Does Sago palm respond to nitrogen application?

Sago palm (Metroxylon sagu Rottb.) is widely found in the tropical lowland forest and freshwater swamps across Southeast Asia and New Guinea. Sago, the starch extracted from the pith of sago palm stems, is a staple food for the lowland peoples of Papua New Guinea and the Moluccas (http://en.wikipedia.org/wiki/Sago).

In recent years, the plant has received increased scientific interest as new uses for sago starch like in the manufacture of alcohol, citric acid, bio-ethanol and biodegradable plastics are being explored. One important research issue is on how to increase sago production since, like most wild plants, the mineral nutrition of sago palm is still poorly understood. Little scientific information is also available about its response to fertilizer application.

In a new study published in the international journal Soil Science and Plant Nutrition, Lina and co-workers (Lina et al. 2009) found that N uptake of sago palm increased significantly but inconsistently with increasing N application. The few significant increases in N uptake that were observed did not translate into significant improvements in the growth parameters of sago plant, except for the number of leaflets in the pot experiment. No significant difference was likewise observed between the fertilizer use efficiency at the two fertilization rates (50 and 100 N kg ha-1) for either sago seedling or 2-year-old sago plants.

The study demonstrated that sago palm did take up N from the added fertilizer at low rates. Moreover, it showed that the growth parameters of sago plant are not sensitive to N application suggesting that the form of N and the timing of N fertilization are important factors for sago production.

Reference
Lina Suzette B., Okazaki M, Kimura DS, Yonebayachi K, Igura M, Quevedo MA, and Loreto AB. 2009. Nitrogen uptake by sago palm (Metroxylon sagu Rottb.) in the early growth stages. Soil Science and Plant Nutrition 55: 114-123.

Sofja Kovalevskaja Award for Top Level Junior Scientists and Scholars

The Alexander von Humboldt Foundation based in Bonn, Germany, announces that it now accepts application for the prestigious Sofja Kovalevskaja Award for Top Level Junior Scientists and Scholars. Below is the official announcement from Dr. Georg Schütte, Secretary General of the Foundation:

Dear Sir or Madam,

Political debate on higher education is currently focused on enhancing the internationalisation of Germany as a research location. Endeavours are underway to improve the showcasing of German research and to create offers designed to promote collaboration between German and foreign researchers. The Alexander von Humboldt Foundation is delighted to be able to contribute to this by announcing once again the Sofja Kovalevskaja Award for Top Level Junior Scientists and Scholars. This attractively endowed research award is an outstanding career opportunity for junior research talents of all disciplines from abroad to establish their own junior research groups at German research institutions.

The award recognises outstanding talent, above average initiative and a creative approach to research and grants exceptional research conditions: The award amount totalling up to 1.65 million EUR provides award winners with valuable risk capital, enabling them to put innovative research ideas into practice. They may spend five years working on research projects at an institute of their own choice, untroubled by administrative constraints. Furthermore, building up their own working groups allows the award winners to lay important foundations for a promising research career at a very early stage. The programme is funded by the Federal Ministry of Education and Research.

Scientists and scholars of all disciplines from abroad with outstanding qualifications, who have completed their doctorates within the last six years, are eligible to apply. The programme is also open to German academics working abroad. Applications must be submitted by 15 October 2009.

We should be very grateful if you would help us to search for international research talents. For example by disseminating the announcement at your institution or asking researchers you know to draw the attention of junior researchers who might be potential candidates to the award. Details of the application procedure for the Sofja Kovalevskaja Award can be found on our website at http://www.humboldt-foundation.de/SKP_en

Please do not hesitate to contact Dr. Oliver Lange (0228-833-274, oliver.lange@avh.de) or Monika Appmann (0228-833-186, monika.appmann@avh.de) if you have any further questions regarding the Sofja Kovalevskaja award.

With many thanks for your support and kind regards,

Dr. Georg Schütte

Secretary General

Alexander von Humboldt Foundation

Report on the 12th PSSST Conference held on May 21-22, 2009 in Davao City

Contributed by Judith Carla P. dela Torre (PhilRice)

The 12^th Annual Meeting and Scientific Conference of the Philippine Society of Soil Science and Technology, Inc. (PSSST) was held at Eden Nature Park, Toril, Davao City last May 21-22, 2009. About 140 members from the different international and local institutions, agencies, and state colleges and universities participated in the said event. With this year’s theme titled “Enhancing Soil Productivity and Environmental Quality”, scientists, researchers, extension workers, and students presented their paper and posters to help in finding solutions to issues like soil erosion, decreasing soil fertility and climate change; and to achieve better soil productivity for our country’s sustainable food production program.

The keynote address on “Rice Science for Food Self-sufficiency” was given by Atty. Ronilo A. Beronio, Executive Director of PhilRice. He discussed the rice self-sufficiency program to be achieved by 2013 and challenged soil scientists to educate farmers on how to make soil productive, to lead and preach the science of managing available farm and soil resources, and to effectively explain the synergistic effects of various fertilizers on plant growth.

The three plenary papers were: (1) Integrated Soil and Crop Nutrient Management for Vegetables in the Southern Philippines by Dr. Christopher Dorahy of ACIAR, Australia; (2) Facts and Myths of Organic and Inorganic Fertilizers by Dr. Cezar P. Mamaril of PhilRice; and (3) Enriched Potting Preparations (EPP) for Various Crops by Dr. Eduardo P. Paningbatan of UPLB.

The technical session was divided into three categories: junior, senior-competing, and senior-non-competing. For the junior category, three PSSST scholarship grantees presented their undergraduate thesis and competed for the best paper. At the same time, ten papers /presentations competed for the senior category while five others presented for the non-competing (senior) category. Moreover, 19 posters were presented and judged for the best poster award.

