Do you need a soil health test?

Charlie White Department of Plant Science

Penn State College of Agriculture

High crop yields Erosion control Water quality Carbon sequestration Disease suppression Global biodiversity

Chem

ical

N

utrie

nts

What is soil health? Soil functioning to provide a multitude of services for farms, the environment, and society… Soil Health Soil Biogeochemistry

Soil Health Testing Services are Commercially Available

• Cornell Soil Health Test • Woods End Laboratory Soil Health Tool

– Integrates “Solvita” test and “Haney” test • Traditional soil testing labs??

Soil Health Indicators Measured by Each Testing Lab

Soil health indicator Cornell Woods

End Traditional

Soil Test Lab Soil Organic Matter $ $$ Active Carbon (POXC) $$ Water Soluble Carbon $ Microbial Respiration $ $ Amino/Protein Nitrogen $$ $ Nitrate Nitrogen $$ Soil-borne Diseases Soil Chemistry (P, K, Ca, Mg, pH) $ $$

Soil Compaction $ Aggregate Stability $ $ Available Water $$ Soil Texture $$

Package Costs $=$50/$30 $$=$95/$55 =Add-ons at $5-20

Can these basic measures be calibrated to predict specific soil health services?

Chem

ical

High crop yields Erosion control Water quality Carbon sequestration Disease suppression Global biodiversity

Organic Matter

Organic Matter Organic Matter

Nut

rient

s

Are there basic measurements already offered by traditional labs that can predict soil health?

Soil Health

Soil Health Testing Projects Pennsylvania Soil Health Survey: 2015-2016 • Penn State Extension Educators identified farms, collected soil samples • Long-term research plots at Penn State • Compared

– Woods End Soil Health Tool Premium ($55-$75) – Cornell Soil Health Test Standard ($95) – PSU % organic matter and Mehlich 3 nutrients ($14)

• 27 samples collected from 0-8” depth Maryland and Virginia Soil Health Survey: 2008-2009 • Farms throughout MD and Northern VA requested soil health sampling • Submitted samples to Cornell for the prototype soil health test package • 37 samples collected from 0-6” depth $8,383 worth of soil testing services…

Thank You Northeast SARE!!!

Distribution of % Organic Matter and Soil Texture

0

2

4

6

8

10

12

14

1 2 3 4 5 6 7

# O

bser

vatio

ns

% Organic Matter

PAMD, VA

y = 0.926x + 0.707 R² = 0.9615

1

2

3

4

5

6

7

8

1 2 3 4 5 6 7 8

Corn

ell %

OM

PSU AASL %OM

Inconsistency across labs in soil organic matter measurements • Woods End reports raw % Loss on Ignition • Cornell % OM is ~ 0.5 % points greater than PSU • These discrepancies caused confusion and concern among the

county Extension Educators

Soil Health Measurements Active Carbon (or Permanganate Oxidizable Carbon)

– Carbon in soil organic matter oxidized by weak solution of potassium permanganate

– Only available via Cornell Soil Health Test – Correlated to total soil organic matter and microbial

biomass – Sensitive to short-term changes in soil management

Comparison of Soil Health Indicators to % Organic Matter

Active Carbon (POXC)

y = 307.27ln(x) + 161.79 R² = 0.61

0

100

200

300

400

500

600

700

800

900

1000

0 1 2 3 4 5 6 7 8 9

POXC

(mg

C/kg

soil)

% Organic Matter

PAMD, VA

Soil Health Measurements Microbial Activity

– Quantity of CO2 respired by microbes over 24 or 96 hours in a lab incubation of re-wetted soil

– Indicator of size of microbial population and availability of organic matter to decompose

– Potential indicator of N mineralization – Available via Woods End Soil Health Tool, Cornell Soil Health Test,

certain soil testing labs including Agri-Analysis and Dairy One ($30 @ Agri-Analysis)

Comparison of Soil Health Indicators to % Organic Matter

Microbial Respiration

Woods End =24 hr CO2 Burst

Cornell =96 hr CO2 Burst

y = 10.91x + 55.47 R² = 0.59

020406080

100120140160180

0 2 4 6 8 10

mg

CO2-

C/kg

soil/

24hr

Woods End % LOI

y = 0.10x2 - 0.49x + 1.14 R² = 0.86

0

0.5

1

1.5

2

2.5

3

3.5

0 2 4 6 8

g CO

2/kg

soil/

4d

Cornell %Organic Matter

Soil Health Measurements Labile Organic Nitrogen

– Organic nitrogen forms that can easily be mineralized by soil microbes: proteins and amino acids

