MORE ABOUT SOILS

toiletquietInternet and Web Development

Dec 5, 2013 (3 years and 10 months ago)

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MORE ABOUT SOILS


September 11, 2013

&

September 18, 2013

Web Soil Survey


http
://websoilsurvey.nrcs.usda.gov/app/



Uses:


General management decisions


Land use decisions


Required for Concentrated Animal Feeding Operations
(CAFO) siting


Soil Survey:


S
oil map for a land area
plus
soil descriptions
plus

predicted use and limitations

Soil limitations for a CAFO (example
)


H
igh
seasonal water table


Slow
permeability


Low
bearing strength


High
shrink/swell capacity


Corrosive
to metal and concrete


Creating a Soil Survey

Soil Properties


Horizons


Color


Texture


S
tructure


O
ther physical, chemical and
mineralogical characteristics

Landscape Features


Vegetation


Rocks


Slopes


Streams


Drainage
-
ways


Lakes


roads,


Dams


Gravel pits


Soil Scientists compare
and classify
soils, analyze how the
soils will support different uses, and plot the soil location on
aerial
photographs.

SoilWeb



WSS App


N
ew, free
smartphone
App
(http://
casoilresource.lawr.ucdavis.edu/drupal/node/902)


Gives users access
soil survey
information on iPhones
and
Androids


Combines
online soil survey information with the GPS
capabilities of
smartphones


Particularly
useful for those working in the
field


Soil Testing After a Dry Growing Season


Yield
is the most important factor impacting P and K removal
rates


Corn and soybean return
about 1/4
to
1/3
of the total
P,
and
about
2/3
of the total
K,
to the soil


Grain
yields and nutrient removal levels are lower than
normal
after a drought


But, do not assume
that lower removal rates and lower
yields will result in greater P and K levels in the soil
next
year


Soil
testing for P, K, and pH should be used to determine the
need for fertilization or lime
applications

Soil Testing


Certified
commercial laboratories offer plant and soil
testing analysis services for growers in
Indiana


Purdue Agronomy list:
www.ag.purdue.edu/agry/extension/Pages/soil
-
testing
-
labs.aspx


Biology of Soil Compaction


Soil
compaction: soil
particles are pressed together,
limiting the space for air and
water


Soil compaction can reduce farm yields (and profits)


Factors that contribute to compaction:


Farm machinery weight and traffic


Rain, especially heavy rains


Tillage


Low organic matter (OM)
(makes
soil more susceptible to
compaction)

Biology of Soil Compaction


Soil compaction causes:


Restricted root growth


Poor root zone aeration


Poor drainage, which causes



Reduced oxygen in the root zone


Increased loss of nitrogen

Soil Compaction


Sub
-
soil tillage to break up a compacted layer


Used to reduce compaction and related problems
(lack of water infiltration and aeration)


Soil is generally disturbed 12
-
18 inches deep


Expensive, requires: fuel
, labor, equipment and
time


Note: additional compaction can occur if the soil is
sub
-
soiled when wet

Soil
Compaction

Sub
-
soiling


Usually helps,
but effects are often temporary unless
management
changes



Re
-
compaction of
soil is caused by the same forces that
cause compaction in the first place:


E
quipment traffic


Rainfall (especially heavy rains)


Gravity


Low organic matter (OM)

Organic Matter
& Soil Compaction


Organic residues on the soil surface cushion
the soil from compaction because they can be
compressed and regain their shape


OM that is attached to soil particles (esp. clay)
reduces soil compacting


OM binds microaggregates and
macroaggregates in soil (macroaggreates
improve soil tilth)


Excessive
traffic
breaks
up organic
residues

Soil Carbon


Tillage has decreased soil organic levels, and therefore,
soil organic carbon by 60% in the last hundred years


Carbon provides energy for soil microbes, stores
nutrients, and recycles nutrients in the soil


Types: active carbon and humus


Humus (old carbon, >1,000 years old) is the most stable
carbon


Humus


Binds soil
microparticles

together to form
microaggregates


Not
water soluble


Not
readily consumed by microorganisms


More resistant to tillage and degradation
than active
carbon

Active Carbon


Plant sugars, polysaccharides, and glomalin


Consumed by microbes for energy


Reduced with tillage


Stabilized under natural vegetation and no
-
till
systems using a continuous living cover


Part of the “glue” that binds microaggregates into
macroaggregates


Macroaggregation

improves soil structure and
lowers bulk density, helping to keep soils from
compacting

Soil Clods


Clods are made by humans


Clods do not exist in the natural world


Tilling exposes clay to sunlight, heating and
drying which forms clods (as bricks and clay tile
are formed by heating and drying wet clay)


Moisture and organic residues keep clay particles from
chemically binding by keeping clay particles physically
apart

