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Soil Quality Why it Matters


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Title: Soil Quality Why it Matters

Soil Quality --Why it Matters
  • Rhonda Janke
  • Assoc. Prof. and Ext. Specialist, KSU
  • Sustainable Cropping Systems

Definition of Soil Quality
Soil Fertility Physical Properties Biological
The ability of soil to function to supply
plants with adequate nutrients, have good
drainage and aeration, promote root growth and
biological activity.
A Definition of Soil Quality
Context soil type, slope, climate.
Problems -Salinity -Low in nutrients -Erosion -Dr
  • Soil Quality
  • - High OM
  • - Tilth
  • - Infiltration
  • Nutrient buffering

Soil is OK
Soil is not Dirt
Soil Tests for Quality physical, chemical,

Physical Tests -- Soil Texture
  • Fill a jar 2/3 with soil.
  • Fill the same jar about 7/8 full of water. Add
    detergent (optional) to break up aggregates.
  • Shake well.
  • Measure height of settling at 30 seconds, 30
    minutes, and 24 hours or -- look at particle
    size differences sand, silt, and clay layers.

Simple calculations
  • 30 seconds sand.
  • 30 minutes sand silt.
  • 24 hours (total) sand silt clay.
  • Subtract 30 minute from 24 hr to get clay.
  • Subtract 30 sec. from 30 min. to get silt.
  • Take each fraction (in mm) divided by the total
    to get sand, silt, and clay.
  • Use a texture triangle to determine soil texture
    classification. More than 50 of any one texture
    determines primary qualities.

Texture largely determined by parent material of
soil, past erosion, and new deposits (such as
topsoil addition)
  • Sandy soil good drainage, but doesnt hold
    water or nutrients well. (particles 0.05 to 2 mm)
  • Silt moderate drainage, moderate nutrient and
    water holding capacity. (0.002 0.05 mm)
  • Clay poor drainage, can supply K mineral,
    shrink/swell with water (
  • All of these characteristics are helped with the
    addition of organic matter, especially composts.

Any type of container with straight sides will
Can also examine macro-organic matter flotation
with the same system.
Grass sod
Ag field with no residue
Various garden plots
Macro-organic matter is important because it
feeds the active organic matter pool, that
promotes water stable aggregates, infiltration,
and other positive soil attributes.
Organic Matter Pools
Active OM
Stable OM
Soil Test for OM
Macro-Organic Matter (mulch, residue, roots,
large pieces of compost, etc.)
Active Decomposing Organic Matter (particulate
OM or POM)
Humus test
Stable Humus
Humus test results
using LaMotte humus index test.
Newer garden soil with mulch 1.0
Improved garden soil 3.0
Near-by ag field (with subsoil) 0
Fresh worm compost 5
Water Stable Aggregates
  • Formed by the aggregation of clay (smallest
    particles), followed by gluing together of
    macro-aggregates with bacterial secretions,
    fungal hyphae, and root hair bonding.

To measure water stable aggregates
  • Use a stack of sieves under water.
  • Demonstrate with a few aggregates in a shallow

Field soil
Prairie soil
To measure the effect of water stable aggregates
  • Assemble filter paper, funnel, and jar.
  • Add 1 scoop (dry) soil.
  • Gently add 1 scoop water and start timer.
  • Record first reading when water is not visible.
  • Repeat with 2nd scoop of water.

  • First scoop
  • Field 38 seconds
  • Prairie 20 seconds.
  • Second Scoop
  • Field 206 minutes.
  • Prairie 115 minutes.
  • Faster infiltration means that more rainfall will
    soak in to your soil.

Notice the lack of soil structure on the left
(field soil) and the presence of water stable
aggregates on the right (prairie soil)
A similar test can be run in the field. Use a
section of irrigation pipe or coffee can to
create an infiltrometer.
Figure 14. Illustration of an infiltrometer
In a 6 inch diameter ring, pour 1 7/8 cup water.
Measure amount of time to soak in. Repeat
Four Ways to Improve Infiltration
  • Adding organic matter
  • Adding organic matter
  • Adding organic matter
  • Dont work the soil when wet!!!


Prairie Soil vs. Ag Soil

N and P in the organic matter pools.

