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Soil Quality and Organic Farming

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Soil Quality and Organic Farming HORT 390 Fall 2006 Soil is more than nitrogen (N) phosphorus (P) and potassium (K) Nitrogen deficiency symptoms (poor growth, yellow ... – PowerPoint PPT presentation

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Title: Soil Quality and Organic Farming


1
Soil Quality and Organic Farming
  • HORT 390
  • Fall 2006

2
Soil is more than nitrogen (N) phosphorus (P)
and potassium (K)

3
Nitrogen deficiency symptoms(poor growth, yellow
OLDER leaves)

Celery Plant Growth dwarfed foliage pale green
and older leaves yellow and die early.
Carrot Growth dwarfed and thin leaves pale
green and older leaves yellow and red tints and
die off early.
Tomato Growth dwarfed, thin and upright habit
stem and petioles rigid leaves pale green,
occasional purplish tints, older leaves
yellowing.
from The Diagnosis of Mineral Deficiencies in
Plants by Visual Symptoms by Thomas Wallace,
M.C., D.Sc., A.I.C. Published by His Majesty's
Stationary Office 1943
4
Phosphorus deficiency symptoms(poor root growth,
purple color)

Growth stunted leaves lustreless green and dull
purple tints.
Leaves strong purple tints.
Growth dwarfed and thin leaflets droop, curl
backward and develop strong, dull purple tints.
from The Diagnosis of Mineral Deficiencies in
Plants by Visual Symptoms by Thomas Wallace,
M.C., D.Sc., A.I.C. Published by His Majesty's
Stationary Office 1943
5
Potassium deficiency(burning at leaf edges,
dont confuse with insect damage)

Internodes short, leaves relatively long
marginal and tip browning of leaves.
Leaflets slight marginal and intervenal chlorosis
followed by brown marginal scorching scorched
margins curled foward.
Intervenal chlorosis near margins followed by
marginal scorch.
6

Prairie Soil vs. Ag Soil

N and P in the organic matter pools.
7
Fertility Amendment Options- Nitrogen (N)
  • Organic Sources
  • Cow manure .5-1.5
  • Horse manure 0.6
  • Chicken manure 2-4
  • Sheep 3-4
  • Alfalfa hay 2.5
  • Blood meal 13
  • Soybean meal 7
  • Fish meal 10
  • Vetch 3.1
  • Compost 1-3
  • Fertilizers
  • Ammonium nitrate 33
  • Anhydrous ammonia 82
  • Ammonium sulfate 21
  • Potassium nitrate 13
  • Urea 46

8
Fertility Amendment Options- Phosphorus (P2O5)
  • Organic Sources
  • Cow manure .7-1.6
  • Horse manure .7-1.2
  • Chicken manure 4.5-6.0
  • Sheep 1.2-1.6
  • Alfalfa hay 0.5
  • Blood meal 2
  • Soybean meal 1.2
  • Fish meal 6
  • Vetch 3.1
  • Bone meal 15
  • Compost 0.5-1.5
  • Fertilizers
  • Phosphoric acid 54
  • Superphosphate 20
  • Concentrated superphosphate 46
  • Rock phosphate 30 (but availability very low)
  • Colloidal phosphate 22 (availability low, but
    better than rock)
  • Note Rock and colloidal sources allowed in
    organic production.

9
Fertility Amendment Options- Potassium (K20)
  • Organic Sources
  • Cow manure 2.4-3.6
  • Horse manure 1.2-2.2
  • Chicken manure 1.2-2.4
  • Sheep 3-4
  • Alfalfa hay 2.5
  • Blood meal 1
  • Soybean meal 1.5
  • Vetch 2.5
  • Wood ash 5-7
  • Greensand 5 (low availability)
  • Compost 0.5-2
  • Fertilizers
  • Potassium nitrate 44
  • Potassium chloride 62
  • Potassium sulfate 53 (allowed in organic
    production if mined and not refined)

10
Fertility Amendment Options-Pros and Cons
  • Organic Sources
  • Can be bulky, best if locally available.
  • Sometimes less expensive, sometimes more
    expensive
  • Most contribute to organic matter pool and
    long-term fertility
  • Must wait at least 90 to 120 after raw manure
    application to harvest food crops.
  • Fertilizers
  • Convenient, available for purchase.
  • Soluble, plant available
  • Many contribute to the salt index of the soil,
    and also most lower the pH (see Knotts handbook
    for details)

11
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
12

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
micro-nutrients
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.
13
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)
14

Practices that deplete your soil savings
account.
  • 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.

15
Definition of Soil Quality
Soil Fertility Physical Properties Biological
Activity
The ability of soil to function to supply
plants with adequate nutrients, have good
drainage and aeration, promote root growth and
biological activity.
16
Soil is not Dirt
17
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.

18
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 (lt0.002 mm)
  • All of these characteristics are helped with the
    addition of organic matter, especially composts.

19
Can also examine macro-organic matter flotation
with the same system.
Grass sod
Ag field with no residue
Composts
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.
20
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
21
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
22
Soil biological test interpretation
  • The let it rot test
  • More soil biological activity results in faster
    rate of decomposition of cellulose material
    (paper, cloth, wood, etc.)
  • In general, soil microbial diversity and
    abundance is a good thing.
  • Detailed fungal and bacterial counts can be
    performed by professional labs, but the results
    may not be very repeatable. Also expensive.

