Soil Fertility and Soil Fertility and Amendments for Amendments for Rangeland ReclamationRangeland Reclamation

Jay Norton, Soil Fertility SpecialistJay Norton, Soil Fertility SpecialistUniversity of WyomingUniversity of Wyoming

http://uwyo.edu/soilFerthttp://uwyo.edu/soilFert

BLRS Soils Workshop, May 30, 2009BLRS Soils Workshop, May 30, 2009

soil amendment:soil amendment: Any material that is Any material that is worked into the soil or applied on the worked into the soil or applied on the surface to enhance plant growth.surface to enhance plant growth.

For this discussion includes:For this discussion includes:

–– Organic materials like manure & compost;Organic materials like manure & compost;

–– Fertilizers;Fertilizers;

–– Inoculants like Inoculants like mycorrhizaemycorrhizae and compost tea.and compost tea.

Often not necessary for ecological Often not necessary for ecological restoration, but on drastically disturbed sites restoration, but on drastically disturbed sites may be needed as remediation measure.may be needed as remediation measure.

ConceptsConcepts

Goal is to recover site structure, Goal is to recover site structure, functions, and values following functions, and values following development activities;development activities;

Goal is NOT to Goal is NOT to changechange site potential site potential but restore it by;but restore it by;–– Remediation: restoring soil attributes lost Remediation: restoring soil attributes lost

during stripping, stockpiling, spreading, during stripping, stockpiling, spreading, and cultivating;and cultivating;

–– Enhancement: facilitating germination Enhancement: facilitating germination and establishment of native plants.and establishment of native plants.

Presentation overviewPresentation overview

Fertility of rangeland soils;Fertility of rangeland soils; Types of soil changes that result from Types of soil changes that result from

stripping, stockpiling, and replacing stripping, stockpiling, and replacing topsoils;topsoils;

Determining needs for amendments;Determining needs for amendments; Applying amendments to meet needs.Applying amendments to meet needs.

High nutrient content:High nutrient content:

–– Leaching losses are minimal;Leaching losses are minimal;

Evaporation far exceeds precipitation:Evaporation far exceeds precipitation:

–– Elements released through weathering of Elements released through weathering of soil parent materials accumulate as salts;soil parent materials accumulate as salts;

–– Soluble components move UP, not down;Soluble components move UP, not down;

Alkaline pH (>7.0) from abundance of Alkaline pH (>7.0) from abundance of base base cationscations, including CaCO, including CaCO33

–– Ties up P and some micronutrients;Ties up P and some micronutrients;

Low productivity:Low productivity:

–– Low soil organic matter content Low soil organic matter content concentrated near surface;concentrated near surface;

–– Low water and nutrient holding capacity;Low water and nutrient holding capacity;

–– Low nutrient content;Low nutrient content;

0

1

2

3

4

5

6

7

8

9

10

11

12

Jan

Feb MarAprMay Ju

n JulAugSep OctNovDec

Average Precipitation (Tot. 7.7)Pan Evaporation (Tot. 54.0)

Fertility of semiarid soilsFertility of semiarid soils

Fertility of semiarid soilsFertility of semiarid soils Montana and Wyoming soil tests usually indicate needs for supplemental

nitrogen, phosphorus, and often sulfur for crop growth; N is most limiting to growth and yieldN is most limiting to growth and yield::

–– Soil organic matter is ONLY native source;Soil organic matter is ONLY native source;–– Becomes available in pulses of decomposition in spring and folloBecomes available in pulses of decomposition in spring and following rainfall;wing rainfall;

–– Plants are adapted to low, pulsing N availability;Plants are adapted to low, pulsing N availability;

–– Most common Most common fertlizerfertlizer is Urea, which must be incorporated to avoid volatilization;is Urea, which must be incorporated to avoid volatilization;

–– Excess available N changes composition toward weedy species;Excess available N changes composition toward weedy species;

P is second most limitingP is second most limiting;;–– From weathering rock and decomposing SOM;From weathering rock and decomposing SOM;–– Applied as phosphate (PApplied as phosphate (P22OO55); less soluble but is rapidly tied up in soil minerals ); less soluble but is rapidly tied up in soil minerals

because of abundant CaCO3;because of abundant CaCO3;

S is often applied as ammonium sulfateS is often applied as ammonium sulfate;;–– S can mitigate high pH improving conditions for seedling establiS can mitigate high pH improving conditions for seedling establishment;shment;

Micronutrients: High pH soils can limit availability of Zn, Fe aMicronutrients: High pH soils can limit availability of Zn, Fe and othersnd others;;–– Often applied as liquid.Often applied as liquid.

