Properties of rice soils affecting methane production potentials: 2. Differences in topsoil and subsoil uri icon

abstract

  • Methane (CH(4)) is one of the important greenhouse gases accounting for 15% of the total enhanced greenhouse effect. A laboratory experiment was conducted with nine soils from the Philippines and two soils from India to determine the CH(4) production potential of topsoil and subsoil, and to assess the role of different fractions of soil organic C in influencing CH(4) production potential. CH(4) production potentials of topsoils varied in a wide range from 20 mug g(-1) soil (Urdaneta soil) to 837 mug g(-1) soil (Pila soil) over 100 d of incubation. In contrast, CH(4) production potentials of subsoils were low (<2 mu g g(-1) soil over 100 d of incubation). The topsoil was the main source of CH(4) in the flooded rice soils contributing 99.95% to the total CH(4) production while the subsoil contributed negligibly (0.05%). CH(4) production potentials of the topsoils showed significant correlation with cation exchange capacity (CEC), total N and available K contents of soils. For the subsoils, CH(4) production potentials had a significant correlation with available P and clay contents of the soils. Considering the differences in all the soil properties and the CH(4) production potentials between topsoils and subsoils, a significant relationship of CH(4) production potential with CEC, available K and enriched C (extra C content of topsoil compared to that of subsoil) was obtained. Two carbon fractions, water soluble C (H(2)O-C) and carbon mineralised under anaerobic conditions (AnMC) affected total CH(4) production indirectly rather than directly.

publication date

  • 2002
  • 2002