North Central Regional Research Publication No. 221 (Revised) Recommended Chemical Soil Test Procedures for the North Central Region Agricultural Experiment Stations of Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, Pennsylvania, South Dakota and Wisconsin, and the U.S. Department of Agriculture cooperating. Missouri Agricultural Experiment Station SB 1001 Revised January 1998 (PDF corrected February 2011) Foreword Over the past 30 years, the NCR-13 Soil Testing Agricultural Experiment Stations over the past five and Plant Analysis Committee members have worked decades have been used to calibrate these recom- hard at standardizing the procedures of Soil Testing mended procedures. Laboratories with which they are associated. There NCR-13 wants it clearly understood that the have been numerous sample exchanges and experi- publication of these tests and procedures in no way ments to determine the influence of testing method, implies that the ultimate has been reached. Research sample size, soil extractant ratios, shaking time and and innovation on methods of soil testing should con- speed, container size and shape, and other laboratory tinue. The committee strongly encourages increased procedures on test results. As a result of these activi- research efforts to devise better, faster, less expensive ties, the committee arrived at the recommended pro- and more accurate soil tests. With the high cost of fer- cedures for soil tests. tilizer, and with the many soil related environmental Experiments have shown that minor deviations concerns, it is more important than ever that fertilizer in procedures may cause significant differences in test be applied only where needed and in the amount of results. It is to the advantage of all laboratories that each element needed for the response goal. The best the credibility of soil testing be enhanced. The adop- hope of attaining this goal is better soil tests and bet- tion of these recommended procedures by all labora- ter correlations with plant response. NCR-13 stands tories would be a major step toward improving the ready to evaluate promising new soil tests, and with image of soil testing and, hopefully, the integrity of clear justification will move quickly to revise their rec- fertilizer recommendations based on soil tests. ommendations. Calibration studies conducted by the North Central Past Administrative Advisors of NCR-13 M. B. Russell 1966-68 R. R. Davis 1969-74 Clive Donoho, Jr. 1975-83 Leo Walsh 1984-90 Ben Jones 1991-92 H. R. Lund 1993 Jim Brown 1994 Robert Gast 1995 Don Holt 1996 Boyd Ellis 1997 Contents Acknowledgments . 2 Introduction . 3 Chapters 1. Soil Sample Preparation . 5 R. H. Gelderman and A.P.Mallarino 2. Standard Soil Scoop . 7 T. R. Peck 3. Laboratory Factors of Importance to Soil Extraction . 11 R. Eliason 4. pH and Lime Requirement . 13 M. E. Watson and J. R. Brown 5. Nitrate-Nitrogen . 17 R. H. Gelderman and D. Beegle 6. Phosphorus . 21 K. Frank, D. Beegle and J. Denning 7. Potassium and Other Basic Cations . 31 D. Warncke and J. R. Brown 8. Sulfate-Sulfur . 35 S. Combs, J. Denning and K.D. Frank 9. Micronutrients: Zinc, Iron, Manganese and Copper . 41 D. A. Whitney 10. Boron . 45 M. E. Watson 11. Chlorides . 49 R. H. Gelderman, J. L. Denning and R. J Goos 12. Soil Organic Matter . 53 S. M. Combs and M. V. Nathan 13. Soil Salinity . 59 D. A. Whitney 14. Greenhouse Root Media . 61 D. Warncke 15. Laboratory Quality Assurance Program . 65 B. Hoskins and A. Wolf Glossary of Soil Testing Terms . 71 D. Warncke and K. Frank for the North Central Region 1 Acknowledgments Official NCR-13 Representatives This publication is sponsored by the Agricultur- North Dakota, Ohio, Pennsylvania, South Dakota and al Experiment Stations of Illinois, Indiana, Iowa, Wisconsin. The 1996-97 official representatives are Kansas, Michigan, Minnesota, Missouri, Nebraska, listed below. Boyd Ellis, Administrative Advisor J. R. Brown, Editor Illinois – T.R. Peck Indiana – Sylvie Brouder Iowa – Antonio Mallarino Kansas – David Whitney Michigan –Daryl D. Warncke Minnesota – George Rehm Missouri – J. R. Brown* Nebraska – Ken Frank North Dakota – Larry J. Cihacek Ohio – Maurice Watson Pennsylvania – Douglas Beegle South Dakota – Ron Gelderman Wisconsin – Sherry Combs Authorship The authors and co-authors of the chapters in resentatives to the NCR-13 committee with the fol- this edition of Recommended Chemical Soil Test Pro- lowing exceptions: cedures for the North Central Region are official rep- J. Denning – University of Nebraska Soil and Plant Analytical Laboratory R. Eliason – University of Minnesota Soil Testing and Research Analytical Laboratory R. J. Goos – Soil Science Department, North Dakota State University B. Hoskins – Plant, Soil and Environmental Sciences, University of Maine M. V. Nathan – Soil and Plant Testing Services, Missouri Extension Service A. Wolf – Agricultural Analytical Services Laboratory, Pennsylvania State University *Manjula Nathan after 9-1-97 2 Recommended Chemical Soil Test Procedures Introduction Following printing in January 1998, errors were discovered on pages 26 and 56 and corrected on the PDF file. Some printed copies were corrected with stickers. An error on page 24 of the PDF was discovered and corrected in February 2011. This error was not in the printed version. 