Soil Health Concept and Initiatives in the Philippines

What is Soil Health? 

Although not yet clearly defined, soil health has become a widely used term globally, even beyond the scientific community. This may be because the term “health,” defined by the Cambridge Dictionary as “the condition of the body and the degree to which it is free from illness, or the state of being well,” is easily understood by many people. By humanizing the condition of soil through the term “soil health,” issues such as soil degradation become more accessible and easier to understand for individuals from diverse backgrounds. 

A "healthy soil" used for intensive vegetable production in Cabintan, Ormoc, Leyte

Zethof et al. (2026) noted that the current popularity of soil health is unparalleled in the field of soil science. However, they question whether the term is merely a clever marketing strategy or if it has the potential to advance soil science beyond simple popularization. 

The Food and Agriculture Organization (FAO) has reported that the concept of a “healthy soil” has not yet been officially defined, despite being widely used for more than a decade. Soil health generally refers to the performance or functioning of soil, rather than its intrinsic physical, chemical, or biological properties. The Intergovernmental Technical Panel on Soils (ITPS) defines soil health as “the ability of the soil to sustain the productivity, diversity, and environmental services of terrestrial ecosystems.” 

A "sick soil" (unhealthy soil) due to salinity (seawater intrusion) in Matalom, Leyte

Soil health evolved from earlier, more technical terms such as soil quality and soil fertility. Soil quality is one of the three components of environmental quality, alongside water and air quality. While water and air quality are primarily defined by levels of pollution affecting human and animal health or natural ecosystems, soil quality is broader. It is defined as “the capacity of a soil to function to sustain biological productivity, maintain environmental quality, and promote plant and animal health” (Bünemann et al., 2018). In his book Pedologie oder allgemeine und besondere Bodenkunde, F.A. Fallou, one of the founders of soil science, introduced the term soil quality (Qualitas), although with a different meaning (Asio, 2005). 

A sick soil due to high acidity (soil pH below 4.5) in Quinapondan, Eastern Samar

Furthermore, soil fertility originated from the German term “Bodenfruchtbarkeit” and focuses primarily on crop production. According to the FAO, soil fertility is “the ability of the soil to supply essential plant nutrients and soil water in adequate amounts and proportions for plant growth and reproduction, in the absence of toxic substances that may inhibit plant growth.” 

Soil Health Initiatives in the Philippines 

In the Philippines, the National Soil Health Initiatives are being championed by Congressman Adolph Edward “Eddiebong” G. Plaza, the 2nd District Representative of Agusan del Sur. His soil health initiatives focus on several key areas, including the formulation of a national soil health strategy and the implementation of a “From Lab to Land” approach. This approach promotes the use of advanced soil testing laboratories and modern technologies, such as drones, to monitor soil moisture, fertility, and erosion risks. It also encourages crop diversification and land rehabilitation. 

Congressman Eddiebong Plaza addressing the participants of the Stakeholders' Forum
he organized on Dec 3-5, 2025

Congressman Plaza’s partners and collaborators include ACIAR-SLAM (Dr. Johnvie Goloran), Griffith University (Prof. Chengrong Chen), DOST-PCAARRD, the Department of Agriculture–Bureau of Soils and Water Management (DA-BSWM), Agusan del Sur State University (ADSSU; Pres. Joy Capistrano), Southern Leyte State University–Hinunangan (SLSU-Hinunangan; Dr. Ian Navarrete), and the Society for the Advancement of Philippine Soil Science (SAPSS; Dr. VB Asio). 

In support of this initiative, Congressman Plaza organized the Stakeholders’ Forum on Soil Testing Protocols and Information Systems, held on December 3–5, 2025, in Prosperidad, Agusan del Sur. 

References 

Asio, V. B. (2005). "Comments on" Historical development of soil and weathering profile concepts from Europe to the United States of America"." Soil Science Society of America Journal 69: 571-572.

 Bunemann, E. K., Bongiorno, G., Bai, Z. G., Creamer, R., De Deyn, G. B., de Goede, R. G. M., ... & Brussaard, L. (2018). Soil quality-A critical review. Soil Biology and Biochemistry, 120, 105-125. 

Zethof, J. H., Kalbitz, K., & Jungkunst, H. F. (2026). Soil Health—What Is It Good for?. Journal of Plant Nutrition and Soil Science.

Impact of intensive vegetable production on the organic matter, nitrogen, and phosphorus levels of a volcanic soil (Andisol)

by Niezel Jane D. Estrellanes

Volcanic soils such as Andisols have many unique properties not usually found in soils derived from other parent materials (http:/www.ctahr.hawaii.edu). They are often very young and acidic depending on which type of volcanic materials they come from. They also largely consist of non-crystalline minerals such as allophane and imogolite (Nanzyo et al., 2002) which form strong bonds with organic matter thereby protecting it from decomposition. Andisols are usually light textured and are easy to till. However, they form strong complexes with phosphorus, rendering this element unavailable to plants.

