University of Wisconsin-Madison Department of Soil Science 2006 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

University of Wisconsin-Madison Department of Soil Science 2006 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 NH 3 from alkaline digestion Titration or colorimetric determination of NH 3 -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 Multiple soils Multiple cropping systems Variety of management practices Wide range of N-response

Iowa ISNT Evaluation Sites   18 Replicated N Rate Sites  Research Farm and Producer Fields  Corn-Soybean Rotation   43 Replicated N Rate Sites  Soil Nitrogen and Carbon Management Project  Producers Fields  Corn-Soybean Rotation  First-Year of N Rate Application

University of Wisconsin-Madison Department of Soil Science 2006 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

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

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 rotationEONRISNT (0-15 cm sample depth) ----kg ha mg kg Corn/corn Alfalfa/corn0179 Alfalfa/corn/corn69193 Soybean/corn136192

University of Wisconsin-Madison Department of Soil Science 2006 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

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

University of Wisconsin-Madison Department of Soil Science 2006 Hydrolyzable N fractionation Hydrolyzable organic N fractions –Total hydrolyzable N –Hydrolyzable ammonium (NH 4 -N) –(Amino sugar + NH 4 -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

Hydrolyzable N Fractionation Acid digestion –6 M HCl –12-hour digestion Sample neutralization Diffusion or steam distillation of hydrolyzable N fractions

University of Wisconsin-Madison Department of Soil Science 2006 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

University of Wisconsin-Madison Department of Soil Science 2006 Relationships between soil organic N fractions and corn response to N fertilization† N-Fraction r 2 p > f ‡ Total hydrolyzable N NH 4 -N NH 4 +Amino sugar-N Amino sugar-N Amino acid-N † 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

University of Wisconsin-Madison Department of Soil Science 2006 Relationship of amino sugar-N to relative yield

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

University of Wisconsin-Madison Department of Soil Science 2006 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

University of Wisconsin-Madison Department of Soil Science 2006 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