The following recognitions were awarded by Dr. Danilo M. Mendoza, PSSST President and Dr. Cezar P. Mamaril, Advisory Board Member:

Paper/Oral Presentation

Junior Category

Best Paper- Effects of Varying Soil Moisture Levels on the Growth and Development of Lakatan (Musa acuminate Colla.) (Kathy Tafere)

Senior Category

Best Paper – Studying the Effects of Drought on Rice Production in Nueva Ecija Using Remote Sensing Technology (Judith Carla P. dela Torre)

Second Place – Banana Fertilization at the FPO Plantation: Evaluation of Soil and Leaf Analysis Results (Ma. Asuncion L. Salibay)

Third Place – Performance of Bio-fertilizers in Irrigated Lowland Rice presented (Michelle B. Castillo)

Poster Paper

Best Poster – Can we use commercially available fertilizers for Soil NPK test? (Julie D. Elijay, Constancio A. Asis, Jr., and Jesiree Elena Ann P. dela Torre)

Second Place – Fate of Soil Nutrient after Rice Straw Incorporation (Corazon A. Santin, Jesusa M. Rivera and Evelyn F. Javier)

Third Place – PALAYAMANAN Model in Rainfed Rice Ecosystem in Nueva Ecija (Jesusa M. Rivera, Rizal G. Corales, Leylani M. Juliano, Sandro D. Cañete, Ailon Oliver V. Capistrano, Jeny V. Ravis, Jehru C. Magahud, and Madonna C. Casimero)

Continuous cultivation does not always decrease soil organic carbon content

It is generally known that continuous cultivation causes a decline in soil organic carbon and nutrient contents. This has been shown by many years of research on upland soils starting with the classic study by Nye and Greenland (1960). Our studies in the volcanic mountain of Leyte, Philippines, have also confirmed this (e.g. Asio et al., 1998; Navarrete and Tsutsuki, 2008).

But a recent paper by Benbi and Brar (2009) published in the international journal Agronomy for Sustainable Development does not support this widely held view. In fact, they showed that intensive cultivation increased soil organic carbon by 38 % after 25 years. These researchers evaluated the impact of intensive cultivation of an irrigated and optimally fertilized rice-wheat system in Punjab, India, and found that intensive cultivation enhanced carbon sequestration due to improved crop productivity, greater belowground C transport to the soil and reduced organic matter decomposition during the wetland rice season.

Results of the study also revealed that the rice-wheat cropping in alkaline soils creates a favourable pH environment by lowering soil pH towards neutrality. During the 25-year period, the soil pH declined from 8.8. to 7.7 which resulted in the improvement in nutrient availability. Continuous application of phosphoric fertilizer led to build-up of soil P and the magnitude of accumulation was proportional to the amount of fertilizer applied.

References

Asio V.B., R Jahn, K. Stahr, and J. Margraf. 1998. In: Soils of Tropical Forest Ecosystems (A. Schulte and D. Ruhiyat, eds.). Springer Verlag, Berlin, pp: 29-36.

Benbi D.K. and J.S. Brar. 2009. A 25-year record of carbon sequestration and soil properties in intensive agriculture. Agron. Sustain. Dev. 29: 257-265.

Navarrete IA and K Tsutsuki. 2008. Land-use impact on soil carbon, nitrogen, neutral sugar composition and related properties in a degraded Ultisol in Leyte, Philippines. Soil Science and Plant Nutrition 54: 321-331.

Nye P.H. and D.J. Greenland. 1960. The soil under shifting cultivation. Commonwealth Agricultural Bureau, England.

Organic fertilization improves soil fungi population

While organic fertilization is now widely known to improve the general soil quality, more data from field experiments are still needed to support this notion. Cwalina-Ambroziak and Bowszys (2009) carried out a 3-year field experiment to determine the influence of organic fertilization on the community of soil fungi as compared to no fertilization and NPK fertilization only. Findings of the study revealed a significantly higher total number of fungal colony-forming units in soil applied with organic fertilizer than in soil without fertilizer application and the one applied with NPK mineral fertilizers. Moreover, pathogen population was highest in soil without fertilization and lowest in the soil added with organic fertilizer.

The study demonstrated that organic fertilization has a positive influence on the structure of soil fungi communities. This was particularly more observable in the qualitative changes in fungi composition than in the changes in fungi numbers. Results of the study support the findings of other researchers that organic fertilization stimulates the growth of soil microorganisms and that it protects the plants against pathogens of the genus Pythium and Phytophthora.

According to Terekhova (2007) fungal communities represent one of the most important functional and structural components of biological systems. Fungi affect the properties of the soil via the regulation of pedogenic processes; the composition of soil organic matter; the soil structure status; the soil acidity; the soil temperature characteristics; and certainly via the regulation of the functioning of soil microbiota.

References

Cwalina-Ambroziak B. and T. Bowszys. 2009. Changes in fungi communities in organically fertilized soil. Plant Soil Environ 55: 25-32.

Terekhova V.A. 2007. The importance of mycological studies for soil quality control. Eurasian Soil Science 40: 583-587.

Leaf decomposition of exotic and native tree species: rates and effect on soil

Decomposition of organic materials on the forest floor is a vital link between the various components of the forest ecosystem. Through this process, mineral nutrients bound to the biomass are released into the soil and then subject to uptake by plants, fixation by soil components, and losses through leaching and erosion. Decomposition can have considerable influence on the biological and chemical properties of the forest soil depending on the kind of organic material, soil properties, climate, and the availability of decomposers (e.g. Gartner and Cardon, 2004).

Exotic tree species are introduced species from other regions. They are widespread in tropical and subtropical countries since they are popular as reforestation species even in harsh environments (Nyland, 1996) due to their ability to adapt easily to variable site conditions (Weidelt, 1976). Many are considered economically viable because of their fast growth characteristic. Farmers value exotic species more than the native ones because of forestry extension recommendations and desirable cultural attributes (Cromwell and Bradie, 1996). In the Philippines, the most well-known exotic tree species belonging to this group are Mahogany (Sweitenia macrophylla King), Gmelina (Gmelina arborea Roxb.) and Teak (Tectona grandis Linn.).

Native tree species are species which originated from the region where they are growing. Among the more commonly known Philippine native tree species are Bagtikan (Parashorea plicata Brandis), Hagakhak (Dipterocarpus validus Blume) and Narra (Pterocarpus indicus Willd.). The first two species belong to Dipterocarpaceae family, the latter to the Fabaceae.

Presently, there is widespread notion that the use of exotic tree species for reforestation causes negative ecological effects such as soil degradation (Sawyer, 1993). Lindsay and French (2005) cited early studies showing that there are strong positive feedbacks between plant species composition and soil properties such that introduction of a new species can change nutrient cycling and soil properties. It is also believed that native tree species have positive effects on the site. However, very little data exist to support these claims.

