• Soil organic matter content and soil structural stability are usually measured for determining soil quality• Any further characterization of the organic fraction of the soil is limited by the availability of specialized equipment and increasing expenses

• Methods need to be simplified and made cheaper for routine applications

INTRODUCTION• Soil polysaccharides contribute to aggregate stabilization and serve as a substrate for soil organisms

OBJECTIVESObjectives of this study were:1. to select accurate and easy methods for rapid

extraction, purification and measurement of soil polysaccharides at low cost

2. to test the proposed methods in determining soil quality for different land uses

MATERIALS and METHODS

Location: Eastern South Dakota, USA (Colman, SD)

• CROPLAND - annual crops for >80 years• CONVERTED cropland - 3-year perennial grasses & forbs • PASTURE - perennial pasture for >80 years• PRAIRIE - prairie remnant not cropped or pastured• Topsoil samples (0-15 cm depth), taken with a spade (n=3),

and air-dried (p/p0=0.28) at 25°C

Soil series: Egan silty clay loam fine-silty, mixed, superactive, mesic Udic Haplustoll

SOIL POLYSACCHARIDES

ACID EXTRACTION• Weigh 100 mg air dry < 2 mm soil fraction Solubilization • Add 800 L of 6 M H2SO4 and let stand for 30 min

Hydrolysis • Add 4.2 mL of DI water to dilute to 1 M H2SO4

• Autoclave at 121° C (15 psi = 103 kPa) for 30 min

ACID EXTRACTION (adapted from Martens & Loeffelmann, 2002)

Reagents• Deionized H2O (DI)

• 6 M H2SO4

Special equipment• Autoclave (14 L)

SPECTROPHOTOMETRIC QUANTIFICATION• Pipette 250 L of each sample in a glass vial (DI as blank)• Add 250 L of 5 % phenol to each vial• Rapidly add 1.250 mL of 18 M H2SO4 into the solution• Let stand 10 min and then incubate at 30°C for 20 min• Measure absorbance at 490 nm

SPECTROPHOTOMETRIC QUANTIFICATION(adapted from Dubois et al., 1956)

Reagents• Deionized H2O (DI)

• H2SO4 96.5 % v/v • Phenol 5% m/v

Special equipment• Spectrophotometer (490 nm)

WET AGGREGATE STABILITY (WAS) Single sieve mechanical procedure, shaking 1-2 mm air-dry aggregates for 5 min directly immersed in deionized water (Kemper and Rosenau, 1986)

OTHER SOIL QUALITY MEASUREMENTS

WETTING RATE (WETTABILITY) Wetting rate at 100 mm tension on 10-mm diameter air-dry

aggregates (Quirk & Panabokke, 1962)

MICROBIAL ACTIVITY (FDA)Fluorescein diacetate hydrolytic activity

(Eynard & Schumacher, 2010)

Organic Matter (SOM) Mass loss on ignition at 450C for 4 hours

(Cambardella et al., 2001)

Particulate Organic Matter (POM) •Coarse POM = organic particles 2 to 0.5-mm size•Fine POM = organic particles 0.5 to 0.05-mm size

by mass loss on ignition at 450C for 4 hours (Cambardella et al., 2001)

STATISTICAL ANALYSIS •Relations between variables tested by linear regression using SYSTAT 12 (SPSS, 2007)

RESULTS

0

5

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35

Crop 3-year grass Pasture Prairie

po

lys

ac

ch

ari

de

s (

g k

g-1

)

0

20

40

60

80

100

120

140

160

Crop 3-year grass Pasture Prairie

So

il o

rga

nic

fra

cti

on

s (

g k

g-1

)

fine POMcoarse POM

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100

Crop 3-year grass Pasture Prairie

WA

S (

%)

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140

Crop 3-year grass Pasture Prairie

FD

A (

mg

kg

-1h

ou

r-1)

PURIFICATION (adapted from Martens & Frankenberger, 1990)

Materials• Deionized H2O (DI) • 0.22 m Millipore GS filters • SCX + SAX exchange columns

Special equipment• centrifuge (2000 rpm)• vacuum pump 65 kPa• vacuum manifold

PURIFICATION• Let cool, centrifuge, wash residues and collect extract • Filter extract through 0.22 m Millipore GS filters• Purify the filtrate through a solid phase extraction system composed by a SCX and a SAX column

