Regional Experiences With The Illinois Amino Sugar N Test

1. 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

2. 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

3. University of Illinois results for relationship of amino sugar-N and N-fertilizer response Mulvaney et al., 2001

4. Background of the Illinois soil nitrogen test Khan et al., 2001 University of Wisconsin-Madison Department of Soil Science 2006

5. 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

6. 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

7. 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

8. 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

9. 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

10. Results with the Illinois soil nitrogen test in Wisconsin • Critical value of 225 mg kg-1 did not separate responsive from non-responsive sites University of Wisconsin-Madison Department of Soil Science 2006

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

12. Results with the ISNT- Michigan C.A.M. Laboski, Mich. St. Univ.

13. Results of the ISNT - Wisconsin • No significant difference between crop rotations where a large difference in N response was observed

14. 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 University of Wisconsin-Madison Department of Soil Science 2006

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

16. 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

17. 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

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

19. 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

20. Relationships between soil organic N fractions and corn response to N fertilization† N-Fraction r2p > 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. University of Wisconsin-Madison Department of Soil Science 2006

21. Illinois soil nitrogen test compared to total nitrogen

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

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

24. 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 University of Wisconsin-Madison Department of Soil Science 2006

25. 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

26. 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

27. Illinois soil nitrogen test compared to total carbon