We evaluated the effects of incorporation and subsequent decomposition of leaves of exotic tree species (Gmelina arborea, Sweitenia macrophylla and Tectona grandis) and native tree species (Pterocarpus indicus, Dipterocarpus validus and Parashorea plicata) on the quality of forest soil. Forty-two pots filled with an acidic and clayey forest soil and added with fresh leaves of the different tree species were set-up in an open area in Mt. Pangasugan. Retrieval of the first three pots for each treatment was done after two months and the remaining three pots, five months later. Soil samples were collected from each pot and analyzed for pH, OM, total N, available P, and respiration rates.

Our main findings were:

1. Decomposition of the leaves of exotic tree species generally did not change soil pH except that of S. macrophylla which increased soil pH after 5 months. In contrast, the leaves of the native species tended to decrease soil pH particularly in the first two months of decomposition.

2. There was no considerable difference between the effects of the leaves of exotic and those of native tree species on the organic matter and total nitrogen contents of the soil.

3. Available phosphorus content of the soil was significantly increased by the decomposition of leaves of both exotic and native species.

4. The leaves of exotic tree species decompose faster than those of the native species. This finding agrees with that of a separate litter decomposition study by litterbag method conducted at the same site by Aragon (2004).

Source:

Batistel CC and VB Asio. 2009. Effects of leaf decomposition of selected exotic and native tree species on forest soil quality. Annals of Tropical Research (in press)

References

Aragon JA. 2004. Leaf litter decomposition of Dipterocarpus validus Brandis (Dipterocarpaceae) and Gmelina arborea (Verbenaceae) in two forest sites of Mt. Pangasugan. Undergrad Thesis, Leyte State University, Baybay, Leyte. 50 pp.

Cromwell E and A Bradie. 1996. Germplasm for Multipurpose Trees: Access and Utility in Small-farm Communities. ODI London.

Gartner TB and ZG Cardon. 2004. Decomposition dynamics in mixed species leaf litter. Oikos 104: 230-246.

Lindsay EA and K French. 2005. Litterfall and nitrogen cycling following invasion by Chrysanthemoides monilifera ssp. Rotundata in coastal Australia. Journal of Applied Ecology 42: 556-566.

Nyland R 1996. Silviculture (Concepts and Application). McGraw-Hill Co. Inc. Singapore.

Sawyer J 1993. Plantations in the Tropics: Environmental Concerns. IUCN/UNEP/WWWF, Gland, Switzerland.

Weidelt H A 1976. Manual of Reforestation and Erosion Control for the Philippines. German Agency for Technical Corporation LTD (GTZ) Germany.

PSSST holds 12th national scientific conference

The Philippine Society of Soil Science and Technology (PSSST), the country’s national professional organization of soil scientists and soil practitioners, is holding its 12^th Annual Meeting and Scientific Conference on 20-23 May 2009 at Eden Nature Park and Resort, a beautiful man-made resort on the slopes (about 800 m asl) of Mount Talomo, Toril, Davao City.

The conference which aims to meet the challenges in enhancing soil productivity and environmental quality, reflects the state of the art of soil research, development, extension and policy support in the Philippines. It provides an excellent forum for the exchange of research findings and scientific ideas among established and young soil scientists and soil practitioners working at the various universities, colleges, research centers, and government agencies.

I wish to congratulate the officers led by Dr. Danny Mendoza and the members of the society for organizing this very important activity. I hope most members will be able to attend despite the difficult economic situation we are all in right now.

One person deserves a special mention: Dr. Neo Manguiat. It's largely because of his guidance and support that PSSST has been very successful as a professional organization.

The current PSSST officers are: Dr. D.M. Mendoza, President; Ms. C.G. Mangao, Vice-President; Dr. V.M. Padilla, Secretary; Ms. C.D. Bacatio, Tresurer; Dr. P.P. Juico, Auditor; Dr. C.A. Asis, Jr., PRO; Ms. R.N. Atienza, Business Manager; Ms. E.F. Javier, Dr. C.P. Laurea, Dr. E.P. Paningbatan, Jr., Dr. P.B. Sanchez, Mr. M.M. Marquez, Board Members; and Dr. C.P. Mamaril and Dr. I.J. Manguiat, Advisers. Ms. B.C. Magno, Ms. A.C. Marca, and Ms. A.T. Guy, Liaison Officers.

Are the tropical soils in Southeast Asia unique?

The soils in the tropical islands of SE Asia may be distinct from those in other tropical areas like Africa and the Americas because of the unique environmental factors that influenced their formation (Asio et al., 2006; Navarrete et al., 2007). Geologically, much of SE Asia was the result of recent tectonic event and many areas emerged from the sea recently (Hall, 2002). Consequently, it is much younger than Africa and Central and South America. In terms of climate, SE Asia is also different from the other regions. During the drier period of the Quaternary, the effects of climatic changes in landform development were unique because large areas were under the regime of the monsoonal system (Verstappen 1997). Chang et al. (2005) reported that the present climate that prevails in SE Asia is also unique since it is located in the transitional region between the boreal summer Asian monsoon and the boreal winter Asian monsoon. In terms of the soil-forming factor organisms (flora and fauna), biodiversity is high in the region (Myers et al., 2000) because of the effect of climate and geological history (Nakashizuka 2004). Heemsbergen et al. (2004) reported that biodiversity is related to soil processes. Land use systems and soil management practices of farmers in SE Asia are also different from those in other tropical regions suggesting that the influence of man as a factor of soil formation maybe different from farmers in other tropical areas.

References

Asio VB, CC Cabunos, ZS Chen. 2006. Soil Science 171: 648-661.

Chang CP, Z Wang, J McBride, CH Lieu. 2005. J. Climate 18: 287-301.

Hall R. 2002. J. Asian Earth Sci. 20: 353-431.

Heemsbergen DA, MP Berg, M Loreau, JR Van Hal, JH Faber, HA Verhoef. 2004. Science 306: 1019-1020.

Nakashizuka T. J. 2004. J. For. Res. 9: 293-298.

Navarrete, IA, VB Asio, R Jahn, K Tsutsuki. 2007. Australian J. Soil Research 45: 153-163.

Verstappen H.Th. 1997. J. Quaternary Sci. 12: 413-418.

Weathering of basalt and clay mineral formation in Leyte, Philippines

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 comprise over 90% of the Earth’s crust, removes CO₂ 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 CO₂ 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 2700 mm and an average temperature of 28^oC) in Leyte, Philippines. The study site is located in the rain forest on the lower western slope of Mt. Pangasugan having an elevation of 100 m asl. The weathering profile studied is about 4 meters deep, heavy clay, acidic and yellowish red soil classified as Alisol (or Ultisol).

