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Regional Experiences With The
Illinois Amino Sugar N Test
Larry G. Bundy and Jeffery T. Osterhaus
University of Wisconsin-Madison
Madison, Wisconsin
University of Wisconsin-Madison Department of Soil Science 2006
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
University of Wisconsin-Madison Department of Soil Science 2006
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
University of Wisconsin-Madison Department of Soil Science 2006
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
University of Wisconsin-Madison Department of Soil Science 2006
Wisconsin ISNT Experiments
•
•
•
•
•
•
80 experiments
1984-2004
Multiple soils
Multiple cropping systems
Variety of management practices
Wide range of N-response
University of Wisconsin-Madison Department of Soil Science 2006
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
300
Critical value
of 225 mg kg-1
EONR (kg ha-1)
250
200
150
100
50
r2 = 0.0013
n = 80
0
0
50
100
150
200
250
300
350
400
ISNT (mg kg-1)
University of Wisconsin-Madison Department of Soil Science 2006
Results with the Illinois soil
nitrogen test in Wisconsin
• Critical value of 225 mg kg-1 did not separate responsive
from non-responsive sites
300
Critical value
of 225 mg kg-1
EONR (kg ha-1)
250
200
150
100
50
r2 = 0.0013
n = 80
0
0
50
100
150
200
250
300
350
400
ISNT (mg kg-1)
University of Wisconsin-Madison Department of Soil Science 2006
Relationship Between the Illinois N Soil Test (Spring 0-12 Inch
Depth Samples) and Economic N Rate (10:1 Corn:N ratio)
200
2001
2002
2003
Economic N Rate (lb N/acre)
180
160
140
120
100
80
60
40
20
0
0
100
200
300
400
500
600
Illinois N Soil Test (ppm)
J.E. Sawyer, Iowa State Univ., 2003
Results with the ISNT- Michigan
150
EONR (lb N/a)
125
100
75
50
2002
2003
2004
25
0
50
C.A.M. Laboski, Mich. St. Univ.
100
150
200
INST (ppm N)
250
300
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
400
y = 12.9715 + 62.5734x
2
r = 0.88
n = 80
ISNT (mg kg-1)
300
200
100
0
0
1
2
3
4
5
Organic matter (%)
University of Wisconsin-Madison Department of Soil Science 2006
Illinois N Soil Test and Total Soil N
(Spring or Fall 0-12 Inch Depth Samples)
Total Soil N (ppm)
4000
2001
2002
2003
3000
Total Soil N = -41.4 + 6.608*INST, R2 = 0.86***
2000
1000
0
0
100
200
300
400
500
600
Illinois N Soil Test (ppm)
J.E. Sawyer, Iowa State Univ., 2003
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
University of Wisconsin-Madison Department of Soil Science 2006
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
University of Wisconsin-Madison Department of Soil Science 2006
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 Nfertilizer response
University of Wisconsin-Madison Department of Soil Science 2006
Relationships between soil organic N fractions
and corn response to N fertilization†
N-Fraction
r2
p>f‡
Total hydrolyzable N
NH4-N
NH4+Amino sugar-N
Amino sugar-N
Amino acid-N
0.0033
0.0126
0.0039
0.0000
0.1039
0.8517
0.7153
0.8384
0.9898
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.
University of Wisconsin-Madison Department of Soil Science 2006
Illinois soil nitrogen test compared
to total nitrogen
0.26
Total nitrogen (%)
0.24
y = 0.0212 + 7.8992x
r2 = 0.9086
n = 13
0.22
0.20
0.18
0.16
0.14
0.12
120
140
160
180
200
220
240
260
280
Illinois soil nitrogen test (mg kg-1)
300
Relationship of amino sugar-N to
relative yield
N-Fertilizer Response (%)
120
y = 42.5686 + 0.0015x
r2 = 0.00002
n = 13
100
80
60
40
20
0
150
200
250
300
350
-1
Amino sugar-N (mg kg )
University of Wisconsin-Madison Department of Soil Science 2006
400
Hydrolyzable Amino Sugar-N (spring samples) and Corn NFertilizer Response -- 1999-2002 N Rate Sites
N-Fertilizer Response (%)
180
160
0-6 Inch
140
0-12 Inch
120
100
80
60
40
20
0
0
100
200
300
400
500
Amino Sugar-N (ppm)
J.E. Sawyer, Iowa State Univ., 2003
Conclusions - Wisconsin
• ISNT does not correlate with EONR
• ISNT does correlate strongly with OM
• Amino sugar-N does not correlate with Nfertilizer response
• Other hydrolyzable-N fractions do not correlate
with N-fertilizer response
• ISNT is not a practical tool for use in Wisconsin
corn production
University of Wisconsin-Madison Department of Soil Science 2006
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.
University of Wisconsin-Madison Department of Soil Science 2006
Illinois soil nitrogen test compared
to total carbon
3.0
y = -0.5128 + 0.0106x
r2 = 0.8857
n = 13
Total carbon (%)
2.5
2.0
1.5
1.0
0.5
120
140
160
180
200
220
240
260
280
Illinois soil nitrogen test (mg kg-1)
300