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YOUTH & FAMILIESAGRICULTURE HEALTH ECONOMY ENVIRONMENT ENERGY COMMUNITIES

Ecological Soil Management

Doug CollinsWSU Small Farms

Extension Specialist

Growing GroceriesSeptember 30, 2015

Soil: The excited skin of the earth’s surface

Soils are formed from the interaction between parent material, climate, organisms, aspect, and time.

Good dirt here!

During the Pleistocene (2-3 million years ago) large glaciers covered most of the north 1/3 of Washington State.

OSU Special Collections and Archives

Glacial deposition

OSU Special Collections and

Archives

More good dirt here!

Parent material

OSU archive

Even more good dirt here

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Alluvial and aeolian processes transport and deposit parent material

National Archives and Records Administration

Climate influences the speed of weathering for minerals

Vaquero Francis

Aspect influences water and light dynamics Above and below-ground organisms also influence soil development

Farming practices also influence soil processes

organism

Cover cropping is a management practice to influence soil processes

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Time is also an important factor in soil processes.

Photo by Wolfgang Staudt

Soils are stratified vertically by horizons. Soils in the same soil series have similar characteristics

There are more than 20,000 soil series

• Soils formed on glacial terracesLynden, Kickerville, Laxton, Tromp

• Soils formed on flood plains:Mt. Vernon, Puyallup

Ecological Soil Management Outline

I. Natural history, soil formation, general soil information

II. Soil fertility, productivity, health, and tilth

III. Soil nutrients, nutrient pools and pH

IV. Organic matter, nitrogen mineralization and cover crops

V. Compost and other amendments

VI. Double Digging Experiment

November 11: Interpreting soil test

Photo by Dennis Wilkinson

Fertility is one component of soil health and productivity.    A fertile soil may not be a productive soil  

Productivity

Limits to productivity:

•Light

•Water

•Nutrient availability

•Plant pathogens/pests

•Herbicide use

•OverworkedPhoto by Kate Halstead

“Quality” or “healthy” soil has the continued capacity to provide functions and does not degrade the surrounding environment

Gene Williams, Snohomish County Surface Water Management

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Soil with good tilth contains:

•Stable soil aggregates

•Even moisture levels

•Pathways for air and water

•Good drainage

Extremes such as excessive tillage can degrade soil tilth.

0.05mm

..

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.

. ...

..

...

. ...

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sand

silt

clay

Soil texture

Particle size distribution affects:

•Drainage

•Aeration

•Water retention

•Nutrient exchange

Soil texture is inherent and cannot be changed

websoilsurvey.nrcs.usda.gov

Soil texture can be estimated by hand with the ribbon test.

http://soils.puyallup.wsu.edu/video_soiltexture/

Organic matter

Adding organic matter:

• Helps build soil structure

• Improves water retention

• Adds slow-release source of nutrients

Photo by Craig Cogger

Mix organic matter into the soil by hand or with a machine

Photo by Amy Zarrett

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Double digging to add organic matter and improve tilth Organic matter can be left on the soil surface

Percentage of elements present in a healthy plant

Macronutrients MicronutrientsCarbon (C) 45.00% Chlorine (Cl) 0.01 %

Oxygen (O) 45.00% Iron (Fe) 0.01%

Hydrogen (H) 6.00% Manganese (Mn) 0.005%

Nitrogen (N) 1.50% Boron (B) 0.002%

Potassium (K) 1.00% Zinc (Zn) 0.002%

Calcium (Ca) 0.50% Copper (Cu) 0.0006%

Phosphorus (P) 0.20% Molybdenum (Mo) 0.00001%

Magnesium (Mg) 0.20% Nickel (Ni) 0.000001%

Sulphur (S) 0.20%

Percentages by plant dry weight

Plant Nutrients

NitrateNO3

-Ammonium

NH4+

PhosphorusH2PO4

-

PotassiumK+

Ions are forms of nutrients available for plant uptake

Anions(negative)

Cations(positive)

Nutrient pools:  Parent material (e.g. rocks/minerals), is a source of very slowly available nutrients.

Mineralse.g.: Hornblende (Ca2Al2Mg2Fe3Si6O22(OH)2)

Potassium Feldspar (KAlSi3O8)

K+

Fe2+

Mn+

Elements unavailable

Weatheringphysical and chemical

Elements available

“nutrients”

Ca2+

Parent material = rich, frugal uncle – v. slowly available

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Mineralizeable = Stocks and Bonds – slowly available

Parent material = rich, frugal uncle – v. slowly available

Organic matter

unavailablemineralization

available

NH2

PO3

SH

PO4-

SO42-

NH4+ NO3

-

NH2

C-C-C-C-

Nutrient pools:  Organic matter is a source of slowly available nutrients.

Adsorbed nutrients= Checking acct– quickly available

Mineralizeable = Stocks and Bonds – slowly available

Parent material = rich, frugal uncle – v. slowly available

K+ NH4+ Ca2+ SO4

2-

soluble, available

- - - -- - - - -

Ca2+ K+

clay OM

- - --

- -

Mg2+

K+

Nutrient pools:  Surfaces of humus and clay store quickly available nutrients.