Results revealed that much of the basic cations Ca, Mg, K, Na, and part of Si have already been lost from the weathering product (saprolite and soil). This was however accompanied by the accumulation of Al, Fe, C, and H2O. The extent of weathering as indicated by the loss of elements based on the total elemental composition of fresh rock and of saprolite and soil was closely related to the cation composition of the stream water in the study site. Relative rates of loss of bases and silica revealed the sequence: Ca>K>Na>Mg>>Si for the soil, and Ca>Na ≥ Mg>K for the stream water. The ratio Na : (Na+Ca) of the stream water indicated that its major source of cations was rock weathering.

Results also showed that the intensive basalt weathering has resulted in the formation and abundance of kaolinite and halloysite clay minerals (see above TEM micrograph) as well as goethite in the highly weathered soil. The idea that weathering moves to a system composed of SiO₂, Al₂O₃, Fe₂O₃, and H₂O (residua hypothesis of Chesworth) appears to be supported by the results of this study.

Reference
Asio VB and R Jahn. 2007. Weathering of basalt and clay mineral formation in Leyte, Philippines. Philippine Agricultural Scientist 90 (3): 204-212.

Soil distribution in the Philippines

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 may be 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 common in alluvial plains and coastal areas.
Gleysols (Entisols, Inceptisols). These are the poorly developed wet soils in alluvial plains and marshes. They are used chiefly for lowland rice production. Together with Histosols, Gleysols are the dominant soils of wetlands.
Cambisols (Inceptisols). These are weakly developed soils showing poor horizon B development. They occur in association with Gleysols although they can also be found in mountainous areas.
Fluvisols (Entisols). These are the undeveloped soils commonly found along rivers. Periodic deposition of river sediments retards soil development.
Vertisols (Vertisols). These are the clayey soils in lowland areas that produce large cracks on the surface during the dry season. They are very fertile and are widely used for lowland rice production. A typical example can be found in Mangaldan, Pangasinan.
Histosols. These are found in swamps, marshes, shallow lakes, and depressions. The saturated condition favors the accumulation of organic materials. Large areas are found in Leyte, Samar, and Surigao.

Soils in young and unstable uplands

Uplands are undulating as well as hilly lands ranging in elevation from near sea level to about 1000 meters. Many upland areas around the country are the result of recent volcanic activity or geologic uplift. These are young landscapes underlain by young volcanic deposits or reef limestone and thus have also poorly developed soils.

Leptosols (Entisols, Inceptisols). These are the shallow soils (less than 50 cm deep) in rocky areas. Many soils derived from limestone in various islands have very thin solum and thus they belong to Leptosols.
Andosols (Andisols). These are the poorly developed soils on young volcanic landscapes in the mountains of Negros, Leyte, Bicol, Taal, and other volcanic areas of the country. The soil is soft and very friable and appears dark due to the high organic matter content. Except for their very low P availability, the properties of these soils are generally favorable for crop production.
Chernozems (Mollisols). These are very fertile soils due to their organic matter-rich topsoil. They can be found in limestone areas in Leyte, Bohol, and other islands.

Soils in old and stable uplands

Old uplands were formed by volcanism or geologic uplift millions of years ago. They typically occur on the lower slopes of volcanic mountains. Soils in these areas are well-developed or highly weathered.

Ferralsols (Oxisols). These are the very deep, red, acidic, and very infertile soils found in old landscapes in Palawan, Mindanao, and Samar.
Acrisols and Alisols (Ultisols). These are the reddish, clayey, acidic soils widespread in hilly and mountainous areas throughout the archipelago.
Luvisols (Alfisols). These are the well-developed soils with high base saturation (fertile) found in old alluvial terraces in various areas in the Philippines.

(Photo above shows the typical soil-landscape relationship in the volcanic island of Leyte)

References

Asio VB. 1996. Characteristics, weathering, formation and degradation of soils from volcanic rocks in Leyte, Philippines. Hohenheimer Bodenkundliche Hefte vol. 33, Stuttgart.

Asio VB, PP Garcia, GAA Garcia. 2005. Development of a new soil map of Leyte. Unpublished project report, VSU, Baybay, Leyte.

Barrera A, F Aristorenas, JA Tingzon. 1954. Soil survey of Leyte province, Philippines. Soil Survey Report No. 18, Bureau of Print, Manila.

Bureau of Soil and Water Management (undated). Soil map of the Philippines (1:7,500,000). http://www.fap.org/ag/AGL/swlwpnr/reports/y_ta/z_ph/phmp231.htm#s133.

Hall R. 2002. Cenozoic geological and plate tectonic evolution of SE Asia and the SW Pacific: model and animation. J. Asian Earth Sci. 20: 353-431.

Hirayama R, R Carating, T Ohkura, V Castaneda, M Vinluan. 2002. The soils of the Philippines. Proc. 3rd and 4th symposia on collection building and natural history studies in Asia and the Pacific Rim (T Kubodera et al., eds). National Science Museum Monographs 22: 109-113.

Concentration affects plant uptake of inorganic and organic forms of N

It is now recognized that plants take up N from the soil in three forms: nitrate, ammonium, and amino acids (dissolved organic N). Although scientific evidence on plant uptake of amino acids has existed in the last few decades, it is only recently that the contribution of amino acids to plant nutrition has been recognized (see Warren 2009 and literatures cited). So the traditional view that organic N has to be mineralized first into nitrate and ammonium in order to be available to the plant is not anymore valid.

Different plant species vary in their preference for N forms. For instance, early successional plant species are known to have a higher capacity for nitrate uptake than late successional species. Uptake of N in the form of ammonium and amino acids is thus more important for the latter species. In a recent study to test the hypothesis that substrate concentration affects plant preference for N forms, Warren (2009) used the herb Ocimum basilicum and the evergreen tree Eucalyptus regnans. He placed roots of intact seedlings in equimolar mixtures of nitrate, ammonium and glycine (amino acid). His results revealed that substrate concentration influenced the preference of both plants for N forms. This means that whether the plant prefers one N form over another (e.g. nitrate over ammonium and amino acid or vice versa) depends on their concentrations in the growth medium or soil.

Reference

Warren CR. 2009. Does nitrogen concentration affect relative uptake rates of nitrate, ammonium, and glycine? J. Plant Nutr. Soil Sci. 172: 224-229.