Organic Matter and Nitrogen


Organic Matter and Phosphorus


Banking on Soil Nutrient Levels
Your Checking Account -- Mineral N, available P
and K -- This is an indication of what will be
available that growing season -- Soil pH will
influence the availability of these and
Your Savings Account -- Organic matter content,
total N, total P, clay release of K. -- These are
slowly available, but can accumulate over time to
be available later. -- This is sometimes called
nutrient buffering.
How to build up your soil savings account.
Local, on-farm sources - cover crops, annuals
and perennials. - hay mulch - compost - raw
manure (use with caution, not on leafy crops) -
wood chips, ash (also use with care)
Purchased products - alfalfa and soybean meal
(N) - bone meal, rock phosphate (P) - lime (for
pH) - sulfur (to lower pH) - blood meal (for N)

Practices that deplete your soil savings
  • Too much tillage.
  • Bare ground (no mulch on top).
  • No living crops (no roots in the soil).
  • Soluble fertilizers without concurrent addition
    of carbon rich mulches or composts.

Lab soil fertility tests available
Organic Matter Pool, or Savings Account
Available Nutrient Pool, or Checking Account
-- Organic matter -- Total N P -- Total C N
Extractable N, P, K, pH and micro-nutrients
In addition to laboratory tests, quick tests are
available for soil nutrients (N, P, K) and pH.

Most kits based on simple extraction methods,
combined with color charts for interpretation.
Nitrogen (NO3)
Test strips and other methods can use a 11 soil
water extraction
  • 1 scoop soil (1/8 c.)
  • 1 scoop Dist. Water
  • Put on lid and shake.
  • Let settle a few minutes.
  • Filter to get clear liquid.
  • Can test with Hach test strips for pH, NO3, and
    NH4. E. coli (microbial test) may also be useful.

Test strips
Hach test strip measure pH from 4 to 9, and NO3
from 0 to 50 ppm NO3-N. Ammonia nitrogen (NH4)
test also available.
3-M Petri plates develop pink colonies with
coliform bacteria, and blue colonies with E. coli
(intestinal) bacteria. Incubate for 48 hrs.
Example results from my garden
Drinking water
GH with Parsley
Composting Area
Livestock Water
Comparison of test kits to KSU lab values r2 or
correlation value (higher is better)
Cost Comparison
  • LaMotte EL Combination kit costs 41.95 for pH
    (30) and N, P, K (15), or 0.56 per test.
  • Hach pH strips are 13.50 per 50, or 0.27 per
    test, and nitrate strips are 15.00 per 25, or
    0.61 per test.
  • LaMotte Humus test is 74.25 for 50 tests, or
    1.49 per test.
  • KSU combination test is 10.50 for pH, N, P, K,
    and OM. (10.00 for total NP)

Total LaMotte 116.20 for above tests. Total KSU
for same quantity is 490.
Soil biology important, but difficult to
Soil biological tests include earthworm counts
(by hand), extraction of soil insects with light
above and funnel below into a jar. No accurate
tests yet for microbial species diversity. Soil
respiration rate tests also available, but
difficult to interpret.
Soil Biology Cont.
The will it rot? soil test.
  • Wet filter paper.
  • Place in bottom of flat covered dish.
  • Fill dish with moist soil.
  • Add a little more water
  • if needed.
  • Incubate and watch.
  • Observe the amount of decomposition after certain
    length of time.
  • Examples (see photos) incubated for 1 week
    at 95o F.

Garden soil
Worm compost
Field soil
Summary of tests for soil quality
  • Physical
  • Texture
  • Macro-organic matter
  • Water stable aggregates
  • Infiltration rate (lab field)
  • Bulk density
  • Water holding capacity

Summary of tests for soil quality
  • Chemical
  • pH
  • Nitrogen (NO3 and NH4)
  • Phosphorus
  • Potassium
  • Organic Matter (lab)
  • Humus (quick test)
  • Total N P in OM (lab)

Summary of tests for soil quality
  • Biologial
  • Earthworms
  • Soil insects and other arthropods
  • Coliform bacteria E. coli
  • Respiration rate
  • Simple will it rot test with filter paper or
    other materials.

Good Roots Need Good Soil
  • Many sick plants dont have a disease, they
    just need better roots/soil.
  • Good soil conditions can also help plants fight
    off disease and insect pests (like a healthy
    immune system in a person).
  • Try to improve the subsoil and also the topsoil.
    Limit compaction, and keep adding organic matter
    over a period of years.

Close observation of your soil is probably one
of the best results of doing your own soil tests.

For more information
  • http// (to get to all KSU
    publications, soil test lab info, etc.)
  • http// (for Citizens
    Guide to Soil and Water Testing)
  • http// (fact sheets
    and other info on soil quality)
  • http// (copies of other soil
    quality publications, compost testing)
  • http// or other book seller (for
    copies of Soul of the Soil.)

Product Related Web Sites
  • http// (compost testing,
    respiration rate tests)
  • http// (for nutrient and humus
    test kits)
  • http// (for nitrate, pH, and ammonia
    test strips)
  • http// (for E. coli plates, order
    6484 EC plates, 70 for 50, also need pipets)