Fig. 3. Activities of major cations (Ca²⁺, Mg²⁺, K⁺, Na⁺) and anions (SO^-₄, Cl^-) in soil solutions extracted from soil samples of sandy loam and clay loam (incubated for up to 64 d after rewetting). Activities were plotted against that of NO^-₃, which increased substantially during nitrification. Dotted lines indicate the activities of the same ions in the four designed treatments for comparison (AN ± Al, LN ± Al).