– Woods End Soil Health Tool uses SLAN test • Solvita Labile Amino Nitrogen

– Cornell Soil Health Test now uses ACE Protein Index • Used to use 7 day anaerobic N mineralization

Comparison of Soil Health Indicators to % Organic Matter

Labile Organic Nitrogen

Woods End =Solvita Labile Amino N (SLAN)

Cornell =ACE Soil Protein Index (now) 7d anaerobic mineralization (previously)

y = 53.03x - 126.81 R² = 0.85

0

50

100

150

200

250

300

350

0 2 4 6 8 10

SLAN

Woods End % LOI

y = 0.77x2 - 3.76x + 8.91 R² = 0.93

0

5

10

15

20

25

0 2 4 6 8

ACE

Prot

ein

Inde

x

y = 3.30x + 2.92 R² = 0.66

05

101520253035

0 2 4 6 8

mg

N/k

g so

il/7d

Cornell % Organic Matter

Soil Health Measurements Aggregate Stability

– Ability of soil aggregates to resist erosion, slaking, crusting

– Important for water infiltration, aeration, rooting Soil Crumbled and Dried

Soil Saturated then Dried

Comparison of Soil Health Indicators to % Organic Matter Aggregate Stability

Woods End Measured volumetrically

Cornell Measured by weight

y = 0.06x + 0.06 R² = 0.43

0%

10%

20%

30%

40%

50%

60%

70%

0 2 4 6 8 10

Aggr

egat

e St

abili

ty

Woods End % LOI

y = 9.48x + 6.26 R² = 0.43

0

20

40

60

80

100

0 2 4 6 8 10

Aggr

egat

e St

abili

ty (%

)

% Organic Matter

PAMD, VA

Regression Model including soil texture: AgStab = 18 + 9.8 * %OM – 1.1 * %Clay R2 = 0.54, RMSE=15

Soil Health Measurements Available Water Capacity (AWC) – Cornell Only

– Water retained in the soil between field capacity and permanent wilting point (g water/g soil)

– A function of pore size distribution (controlled by soil texture) and organic matter

– AWC = 0.57 + (0.016*%OM) - (0.0058*%Sand) - (0.0043*%Silt) , r2=0.66 and RMSE = 0.04

For every 1% of organic matter you gain 0.16 inches of water in the plow layer, ~ half a day’s worth of corn evapotranspiration during pollination and grain fill

Soil Health Measurements Soil Chemistry

– Nutrient Levels, pH – Important for healthy crops – Cornell Soil Health Test uses modified Morgan’s extract – Woods End Soil Health Tool uses H3A extract – Standard soil extract in Pennsylvania is Mehlich 3

H3A extract compared to Mehlich 3 H3A (named after Haney, Haney, Hossner, and Arnold)

• Contains lithium citrate, oxalic acid, malic acid, citric acid, EDTA, DTPA • Designed to be a ‘universal’ soil extract • Adjusts to native pH of each soil tested, so can be used across many regions • Can extract nitrate and ammonium • Embraced by the soil health movement because ingredients in the extract are

similar to root exudates • Has not been extensively calibrated to predict fertilizer requirements Mehlich 3 • Contains acetic acid, EDTA, ammonium nitrate, ammonium flouride, nitric acid • Designed to be a ‘universal’ soil extract for neutral to acidic soils • pH of 2.5 is 1,000 to 10,000 times more acidic than native soil, but is necessary

to extract phosphorus from minerals that are sparingly soluble • Can’t extract nitrate and ammonium because they are ingredients in the extract • Is well calibrated to predict fertilizer requirements

H3A is highly correlated with Mehlich 3 for P, K, and Mg

R² = 0.7365

010203040506070

0 100 200 300

H3A

P (p

pm)

Mehlich 3 P (ppm)

R² = 0.8712

0

50

100

150

200

250

300

0 200 400 600

H3A

K (p

pm)

Mehlich 3 K (ppm)

R² = 0.8843

0

100

200

300

400

500

600

0 200 400 600

H3A

Mg

(ppm

)

Mehlich 3 Mg (ppm)

R² = 0.0648

0

500

1000

1500

0 1000 2000 3000

H3A

Ca

(ppm

)

Mehlich 3 Ca (ppm)

But not for Ca!