One of the sampling sites in the central volcanic highlands of Ormoc, Philippines

This thesis research, a component of the Australian Center for International Agricultural Research (ACIAR) Soil Project based at the Visayas State University, evaluated the impact of intensive vegetable production on the nitrogen and phosphorus levels of volcanic soils in the central highlands of Leyte specifically in Cabintan, Ormoc City, Philippines. Twelve sampling sites (vegetable farms) including a reference site were chosen for this study. The objective was to find out if the continuous and heavy application of fertilizers for intensive vegetable production have caused the accumulation of nitrogen and phosphorous in Andisols.

Location of the sampling sites in Cabintan, Ormoc City

Soil samples were taken from the following soil depths 0-20, 20-40, 40-60, 60-80, and 80-100 cm using a soil auger. They were air-dried and passed through 2-mm sieve and analyzed for selected physical and chemical parameters such as pH (H2O, KCl, and NaF), available phosphorus, and particle size distribution. Enough 2-mm samples were also ground further and allowed to pass through 0.425-mm for organic matter content and total N analysis. 

Soil OM contents of the sampling sites. Sites 2, 4, 6 and 7 have much 
higher values than the reference site 12.

Soil N contents of the sampling sites. Most of the sites have much higher 
N levels than the reference site 12

Soil available P contents of the sampling sites. Reference site (12) has 
much lower P levels compared to all other sites.

Results revealed that the majority of the vegetable farms sampled showed higher amounts of organic matter (OM), nitrogen (N), and available phosphorus (P) than the reference site (secondary growth forest). This clearly indicates the impact of the high and continuous application of chemical and organic fertilizers (chicken manure). The very high nitrogen contents of the soils point out to nitrogen pollution which could have a serious negative impact on the groundwater quality. The high available phosphorus contents of the soils suggest improvement of the supply of this nutrient to the crops considering the fact that it is the major limiting nutrient to crop production in Andisols.

Based on the results it can be concluded that:

a. The intensive vegetable production has increased the nutrient status of the Andisol; 

b. The frequent and high rates of fertilizer application for the intensive vegetable production have greatly increased the nitrogen and phosphorus contents of the Andisol soil.

c. Nitrate and phosphate pollution of the groundwater and the nearby rivers may result from intensive vegetable production. 

Rice production in Eastern Samar: is there a bright future?

By Luz Geneston Asio, PhD

Department of Agronomy, VSU, Baybay City, Leyte

Eastern Samar has been consistently ranked as one of the poorest provinces in the country (www.faq.ph). A major reason for this is the low agricultural productivity due to several reasons: frequent typhoons, lack of government support, lack of political will, old farming methods, and many others.

During our one-week fieldwork in the province this July, we traveled to interior barangays, observed crop production practices and technologies interviewed farmers and technicians to get a picture of the real reasons for the low rice productivity of the province.

A poor rice farmer in San Jose village in Borongan City

Very striking across most of Eastern Samar is the widespread occurrence of uncultivated or only partly cultivated alluvial lands particularly near river systems. Such lands generally have great potential for intensive and highly productive rice production due to their generally flat topography. But most areas are idle and covered with Cyperus sedge and other grasses due to the lack of any irrigation system to supply the fields with sufficient water. Our field observations indicate that enough water lies beneath the land surface but nothing is done to tap it (e.g. deep wells) to support rice production.

An idle former rice land in Dolores, Eastern Samar

Only partly cultivated alluvial plain in San Julian, Eastern Samar

In many areas, we observed that farmers are planting modern rice varieties but are managed in the traditional way. For example, the modern rice varieties need proper spacing to grow well but most farmers are still practicing random planting without proper spacing. Farmers also complained that they received seeds and a small amount of fertilizers from the Department of Agriculture only once. It did not help them improve their production.

Modern rice variety planted at random (without proper spacing)

Shortly after planting, the soil dries up due to the absence of an irrigation system

Modern rice varieties are high yielding. Meaning, they are capable of producing high grain yields but they need high amounts of nutrients from the soil for them to attain their yield potential. Unfortunately, most farmers do not apply fertilizers or apply only insufficient amounts of fertilizers. The explanation by some agricultural technicians that the modern varieties need fewer fertilizers than the traditional varieties is simply not correct.