23
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
24
Soil Respiration Rate the reality
  • More CO2 (carbon dioxide) coming off the soil
    means the soil is respiring (breathing) more.
    This indicates either a high rate of respiration
    of existing organisms, or high numbers, or both.
  • Having more organisms is a good thing, but a high
    respiration rate also means your soil system is
    burning off carbonwhich lowers your organic
    matter levels, which is a bad thing.
  • High respiration rate is a result of optimal
    temperatures, moisture, and aeration, sometimes
    as a result of tillage.

25
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.

26
To measure water stable aggregates
  • Use a stack of sieves under water.
  • Demonstrate with a few aggregates in a shallow
    dish.

Field soil
Prairie soil
27
To measure the effect of water stable aggregates
28
Procedure
  • 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.

29
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
measurement.
30
Four Ways to Improve Infiltration
  • Add organic matter
  • Add organic matter
  • Add organic matter
  • Dont work the soil when wet!!!

31
What to do with results from the Soil Test Lab
32
Collect sample
Lab does something with it..
Results and recommendations sent to you in the
mail.
Put on some fertilizer or other product
33
Soil Tests the art and the science
Action
Representative sample collection
Late spring nitrate test
Manure and compost credits
sample handling, drying.
Cropping history and legume credits
Lab accuracy, differences of methods.
Organic matter levels
Interpretation of the lab values low, medium,
high, very high.
Recommendations for fertility amendments
Intended crop
Previous crop
34
Idealized fertilizer response curve
Yield
Low
High
Fertilizer rate
35
Nutrient levels a story about Goldilocks and
the three bears..

36
Hypoxia - The dead zone, a 6,000-square-mile
area in the Gulf of Mexico that is almost totally
devoid of life, persists despite
conservationists ongoing efforts to rein it in.
First mapped in the mid-1980s, the zone is
caused by nitrogen fertilizer runoff, which flows
from inland farms down the Mississippi River and
into the gulf. Nitrogen causes huge summer algal
blooms that decompose and sink to the bottom,
where bacteria feast on them and, in the process,
suck vital oxygen from the seawater.
Courtesy of SEAWiFS/NASA/ GSFC/Orbimage   Brownish
water from the Mississippi River billows into
the Gulf of Mexico in this 2000 image.
37
Interpretation of chemical tests
  • How much is just right?
  • How do you know if there is not enough?
  • When is there too much?

38
Several options for fertilizer recommendations
include
  • Replacement calculate anticipated needs of crop
    (in lb/A) and apply that level (minus soil test
    level). Allow for fertilizer use efficiency of
    only 50, and also 25 to 50 from organic sources
    in application year.
  • Sufficiency based on previous research,
    estimate average fertilizer amount to achieve 90
    to 95 of maximum yield. Little consideration of
    future nutrient levels.
  • Build-maintenance attempt to minimize the
    probability of P or K limiting crop yield, and
    also build soil test levels over a 4 to 8 year
    period.
  • FBTSOYP common method, observe plants, and
    track soil test levels periodically.

39
Ways to detect nutrient deficiencies
  • Visual symptoms use your crop as a bioassay.
    This could be costly if levels are too low.
  • Tissue testing. This more common with perennial
    crops, large scale cropping. Requires
    standardized controls with known developmental
    age/stage, certain plant part (e.g. petiole of
    the 4th leaf from the growing tip,
  • Soil test Promoted for years, practiced by some.

40
When looking at plant symptoms, remember that
  • Symptoms indicate lack of plant availability or
    uptake of the nutrient.
  • This could be due to low levels in the soil, OR.
  • Root system of the plant is stunted. This could
    be due to soil compaction, poor
    aeration/flooding, not enough irrigation, or
    other reason. Look at the roots.
  • Blossom end rot in tomatoes in KS often occurs
    with the first fruit, before the roots are fully
    developed. (Marr, pers. comm.)
  • Mycorhizae can improve root function.

41
Understanding pH
  • (chart of nutr. Avail. Here)

42
How to adjust soil pH
  • Add liming products to raise pH. See various
    sources in publications. Not commonly needed in
    KS unless using fertilizers that acidify the
    soil.
  • Add sulfur to lower pH. Ammonium sulfate works
    fastest, but elemental sulfur allowed by organic
    standards. See sheets for rates.
  • Soils with high exchange capacity (CEC) will
    require more product to change the pH.

43
Summary --A Definition of Soil Quality
Context soil type, slope, climate.
Problems -Salinity -Low in nutrients -Erosion -Dr
ainage
  • Soil Quality
  • - High OM
  • - Tilth
  • - Infiltration
  • Nutrient buffering

Soil is OK
44
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45
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46
For more information
  • http//www.oznet.ksu.edu/ (to get to all KSU
    publications, soil test lab info, etc.)
  • http//www.oznet.ksu.edu/kswater (for Citizens
    Guide to Soil and Water Testing)
  • http//soils.usda.gov/sqi/index.html (fact sheets
    and other info on soil quality)
  • http//www.woodsend.org/ (copies of other soil
    quality publications, compost testing)
  • http//www.amazon.com or other book seller (for
    copies of Soul of the Soil.)

47
Product Related Web Sites
  • http//www.woodsend.org/ (compost testing,
    respiration rate tests)
  • http//www.lamotte.com (for nutrient and humus
    test kits)
  • http//www.hach.com (for nitrate, pH, and ammonia
    test strips)
  • http//www.3m.com (for E. coli plates, order
    6484 EC plates, 70 for 50, also need pipets)
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