Soil organic matter and texture can predict many soil health indicators Soil health indicator Cornell Woods

End Traditional

Soil Test Lab Soil Organic Matter $ $$ Active Carbon (POXC) $$ Water Soluble Carbon $ Microbial Respiration $ $ Amino/Protein Nitrogen $$ $ Nitrate Nitrogen $$ Soil-borne Diseases Soil Chemistry (P, K, Ca, Mg, pH) $ $$

Soil Compaction $ Aggregate Stability $ $ Available Water $$ Soil Texture $$

A biogeochemical perspective on soil health… If you think about soil carbon and nitrogen cycling processes as pools and fluxes…

If you can model the C fluxes with first order rate constants…

• Then all C pools and all C fluxes are linearly related to each other • When pools are in equilibrium, any one pool (or combination of pools) can

predict every other pool size • Pools with shorter mean residence time (size/rate) are more dynamic and will

equilibrate faster

Particulate Organic Matter

CO2 Burst Water Soluble Organic C

Labile N

Microbial respiration increases while cover crops are growing

30

40

50

60

70

80

90

Mic

robi

al R

espi

ratio

n

(mg

CO2/

kg so

il/24

hr)

Rye

Pea

Clover

Radish

Oat

Canola

Fallow

What does it mean to be labile today? • A new view of soil organic matter has emerged1, 2

– Simple molecules predominate – Stability is conferred through organo-mineral

complexes – Can soil tests of ‘labile’ fractions be reconciled with

new soil organic matter theories?

2 Figure Source: M. Kleber et al. Biogeochemistry (2007) 85:9-24. 1Schmidt et al. Nature (2011) 478(7367): 49–56.

Can models to predict soil health services be calibrated with cheap, easily understood, widely available measurements?

A case study on NO3- leaching and N supply to corn as affected by

soil and cover crop management

3-species Mixtures 4-species Mixture Monocultures Red Clover

(RC) Austrian Winter Pea +

Crimson Clover + Triticale (AWP+CC+Tr)

Austrian Winter Pea + Canola + Red Clover + Rye (AWP+Ca+RC+Ry)

Rye (Ry)

Crimson Clover + Forage Radish + Rye

(CC+FR+Ry)

Ladino Clover + Red Clover + Sweet Clover

(LC+RC+SC)

Austrian Winter Pea + Red Clover + Rye

(AWP+RC+Ry)

Montour Centre Lancaster Berks

Tested a wide range of cover crop mixtures to develop models that could inform management • Measured potential nitrate leaching with buried anion exchange

resin bags • Measured relative corn yield following cover crop termination

Models to Predict Relative Yield and Nitrate Leaching

Relative Yield = 1.06 – 0.029 * Fall Cover Crop C:N – 0.0048 * Spring Cover Crop C:N + 0.0011 * Spring Cover Crop N + 0.093 * Soil %C

Potential Nitrate Leaching = 3.7e0.053*AugustSoilNO3-

* e0.025*FallWinter-killedBiomassN

* e0.015*FallCanolaBiomassN

* e–3.1*FractionalNon-LegumeSeedingRate

Fall Growing Degree Days Spring Growing Degree Days

Decision support tool to guide cover crop mixture management

Pros and Cons of Soil Health Testing Pros: • Detailed information on soil processes • Testing integrates physical, chemical, biological indicators • Can reveal specific soil health limitations to address • Pushing the envelope, expanding our understanding!

Cons: • Most tests lack well-defined interpretations and calibrations,

limiting their use as a management tool • Testing packages are constantly changing • Expensive • Long turnaround time

Where do we go from here?

Feel free to contact me for more information: Charlie White - cmw29@psu.edu - 814-863-9922

This presentation is a training initiative of the Northeast SARE Pennsylvania State Program

Research supported by USDA OREI and AFRI grants

• Learn from biogeochemical theories • Develop calibrations to response variables of interest • If possible, use soil tests that are cheap, well understood, widely

available