Organic matterOrganic matter

Plant residues & humus;Plant residues & humus; Store of timeStore of time--release release

nutrients;nutrients; UWyoUWyo soil lab assumes 20 lbs soil lab assumes 20 lbs

of N per year for each 1 % of N per year for each 1 % SOM;SOM;

Many other attributes:Many other attributes:–– Increases waterIncreases water-- and nutrientand nutrient--

holding capacity;holding capacity;–– Improves Improves tilthtilth;;–– Dark color.Dark color.

0 10 20 30 40 50 60 70Organic C, g/kg

0

10

20

30

40

Cat

ion

exch

ange

cap

acity

, cm

o l(+

)/kg

pH = 4.0-4.5slope = 0.122

pH = 5.0-5.5slope = 0.263

pH = 8.2slope = 0.495

Fertility reduction with Fertility reduction with disturbancedisturbance

Cultivation effect: aeration stimulates decomposition and loss of SOM:– Repeated disturbance exacerbates losses;– Great Plains farmlands have lost >60% original SOM;

Lack of SOM inputs: – Rangeland soils maintain 1-2% SOM because annual plant residue

inputs balance losses;– Stockpiling stimulates loss, but eliminates inputs;

Mixing:– Dilution: SOM concentrated at surface is mixed with low-SOM

subsurface, even at 6” salvage depth;– Degradation: Subsoils are zones of accumulation of salts and clay;– Increased salts, pH, and clay may cause drought, toxicity, and nutrient

deficiencies; Possible loss of beneficial soil microbes:

– Long-term storage of dry soil without plant inputs can reduce populations of mycorrhizal fungi and other beneficial microbes.

Changing the soil profileChanging the soil profile

0.0 0.5 1.0 1.5

0

10

20

30

40

50

60

Depth

(in)

SOM (%

0.0 0.5 1.0 1.5

0

10

20

30

40

50

60

Depth

(in)

SOM (%

A

Btk

Bk2

2Cr

AB

Bk

0.0 0.5 1.0 1.5

0

10

20

30

40

50

60

Depth

(in)

SOM (%

42% reduction at surface

Determining NeedsDetermining Needs

Soil sampling: take at least 20 cores or Soil sampling: take at least 20 cores or shovel samples from depth of undisturbed A shovel samples from depth of undisturbed A horizon (usually 2horizon (usually 2--3 inches):3 inches):–– All around the pad after topsoil is All around the pad after topsoil is respreadrespread and and

soon before seedbed prep;soon before seedbed prep;–– From a matched undisturbed area;From a matched undisturbed area;

Mix samples from each area in bucket and Mix samples from each area in bucket and place a place a subsamplesubsample in a well marked 1in a well marked 1--gallon gallon ziplockziplock bag;bag;

Open the bags to air dry over night;Open the bags to air dry over night; Soil labs usually require at least a month.Soil labs usually require at least a month.

Routine test: $20Routine test: $20–– Includes N, P, SOM, salts, pH, Includes N, P, SOM, salts, pH,

lime, texture;lime, texture; K, Fe, Zn: $4.00 eachK, Fe, Zn: $4.00 each Actual data is more important Actual data is more important

than fertilizer recommendation;than fertilizer recommendation; For accurate recommendation For accurate recommendation

must provide yield from clipping or must provide yield from clipping or ESD.ESD.

