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Tropical regions occur between the Tropic of Cancer and the Tropic of Capricorn. The tropics include approximately 40% of the land surface and is the largest ecozone of the earth. According to Köppen (1931), the tropics are characterized by an annual mean air temperature above 18°C through­out the whole year. The largest climatic variation is introduced by the variability of precipita­tion, reaching from nearly 0 mm in the Saharan and Atacama Desert to 11,700 mm on Mt. Waialeala in Hawaii (Eswaran et al., 1992). An Afisol (Luvisol) soil derived from mudstone in Eastern Samar, Philippines According to Uehara and Gillman  (1981), "t ropical soils" is a common name used to identify any soil that occurs in the tropics. They noted that like most common names, the term lacks precision, but it is more readily understood by a larger audience than are the scientific names. In contrast, Sanchez (1976) argued against the use of the term "tropical soils" since it does not accur...

Weathering is the alteration by chemical, mechanical, and biological processes of rocks and minerals at or near the Earth’s surface, in response to environmental conditions. Highly weathered soils (or strongly weathered soils) are soils that have undergone prolonged and intense weathering under the net leaching environment of the humid tropics. They are commonly found on stable and old geomorphic surfaces underlain by easily weatherable rocks such as ultrabasic and basic rocks as well as by pre-weathered sediments (Beinroth, 1982). These soils are clayey, deep, reddish, acidic, and have low nutrient status. According to Jackson et al. (1948), highly weathered soils are characterized by weathering stages of 10 to 12 wherein the clay fraction is dominated by 1:1 phyllosilicates (kaolinite & halloysite), aluminum oxide (gibbsite), and iron oxides (goethite and hematite). This mineralogical characteristic is also predicted by the “residua hypothesis” of Chesworth (1973) which states th...

The latest issue of the International Union of Soil Sciences (IUSS) bulletin is now available . The bulletin, the official publication of IUSS (formerly International Society of Soil Science or ISSS) with approximately 60,000 members worldwide, has a long and distinguished history. The first volume was produced by  F.A.van Baren and published in 1952. The society president at the time was the renowned soil scientist, Prof. R. Tavernier from Gent, Belgium. IUSS Bulletin 122 (June 2013) In the Introduction of the maiden issue, Prof. Tavernier wrote that “the bulletin of the International Society of Soil Science aims to pass on official information about all important events concerning the life and activity of the Society to its members and to National Societies and Regional Groupings as well as to Research Institutes. We hope that this bulletin will satisfy our members’ wishes, who have expressly shown their desire to be informed about these activities and about the development of So...

The Visayas State University (VSU), through the Philippine Higher Education Research Network (PHERNet) of the Commission on Higher Education (CHED), is spearheading a research project on enhancing farm productivity and environmental quality in climate change vulnerable marginal uplands in Eastern Visayas. As part of the project activities, the university will organize a National Conference on Development Initiatives in the Philippine Philippine Marginal Uplands, with the theme, "Enhancing farm productivity and environmental quality of Philippine marginal uplands: A scan of the past and a look into the future." The conference will be held on 22-24 October 2013 at VSU, Baybay City, Leyte.

The Department of Agronomy and Soil Science at Visayas State University in Leyte, Philippines joins the global community of more than 60,000 soil scientists in celebrating the World Soil Day today, December 5. Our soil science program at VSU is now more than 30 years old. It produced the first batch of BSA (Soil Science) graduates in 1980. It is now among the top soil science programs in the Philippines.  Many of our BS alumni have become very successful professionals/scientists in various academic and research institutions in the Philippines and other parts of the world.  We are very proud to name a few: Dr. Leticia S. Sonon , University of Georgia, USA Dr. Marife D. Corre , University of Goettingen, Germany Dr. Nilda R. Burgos , University of Arkansas, USA Dr. Sergio M. Abit Jr ., Oklahoma State University, USA Dr. Joel Bandibas, National Institute of Advanced Industrial Science & Technology (AIST), Japan Dr. Constancio Asis, Jr., Philippine Rice Research Institute (Phil...