Adsorbed nutrients= Checking acct– quickly available

Soil solution = Cash – available now

Mineralizeable = Stocks and Bonds – slowly available

Parent material = rich, frugal uncle – v. slowly available

K+ NH4+ Ca2+ SO4

2-

soluble, available

Nutrient pools:  Nutrients in the soil solution are immediately available.

Typical CEC values for different soil textures

Soil Type CEC meq/100g

Sands (light colored) 3 to 5

Sands (dark colored) 10 to 20

Loams 10 to 15

Silt Loams 15 to 25

Clay and clay loams 20 to 50

Organic soils 50 to 100

Soil pH and nutrient availability

pHMeasure of how acid or

alkaline a substance is

(related to H conc.)

6.0 to 7.5 ideal for most crops

Blueberries 4.5 to 5.5

pH VALUE TABLE

4.0 5.0 6.0 6.6 7.0 7.6 8.5 9.0 9.5 10.0

ACID NEUTRAL ALKALINE

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Nitrogen cycles from cover crops and amendments through the microbial biomass

IsopodsCollembolaearthworms

nematodes

Microbial Biomass

Bacteria Fungi

available N Soil OM

protozoa

atmospheric N2

amendment

legume

C, N

N excreted

Soil organic matter is split between active organic matter and humus.

AirWater

Silt

Clay

Sand Organic Matter

Living Organisms

Soil Humus

Active Organic Matter

Cover crops improve soil quality, protect soil, smother weeds, take up excess nutrients from the soil, and legumes add nitrogen

Clover & rye mix in garden bed, 7 days after planting

Vetch & rye mix in farm field, 45 days after planting

PAN from organic fertilizers ranges from $5 to $9 per pound. Legume cover crops can provide PAN at $1 to $3 per pound.

Cover Crops for Home Gardens East of the Cascades: WinterCover Crop Comments Planting Rate Planting Date

lbs/a c/100ft2 Aug Sept Oct Nov

Cereal Rye Hardy 180 1

Winter Wheat 180 1

Winter Oats 180 1 ½

Triticale 180 1

Annual Ryegrass Good in wet 90 ½

Spring Barley Winterkills 180 1

Spring Oats Winterkills 180 1 ½

Hairy Vetch Reliable 90 ½

Crimson Clover 20 ¼

Austrian Winter Pea Not wet soil 90 1

Fava Beans-small May winterkill 100 1

Mustard/Canola Winterkills 20 1/8

Cover Crops for Home Gardens West of the Cascades: WinterCover Crop Comments Planting Rate Planting Date

lbs/a c/100ft2 Aug Sept Oct Nov

Cereal Rye Hardy 180 1

Winter Wheat 180 1

Winter Oats 180 1 ½

Annual Ryegrass Good in wet 90 ½

Spring Barley Winterkills 180 1

Spring Oats Winterkills 180 1 ½

Hairy Vetch Reliable 90 ½

Crimson Clover Soil builder 20 ¼

Red Clover Soil builder

Austrian Winter Pea Not wet soil 90 1

Fava Beans-small May winterkill 100 1

Phacelia Pollinators 20 1/8

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Cover Crops for Home Gardens East of the Cascades: Summer

Cover Crop Comments Planting Rate Planting Date

lbs/a c/100ft2 Apr May June July Aug

Buckwheat Short season 50 1

Brassicas Short season 15 1/8Crimson Clover Legume 30 ¼

Red Clover Legume 15 ¼

Sweet Clover Legume 20 ¼

Annual Alfalfa Legume 20 ¼

Sorghum/Sudan Hot weather 50 1/8

Millets Hot weather 20 1/8

Cover Crops for Home Gardens West of the Cascades: Summer

Cover Crop Comments Planting Rate Planting Date

lbs/a c/100ft2 Apr May June July Aug

Buckwheat Short season 50 1

Brassicas Short season 15 1/8Crimson Clover Legume 30 ¼

Sorghum/Sudan Hot weather 50 1/8

Fava Bean Cool weather 100 1

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Compost management

Compost appliedat 10 ton / acre

Compost appliedat 2 ton / acre

Carbon to Nitrogen (C:N) ratio between 10:1 and 20:1

Goals for application influences type and amount

C:N ratio of different amendments

Hot : less than 10:1

Cool : 15:1 to 25:1

Woody : over 30:1

Photo by: Scot Nelson

C:N less than 10:1 HOT

•Easy to over-apply

•Leads to excess nutrient levels

•Potential to harm crop

•Degrade water quality

Fish and feather meals

Poultry/ Fresh rabbit manure

Seed meals

Photos by Peter Moon, O2 Composting

C:N from 15:1 to 25:1 COOL

•Slow-release nitrogen

•Use as soil amendment

•Releases additional nutrients in subsequent seasons

Composted:

•yard debris

•most manures

•biosolids

Fresh materials:

•yard debris

•coffee grounds

•dairy manure solids

C:N over 30:1

•Straw

•Sawdust

•Paper waste

•Horse bedding

•Leaves

•Nitrogen immobilization

•Use as mulch

•Carbon resource in compostPhoto by Andy Bary, WSU

Practice ‘safe’ manure

•Incorporate compost well before planting

•Apply to rotation crops not harvested as food

•Use legumes instead

•Use processed, not raw, manures

•“Waiting periods” between application and harvest (90 or 120 days for National Organic Program) are general recommendations, not infallible truth. Also raw versus cooked foods.

