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This article in SSSAJ

  1. Vol. 73 No. 5, p. 1575-1586
    Received: Sept 23, 2008

    * Corresponding author(s): harry.schomberg@ars.usda.gov
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Assessing Indices for Predicting Potential Nitrogen Mineralization in Soils under Different Management Systems

  1. Harry H. Schomberg *a,
  2. Sirio Wietholterb,
  3. Timothy S. Griffinc,
  4. D. Wayne Reevesa,
  5. Miguel L. Cabrerad,
  6. Dwight S. Fishera,
  7. Dinku M. Endalea,
  8. Jeff M. Novake,
  9. Kip S. Balkcomf,
  10. Randy L. Raperf,
  11. Newell R. Kitcheng,
  12. Martin A. Lockeh,
  13. Kenneth N. Potteri,
  14. Robert C. Schwartzj,
  15. Clinton C. Trumank and
  16. Don D. Tylerl
  1. a USDA-ARS, J. Phil Campbell, Sr., Natural Resource Conservation Center, Watkinsville, GA 30677
    b Empresa Brasileira de Pesquisa Agropecuária (Embrapa Trigo), Passo Fundo, Rio Grande do Sul, Brazil 99001-970
    c Friedman School of Nutrition Sci. and Policy, Tufts Univ., Boston, MA 02111
    d Univ. of Georgia, Dep. of Crop and Soil Sciences, Athens, GA 30602
    e USDA-ARS, Coastal Plains Soil, Water, and Plant Res.Ctr., Florence, SC 29501
    f USDA-ARS, National Soil Dynamics Lab., Auburn, AL 36832
    g USDA-ARS, Cropping Systems and Water Quality Res. Unit, Columbia, MO 65211
    h USDA-ARS, National Sedimentation Lab., Oxford, MS 38655
    i USDA-ARS, Grassland Soil and Water Res. Lab., Temple, TX 76502
    j USDA-ARS, Southern Plains Conserv.Production Rese. Lab., Bushland, TX 79012
    k USDA-ARS, Southeast Watershed Res. Lab., Tifton, GA 31793
    l Univ. of Tennessee, Biosystems Engineering and Soil Science Dep., Jackson, TN 38301


A reliable laboratory index of N availability would be useful for making N recommendations, but no single approach has received broad acceptance across a wide range of soils. We compared several indices over a range of soil conditions to test the possibility of combining indices for predicting potentially mineralizable N (N0). Soils (0–5 and 5–15 cm) from nine tillage studies across the southern USA were used in the evaluations. Long-term incubation data were fit to a first-order exponential equation to determine N0, k (mineralization rate), and N0* (N0 estimated with a fixed k equal to 0.054 wk−1). Out of 13 indices, five [total C (TC), total N (TN), N mineralized by hot KCl (Hot_N), anaerobic N (Ana_N), and N mineralized in 24 d (Nmin_24)] were strongly correlated to N0 (r > 0.85) and had linear regressions with r 2 > 0.60. None of the indices were good predictors of k Correlations between indices and N0* improved compared with N0, ranging from r = 0.90 to 0.95. Total N and flush of CO2 determined after 3 d (Fl_CO2) produced the best multiple regression for predicting N0 (R 2 = 0.85) while the best combination for predicting N0* (R 2 = 0.94) included TN, Fl_CO2, Cold_N, and NaOH_N. Combining indices appears promising for predicting potentially mineralizable N, and because TN and Fl_CO2 are rapid and simple, this approach could be easily adopted by soil testing laboratories.

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