mortiz085

Lowland rice cultivation can enhance the proliferation of snails resulting in the accumulation of calcium carbonate (CaCO3) in the topsoil. Frank Moormann and Nico Van Breemen, well-known Dutch pedologists, first observed this phenomenon in Central Luzon, Philippines, while visiting the experimental sites of the International Rice Research Institute in the 1970s. H.U. Neue, head of the Soils Department of IRRI at the time, encouraged this writer to investigate the phenomenon. Our research revealed that such biological accumulation of CaCO3 which we named biocalcification , occurs in several rainfed and irrigated rice-growing areas in the Philippines (Asio, 1987; Asio and Badayos, 1998). The figure below shows the proposed generalized model of biocalcification in rice fields. It consists of two stages. Stage 1 is on the proliferation of snails which is generally dependent upon the calcium content of the soil or irrigation water. Moormann et al. (1976) suggested that calcium, of which s...

Contributed by Juvia P. Sueta, University of Göttingen, Germany There is growing interest in the use of indigenous tree species in reforestation programs at present. Thought to be well adapted to their native areas, indigenous tree species are able to survive well and strongly influence the soil. However, the lack of published data on their performance often limits their full use and casts uncertainties on whether they have beneficial or negative impacts on the soil. To better understand the role of trees in improving soil quality, an understanding of how nutrient availability changes with time is important (Kelly and Mays, 1999). In this study which we conducted at the VSU-GTZ reforestation project site (see photo) in Mt. Pangasugan, Leyte, Philippines, we looked at the influence of two native tree species- Parashorea plicata and Dipterocarpus warburgii - on the nature and rate of changes on the chemical properties of a highly weathered soil following a change in land use from Impera...