Effects of elevation on N cycling in tropical forests

Scientists predict that tropical regions will receive the most dramatic increase in nitrogen (N) deposition over the next decades. This is due to increased fertilizer use, legume cultivation, fossil fuel consumption and biomass burning. There is thus a need for a better understanding of N cycling in tropical forest ecosystems. In a recent study by Arnold et al. (2009) across an Andosol (young volcanic ash soil) toposequence in Ecuador (Equitorial South America), it was revealed that gross rates of N transformations, microbial N turnover time, and δ¹⁵ N signatures in soil and leaf litter decreased with increasing elevation, indicating a decreasing N availability across the toposequence. Accompanying the above-mentioned trend was a decreasing degree of soil development with increasing elevation as indicated by declining clay content, total C, total N, effective cation exchange capacity and increasing base saturation. The study also revealed that soil N-cycling rates and δ¹⁵ N signatures were highly correlated with mean annual temperature but not with mean annual rainfall. Microbial immobilization was the largest fate of produced NH₄⁺ whereas nitrification activity was only 5-11% of gross NH₄⁺ produced. A fast reaction of NO₃^- to organic N which suggests abiotic NO₃^- immobilization, was also observed.

Reference

Arnold J, Corre MD, Veldkamp E. 2009. Soil N cycling in old-growth forests across an Andosol toposequence in Ecuador. Forest Ecology and Management 257: 2079-2087.

Relation between nutrient status of rainforest trees and environmental factors

The mineral nutrition of native plant species is still poorly understood. This is particularly true for the various tree species in rain forest ecosystems. In order to evaluate the mineral nutrient status of the dominant tree species and its relation to environmental factors such as elevation, slope, landscape position, and soil nutrient status, Z.S. Chen and co-workers (Wu et al., 2007) collected leaf, stem, and wood samples for nutrient analysis from a total of 636 trees belonging to 20 dominant species from 27 contiguous 20m x 20m quadrants along an altitudinal transect in a subtropical rain forest in southern Taiwan. They also collected composite soil samples from the 0-5 and 5-15 cm depths in each quadrant for chemical analysis.

Their results revealed that leaf concentration was better correlated with the environmental factors than stem and wood nutrient concentrations. This means that leaf analysis is more appropriate than stem and wood analyses to evaluate the nutrient status of native tree species. They also found wide concentration ranges for most mineral nutrients except P and Cu and most tree species were clustered at the lower end of the concentration ranges indicating they have low nutrient status. Among the macronutrients, P had the lowest and narrowest foliar concentration (0.25-2.8 g kg^-1) confirming the results of other studies from other tropical areas that P is the most limiting nutrient in tropical ecosystems. For the micronutrients, the lowest concentration was shown by Cu (3.88-17 mg kg^-1). A few tree species were found to accumulate (called “accumulator species”) nutrients like N, P, K, Ca, Mg, Cu and Zn indicating high absorption capacity for these nutrients. Foliar mineral nutrient concentration of the trees was generally correlated with the environmental factors such as elevation, topographic position, slope, vegetative type and soil nutrient status.

Reference

Wu CC, Tsui CC, Hseih CF, Asio VB and Chen ZS. 2007. Mineral nutrient status of tree species in relation to environmental factors in the subtropical rain forest of Taiwan. Forest Ecology and Management 239: 81-91.

Nitrate and phosphate leaching from Lake Danao soil (Leyte, Philippines)

Nitrogen and phosphorus are the most important nutrients that also function as environmental pollutants (Logan, 2000). The natural levels of these nutrients in soils are not high enough to cause environmental pollution. But the heavy and long-term use of chemical and organic fertilizers can lead to leaching of nitrate (NO₃^-) and phosphate (PO₄^3-) from the soil and thereby result in the contamination of the groundwater as well as of nearby surface waters such as rivers and lakes (e.g. Scheffer and Schactschabel, 1992; Logan, 2000). High nitrate level in surface waters contributes to fish kills and makes the water unsafe for animal and human consumption. Increased phosphate concentration in surface waters leads to eutrophication since phytoplankton in these waters respond to increased P level since it is a major limiting nutrient in fresh water ecosystems (Logan, 2000; Toor et al., 2003). The resulting accelerated growth of water plants and general degradation of water quality, limit the use of the affected surface waters for fisheries, recreation, industry and drinking (Lal and Stewart, 1994). According to WHO (1993) drinking water contamination with nitrate is presently the environmental issue of greatest concern in N management.

Lake Danao (also called Imelda Lake in former times) is a natural lake with an area of 1.9 km² in the form of guitar located at 700 m above sea level (ASL) in the central highlands of Leyte, Philippines (see photo). Surrounded by mountains with young loamy volcanic soils (Andisols), the lake provides water for home consumption and industrial uses, and opportunities for livelihood of people living nearby. It is a national reserve and popular tourist attraction due to its beautiful scenery and generally cooler climate than the lowlands of Leyte. In a recent Lake Danao watershed management study which was part of a VSU-Cornell University collaborative research and funded by USAID-ALO, it was revealed that there has been increasing signs of ecological degradation of the lake ecosystem in the last decade (Garcia et al., 2005). For example, many areas on the mountain slopes around the lake have been converted into agricultural farms which often use fertilizers and pesticides. Detergents used in households in the community on the bank of the lake can contribute substantial amount of P to the lake through leaching.

Until now there is lack of published data on the capacity of Philippine soils to filter pollutants as well as on the environmental impacts of the application of chemical and organic fertilizers to soils bordering surface water bodies like lakes and rivers. According to Sharpley et al. (2003) leaching of P is generally low except in sandy, acid organic, or peaty soils with low P fixation capacity and in soils where the preferential flow of water can occur rapidly through macropores and earthworm holes. Toor et al. (2003) observed that P leaching occurs in grassland soil largely in the form of organic P. Considering that the Lake Danao soil has very high porosity and organic matter content, it was thought that addition of fertilizers may enhance not only nitrate leaching but phosphate leaching as well despite of it being an Andisol.

In view of the above a laboratory study was conducted to find out if Lake Danao soil allowed leaching of nitrate and phosphate after addition of chemical fertilizers and manure. The leaching experimental set-up was designed and constructed using PVC cylinders containing the Lake Danao soil and amended with various amounts of poultry manure and chemical fertilizers like urea and solophos. The treatments were based on the application rate employed by the farmers around the lake. Results revealed that high amount of nitrate was leached from the soil amended with urea but only small amount in soil added with poultry manure. Findings also showed low amount of phosphate that was leached from the soil amended with either poultry manure or chemical fertilizer. Although field verification of the results maybe necessary, the study implies that the practice of using urea by the farmers can lead to eutrophication of the nearby lake. The use of poultry manure as fertilizer will minimize the said environmental effects.

