Soil Organic C:N vs. Water-Extractable Organic C:N


Traditionally, soil-testing laboratories have used a variety of methods to determine soil organic matter, yet they lack a practical method to predict potential N mineralization/immobilization from soil organic matter. Soils with high micro-bial activity may experience N immobilization (or reduced net N mineralization), and this issue remains unresolved in how to predict these conditions of net mineralization or net immobilization. Prediction may become possible with the use of a more sensitive method to determine soil C:N ratios stemming from the water-extractable C and N pools that can be readily adapted by both commercial and university soil testing labs. Soil microbial activity is highly related to soil organic C and N, as well as to water-extractable organic C (WEOC) and water-extractable organic N (WEON). The relationship between soil respiration and WEOC and WEON is stronger than between respiration and soil organic C (SOC) and total organic N (TON). We explored the relationship between soil organic C:N and water-extractable organic C:N, as well as their relationship to soil microbial activity as measured by the flush of CO2 following rewetting of dried soil. In 50 different soils, the relationship between soil microbial activity and water-extractable organic C:N was much stronger than for soil organic C: N. We concluded that the water-extractable organic C:N was a more sensitive measurement of the soil substrate which drives soil microbial activity. We also suggest that a water-extractable organic C:N level > 20 be used as a practical threshold to separate those soils that may have immobilized N with high microbial activity.

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Haney, R. , Franzluebbers, A. , Jin, V. , Johnson, M. , Haney, E. , White, M. and Harmel, R. (2012) Soil Organic C:N vs. Water-Extractable Organic C:N. Open Journal of Soil Science, 2, 269-274. doi: 10.4236/ojss.2012.23032.

Conflicts of Interest

The authors declare no conflicts of interest.


