Managing Soil to Keep It
Productive
Developed by:
Hudson Minshew
Oregon State University Extension Service
Susan Donaldson
University of Nevada Cooperative Extension
NRCS, Bozeman, Mont.
Part One: Fertilizing
What do my soil test results
mean?
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What nutrients do plants need?
How can I supply those nutrients?
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What kind of information does
my soil test report provide?
Particle size analysis
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Soil organic matter
content
pH
Soluble salts
Nutrient content
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USDA NRCS
Particle size analysis
Provides the
relative
percentages of
sand, silt, and clay
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Allows
determination of
soil textural class
A loamy texture is
generally best for
most plants
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NRCS, Bozeman,
Mont.
Soil organic matter (OM)
Living or dead
plant and animal
residue
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Measured in %
OM content is
highly variable
Generally, 3 to 8 %
OM content is
good for plants
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UNCE, Reno, Nev.
pH
Indicates relative acidity or alkalinity
pH 7 = neutral; less than pH 7 = acid;
more than pH 7 = alkaline or basic
Adapted from library.thinkquest.org by A. Miller
Soil pH
and
nutrients
Adapted from www.soil.ncsu.edu by A. Miller
Widest part of the bar indicates maximum availability
What makes soils acid?
Acid soils: pH is below 7
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Soils become acid due to heavy
rainfall that weathers soils quickly
Basic cations such as calcium,
magnesium, and potassium are
leached from the soil profile
This natural weathering process
makes soils acid
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Raising the pH of acid soils
Add lime to raise the pH (making soil
less acid)
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Lime most often consists of calcium
carbonate
Plant response will be relatively slow,
taking weeks or months
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What makes soils alkaline?
Alkaline soils: pH is above 7
Soils that have not been greatly weathered
or leached
Soils high in calcium
Reduces solubility of all micronutrients
Adapted from library.thinkquest.org by A. Miller
Example of crop grown in
alkaline soil
http://ag.arizona.edu
Adapted from ag.arizona.edu by A. Miller
Soluble salts
A measure of inorganic
chemicals that are more
soluble than gypsum,
such as sodium,
calcium, magnesium,
chloride, sulfate and
bicarbonate
Salty soils are a problem
in arid regions or in
poorly drained soils
USDA NRCS
Classifying salt-affected
soils
Electrical conductivity measurements
(EC)
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Exchangeable sodium percentage
(ESP)
Salt-affected soils are commonly
classified for management purposes
into three groups: saline, sodic, and
saline-sodic based on EC and ESP
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Managing salt-affected soils
Select plants that can tolerate salinity
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Avoid excess or salty forms of
fertilizers
Incorporate organic matter
If appropriate, add sulfur to lower the
pH
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Managing salt-affected soils
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In soils with good drainage,
periodically leach the salts below root
zone with high quality irrigation water
(avoid if high water table present)
Check with your local Extension office
for help
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Plant nutrients
Substances necessary for plant
growth
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Some, such as hydrogen, oxygen and
carbon, come from the air and water
Others, such as nitrogen and
phosphorus, may need to be added
Excess or improper use of fertilizers
may result in water pollution
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Macronutrients
N = nitrogen
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P = phosphorus
K = potassium
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More macronutrients
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H = hydrogen
Ca = calcium
O = oxygen
Mg = magnesium
C = carbon
S = sulfur
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Micronutrients
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Fe = iron
Ni = nickel
Mn = manganese
Cu = copper
Zn = zinc
Co = cobalt
B = boron
Cl = chlorine
Mb = molybdenum
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Six questions to ask yourself
before you add fertilizer
1. Which elements do I need?
(N, P, K, S, Ca)
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2. How much do I apply?
3. What type of material do I use?
4. Which application method is best?
5. When is the best time to apply it?
6. Will I get a return on my investment?
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Types of fertilizers
Chemical fertilizers
Organic fertilizers (bone meal,
compost, manure, etc.)
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www.farmphoto.com
WAY TO GROW
What’s in
the bag?
FERTILIZER
28 – 14 - 5
GUARANTEED ANALYSIS
Total nitrogen
6% Ammonium nitrogen
14% Urea nitrogen
Available phosphoric acid
Soluble potash
28%
NPK formula
Nitrogen content
14%
5%
Derived from sulfur-coated urea,
etc.
Product name
Phosphorus content
Potassium content
Specific sources
How much fertilizer do I need to
apply?