Source:

Magahud JC and VB Asio. 2009. Nitrate and phosphate leaching from Lake Danao Andisol treated with manure and chemical fertilizer. Paper presented during the National Scientific Conference of the Philippine Society of Soil Science and Technology (PSSST), 20-23 May 2009, Davao City, Philippines.

References

Garcia P.P., E.A. Saz, V.B. Asio, T.A. Patindol and Z.M. de la Rosa. 2005. Multisectoral watershed planning in Lake Danao Natural Park through participatory approaches. Final Project Report, LSU-Cornell University ALO Project, 61pp.

Logan, T.J. 2000. Soils and environmental quality. In: Handbook of Soil Science (M.E. Sumner, ed.). CRC Press, Boca Raton, pp: G155-G169.

Scheffer F. and P. Schachtschabel. 1992. Lehrbuch der Bodenkunde. (13th ed.). Ferdinand Enke Verlag, Stuttgart, 491pp.

Sharpley AN, T Daniel, T Sims, J. Lemunyon, R Stevens, R Parry. 2003. Agricultural phosphorus and eutrophication. 2nd ed. USDA-ADS, ARS-149, 44pp.

Toor G.S., L.M. Condron, H.J. Di, K.C. Cameron and B.J. Cade-Menun. 2003. Characterization of organic phosphorus in leachate from a grassland soil. Soil Biol. Biochem.5: 1317-1323.

World Health Organization. 1993. Guidelines for Drinking Water Quality, Volume 1. Recommendations. Second Edition. WHO Geneva. 110 pp.

The original Handbook of Soil Science by E. Blanck

One of the most influential books on soil science in the 20^th century was the Handbuch der Bodenlehre (Handbook of Soil Science), a 10-volume book edited by Professor Edwin Blanck of the University of Göttingen, Germany, and published by Verlag von Julius Springer, Berlin, from 1928-32 (see photo). The book presented the state of the art in soil science until the late 1920s. According to the prominent soil scientist Professor Dan Yaalon of Hebrew University, modern soil research took off at an accelerated rate as a result of the publication of this monumental book by Blanck (Yaalon and Berkowicz, 1997). The contents of the different volumes are as follows: Volume 1- The Natural Science Principles of the Origin of Soils; Volume 2- The Climatic Principles of the Formation and Weathering of Soils; Volume 3- The Distribution of Soil types on the Earth’s Surface, Regional and Zonal Soil Science; Volume 4- Non-climatic Soil Formation, the Soil Forms in Germany and Fossils Weathering; Volume 5- The Soil as the Topmost Layer of the Earth’s Surface and its Geographic Importance; Volume 6- The Physical Properties of Soils; Volmue 7- The Chemical and Biological Properties of Soils; Volume 8 and 9- Applied or Special Soil Science (Soil Technology); Volume 10- The Methods of Cultivating Soils. Although Prof. Blanck was the main editor, he was assisted by a team of editors which was responsible for each volume. Each volume consisted of several chapters contributed by different authors. Prof. Hans Jenny who was still in Zurich at the time contributed a chapter on high mountain soils which appeared in Volume 3.

(A complete set of this handbook is found in the library of the Soil Science and Soil Protection Division, Institute of Agricultural & Nutritional Sciences, Faculty of Natural Sciences III, University of Halle-Wittenberg, Germany)

Reference:

Yaalon, D.H. and S. Berkowicz. 1997. History of Soil Science-international perspectives. Advances in Geoecology 29, Catena Verlag, 438pp.

The importance of N:P ratio

Soil fertility in terrestrial ecosystems has received increased attention from ecologists since it is now widely recognized that nutrient availability drives ecosystem functioning and processes (Wardle and Zackrisson, 2005). N and P are believed to be the most limiting nutrients in many terrestrial ecosystems particularly forests. Availability of N and P vary considerably during soil development as P is lost through leaching and fixation while N accumulates through biological N fixation (Walker and Syers, 1976; Crews et al., 1995). Thus, young soils have the tendency to be N limited while old soils are P limited. Ecosystem studies have confirmed this relationship of N and P indicated by the N:P ratio. It has been found that the leaf N:P ratio can detect nutrient limitation for wetland terrestrial ecosystem. An N:P ratio >16 indicates P limitation which is in clear agreement with the Redfield ratio (Redfield, 1958) for marine ecosystems. An N:P ratio <14 indicates N limitation and between 14 and 16 means either N or P is limiting (Koerselman and Meuleman (1996). It has also been reported that P limitation relative to N is widespread in terrestrial ecosystems (Elser et al., 2000a and 2000b) and that it is the cause of biomass decline in forest ecosystems in strongly weathered soils (Wardle et al., 2004a). Kitayama (2005) argued, however, that despite P limitation, tropical rain forests in Southeast Asia are still able to maintain high biomass as a result of high species diversity.

Elemental stoichiometry or the ratio of key elements such as carbon (C), nitrogen (N), and phosphorus (P) in organisms is useful in analyzing how the organisms influence or is being influenced by the ecosystem in which they are found (Elser and Dobberfuhl, 1996). While the elemental stoichiometry (Redfield ratio) of 106 C: 16 N: 1P is well-established for marine ecosystems it is just starting to be applied to terrestrial ecosystems. Thus, Elser and Urabe (1999) suggested that scientists working in other ecosystems (e.g. forest) might profitably apply stoichiometric approaches to food web dynamics and nutrient cycling. This is particularly valid for terrestrial systems since autotroph biomass N:P in terrestrial and freshwater systems has been found to be closely similar (Elser et al., 2000b)

References

Crews T.E et al. 1995. Changes in soil phosphorus fractions and ecosystem dynamics across a long chronosequence in Hawaii. Ecology 76: 1407-1424; Elser, J.J., Dobberfuhl, D.R., 1996. Organism size, life history, and N:P stoichiometry. Bioscience 46, 674-685; Elser, J.J. et al. 2000a. Biological stoichiometry from genes to ecosystems. Ecology Letters 3, 540-550; Elser, J.J, et al.2000b. Nutritional constraints in terrestrial and freshwater food webs. Nature 408, 578-580; Kitayama, K., 2005. Comment on ecosystem properties and forest decline in contrasting long-term chronosequences. Science 29, 633b; Koerselman, W., Meuleman, A.F.M., 1996. The vegetation N:P ratio: a new tool to detect the nature of nutrient limitation. Journal of Applied Ecology 33, 1441-1450;Redfield, A.C., 1958. The biological control of chemical factors in the environment. Am. Sci. 46, 205-221; Wardle, D.A., Zackrisson, O., 2005. Effects of species and functional group loss on island ecosystem properties. Nature 435:806-810;Warlde, D.A et al.2004a. Ecosystem properties and forest decline in contrasting long-term chronosequences. Science 305:509-513; Wardle, D.A. et al. 2004b. Ecological linkages between aboveground and belowground biota. Science 304: 1629-1633.