[1] K. Alef, T. H. Beck, L. Zelles and D. Kleiner, “A Comparison of Methodsto Estimate Microbial Biomass and N-Mineralization in Agricultural and Grassland Soils,” Soil Biology and Biochemistry, Vol. 20, No. 4, 1988, pp. 561-565. doi:10.1016/0038-0717(88)90073-9
[2] K. P. Dierksen, G. W. Whittaker, G. M. Banowetz, M. D. Azevedo, A. C. Kennedy, J. J. Stein and S. M. Griffith, “High Resolution Characterization of Soil Biological Communities by Nucleic Acid and Fatty Acid Analyses,” Soil Biology and Biochemistry, Vol. 34, No. 12, 2002, pp. 1853-1860. doi:10.1016/S0038-0717(02)00198-0
[3] W. R. Cookson, D. A. Abaye, P. Marschner, D. V. Murphy, E. A. Stockdale and K. W. T. Goulding, “The Contribution of Soil Organic Matter Fractions to Carbon and Nitrogen Mineralization and Microbial Community Size and Structure,” Soil Biology and Biochemistry, Vol. 37, No. 9, 2005, pp. 1726-1737. doi:10.1016/j.soilbio.2005.02.007
[4] B. Drigo, G. A. Kowalchuck and J. A. van Veen, “Climate Change Goes Underground: Effects of Elevated Atmospheric CO2 on Microbial Community Structure and Activities in the Rhizosphere,” Soil Biology and Biochemistry, Vol. 44, No. 5, 2008, pp. 667-679. doi:10.1007/s00374-008-0277-3
[5] R. L. Haney, W. F. Brinton and E. Evans, “Soil CO2 Respiration: Comparison of Chemical Titration, CO2 IRGA Analysisand the Solvita Gel System,” Renewable Agriculture and Food Systems, Vol. 23, No. 2, 2008, pp. 171-176. doi:10.1017/S174217050800224X
[6] E. A. Paul and N. G. Juma, “Mineralisation and Immobilization of Soil Nitrogen by Microorganisms,” In: F. E. Clark and T. Rosswall, Eds., Ecological Bulletin 33, Stockholm, 1981, pp. 197-204.
[7] R. L. Tate, “Soil Microbiology,” Wiley, New York, 1995.
[8] G. Bengtston, P. Bengtson and K. F. Mansson, “Gross Nitrogen Mineralization-, Immobilization-, and Nitrification Rates as a Function of Soil C:N Ratio and Microbial Activity,” Soil Biology and Biochemistry, Vol. 35, No. 1, 2003, pp. 143-154. doi:10.1016/S0038-0717(02)00248-1
[9] M. S. Booth, J. S. Stark and E. Rastetter, “Controls on Nitrogen Cycling in Terrestrial Ecosystems: A Synthetic Analysis of Literature Data,” Ecological Monographs, Vol. 75, No. 2, 2005, pp. 139-157. doi:10.1890/04-0988
[10] J. Luxh?i, S. Bruun and B. Stenberg, T. A. Breland and L. S. Jensen, “Prediction of Gross and Net N Mineralization-Immobilization-Turnover from Respiration,” Soil Science Society of America Journal, Vol. 70, No. 4, 2006, pp. 1121-1128. doi:10.2136/sssaj2005.0133
[11] J. E. Barrett and I. C. Burke, “Potential N Immobilization in grassland Soils across a Soil Organic Matter Gradient,” Soil Biology and Biochemistry, Vol. 32, No. 11-12, 2000, pp. 1707-1716. doi:10.1016/S0038-0717(00)00089-4
[12] J. A. vanVeen, J. N. Ladd and M. J. Frissel, “Modelling C and N Turnover through the Microbial Biomass in Soil,” Plant and Soil, Vol. 76, No. 1-3, 1984, pp. 257-274. doi:10.1007/BF02205585
[13] B. H. Janssen, “Nitrogen Mineralization in Relation to C:N Ratio and Decomposability of Organic Materials,” Plant and Soil, Vol. 181, No. 1, 1996, pp. 39-45. doi:10.1007/BF00011290
[14] R. G. Woodmansee and D. A. Duncan, “Nitrogen and Phosphorus Dynamics and Budgets in Annual Grasslands,” Ecology, Vol. 61, No. 4, 1980, pp. 893-904. doi:10.2307/1936759
[15] R. L. Haney and E. B. Haney, “Simple and Rapid Laboratory Method for Rewetting Dry Soil for Incubations,” Communications in Soil Science and Plant Analysis, Vol. 41, No. 12, 2010, pp. 1493-1501. doi:10.1080/00103624.2010.482171
[16] J. R. Burford and J. M. Bremner, “Relationships between the Denitrification Capacities of Soils and Total, Water-Soluble and Readily Decomposable Soil Organic Matter,” Soil Biology and Biochemistry, Vol. 7, No. 6, 1975, pp. 389-394. doi:10.1016/0038-0717(75)90055-3
[17] E. A. Davidson, L. F. Galloway and M. K. Strand, “Assessing Available Carbon: Comparison of Techniques across Selected Forest Soils,” Communications in Soil Science and Plant Analysis, Vol. 18, No. 1, 1987, pp. 45-64. doi:10.1080/00103628709367802
[18] R. G. Qualls and B. L. Haines, “Biodegradability of Dissolved Organic Matter in Forest Throughfall, Soil Solution and Stream Water,” Soil Science Society of America Journal—Abstract, Vol. 56, No. 2, 1992, pp. 578-586. doi:10.2136/sssaj1992.03615995005600020038x
[19] T. DeLuca and D. R. Keeney, “Soluble Organics and Extractable Nitrogen in Paired Prairie and Cultivated Soils of Central Iowa,” Soil Science, Vol. 155, No. 3, 1993, pp. 219-228. doi:10.1097/00010694-199303000-00008
[20] Alexander and Martin, “Introduction to Soil Microbiology,” Second Edition, Wiley, New York, 1977.
[21] D. M. Sylvia, J. J. Fuhrmann, P. G. Hartel and D. A. Zuberer, “Principles and Applications of Soil Microbiology,” Prentice Hall, New Jersey, 1988.
[22] L. E. Jackson, J. P. Schimel and M. K. Firestone, “Short-Term Partitioning of ammonium and Nitrate between Plants and Microorganisms in an Annual Grassland,” Soil Biology and Biochemistry, Vol. 21, No. 3, 1989, pp. 409-416. doi:10.1016/0038-0717(89)90152-1

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