Effects of long‐term ammonium sulphate fertilization on the ph and elemental distribution at three soil depths of South‐Western Nigeria soil

Abstract

Ammonium sulphate applied continuously for six years steadily decreased the soil pH, the lowest pH occurring in the 0–15cm depth. At 80 kg N/ha, organic matter was significantly decreased while NO₃‐N increased, with the reverse occurring at the 120 kg/ha N treatment. Extractable Ca decreased sharply, particularly in the surface soil with increasing N application. Topsoil (0–15cm) cation exchange capacity (CEC) was unaffected by N treatments, whereas in the lower soil depths CEC was significantly lower at the 80 and 120 kg/ha N treatments. Nitrogen treatments steadily decreased %BS in all soil depths.

Soil extractable Fe and Mn increased with increasing rates of N, while Cu and Zn were unaffected. Surface soil pH (0–15cm) established a significantly positive relationship with pH, P, Ca, and %BS in lower soil depths and a negative relationship with Mg and CEC. The use of nitrogeneous fertilizers in tropical soils should be preceded by an efficient soil testing programme.

Keywords:

• N fertilization
• (NH₄)₂SO₄
• soil fertility