Porous Mineral Amendments Enhance Nitrogen Mineralization via Improvement of Soil Aeration and Water Retention Characteristics

Red soils are characterized by a clay texture, resulting in low nitrogen (N) mineralization (N). Amendments provide a means to ameliorate N. To investigate the effects of different types and dosages of amendments on N in red soil, an incubation experiment is necessary to understand the underlying mechanisms. A 15-day batch experiment was carried out with diatomite (Si), porous ceramic (Pc), and zeolite (Zl) applied to a red soil at rates of 0%, 1%, 2%, 5%, and 10% (by weight). According to the results, Zl had superior effects on N and nitrification than Si and Pc. Cumulative mineralized N (C ), cumulative nitrate N content (C ), N promoting rate (NMPR), and nitrification promoting rate (NPR) reached 24.9 mg kg, 19.4 mg kg, 94.8%, and 136.4%, respectively, with Zl at a 10% amendment rate. The NMPR and NPR of Zl increased rapidly under amendment rates > 2%. However, N was inhibited at low Si and Pc dosages. C and C were significantly positive with field water capacity (FWC), wilting point (WP), capillary porosity (CP), and pH, but negative with bulk density (BD) when amended with Si and Zl. Furthermore, WP and BD have been identified as the primary factors influencing N and nitrification. The results indicate that N and nitrification enhancement were not only linked to improved aeration and water retention in soil following amendments but also depended on amendment type; 2–5% Zl improves N and nitrification in clay-textured and acidic red soil, which enhances our understanding and could facilitate N availability evaluation following mineral amendments.