Basic soil improvement
description
Transcript of Basic soil improvement
Dr. Joel GruverSchool of Agriculture
Western Illinois University(309) 298 – 1215
Basic Soil Improvement Techniquesfor Sustainable Farmers
Useful Resources
http://www.sare.org/publications/soils.htm
Managing cover crops profitably, 3rd edition
http://www.sare.org/publications/handbooks.htm
Free downloads
http://soils.usda.gov/sqi/concepts/soil_biology/biology.html
NRCS SOIL BIOLOGY PRIMER
Excellent comprehensive soil science textbook
> $100
< $10
Are you familiar with the “disease
triangle”?
Which factor do you think is
most important?
Do you think agroecologically?
Managing crop residues
Continuous tomatoes
All of these strategies are being used successfully by some farmers/gardeners. Only you can
determine the best fit for you.
Growing under cover may be the most effective organic
strategy for improving crop health and productivity
Have any of you visited Monticello ?
Jefferson made good use of microclimates
Thomas
Jefferson
Garden in
Gruverland
Inspired by Monticello, my family decided to make better use of microclimates
Understanding the soil environment
Sand and silt
are the bones of the
soil skeleton
http://www.ecogrowth.com.au/soil.htm
Soil skeletons
Clay and humus are the soil skin
and connective tissues
humusclay minerals
http://www.ccma.csic.es/dpts/suelos/Brady and Weil (2002)
Why is the soil skin important ?
Adsorption of water films
Adsorption of organic and
inorganic chemicals
Ion exchange
Catalysis of chemical reactions
Habitat for bacteria
Get to
know your
soil’s body
parts !
The jar test
TEXTURE BY FEEL
Textural
triangle
12
textural
classes
http://www.oneplan.org/Images/soilMst/SoilTriangle.gif
Loamy soils
Loamy soils have the most favorable physical properties
Potting media criteria
High moisture retention and rapid drainage
It can be difficult to optimize both
moisture retention and drainage in
real soils
It is rarely cost effective for farmers to change the texture or other inherent properties of
the soils on their farms
≠
Understanding inherent differences in soil properties
WEB SOIL SURVEY- a great source of info on soil inherent properties
What are these
crazy people
trying to do ?
Location:
Laurenburg, NC
Date: 1961
Very deep plowing as part of a futile effort to create deep “Prairie” soils in North Carolina
http://www.grdc.com.au/growers/gc/gc48/conference1.htm
The soil fabric
Good Tilth Poor Tilth
The soil pore
network serves
as a respiratory
and circulatory
system
http://www.mtm.kuleuven.ac.be/Research/NDT/IDO_SHerman_final.ppt
Field Capacity
Permanent wilting point
Plant available water
Pore size
10- 30 μm
Drainage pores
Unavailable water
Adapted from Buol (2000)
Easily available
Understanding your soil’s respiratory and
circulatory system
0.2
μm
After adding water1.0% C 1.4% C
Do you scavenge and hoard organic materials from far and wide?
This can be a good soil building strategy but
should not be a permanent strategy in a world with finite organic
resources.
Is it time to reduce your farm’s foot print?
There is a lot more to soil organic matter management than just increasing OM
inputs !!
What is happening on your farm?
accumulate in soil?
Why does
matorganic ter
Most soil microbes are unculturable
..and the soil microbes that are culturablecan digest almost
everything organic at rates hundreds of
times faster than decomposition in field
soils
Understanding organic resource quality
(Giller, 2000)
aka digestibility
C:N ratio > ~ 20
Relationship between fine mineral fraction and SOM
Magdoff and Weil (2004)
Soils with more fine particles
normally retain more SOM
Weak relationship between clay content and SOC for 1261 agricultural soils in England and Wales
Webb et al.(2003)
Clearly many factors other than clay
affect C accumulation
Temperature affects SOM dynamics
Brady and Weil (2002)
Temperature
Organic matter destruction by aerobic organisms
Organic matter synthesis by plants
Org
anic
mat
ter
pro
du
ctio
nO
rgan
ic m
atte
r co
nsu
mp
tio
nO
M p
rod
uct
ion
an
d c
on
sum
pti
on
Your farmin 50 yrs
~ 70 F mean annual temp
Interstream divide
SOIL DRAINAGE CLASSES
Poorly drained
Somewhat poorly drained
Moderately well drained
Poorly drained
Well drained
Interfluve
Valley floorBackslope
Shoulder
LANDSCAPE POSITIONS
Landscape position affects SOM dynamics
Where does the most OM accumulate?
http://www.extension.umn.edu/distribution/cropsystems/components/7402_02.html
Agriculture normally accelerates loss of SOM
OM enriched sediment
OM depleted top soil
Erosion has caused major redistribution of OM
Artificial drainage has greatly increased the number of days when soils are suitable for field operations
but has also contributed
to many environmental
problems
Pollution of water resources Loss of SOM
Adapted from Magdoff and Weil (2003)
47
Identify 2 methods of increasing
SOM.