Contributed by Dr. Ian A. Navarrete Humboldt Fellow Soil Science of Tropical and Subtropical Ecosystems Buesgen Institute University of Göttingen, Germany Geoecology, a term coined some 41 years ago by the geomorphologist Carl Troll who was at the time professor at the University of Bonn, Germany, is a broad integrative term to the study of forms and functions of terrestrial geoecosystem (Huggett, 1995). It emphasizes the interdependency and/or inter-relationships of the ecological biosphere with landscape and hence sometimes equated with landscape ecology. For example, the movement and distribution of solutes across soil landscapes are influenced by the geomorphic position in the soil within the landscape thus influencing soil genesis (Sommer and Schlichting, 1997) and vegetation development (Huggett, 1975).  Fig 1. Relation of primary forest and grasslands of Samar During our fieldwork at the Samar Island Natural Park (along the Paranas-Taft road at about 300 m above sea level) i...

Contributed by Dr. Ian A. Navarrete Humboldt Fellow Soil Science of Tropical and Subtropical Ecosystems Georg-August Univesity Göttingen Gottingen, Germany Soil degradation, a process that lowers the capacity of the soil to produce goods or services, is a prevalent agricultural and environmental problem in the Philippines (Asio et al. 2009). However, to date, the nature and characteristics of degraded soils in the Philippines have been poorly understood, in that there have been few studies on this subject (Asio et al. 2009; Navarrete et al. 2009). Altho ugh various crop production technologies have been developed for marginal areas these technologies have not been successfully adapted by farmers or have failed to alleviate crop production (Cramb 2001). Cramb further stated that the introduction of unsuitable soil management technologies to farmers has intensified the soil degradation processes occurring in these areas. Thus, knowledge on the characteristics and fertility status of degr...

Geology Mt. Pangasugan is generally built up by andesitic and basaltic pyroclastic rocks (referred to as Pangasugan formation) which are mostly of Quaternary and Tertiary origin. This rock formation is characterized by weak consolidation, lithologic disco ntinuities, abundance of rock outcrops, and shearing due to the occurrence of the Philippine fault line approximately at the center of the mountain range. Minor earthquakes are relatively frequent in the area. All these geological characteristics indicate that the area is unstable. Geomorphology The morphology of Mt. Pangasugan is largely the result of the combined effects of volcanism, erosion, faulting and tectonic uplift. Mt. Pangasuagn rises abruptly from the narrow alluvial coastal plain along the Camotes Sea into a vertical wall-like rock mass with a maximum height of about 1100 m above sea level (asl). The air distance between the sea level and the peak of the mountain is less than 3 km. This short distance suggests extremel...

The classical view about soils of tropical rain forest ecosystems is that these soils are old, acidic, and infertile. It is now widely acknowledged that this view which has greatly influenced research and management of the fragile rain forest ecosystem during the last several decades is largely a misconception. Although highly weathered soils (Oxisols or Ferralsols) are the most dominant soils in the humid tropics, tropical soils range from relatively young fertile soils (e.g. Inceptisols) to the highly weathered infertile soils (e..g. Oxisols). The extent of highly weathered soils is less in geologically young areas like in much of SE Asia. More detailed investigations of rain forest soils are vital for the sustainable management of this threatened ecosystems. These could also lead to a better understanding of the response of rain forests to climate change. Navarrete et al. (2009) recently conducted a study to evaluate the physical, chemical and mineralogical characterisitics of rain ...

