOM pool
plant- derived material (plant tissue, fungal spores & hyphae, charcoal)
Earthworms are the
Predominant group of soil invertebrates in most soils
what soil layers do earthworms inhabit
Diff. species inhabit diff. soil layers
how much orgsnic matter do earthworms consume
Consume 2-30x their own weight in soil & SOM/day
earthworms gains nutrients from
from soil: bacteria & fungi
1)sticky, nutrients & microbial inoculations from warm 2) redistribute SOM
Casts = what it does to soil and what is it?
earthworms help the soil by doing what?
altering soil structure(aggregation, porosity), mixing the soils making it more diverse
Aggregates What are they? what are they defined by
The arrangement or structure of soil particles held in a single mass or cluster. Aggregates are defined by their shape, size & distinctness.
energy is treated like a
fertlizer orgsnic matter and soil particle =
multipple aggregates=
soil structure
comprised of fine sand grains,small silt grains, clay, organic debris bound by root hairs, fungal
Macro-aggregate =
compromised of many micro-aggregates bound together by sticky network of fungal hyphae & fine
what influence the formation of aggregates
Both biological & physical- chemical (abiotic) processes
One reason aggregates are desirable because their
presence leads to more macropores =better soil structure
Retain :
How do we create aggregates and/or retain them?
Why do we till?
Loosen the surface soil
Negative effects of tillage
Increases soil compaction
compaction over time? via?
via bulk density measurements
Bulk density
the mass of a unit volume of
Bulk density measurements is an
indirect measure of soil pore space, with changes with more aggregation, by measuring the solids
How to measure soil bulk density?
weight of oven dry soil/ volume of soil
1.0-2.0 g/cm3
Generally mineral soils have a bulk density of
indulgent items meat beer wine cheese
1st, Whole Foods Market opened in 1980 in TX. Concept: lg., natural-foods store that included
lower bulk density =
lower weight more pore space
higher bulk density
less pore space
List the ways that plants rely on soil.
physical support ,gas exchange, water retention and filtering , temperature moderation, protection from toxins and nutrient supply
parent material, climate,biology, topography ,time
What factors influence soil development and inherent soil properties?
o, a
Which layers of the soil horizon typically comprise the plow layer?
air 20-30 percent water 20-30 percent mineral 45 percent and organic material 5 percent
In an average soil sample, what is the % mineral fraction, organic matter, air and water?
...sand silt clay
What are the 3 particle sizes in soil that comprise soil texture and influence pore space size?
What comprises soil organic matter (SOM)?
... biotic organisms that breakdown :plants, insects ,animals microbes and fungi
utisols low ph , yellow orange due to irox oxide. weathered
What is the dominate soil order in GA & the SE? Describe its main characteristics.
Where can one find information about soils in their area?
...county soil surveys , uga soil testng handbook, soil analysis
... start with left
Know how to read a soil texture triangle.
sandy soil: quick Clayey soil : slow
compare the drainage rate of a sandy soil with a clayey soil.
Define CEC.
# of moles of positive charge absorbed per unit mass
...Negative charges on soil surface
What is the predominate type of charge associated with the surface area of clay particles or organic matter?
clay soil has high cec
Which type of soil (sandy or clay) typically has a higher CEC?
Why do we add lime to soil?
1)change chemical make up of root zone
...lime: calcium carbonate caco3
What is the difference between regular agric. lime and dolomitic lime?
What is a symptom of low pH or aluminum toxicity in plants?
low ph: poor plant growth, inability of soil microorganisms to function, stunted root growth,
bacteria , fungi,actinomycetes
What are the 3 most prevalent (#'s) types of organisms living in a typical tablespoon of soil?
...plants: primary producers
22) What forms the basis of the soil food web?
Describe the rhizosphere.
...zone of chemical, biological and physical inffluence generated by root growth and actively about 5 mm in width: zone in which plant root interacts with the surrounding soil
What are plant residues? Give 2 examples of source material.
Residues are plant tissues left behind and/or donated to the soil system
Why are plant residues desirable in an agric. system?
... control erosion, source of organic matter back into soil
...different compostitions decompose at different rates
Why don't plant residues break down at an even rate?
1)Living organisms
What comprises SOM?
name a few practices that encourage aggregate formation? Same for aggregate destruction.
Loosen the surface soil
What are the pros- and cons- of tillage?
no-till system machine what it does
roller- crimp plants - no till system
limit root growth
Why is soil compaction detrimental?
measure bulk density over time
What is one way to assess potential soil compaction over time?
...South east: hot humid temperate regions, old landscap
How does the SE compare to the Mid-west region in terms of inherent SOM content? Why?
crop with a high nitrogen requirement
after planting a legume crop plant a
nitrogen fixing crops belong to the _______ family
which life stage of the lady bird beetle eats most aphids
use of allopathic crops may result in
weed suppression ,reassessment of crop rotation plan, nematode suppression , damage to sensitive crops
considerations for plant cultivar choice =
1)market preference 2)extension or farmer network recommendations 3)disease resistance 4)hardiness zone
1)adequate moisture,
what conditions are needed for mushroom logs to fruit
adalia is parastic or predator ?
aphidius is parastic or predator?
Current log weight=
fresh weight/ codw
organic foods production act
(large amorphous mixture of complex organic substances no longer identifiable as tissues)
moldboard, turning and mixing of soil
Describe an aggressive tillage action and what machine does it
less aggressive tillage action
anisel plow- ripper and break soil
mucigel define
a sticky substance comprised of sugars, organic acids, vitamins, enzymes & amino acids