Relation between N mineralization and latitude

The global distribution of soils is a function of climate and thus is related to latitude. Consequently, soil processes are known to vary with latitude. But a recent study by Jones et al. (2009) which used soils collected from 40 latitudinal points from the Arctic through to Antarctica, showed that this is not the case for key soil processes like the turnover of amino acids (amino acids represent a key pool of carbon and nitrogen in soil and their availability to plants and microorganisms is considered a major driver in regulating ecosystem functioning). They found that “soil solution amino acid concentrations were relatively similar between sites and not strongly related to latitude. In addition, when constraints of temperature and moisture were removed, they demonstrated that soils worldwide possess a similar innate capacity to rapidly mineralize amino acids. Similarly, they showed that the internal partitioning of amino acid-C into catabolic and anabolic processes is conservative in microbial communities and independent of global position. This supports the view that the conversion of high molecular weight (MW) organic matter to low MW compounds is the rate limiting step in organic matter breakdown in most ecosystems.”

Reference

Jones DL, K Kielland, FL Sinclair, R A Dahlgren, KK Newsham, JF Farrar, DV Murphy. 2009. Soil organic nitrogen mineralization across a global latitudinal gradient. Global Biogeochem. Cycles, 23, GB1016, doi:10.1029/2008GB003250

Fate of nitrate in the capillary fringe and shallow groundwater

Nitrate pollution of groundwater systems is a serious problem in many countries. Application of nitrogen-containing fertilizers to irrigated crops is widely known as the major cause of nitrate pollution in groundwater systems. Nitrate is assumed to move downward through the vadose zone (unsaturated zone) and then move horizontally in the groundwater. But a recent study revealed that this may not be the case. Abit et al. (2008) evaluated the fate of nitrate in the capillary fringe (i.e. the subsurface layer at the boundary between the vadose zone and the zone of saturation) and shallow groundwater for a sandy soil with shallow water table. They found that nitrate entered the capillary fringe from the unsaturated zone then moved horizontally in the capillary fringe until it was partially carried into the groundwater by the fluctuating water table following rain events.

Reference

Abit SM, Amoozegar A, Vepraskas MJ, Niewoehner CP. 2008. Fate of nitrate in the capillary fringe and shallow groundwater in a drained sandy soil. Geoderma 146: 209-215.

Land use change decreases carbon, nitrogen, and sugar contents of tropical soil

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 the lowest non-cellulosic sugar content while the secondary forest had the highest.

Reference
Navarrete IA and K Tsutsuki. 2008. Land-use impact on soil carbon, nitrogen, neutral sugar composition and related properties in a degraded Ultisol in Leyte, Philippines. Soil Science and Plant Nutrition 54: 321-331.

Clay minerals in soil have antibacterial properties

Clay minerals are a major component of soils. They are an important source of negative charge which enable the soil to hold nutrients and pollutants. In recent years, the medicinal effect of clay minerals has gained increased interest among medical researchers.

In a recent paper in the Journal of Antimicrobial Chemotherapy, Haydel et al. (2008) reported:
"The capacity to properly address the worldwide incidence of infectious diseases lies in the ability to detect, prevent, and effectively treat these infections. Therefore, identifying and analyzing inhibitory agents are worthwhile endeavors in an era when few new classes of effective antimicrobials have been developed. The use of geological nanomaterials to heal skin infections has been evident since earliest recorded history, and specific clay minerals may prove valuable in the treatment of bacterial diseases."

The researchers found that specific clay mineral products have antibacterial properties which have potential to treat numerous human bacterial infections.

Reference
Haydel SE, CM Remenih, and LB Williams. 2008. broad-spectrum in vitro antibacterial activities of clay minerals against antibiotic-susceptible and antibiotic-resistant bacterial pathogens. J. Antimicrob. Chemother. 61: 353-361.

Effects of warfare on soil development

The influence of the physical environment on the outcome of battle is well-known but not the effects of warfare upon the environment particularly the soil. In view of this Hupy and Schaetzl (2008) studied the WWI battlefield of Verdun, France (1916). The battlefield which encompasses an area of 29,000 km², remains one of the most heavily shelled of all time. Their findings revealed that many craters penetrated the shallow limestone bedrock, and blasted out fragments of limestone found on nearby undisturbed soils had already been incorporated into the soil profile. Although the battle happened less than a century ago (88 years), weathering and pedogenesis have already occurred in the soils within the craters. A major pedogenic process noted by the researchers is the accumulation and decomposition of organic matter, which is intimately associated with (and aided by) earthworm bioturbation (soil mixing). The study shows that warfare can cause dramatic changes in the soil and landscape. It also "provides insight into the ability of a landscape to recover following a catastrophic anthropogenic disturbance” wrote Hupy and Schaetzl.

Reference:

Hupy JP and RJ Schaetzl. 2008. Soil development on the WWI battlefield of Verdun, France. Geoderma 145: 37-49

The "home field advantage" in plant litter decomposition

If you collect leaf litter from a Mahogany plantation and put it beaneath Gmelina trees or vice versa, the rate of litter decomposition will not be the same. According to a recent paper by Ayers et al. (2009), leaf litter decomposition is faster beneath the plant species from which the litter had been derived than beneath a different plant species. This is called home-field advantage. The authors observed that home-field advantage is widespread in forest ecosystems and hypothesized that this is due to the specialization of the soil organisms in decomposing litter derived from the plant above it. In other words, soil organisms living beneath the Mahogany trees are specialized in decomposing the leaf litter from this tree species.

Reference: Ayers E et al. (2009). Home-field advantage accelerates leaf litter decomposition in forests. Soil Biology and Biochemistry 41: 606-610.