A farmer in Sulat harvesting his rice (he uses coconut leaves to protect him from the sun)

Quinapundan in the south is the only municipality where rice production appears to be very productive. The municipality possesses a large alluvial plain which is used for intensive rice production. The major reason is the availability of a functional irrigation system which allows farmers to plant two or more croppings of rice a year. We wonder why the local government in this municipality has been very successful in its rice production program but not Borongan, San Julian, Sulat, Taft, Can-avid, Dolores and the other municipalities which have wide areas of alluvial plains which are generally suitable for lowland rice production.

Intensive rice cultivation in Quinapundan, Eastern Samar

The prediction of one high ranking government official who was interviewed on local TV that Eastern Samar will attain rice self-sufficiency in the next five years is not attainable. Not unless of course the politicians will do something drastic to solve the real causes of low rice productivity in the province. 

Just imagine how many tons of rice will be produced once these large idle lands throughout the province will be made productive through a functional irrigation system, proper fertilization, high yielding varieties, and other modern farming methods. Unfortunately, for Eastehanons this is not the priority of the politicians. Thus, we can safely assume that Eastern Samar will continue to be one of the poorest provinces. The future of rice production in the province may not be bright at all.

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All photos were taken and are owned by the author.

Tropical soils: some important aspects of these less understood soils

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), "tropical 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 accurately reflect the soils in the tropics. 

Selected properties of the major tropical soils (Jahn and Asio, 2006)

The name tropical soils is now globally accepted but these soils have remained poorly understood until now. The following are some important aspects of tropical soils (Jahn and Asio , 2006):

1. The tropics,  the world’s largest ecological zone, have a very high potential for plant growth but with soil limitations in vast areas.
2. About one-third of the soils of the world are tropical soils. The most widespread are Ferralsols, Acrisols, Luvisols, Cambisols, and Arenosols.

3. The large proportion of Cambisols (Inceptisols) and Luvisols (Alfisols) in Southeast Asia re­flects clearly the younger age of land surfaces and therefore the short duration of weathering processes.

4. Some soils occur almost exclu­sively within the tropics. About 90% of the Ferralsols (Oxisols), 80% of the Nitisols (Oxisols/Ultisols), and 60% of the Acrisols (Ultisols) are situated in tropical regions.
5. The major soil limitations or soil constraints  are  low cation exchange capacity, low base saturation (low pH, high Al-saturation) and high P retention. They are most widespread in South America, Africa and Southeast Asia (in decreasing order based on area).
6. Physical constraints like high groundwater table, air deficiency, and low soil depth are of lesser significance but govern special requirements for soil management in specific landscapes.
7. Due to severe chemical limitations, proper management of nutrients is the main challenge for effective land-use systems in the tropics.
8. Internal and external fluxes of nutrients are different among soil types and different among tropical landscapes. These have to be considered in ecological land-use systems.
9. To conserve the stock of organic matter in tropical soils (and to increase it in degraded soils), biomass productivity will be a key point for ecological land-use systems.
10. To enable policy-makers as well as land users to establish sustainable and ecological land use systems in the tropics, more precise soil maps and soil information are needed.

References

Eswaran H., J. Kimble, T. Cook & F.H. Beinroth. 1992. Soil diversity in the tropics: Implications for agricultural development. In: Myths and Science of Soils in the Tropics. SSSA Special Publ. No. 29.

Jahn R. and V.B. Asio. 2006. Climate, geology and soils of the tropics with special reference to Southeast Asia and Leyte (Philippines). In: Proc. 11th International Seminar-Workshop on Tropical Ecology, 21-25 Aug 2006, VSU, Baybay City, Leyte, pp: 23-42.

Köppen W. 1931. Grundriss der Klimakunde. W. de Gruyter & Co., Berlin

Sanchez, P.A. 1976. Properties and Management of Soils in the Tropics. Wiley, New York

Uehara G. and G. Gillman. 1981. The Mineralogy, Chemistry, and Physics of Tropical Soils with Variable Charge Clays. Westview  Press, Boulder Colorado.

Organic Fertilizers, Organic Plant Growth Regulator, and Organic Plant Supplement as defined in the new Philippine National Standard for Organic Fertilizer

The new Philippine National Standard (PNS) for Organic Fertilizer was published in 2013 by the Bureau of Agriculture and Fisheries Product Standards (BAFPS) of the Department of Agriculture (PNS/BAFPS 40:2013).

According to this new PNS, Organic Fertilizer is “any product in solid or liquid form, of plant (except by-products from petroleum industries) or animal origin that has undergone substantial decomposition that can supply available nutrients to plants with a total Nitrogen (N), Phosphorus (P) and Potassium (K) of five to seven percent (5-7%). This may be enriched by microbial inoculants and naturally occurring minerals but no chemical or inorganic fertilizer material has been added to the finished product to affect the nutrient content.”