~3”

Determining needsDetermining needs

Goal is to promote germination and Goal is to promote germination and establishment;establishment;

Amending to recover original surface soil Amending to recover original surface soil properties should be best approach:properties should be best approach:–– Compare to levels of SOM and salts in sample Compare to levels of SOM and salts in sample

from undisturbed area;from undisturbed area;–– Amend with organic materials to recover surface Amend with organic materials to recover surface

SOM content;SOM content;–– Amend with S or gypsum to remediate increased Amend with S or gypsum to remediate increased

surface sodium contents;surface sodium contents;–– Fertilizers and other amendments should not be Fertilizers and other amendments should not be

necessary.necessary.

Organic materialsOrganic materials

1% SOM amounts to about 5 tons per acre in the 1% SOM amounts to about 5 tons per acre in the top 3 inches;top 3 inches;

In example, loss is 0.54 %, or about 2.7 tons per In example, loss is 0.54 %, or about 2.7 tons per acre;acre;

Manure: (~1400 lbs or 0.7 ton per cu yard) about Manure: (~1400 lbs or 0.7 ton per cu yard) about one 4one 4--yard spreader full per acre;yard spreader full per acre;

Composted manure or other compost is better Composted manure or other compost is better because of lower salt, weed seed, and nutrient because of lower salt, weed seed, and nutrient content:content:–– Make sure C:N ratio is about 30 or less;Make sure C:N ratio is about 30 or less;–– Saw dust and wood chips (C:N = 375Saw dust and wood chips (C:N = 375--400) are not 400) are not

acceptable and will reduce fertility;acceptable and will reduce fertility;–– Straw (C:N = 75) can provide mulch for moisture benefits, Straw (C:N = 75) can provide mulch for moisture benefits,

but will tie up limited N until it decomposes;but will tie up limited N until it decomposes;–– Know the source to avoid weeds.Know the source to avoid weeds.

SalineSaline--sodicsodic soilssoils

SalineSaline--sodicsodic soilssoils

Plants on saline sites are adapted, but Plants on saline sites are adapted, but disturbance can increase surface disturbance can increase surface concentrations to toxic levelsconcentrations to toxic levels

Flocculated Dispersed

RemediatingRemediating high salt high salt contentcontent

Reducing salts and sodium is very difficult Reducing salts and sodium is very difficult --careful stripping is critical;careful stripping is critical;

Goal is to match original content:Goal is to match original content:–– Agronomic perspective is detrimental and will promote weeds;Agronomic perspective is detrimental and will promote weeds;

For high salts, addition of lowFor high salts, addition of low--salt organic salt organic materials is the only way to reduce (unless you materials is the only way to reduce (unless you can irrigate);can irrigate);

For high exchangeable sodium:For high exchangeable sodium:–– About 50 lbs elemental S per acreAbout 50 lbs elemental S per acre--inch of soil to reduce 1 inch of soil to reduce 1 meqmeq

Na/100 g soil;Na/100 g soil;–– About 300 lbs gypsum for same;About 300 lbs gypsum for same;–– Most alkaline soils have plenty of Ca so use elemental S.Most alkaline soils have plenty of Ca so use elemental S.–– Units: talk with soil testing lab, or see saltUnits: talk with soil testing lab, or see salt--affected soil pub on affected soil pub on

my website: http://my website: http://uwyo.edu/soilFertuwyo.edu/soilFert

Say ESP in undisturbed site is 13 and in Say ESP in undisturbed site is 13 and in reclaimed soil is 23reclaimed soil is 23

ESP (exchangeable sodium percentage = ESP (exchangeable sodium percentage = Na/CEC x 100 (in meq/100g)Na/CEC x 100 (in meq/100g)

ESP undisturbed = 4/31 x 100 = 13ESP undisturbed = 4/31 x 100 = 13

ESP reclaimed = 7/31 x 100 = 23ESP reclaimed = 7/31 x 100 = 23

Reduce Na by 3 Reduce Na by 3 meqmeq requires ~150 lbs S or requires ~150 lbs S or 900 lbs gypsum.900 lbs gypsum.

Fertilizer recommendation Fertilizer recommendation approachapproach Must know accurate Must know accurate ““yield goalyield goal”” or site production: or site production:

–– From ecological site descriptions;From ecological site descriptions;

University of Wyoming Soil testing lab recommends University of Wyoming Soil testing lab recommends 40 lbs N per ton of grass, minus residual N in soil 40 lbs N per ton of grass, minus residual N in soil and from SOM (20 lbs per 1%).and from SOM (20 lbs per 1%).