1997 Revision J. R. Brown This publication was revised in 1980 and 1988 Users of this edition should read Dr. Dahnke’s under the leadership of Bill Dahnke who was the comments carefully and spend some time reflecting North Dakota representative to the NCR-13 commit- upon them. Time has passed and some tend to tee until his retirement. His introduction to those two underestimate the importance of efforts put into soil revisions is included below without change. testing during the past 100 years. The contributions The NCR-13 committee on Soil Testing and of those such as Emil Truog (Wis.), Roger Bray (Ill.), R. Plant Analysis asked me to serve as editor for this A. “Prof.” Olson (Neb.), E. O. McLean (Ohio), E. R. revision, which I deemed an honor and a climax to Graham (Mo.), John Grava (Minn.), Stan Barber (Ind.) my activities in soil testing and soil fertility since Touby Kurtz (Ill.), and many others in the North Cen- 1963. The committee made some changes in this edi- tral Region made to our understanding of soil test tion, which includes the addition of the Mehlich 3 measurements and plant growth relationships must extractant to the recommended phosphorus proce- not be discounted. Learning is a progressive activity; dures (Chapter 6), a chapter on Quality Assurance we must never forget that. and Quality Control (Chapter 15), a glossary, and changes of a lesser nature in other chapters. 1980 and 1988 Edition W. C. Dahnke For more than a century, soil and plant scien- most departments one or more prominent soils tists have been developing methods for determining scholars have been associated with soil testing the levels of plant-available nutrients in soils. One of research over considerable periods of time. This, plus the first quick soil tests for “active” (available) nutri- the fact that many soils in this region are amenable to ents was that of Daubeny (1) in 1845. It involved corrective management, has resulted in the extensive extracting the soil with carbonated water. His sug- use of soil testing in the NCR-13 region. gested test, however, was never put to practical use The preliminary work for this bulletin was done because of analytical difficulties. The first known fer- several years ago when a soil sample exchange was tilizer recommendations based on a soil test were conducted among the member states. The results of made by Dr. Bernard Dyer (2) in 1894. He recom- this exchange indicated that differences in procedure mended that phosphate fertilizer be applied to soils were possibly causing significant differences in soil releasing less than 0.01percent P2O5 (.0044 percent P) test results. A cooperative study among several of the when extracted with 1 percent citric acid. states was conducted to determine the importance of Since 1845, many extracting solutions have procedural differences. For example, temperature, been suggested and tried. Some of the tests have time and speed of shaking, and shape of extraction proved to be very successful in spite of the fact that vessel were found to have an influence on the many different chemical forms of each nutrient amount of phosphorus and potassium extracted (see occur in the soil, each having a different level of avail- Chapter 4). Soil scoops of the same volume but dif- ability to plants. ferent depth and diameter were found to influence Research efforts in developing soil testing as a the amount of soil they hold. To solve this variability useful guide to soil management have been extensive problem, a standard soil scoop was suggested and is in soils and agronomy departments in the region. In described in Chapter 2. for the North Central Region 3 Another purpose of this bulletin is to describe innovation is developed, it will be studied; and, if it the detailed procedures based partly on the above offers improvements over a procedure in this bul- studies for soil pH, lime requirement, phosphorus, letin, it will be adopted in place of or as an alternative potassium nitrate-nitrogen, calcium, magnesium, to the one described herein. In addition to our CEC, zinc, iron, manganese, copper, boron, chloride, research on soil testing procedures we plan to spend sulfate-sulfur, soil organic matter, soluble salts and a substantial amount of time on soil test interpreta- greenhouse media. We believe that use of these pro- tion and fertility recommendations. cedures by all public, private and industrial soil test- A word of caution to readers of this bulletin: A ing laboratories in our region will do much to reduce soil test is only as successful and usable for a region any confusion connected with soil testing and thus as the degree to which it is correlated and calibrated lend greater credibility to its role in the fertility man- for the soils and crops of the area.