Fig. 6. Ammonium sorption in Kennebec and Haynie soils exposed to the swine waste and the (NH₄)₂SO₄ solutions at pH 4.0, 6.0, and 8.0 for 24 h. The initial NH₄⁺ concentration of the solutions was 250 mg NH₄⁺–N L^–1. Different letters within each bar group indicate statistically significant difference (p < 0.05).