Soil Cover & No
-
Till

A continuous living soil cover plus continuous long
-
term no
-
till protects the soil from compaction, because:

1.
Covered soil surface acts like a sponge to help
absorb the weight of heavy equipment traffic

2.
Plant roots create voids and macropores in the soil
that allow air and water movement

3.
Plant roots supply food for microorganisms (esp.
fungi)

4.
Organic residues (from decaying plants, animals,
microbes) are lighter and less dense

5.
Aids in combining microaggregates into
macroaggregates which improves soil structure



Soil
Type
&
No
-
Till


No
-
Till works well on forest soils (historically) No
-
Till may
not work as well on flat
black prairie soils


They tend
to stay wetter and cooler in the spring when
covered with heavy no
-
till
residue


Highly
productive
soils may have residue from
225
bushel corn
which acts like
a
blanket:
good to prevent
erosion
but will have a buffering
effect (warming or
drying
)


Where are these soils?


I
SEE
website
/
Bedrock Geology and Soil Properties/Dominant
Soil Parent Material




Ways to Evaluate & Avoid Compaction


The
amount of soil water present is a critical factor in soil
compaction potential.


S
pring is the
best time of the year
to measure soil
compaction when
the whole profile has usually been
thoroughly moistened during the winter.


If
the soil is too wet and muddy, compaction could be
underestimated because the soil water acts as a lubricant.


If
the soil is too dry, compaction could be overestimated
because roots will be able to penetrate the soil when it re
-
wets.


Ways to
Evaluate &
Avoid Compaction

Checking for soil compaction


Shovel


look for surface crust or platy soil
structure


Soil probe


insert slowly, feeling for increased
resistance


Soil
pentrometer



push in (1 inch/sec.);
resistance > 250
-
300 psi in moist soil is root
-
limiting

Shallow Soil
Compaction


Related
to pressure on the soil surface


Normally removed by tillage operations


May be removed by freeze
-
thaw and wet
-
dry
cycles


Control:


Better
load distribution (larger tire size or more
tires
)


GPS can help maintain controlled traffic

Sub
-
surface Compaction


Related to maximum axle load


Will not be reduced by distributing equipment
weight


Can only be avoided by limiting traffic with
heavy axle loads


A maximum axle load of 10 tons is
recommended (Note: a 1,000
-
bu grain cart can
weigh more than 36 tons)


Low
-
inflation tires with a large footprint may
help (
use minimum allowable tire pressure)

Sidewall Compaction


Caused by planting when soil is too wet


Planter openers push on the side of the soil
furrow, creating a compacted zone


Avoid by not planting when the soil is too wet*


Spoke wheel seed slot closers can be helpful




*Testing for moisture content


how?

Fall
-
Planted Cover Crops


Provide support for livestock and/or manure
spreaders over winter


Plant cover
crops right after harvest of annual
crops to keep living roots in the soil
year
-
round

“Living root systems are probably the best protection
against compaction.”

“Avoiding compaction is a lot more cost
-
effective than
causing it and then having to repair it
.”


Dr. Duiker, Penn State soil mgmt. specialist

The Basics of Soil Compaction

1.
Use no
-
till to help your soil resist and bounce back
from compaction


Increased
organic matter accumulation at the soil
surface


Permanent
burrows of old root channels and
prolific activity of earthworms and fungi in
permanent no
-
till fields also helps make the soil
resist
compaction


Biological
organisms also help alleviate
compaction after it has been
caused

2.
Avoid causing compaction

3.
Remediate compaction only if needed

No
-
till Challenge


Herbicides
were developed
for
weed
control (conventional
tillage)


Highly effective herbicides and herbicide
-
resistant crops (e.g.,
glyphosate) allowed the development of conservation
tillage
and
less soil damage


When any single herbicide mechanism is used repeatedly
without alternative management, selection pressure
becomes intense for plants that can tolerate the herbicide


Several weed
species
exhibit resistance to glyphosate
and many are resistant to other herbicide mechanisms

Herbicide
-
resistant Weeds Threaten Soil Conservation
Gains
, CAST
paper, Feb. 6, 2012 (CAST ~ Council
for Ag Science and
Technology,
www.cast
-
science.org
/)


CAST Recommendations

Mitigating the impact of herbicide
-
resistant weeds
(use a diversity of strategies):


Alternative tillage, including mechanical


Alternative herbicides


Crop rotation (depending on the crops and
management practices used)

In Class Assignment


Work in teams of 2 (assigned):


Reader


Recorder


Read:
On
-
Farm Soil Monitoring for Water Resource
Protection
(WQ
-
43)


Answer the questions


Hand
in before leaving today




Reminder


Lab 3
on Friday