Organic material is still best source of nutrients for Organic material is still best source of nutrients for reclamation:reclamation:–– Time release instead of excess nutrientTime release instead of excess nutrient–– Beef manure: about 12 lbs N per ton with 25% available Beef manure: about 12 lbs N per ton with 25% available

11stst year;year;–– Compost: about half that.Compost: about half that.

Production examples for Production examples for ESDsESDs

Foothill loamy 15Foothill loamy 15--1919”” precipprecip. big sage/bunchgrass: . big sage/bunchgrass: 1600 lbs/ac (32 lbs N/ac 1600 lbs/ac (32 lbs N/ac –– soil N)soil N)

Western foothills and basins, loamy, 10Western foothills and basins, loamy, 10--1414”” precipprecip., big ., big sage/bunchgrass: 900 lbs/ac (18 lbs N sage/bunchgrass: 900 lbs/ac (18 lbs N –– soil test)soil test)

Loamy 7Loamy 7--9" Green River and Great Divide Basins, Mixed 9" Green River and Great Divide Basins, Mixed grass/big sage: 500 lbs/ac (10 lbs)grass/big sage: 500 lbs/ac (10 lbs)

Saline Lowland 7Saline Lowland 7--9" Green River and Great Divide 9" Green River and Great Divide Basins greasewood/inland Basins greasewood/inland saltgrasssaltgrass: 600 lbs/ac (12 lbs): 600 lbs/ac (12 lbs)

Loamy 15Loamy 15--1717”” Northern Plains Precipitation Zone Northern Plains Precipitation Zone Rhizomatous Rhizomatous WheatgrassesWheatgrasses/ Needle and thread/Big / Needle and thread/Big Bluestem: 1900 lbs/ac (38 lbs N/ac)Bluestem: 1900 lbs/ac (38 lbs N/ac)

Ecological site Ecological site descriptionsdescriptions Ecological Site Information System Ecological Site Information System

(ESIS): (ESIS): http://esis.sc.egov.usda.gov/ESIS/http://esis.sc.egov.usda.gov/ESIS/

Click on Click on ESDsESDs;; Click on Click on ““Approved ESD ReportsApproved ESD Reports”” in in

upper left;upper left; Enter Wyoming from dropdown menu Enter Wyoming from dropdown menu

and submit.and submit.

Inoculants & conditionersInoculants & conditioners

In some cases positive response has been In some cases positive response has been reported for reported for mycorrhizalmycorrhizal, compost teas, and , compost teas, and other types of inoculants;other types of inoculants;

Seed treatments are inoculants and some Seed treatments are inoculants and some practitonerspractitoners report positive results;report positive results;

HumatesHumates and other amendments and other amendments recommended at much lower rates than OM recommended at much lower rates than OM contents require may improve structure and contents require may improve structure and nutrient availability;nutrient availability;

Be skeptical!Be skeptical!

Fungi and bacteria are ubiquitous in soils Fungi and bacteria are ubiquitous in soils and increase if available substrates (organic and increase if available substrates (organic materials) are present;materials) are present;

Applying compost or manure brings Applying compost or manure brings microbes along;microbes along;

Applying inoculants without substrate might Applying inoculants without substrate might be waste of money;be waste of money;

Try novel amendments as controlled trials: Try novel amendments as controlled trials: compare areas with and without materials in compare areas with and without materials in same year under same conditions.same year under same conditions.

ConclusionsConclusions

Amend only to recover original conditions;Amend only to recover original conditions; Soil test to compare adjacent undisturbed Soil test to compare adjacent undisturbed

site to reclamation site;site to reclamation site; Pay attention to surface horizon, usually top Pay attention to surface horizon, usually top

22--3 inches;3 inches; Compost is the best amendment to recover Compost is the best amendment to recover

fertility for rangeland plant establishment fertility for rangeland plant establishment and can be applied at economical rates.and can be applied at economical rates.