42
DEPARTMENT of SOIL SCIENCENC STATE UNIVERSITY
(justification statement)
Small increases in OM can
improve macro-aggregation
Superior air/water relationships
Healthier root
growth and function
http://www.arlington.k12.va.us/schools/abingdon/programs/naturalistclub/pic%2012-04/good%20diggin%20shot.JPG
There’s more than one way to collect a soil sample
but results have little value if the sample is not
representative
Composite
sampling
Multiple sub-
samples are
collected from
each management
unit and mixed
together
Recommendations
So what do the numbers mean ???
Analytical results
Have any of you ever had to run a 40
as part of a try-out for a team?
How well does an
athlete’s 40 time
predict their ability
to play the game?
By themselves, extractable nutrient levels are not informative.
Extractable nutrient levels provide an index of nutrient availability that can be interpreted using
results from field experiments.
Meaningful interpretation of soil test results
requires field calibration
100 % yield
50 %yield
http://www.ipm.iastate.edu/ipm/icm/2003/11-17-2003/mehlich3.gif
Soil test P concentration (ppm)
Soil test levels are not directly related to most of the factors controlling nutrient
availability during a growing season.
moisture temperature microbial activity
rooting depth root health
Calibration experiments were not conducted using organic management practices
Understanding nutrient uptake
Transpirational
stream
Ro
ot g
row
th
H20
H20
Root
exudates
activate soil
microbes
http://www.extension.umn.edu/distribution/horticulture/components/M1190fig1.htm
Nutrients that can be easily redistributed
Nutrients that are not easily redistributed
Sampling vegetable crops for tissue analysis
http://www.cahe.nmsu.edu/pubs/_a/a-123.html
http://149.168.222.13/D:/2005/WASTES/Predicti/7000/WAW06343.PDF
Estimated Nutrients available for a single crop
Total nutrient content of DM is adjusted for moisture and availability
Analytical results
Acute root
disease
Feed the soil vs. Feed the crop ?
Chronic root
malfunction
Both strategies are important !
Healthy roots need
available nutrients !
Unhealthy roots in soils with low SOM and poor structure
use nutrients inefficiently…
Plants with poorly
developed roots
tend to have
nutrient deficiency
and drought stress
symptoms
How often
do you
look at
roots ?
How often do you look
at roots?
http://www.tre.umn.edu/growers/nursery_nightmares/nightmares.htm
Raised beds promote healthy roots !!
Faster drainage and soil warming
Greater depth of fertile soil
Restricted traffic
No wheel traffic on
beds
What happened to my soil??
Tillage when a soil is too wet often creates clods that require a period of
wetting and drying and/or freezing and
thawing (in addition to biological activity)
before good structure is restored.
Are you familiar with the fence post principle?
Zone of maximum biological activity and rapid residue decay
Bacteria
Fungi
Algae
Protozoa
Nematodes
Microarthropods
Enchytraeids
Earthworms
Ants, termites, spiders
Mollusks
Others: rodents, snakes,
voles, amphibians, etc.
Microflora
Mesofauna
Megafauna
Microfauna
Macrofauna
The soil stomachPlant roots depend
on an external digestive system
“ the soil food web”
What do bacteria do in soil ?
Colonize aerobic and anaerobic environments
Decompose easily digested organics
Mediate redox transformations
Nourish bacterivores
Fix N
Most N transformations in soil are carried out by bacteria!!
Plant biomass
Soil
What do fungi do in soil ?
Decompose less easily digested organics
Penetrate residues
Stabilize soil structure
Nourish fungivores
Form symbioses with plant roots and soil fauna
Compete with plant pathogens
Parasitize plants and soil animals
Produce toxins e.g. aflatoxin produced by Aspergillus flavus on peanut
Most plant pathogens are fungi but most fungi are not plant pathogens !!
Adapted from Coleman et al. (19??)
detritusphere rhizosphere
Soil organisms are
concentrated
in
HOT
SPOTS !
Detritusphere
surface residue zone
Clean tillage eliminates the detritus layer
Many soil organisms prefer to feed at the surface
Rhizosphere
Zone of root influence
< 10 % of soil volume under prairie vegetation
< 1 % of soil volume under most vegetable crops
Cover crops
Less lossLess loss
Cover
Crops
Adapted from Magdoff and Weil (2004)
Cover crops increase annual root production and function
Feed
livestock
Recent studies indicate that root production is the best
predictor of long-term retention of SOM.
CCs can have many other beneficial effects