Regional Experiences With The Illinois Amino Sugar N Test

Larry G. Bundy and Jeffery T. Osterhaus

University of Wisconsin-Madison

Madison, Wisconsin

Basis for the Illinois Soil N Test

• Amino sugar-N fraction related to corn N response (Mulvaney et al. 2001)– Requires acid hydrolysis of soil N to measure

amino sugar N fraction

• Illinois soil N test (ISNT) proposed (Khan et al. 2001)– Measures amino sugar-N plus other soil N

components– Related to amino sugar –N fraction– Related to corn N response

University of Illinois results for relationship of amino sugar-N and

N-fertilizer response

Mulvaney et al., 2001

Background of the Illinois soil nitrogen test

Khan et al., 2001

Background of the Illinois soil nitrogen test

• Developed in the late 1990’s by University of Illinois researchers

• Low temperature, alkaline digestion

• Diffusion of NH3 from alkaline digestion

• Titration or colorimetric determination of NH3-N sorbed by acid solution

Background of the Illinois soil nitrogen test

• Results showed a relationship between soil amino sugar-N and N-fertilizer response

• Strong correlation of ISNT values to soil amino sugar-N values

• Identified an ISNT critical value of 225 ppm, above which no response to N fertilizer was observed

Wisconsin ISNT Experiments

• 80 experiments

• 1984-2004

• Multiple soils

• Multiple cropping systems

• Variety of management practices

• Wide range of N-response

Iowa ISNT Evaluation Sites

1999-2001 18 Replicated N Rate Sites Research Farm and Producer Fields Corn-Soybean Rotation

2001-2003 43 Replicated N Rate Sites Soil Nitrogen and Carbon Management Project Producers Fields Corn-Soybean Rotation

First-Year of N Rate Application

Relationship of ISNT values to economic optimum N rates in

Wisconsin• Poor relationship of ISNT values to economic optimum N rates

(EONR) over a wide range of:– growing seasons– crop rotations– management histories

• Experimental sites had a wide range of anticipated and observed N response

ISNT (mg kg-1)

0 50 100 150 200 250 300 350 400

EO

NR

(kg

ha-1

)

0

50

100

150

200

250

300Critical valueof 225 mg kg-1

r2 = 0.0013n = 80

Results with the Illinois soil nitrogen test in Wisconsin

• Critical value of 225 mg kg-1 did not separate responsive from non-responsive sites

ISNT (mg kg-1)

0 50 100 150 200 250 300 350 400

EO

NR

(kg

ha-1

)

0

50

100

150

200

250

300Critical valueof 225 mg kg-1

r2 = 0.0013n = 80

Relationship Between the Illinois N Soil Test (Spring 0-12 Inch Depth Samples) and Economic N Rate (10:1 Corn:N ratio)

0

20

40

60

80

100

120

140

160

180

200

0 100 200 300 400 500 600

Illinois N Soil Test (ppm)

Ec

on

om

ic N

Ra

te (

lb N

/ac

re)

200120022003

J.E. Sawyer, Iowa State Univ., 2003

Results with the ISNT- Michigan

C.A.M. Laboski, Mich. St. Univ.

Results of the ISNT - Wisconsin

• No significant difference between crop rotations where a large difference in N response was observed

Crop rotation EONR ISNT

(0-15 cm sample depth)----kg ha-1---- ------------mg kg-1------------

Corn/corn 149 181

Alfalfa/corn 0 179

Alfalfa/corn/corn 69 193

Soybean/corn 136 192

Relationship of ISNT to soil organic matter - Wisconsin

• Strong correlation of ISNT values to soil organic matter (OM) shows that the ISNT is probably measuring a constant fraction of soil organic N rather than a readily mineralizable N pool

Organic matter (%)

0 1 2 3 4 5

ISN

T (

mg

kg

-1)

0

100

200

300

400

y = 12.9715 + 62.5734xr2 = 0.88n = 80

J.E. Sawyer, Iowa State Univ., 2003

Illinois N Soil Test and Total Soil N(Spring or Fall 0-12 Inch Depth Samples)