•NEVER apply manure or manure-based teas to food crops nearing maturity or harvest

Photo by: Len Radin

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Does double digging to establish a garden bed increase yield?

Prior to starting the experiment, compaction increased to 2.5 inches and was essentially impenetrable at 6 to 7 inches

An experiment with 4 replications was conducted to compare soil garden bed preparation with double digging and rototilling.

Initial Soil Parameters

Depth pHlime req

t/aOM%

Pbppm

Asppm

Pppm

Thatch 5.2 15.4 148.3 13.0 168.00‐6 in 5.8 2.6 7.5 63.7 13.2 202.06‐12 in 5.5 1.4 2.2 103.3

After treatments, double dug soils had much less compaction between 8 and 40 inches

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Double digging did not improve lettuce yield. Lettuce plants did look more uniform and healthy with rototilling

Double DugRototilled

Double digging increased carrot yield by 23%

Double Dug Rototilled

Double Dug Rototilled

Double digging did not improve lettuce yield. Lettuce plants did look more uniform and healthy with rototilling

1600 tomatoes, 330 lbs, average of 10.3 lbs/plant (1 plant/4 ft2)

Considerations for ecological soil management

Five soil forming factors - parent material, climate, aspect, time, and organisms - interact to form specific soil types.

Soil nutrients exist in different “pools” withvarying levels of availability. Soil tests approximate nutrient availability.

Utilize cover crops and proper amounts of organic amendments to feed crops, build humus, and develop a bank of slow-release nutrients.

Thank you!

Doug Collins

WSU Small Farms Program

dpcollins@wsu.edu

253-445-4658

All photos were taken by Doug Collins, unless otherwise noted.

Resources

Collins, D.P. 2012. Soil Testing: A Guide for Farms with Diverse Vegetable Crops. Washington State University Extension Publication EM050E. http://cru.cahe.wsu.edu/CEPublications/EM050E/EM050E.pdf.

Collins, D.P., C. Miles, C.G. Cogger, and R. Koenig. 2013. Soil Fertility in Organic Systems: A Guide for Gardeners and Small Acreage Farmers. Pacific Northwest Extension Publication PNW 646.

Horneck, D.A., D.M. Sullivan, J.S. Owen, and J.M. Hart. 2011. Soil Test Interpretation Guide. Oregon State University Extension EC 1478. http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/22023/ec1478.pdf.

Solomon, S. 2007. Growing Vegetables West of the Cascades, 6th Edition. Sasquatch Books, Seattle, WA. 368 pgs.

Cogger, C., C. Benedict, N. Andrews, S. Fransen, and A. McGuire. Cover Crops for Home Gardens –East of the Cascades. Washington State University Extension Publication FS117E. http://cru.cahe.wsu.edu/CEPublications/FS117E/FS117E.pdf

Cogger, C., C. Benedict, N. Andrews, and A. McGuire Cover Crops for Home Gardens – West of the Cascades. Washington State University Extension Publication FS111E. http://cru.cahe.wsu.edu/CEPublications/FS111E/FS111E.pdf

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Extractants are used to indicate plant nutrient availability, not total nutrient content.

Plant Nutrient Common Extractants

NO3- KCl, CaCl2

NH4+ KCL

H2PO4-/HPO4

-2 NH4F/HCL (Bray-P)

NH4F/CH3COOH/HNO3(Melich-P)

NaHCO3 (Olsen-P)

K+ NHaOAc

SO4-2 Ca(H2PO4)2,CaCl2

Zn+2,Fe+3,Mn+2,Cu+2 DTPA,EDTA

H3BO3 Hot Water

Cl- Water

Soil nutrients cycle through different ‘pools’ in the soil Soil tests indicate how much of a nutrient is likely to be available to plants

Different soils will have different initial soil quality. Monitoring through time is the best way to evaluate management

Soil A

Soil B

Time

Soi

l Qua

lity

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In the maritime northwest, nitrogen sampling is done in fall for “report card” nitrate test

NO3- -N in surface foot (ppm)

Low <10

Medium 10-20

High 20-30

Excessive >30

Soil test vs. probability of crop response.

Soil phosphorous transported off-farm can degrade surface water quality.

Photo by: Gene Williams, Snohomish County Surface Water Management

Base Cations

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Reserve acidity is the store of hydrogen ions on exchange sites.  How much lime is required to change the soil pH?

- - - -- - - -

-Ca2+ K+

Mg2+

High reserve acidity

H+

clay

OMH+

H+

H+

H+

H+

H+

H+

H+

-

-

-

-

Mg2+

K+

Low reserve acidity

K+

- - - -- - - -

-Ca2+ K+

H+

Ca2+

Ca2+

-

--

-

H+ H+

H+

Planning for Soil Testing

Group soil tests by management zones: contiguous areas that are planted, fertilized, and otherwise managed together.