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250

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350

400

450

0 5 10 15 20 25 30 35

polysaccharides (g kg-1)

60

min

wa

ter

up

tak

e (

g k

g-1

)

Uptake at 60 = 7.51*polysaccharides + 155.05 R2 = 0.65**

Prairie

0

20

40

60

80

100

120

0 5 10 15 20 25 30 35

polysaccharides (g kg-1)

WA

S (

%)

WAS = 3.86*polysaccharides – 14.52 R2 = 0.63**

FDA = 6.88*polysaccarides – 50.69 R2 = 0.94**

Prairie

0

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160

0 5 10 15 20 25 30 35

polysaccharides (g kg-1)

SO

M (

g k

g-1

)

SOM = 4.28*polysaccharides + 11.02 R2 = 0.94**

• The proposed method consistently measured soil polysaccharides (CV = 0.06 to 0.10)

• Soil polysaccharides in the topsoil were directly related to soil organic matter, wet aggregate stability, hydrolytic microbial activity, and water uptake under tension

• Soil polysaccharide relationships with microbial activity and water uptake were different for the remnant prairie compared to the other land uses

• Measurement of soil polysaccharides complement common measurements of soil quality

• Soil quality under different land uses is being further examined in an on-going research project

CONCLUSIONS

REFERENCES• Cambardella, C.A., A.M. Gajda, J.W. Doran, B.J. Wienhold, and T.A.

Kettler. 2001. Estimation of particulate and total organic matter by weight loss-on-ignition. p. 349-359. In Lal R. et al. (eds.) Assessment methods for soil carbon. Lewis Publ., Boca Raton, FL.

• Dubois, M., K.A. Gilles, J.K. Hamilton, P.A. Rebers, and F. Smith. 1956. Colorimetric method for determination of sugars and related substances. Anal. Chem. 28, 3: 350-356.

• Eynard A., and T. E. Schumacher. 2010. A rapid, cost-effective, and greener FDA method for soil quality analysis. SWCS meeting, St. Louis, MO, July 2010.

• Kemper, W.D., and R.C. Rosenau. 1986. Aggregate stability and size distribution. p. 425-442. In Klute A. (ed.) Methods of Soil Analysis. No. 9 Part 1. Physical and Mineralogical Methods. 2nd ed. American Society of Agronomy-Soil Science Society of America, Madison, WI.

• Martens, D.A., and W.T. Frankenberger Jr. 1990. Quantification of soil saccharides by spectrophotometric methods. Soil Biol. Biochem. 22, 8: 1173-1175.

• Martens, D.A., and K.L. Loeffelmann. 2002. Improved accounting of carbohydrate carbon from plants and soils. Soil Biol. Biochem. 34: 1393-1399.

• Quirk, J.P., and C.R. Panabokke. 1962. Incipient failure of soil aggregates. J. Soil Sci. 13, 1: 60-70.

• Soil Survey Staff, NRCS-USDA. 2010. Official soil series descriptions. http://soils.usda.gov/soils/technical/classification/osd/index.html (accessed October 15, 2010).

• SPSS Inc. 2007. SYSTAT 12 statistics I. Chicago, IL.

SOIL POLYSACCHARIDE MEASUREMENTS IN THE EVALUATION OF SOIL QUALITY FOR MULTIFUNCTIONAL AGRICULTURE

A. Eynard, T. E. Schumacher and R. A. Kohl, South Dakota State University

FDA = 6.88*polysaccarides – 50.69 R2 = 0.94**

0

20

40

60

80

100

120

140

0 5 10 15 20 25 30 35

polysaccharides (g kg-1)

FD

A (

mg

kg

-1h

ou

r-1)

Prairie

FDA = 6.88*polysaccharides – 50.69 R2 = 0.94**

AcknowledgementsSupport was provided by the USDA-NRCS Conservation Innovation Grant Program, South Dakota Agricultural Experiment Station, NC Sun Grant/DOE, and SD Corn Utilization Council. Appreciation is given to the Nature Conservancy and EcoSun Prairie Farms Inc. for providing access to sampling locations.

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Crop3-year grassPasturePrairie