Soil pollution and human health

People living in areas with fertile soils are better nourished than those living in degraded soils due to the higher quantity and quality of food in the former than the latter. Likewise, people living in polluted environments are more exposed to the ill effects of pollutants. The paths of environmental contaminants leading to humans are the following (Logan, 2000):

a) Soilàcropàhuman

b) Soilàlivestockàhuman

c) Soilàcropàlivestockàhuman

d) Soilàsurface watersàfishàhuman

e) Soilàgroundwateràhuman

f) Soilàairàhuman

g) Soilàhuman

The pathways a to e are indirect links between soil and human health and are relatively well-known. The pathways f and g are direct links and are little known and understood.

Direct links between soils and human health is geophagy

Humans ingest soil either involuntarily or deliberately. For the involuntary ingestion, every person ingests at least small quantities of soil. This is because any soil adhering to the skin of fingers may be inadvertently taken in by hand-to-mouth activity. This is especially true for children who like to play outdoors and for people working outside buildings or in the fields. Soil is also an important constituent of household dust and many foods such as fruits, vegetables and tubers crops usually contain some soil particles especially in poor countries. It is estimated that an average adult ingests soil at a rate of 10 mg per day.

Geophagy is the deliberate ingestion of soil by humans and animals. It is practiced by different peoples in all continents but is most common in the tropics particularly in Africa. This phenomenon was already known in the ancient world but the first detailed scientific report about it was written by the great German naturalist and founder of geography Alexander von Humboldt during his expedition of 1799-1804 to South America. Von Humboldt observed that eating soil was practiced by the indigenous Ottomac people in the Orinoco in Venezuela. The reasons for geophagy are still being debated until now but are known to vary from place to place. These include: soil as famine food to appease the pangs of hunger, as medicine and therapeutic (recent research has shown that clay adsorbs and detoxifies toxins and has antimicrobial action), cravings and good taste especially for pregnant women, as source of mineral nutrients to correct deficiencies, and an abnormal appetite for non-food substances. But excessive soil intake can lead to death of an individual due to the toxic effects of some mineral elements like Fe. This is likely to happen if the soil is contaminated with pollutants. Ingesting soil can also cause ingestion of eggs of parasitic worms and other disease-causing organisms (Abrahams, 2002; Dominy et al., 2004).

Another direct link between soil and human health occurs through inhalation. People inhale soil dusts inside their houses and by just walking in the street. The amount of inhaled dusts under normal conditions is generally low and thus is not harmful. But very dusty environments can cause lung problems. Also inhalation of even small amounts of the fibrous dust of serpentine and amphibole minerals commercially called asbestos is dangerous in that it can cause diseases and even cancer.

References

Abrahams, P.W. 2002. Soils: their implications to human health. The Science of the Total Environment 291: 1-32.

Dominy N.J., E. Davoust, and M. Minekus. 2004. Adaptive function of soil consumption: an in vitro study modeling the human stomach and small intestine. Journal of Experimental Biology 207: 319-324.

Logan, T.J. 2000. Soils and environmental quality. In: Handbook of Soil Science (M.E. Sumner, ed.). CRC Press, Boca Raton, pp: G155-G169.

Soil as component of landscapes and ecosystems

Landscape is a three dimensional section of the Earth’s surface with specific pattern of topography, rocks, soil, water and flora and fauna. E. Schlichting (1923-1988) proposed that soils in different positions in the landscape (or catena) exchange materials through transport processes which could be compared to the transfer processes between horizons in a soil profile (Schlichting, 1964). Landscape pedology is an emerging science focusing on soil as part of the landscape particularly on the variability of soil properties at the landscape scale (1-10km) (Sommer, 2006).

Ecosystem is a natural system consisting of a biosystem (community of organisms) interacting with the geosystem (its physical environment). The geosystem includes soil, water, relief, and climate. Soil is a major component of geosystem in that it provides nutrients, water and living space to the organisms in the ecosystem. Two emerging fields of science are ecopedology and geoecology. The former focuses on the ecological role of soil while the latter on the geosystem (soil, rock, water) component of ecosystems.

The two major types of ecosystems are the terrestrial ecosystem (or ecosystem on land) and aquatic ecosystems. In the humid tropics, a common landscape consists of the following terrestrial ecosystem types: forest, agricultural (agro-ecosystem), wetland, urban and mangrove. All the terrestrial ecosystem types are linked by the soil. The transfer of water, nutrients and soil material occurs largely in the soil. The soil also determines to a great extent the biological system that develops in each terrestrial ecosystem type. Further, degradation of the soil in the terrestrial ecosystem also affects the health of the aquatic ecosystem nearby. For instance, in many places in the Philippines, severe soil erosion in the uplands causes heavy siltation of the nearby marine area and thus affecting the survival of marine organisms.

References

Schlichting, E. 1964. Einführung in die Bodenkunde. Verlag Paul Parey, Hamburg, 93pp.

Sommer M. 2006. Influence of soil pattern on matter transport in and from terrestrial biogeosystems- a new concept for landscape pedology. Geoderma 133: 107-123.

Functions of soil

Soil is not dirt. It is a vital life-support system for human survival. Below are the major functions of soil:

a) Production function. Soil acts primarily as a medium for the growth of natural vegetation and cultivated plants. It assures the supply of food, fodder, renewable energy and raw materials. This is also referred to as the forestry and agricultural function of the soil.

b) Ecological regulator. Soil acts as filter, buffer, and transformer of various substances in or that are added to the soil. As a filter, the soil cleans polluted waters that move through it. As a buffer, it resists sudden change in its chemical balance thereby protecting the plants and soil organisms living in it. As a transformer, the soil is able to transform substances through microbiological and biochemical processes. The latter function is vital to the cycling of elements, degradation of toxic substances, decomposition of organic matter and production of greenhouse gases.

c) Habitat and living space. Soil is a habitat for a multitude of flora and fauna which are vital for human life. The largest quantity of organisms on Earth is in the soil. Many of the important antibiotics to treat human diseases are products of soil bacteria. Thus soil management is directly linked to the question of biodiversity. Soil also provides living space for humans and foundation for indrastructure such as roads, buildings, airports and others. Many human illnesses today are caused by soil pollutants that enter the food chain or enter the body through ingestion or inhalation.

d) Cultural heritage. Soil conceals and preserves remnants of past civilizations and plant and animal life. These paleontological and archaeological materials are of great value for the understanding of the history of civilization and the history of Earth.