Effect of Acidity on Nitrogen Mineralization and Nitrification in Atlantic Coastal Plain Soils
1986
Weier, K. L. | Gilliam, J. W.
The objective of this study was to determine the effect of acidity on mineralization, nitrification, and N₂O evolution during these processes on naturally acid soils from the lower Coastal Plain of North Carolina. Six acid surface soils (pH ≤4.5) from the Tidewater region of North Carolina, with a range of organic matter (OM) contents (28-850 g kg⁻¹) were limed to give a range of pH values so that the effect of acidity on mineralization of organic N and nitrification of (NH₄)₂SO₄ could be studied under controlled conditions in the laboratory. Cumulative net mineralization over 21 d was significantly (p <0.01) influenced by acidity in four of the six soils. However, no soil exhibited a significant net mineralization increase between the very acid initial pH value and the pH value to which liming is recommended (pH 4.8-5.2 for Histosols) for crop production. Liming to pH values <7 increased net mineralization in only one soil. Adding a small increment of lime tended to decrease mineralization although this effect was significant in only one soil. Essentially all organic N mineralized was converted to NO⁻₃ at all pH values. However, the very high acidities tended to inhibit the nitrification of NH⁺₄ added as (NH₄)₂SO₄. There was apparently no influence of organic matter content on any of the processes studied except N₂O evolution where the soils with <120 g OM kg⁻¹ evolved the highest amounts of N₂O during nitrification. Much of the N₂O evolution was apparently due to denitrification because addition of nitrapyrin did not eliminate the evolution. It was concluded that the liming of acid soils in the Tidewater Region of North Carolina would have little influence upon N mineralization rates. The recommended pH values of 4.8 to 5.2 for Histosols appears to be adequate for both mineralization and nitrification.
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