Contributed by Janice P. Susaya, Sejong University, Seoul, Korea One of the heavy metals that commonly occur in elevated amounts in natural ecosystems is nickel (Ni). Ni is considered an essential micronutrient for plants, humans, and animals. It can exist in trace amounts in air, food, drinking water, and soils. Although Ni plays an important role in the metabolism of humans and animals, its intake in excesssive amounts or over a prolonged period could pose health ricsks. Studies have shown that children living in polluted areas have hypertrophy of tonsils, enlarged lymphatic nodes, and enlarged livers. There is also evidence that soluble Ni particulate is linked to acute lung injury. High Ni levels in natural ecosystems commonly come from ultramafic rocks (also called ultrabasic rocks). These are intrusive igneous rocks containing less than 45% silica (SiO2) with high concentrations of Ni, Mg, Fe, Cr, and Co. They are found in many places around the world and are common in many place...

First published June 2009. Revised November 2016. Philippine soil science owes its early development to the Americans. The first soil survey was conducted by C. W. Dorsey an American soil surveyor in 1903. In 1921 a Division of Soil and Fertilizer was created under the Bureau of Science which in 1934 was renamed as Division of Soil Survey. In 1951, the Philippine Congress enacted Republic Act No. 622 organizing the Bureau of Soil Conservation with Dr. M. M. Alicante as its first director (BSWM, 2008). Teaching of soil science to students of agricultural science started as early as the 1920s at the University of the Philippines College of Agriculture (UPCA). R. L. Pendleton an American from California was one of the pioneer soil science instructors who taught from 1923 to 1935. Dr. Pendleton was also an outstanding researcher as reflected by the about 50 scientific papers he published (Pendleton, 1942; Carter, 1958). Until about the 1960s, much of the work of soil scientists in the Bur...

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...

Weathering is the physical, chemical, and biological alteration of minerals in rocks, sediments, and soils at or near the Earth’s surface. It is an important link in the global rock cycle and is also an essential process for the formation of soils and landforms. Chemical weathering of silicate minerals which compose over 90% of the Earth’s crust, removes CO 2 from the atmosphere so it helps regulate the Earth’s climate over long time scales. Basalts are among the more easily weathered crystalline rocks thus, weathering of these rocks acts as a major CO 2 sink. Chemical weathering of rocks likewise releases nutrient elements for use by the biota in the ecosystem and also produces clay minerals which are the central components of soils. We studied the weathering of basalt by evaluating the gain and loss of elements, stream water composition, weathering indices, and clay mineral formation in the soil derived from basalt under the humid tropical conditions (average annual rainfall of ...

The distribution of soils in the Philippines is largely controlled by parent material, relief, and vegetation. In general, Philippine soils are younger than the tropical soils in mainland Asia, Central and South America, and Africa. This is because most Philippine islands are geologically young since they were the result of, just like much of Southeast Asia, recent Cenozoic tectonic events and have emerged from the sea recently (Hall, 2002). Philippine soils maybe grouped based on geomorphology and for practical purposes, into: soils in lowland areas, soils in young and unstable uplands, and soils in old and stable uplands. Soils in lowland areas Lowland areas include all flatlands located near sea level. Most of these areas are underlain by recent alluvial sediments. Because of this and due to periodic deposition of sediments during flooding events, the soils in lowland areas are poorly developed. Arenosols (Entisols) . These are weakly developed sandy soils comm...

Land use change is an important ecological driver in the Philippines and other parts of the tropics. It is the major cause of the widespread occurrence of degraded lands in this humid tropical country. Navarrete and Tsutsuki (2008) investigated the effects of land use change in Mt. Pangasugan in Leyte. They found that conversion of forest into secondary land uses like mahogany plantation, rainforestation farm (a form of reforestation using native tree species in combination with fruit trees and some shade-loving crops), coffee plantation, and grassland decreased the soil carbon, nitrogen, and non-cellulosic neutral sugar (mainly arabinose and xylose) contents of the soil. Within land-use type, differences in the above-mentioned soil parameters could be attributed to differences in the vegetation cover, past land use, and the succeeding soil management after land use change. Their findings also revealed that the grassland and rainforestation farm (which was also a former grassland) had ...