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Estimate the amount of
fertilizer needed based on
soil test results, crop needs
and area to receive fertilizer
Most fertilizer
recommendations are in
pounds per 1,000 square
feet, or pounds per acre
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Calculating fertilizer rates
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To convert a
recommendation to
pounds/acre of an actual
fertilizer material, use the
following formula:
Pounds of nutrient recommended X 100
Percentage of nutrient in fertilizer
material
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Calculating land area
Length x Width = Area
If the area is oddly shaped or oval, calculate
using a regular shape that closely fits the
shape of the land to be fertilized
200 ft
150 ft
100 ft
150 ft
Fertilizing with manures
Good source of
nutrients and
organic matter
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Protects soil
from raindrop
impact and
erosion
Local supply
often available
at no cost
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OSU Extension Service
Different sources of manure have
different amounts of nutrients
Poultry manure is
high in nitrogen
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Beef and horse
manure tends to
be lower in
nitrogen
UNCE, Reno, Nev.
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Sheep manure is
high in potassium
Cautions for fertilizing with
manures
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Watch out for
weeds and
pathogens
Know the
manure
nutrient
content
Consider the
salt content
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Univ. of Oregon
Cautions for fertilizing with
manures
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Incorporate or
apply evenly to
avoid
smothering
plants
Don’t apply on
frozen slopes
Avoid leaching
nutrients into
waterways
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UNCE, Reno, Nev.
Nutrient deficiencies
USDA NRCS
Visual symptoms of deficiencies:
Nitrogen
http://agri.atu.edu
Visual symptoms of deficiencies:
Phosphorus
http://agri.atu.edu
Visual symptoms of deficiencies:
Potassium
Corn
Alfalfa
http://agri.atu.edu
http://ipm.iastate.edu
Visual symptoms of deficiencies:
Calcium
http://agri.atu.edu
Visual symptoms of deficiencies:
Zinc
http://agri.atu.edu
Visual symptoms
of deficiencies:
Manganese
http://agri.atu.edu
What we’ve learned
Use soil test results to guide you in
amending your soil
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Test results are only as good as the
sample you collect
Fertilize to meet plant needs, and
avoid costly overuse that may pollute
water
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Part II: Soil Surveys
How to use a soil survey
How to find a map unit
Map unit descriptions
Soil ratings and capabilities
Where do soil surveys come from,
and where can I get one?
USDA NRCS
http://websoilsurvey.nrcs.usda.gov
Why should we use soil surveys?
Contain practical information for the
landowner
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Can prevent management mistake
Help determine the potential of your
land
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How do I use a soil survey?
Locate your property on the “Index to
Map Sheets” page
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Note the number of the map sheet
Find that sheet
Locate your property on the map sheet
Make a list of map unit symbols
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Soil map units
A map unit describes
a soil “type” in the
soil survey
“Map-unit
descriptions” are
found at the
beginning of the
survey
Soil map units are
arranged
alphabetically as well
as numerically in the
soil survey
Soil map unit example
630 Fleischmann
gravelly clay
loam
Number
designation
Soil
textural
class is
part of
map unit
name
Name given by soil
scientists conducting
survey
What can you do with the number?
Determine capabilities and limitations
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See “Summary of Tables” in the soil
survey for additional data on a specific
soil use
For our example soil, can we build a
septic absorption field?
See Table 10: Lists a severe limitation
due to cemented pan
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NRCS Web-based soil surveys
http://websoilsurvey.nrcs.usda.gov/app
Can search by address, or use the map to
zoom in
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Steps in using the site:
– Select area of interest (your property)
– View the soil map and learn about the soil
properties
– Use soil data explorer for additional information
– Create a custom soil report
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What does
all the
information
mean?
USDA NRCS
the Land
Soil
limitations
NRCS, Bozeman, Mont.
Other information
Suitability ratings
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Temperature and precipitation
data
Freeze dates and growing season
Productivity
Building site development
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Other information
Suitability for irrigation
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Physical and chemical properties
(percent OM, pH, permeability,
available water capacity)
Soil surveys can differ in the
information they provide.
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Restrictive features
Cemented pan
Droughty
Erodes easily
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Flooding
Low strength
Restrictive layer
Shrink-swell
potential
the Land
UNCE, Reno, Nev.
Capability classes
Classes I and II—good farmland with few
to moderate limitations
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Classes III and IV—severe to very severe
limitations for growing crops
Classes V and VI—limitations that are
impractical to remove.
Classes VII and VIII—very severe,
unsuited for cultivation.
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Capability classes
USDA NRCS
Land capability and yields
USDA NRCS
To wrap it up...
Soil surveys are generated by
NRCS scientists
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They are available in printed form
or on the Web
Soil surveys are useful for
determining capabilities and
limitations of your soils
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Additional activity:
Use the Web soil survey
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Enter an address
Select “Area of Interest”
Go to “Soil Map”
Clip “Area of Interest” to property
level
Go to “Soil Data Explorer”
Click on “Vegetative Productivity”
Look at “Yields of Irrigated Crops”
Click on “Sanitary Facilities”
Look at “Septic Tank Absorption
Fields”
Generate your custom soil
resource report
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As you use “Soil Data
Explorer” to look at
different features, click
“Add to Shopping Cart”
to add the information
to the report
Click on the “Shopping
Cart” button to get the
report
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