Concurrent Transformation of Lignosulfonate Carbon and Urea Nitrogen in Clay Soil
1994
Xie, R. J. | MacKenzie, A. F. | O'Halloran, L. P. | Fyles, J. W.
Lignosulfonate (LS), a waste product from the pulp and paper industry, can be a potential source of soil organic matter. Its transformation in soil may affect the relative amounts of soil N and organic matter fractions. A clay soil was incubated with urea at rates of 0, 500, or 1000 mg N kg⁻¹ soil and NH₄LS at rates of 0, 25, 50, 100, or 150 g NH₄LS kg⁻¹ soil at 70% field moisture capacity for 60 d. The incubated soil was analyzed for NH₄-N, NO₃-N, and total N. Soil organic carbon was partitioned into humin (HM)C, humic acids (HA)C, and fulvic acids (FA)C. In general, both urea and NH₄LS additions increased total N, NH₄-N, and organic N (difference between total N and NH₄-N) but reduced NO₃-N. The higher the NH₄LS rate, the greater the regression slope of N fractions (except NO₃-N) on urea addition rates, and the higher the urea rate, the greater the regression slope of N fractions (except NO₃-N) on NH₄LS rates, indicating the effect of interaction between urea and NH₄LS on N distribution in the soil. Ammonium LS increased and urea decreased the C/N ratio of soil organic matter. Proportions of HM-C and HA-C decreased while that of FA-C increased with increasing NH₄LS rates. Urea reduced the HA-C and increased the FA-C fraction. The results showed that simultaneous application of urea and NH₄LS can increase soil organic matter content (particularly the FA-C fraction) and enhance N transformation into NH₄-N and organic N fractions and reduce NO₃-N. Contribution from Dep. of Renewable Resource, Macdonald Campus of McGill University.
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