0

1000

2000

3000

4000

0 100 200 300 400 500 600

Illinois N Soil Test (ppm)

To

tal

So

il N

(p

pm

)

200120022003

Total Soil N = -41.4 + 6.608*INST, R2 = 0.86***

Hydrolyzable N fractionation

• Hydrolyzable organic N fractions– Total hydrolyzable N

– Hydrolyzable ammonium (NH4-N)

– (Amino sugar + NH4-N)-N

– Amino sugar-N– Amino acid-N– Unidentifiable hydrolyzable-N

Hydrolyzable N fractions(experiments used)

• 13 experiments

• Multiple crop rotations– Continuous corn– Soybean/corn– Alfalfa/corn– Alfalfa/corn/corn

• Multiple years: 1998, 2001, 2003, 2004

Hydrolyzable N Fractionation

• Acid digestion– 6 M HCl– 12-hour digestion

• Sample neutralization• Diffusion or steam

distillation of hydrolyzable N fractions

Results of soil hydrolysate analysis

• Weak correlation of all fractions to N-fertilizer response

• Amino sugar-N had a poor relationship to N-fertilizer response

Relationships between soil organic N fractions and corn response to N fertilization†

N-Fraction r2 p > f ‡

Total hydrolyzable N 0.0033 0.8517

NH4-N 0.0126 0.7153

NH4+Amino sugar-N 0.0039 0.8384

Amino sugar-N 0.0000 0.9898

Amino acid-N 0.1039 0.2835

† Corn response to N fertilization is defined as: 100 x [(maximum yield – control yield) / control yield]; where maximum yield occurs with a non-limiting N fertilizer rate.

‡ p > f = probability that tabular f ratio exceeds f ratio calculated by analysis of variance.

Illinois soil nitrogen test compared to total nitrogen

Illinois soil nitrogen test (mg kg-1)

120 140 160 180 200 220 240 260 280 300

To

tal

nit

rog

en (

%)

0.12

0.14

0.16

0.18

0.20

0.22

0.24

0.26y = 0.0212 + 7.8992xr2 = 0.9086n = 13

Relationship of amino sugar-N to relative yield

Amino sugar-N (mg kg-1)

150 200 250 300 350 400

N-F

erti

lize

r R

esp

on

se (

%)

0

20

40

60

80

100

120y = 42.5686 + 0.0015x

r2 = 0.00002n = 13

J.E. Sawyer, Iowa State Univ., 2003

Hydrolyzable Amino Sugar-N (spring samples) and Corn N-Fertilizer Response -- 1999-2002 N Rate Sites

0

20

40

60

80

100

120

140

160

180

0 100 200 300 400 500

Amino Sugar-N (ppm)

N-F

erti

lize

r R

esp

on

se (

%)

0-6 Inch

0-12 Inch

Conclusions - Wisconsin

• ISNT does not correlate with EONR• ISNT does correlate strongly with OM• Amino sugar-N does not correlate with N-

fertilizer response• Other hydrolyzable-N fractions do not correlate

with N-fertilizer response• ISNT is not a practical tool for use in Wisconsin

corn production

Experience in Iowa

Illinois N Soil Test (routine test) has not been predictive of corn response to applied N

Hydrolyzable amino sugar-N basis also not well correlated to N response

At this time the Illinois N Soil Test is not recommended for adjusting corn N fertilization on Iowa soils

J.E. Sawyer, Iowa State Univ., 2003

Acknowledgements

The authors are grateful to Dr. John Sawyer and Dr. Carrie Laboski for providing the data from Iowa and Michigan.

Illinois soil nitrogen test compared to total carbon

Illinois soil nitrogen test (mg kg-1)

120 140 160 180 200 220 240 260 280 300

To

tal c

arb

on

(%

)

0.5

1.0

1.5

2.0

2.5

3.0y = -0.5128 + 0.0106xr2 = 0.8857n = 13