Organic Plant Growth Regulator/Promoter is “any compound of organic origin, in liquid or solid form, which in low concentration promotes or modifies physiological process in plants.”

Organic Plant Supplement is “any compound of organic origin in liquid or solid form which in low concentration promotes or modifies physiological processes in plants. Total NPK is not lower than 0.5% and not more than 2.5% (0.5-2.5%) and may contain beneficial microorganisms, micronutrients and plant growth regulators. These plant supplements include, but are not limited to: FPJ (Fermented Plant Juice), FFJ (Fermented Fruit Juice), FAA (Fish Amino Acid), FE (Fish Emulsion), Seaweed Extracts, Vermi Tea, Compost Tea and the like.”

The Technical Working Group which prepared the new/revised PNS was composed of: Dr. Leo P. Caneda, Executive Director, BAFPS (Chair) and the following members: Dr. N.B. Inciong (Professional Regulation Commission), Dr. E.P. Paningbatan Jr (Univ Philippines Los Banos), Dr. E.S. Paterno (UPLB), Dr. P.B. Sanchez (UPLB), Dr. V.C. Cuevas (UPLB), Dr. G.V. Pangga (UPLB), Dr. B.M. Calub (UPLB), Dr. N.E de la Cruz (Central Luzon State University), Dr. V.B. Asio (Visayas State University), Ms. J.B. Lansangan (Fertilizer and Pesticide Authority), Ms. P. Orpia (Bureau of Soil and Water Management), Ms. L.K. Limpin (Organic Certification Center of the Phil), Mr.  A. Aquino (Negros Island Certification Agency), and Mr. P.Belisario (Organic Producers and Traders Association).

Some notes on the soils and use of fertilizers and pesticides by vegetable farmers in Claveria, Misamis Oriental, Philippines

The gently rolling topography which typifies a large portion of the volcanic landscape in Claveria makes it ideal for intensive large-scale vegetable production. The widely grown vegetables include cabbage, beans, tomato, sweet pepper and eggplant.

The breathtaking volcanic landscape of Claveria, Misamis Oriental

But the strongly weathered soils which range from Oxisols in the lower slopes (about 400 to 600 m above sea level or asl) to Ultisols in the upper slopes (about 600 to 900m asl) are a major constraint to vegetable production in the area. Oxisols (also called Ferralsols) and Ultisols (also called Alisols and Acrisols) are clayey, reddish, acidic and nutrient-poor soils although they generally have good physical properties like good structure and moderate to high porosity. As in other volcanic landscapes, the oldest and most infertile soils (Oxisols) are formed on the older and stable lower slopes.

Dr. Apol & Nelds Gonzaga, Ruby Gabaca, Dr. Steve Harper & myself in front of an Ultisol soil at 920m asl. 

Farmers are apparently aware of the chemical and nutrient limitations inherent in these soils. That is why they apply lime and a variety of chemical and organic fertilizers. Rates of application are, however, not based on soil/plant tissue analysis but on what the farmers perceive as necessary. Thus, the rates appear to be insufficient in the case of lime, but excessive for the chemical fertilizers. This undoubtedly increases the production cost and can lead to more soil and environmental problems like acidification and groundwater pollution, respectively.

Heavy fertilizer application is done starting at planting of vegetables

Pest and diseases are also greatly affecting vegetable production in the Claveria landscape. As a result, farmers practice excessive application of pesticides which poses a serious threat to the health of the farming families, the consumers in urban centers, and the environment in general. The lack of awareness among farmers about the proper application of pesticides can be seen from their improper handling of these hazardous chemicals and from the fact that they just leave the pesticide containers at the farm borders.

It is common for farmers to mix two pesticides with water and spray the cocktail to the vegetables twice a week

The above observations strongly justify the urgent need for research on soil and nutrient management as well as integrated pest management in Claveria.

Potassium availability in soils

Potassium (K) is second to nitrogen in terms of the amount absorbed by higher plants. Optimum K level for plant growth ranges from 2 to 5% of plant dry weight (Marschner, 1995). Unlike P, K is present in relatively large quantities in soils coming from the weathering of primary minerals such as feldspars, mica, and others. But it is commonly deficient in highly weathered or old soils. Total K contents of soils range between 3000 and 100,000 kg/ha in the upper 20 cm of the soil profile (Sparks, 2000). The behavior of K in the soil is influenced primarily by CEC and mineral weathering and not by biological processes.

Interrelationship of various forms of soil K (modified from Sparks, 2000)

K in the soil occurs in 4 forms: solution K, exchangeable K, nonexchangeable K, and mineral K (Sparks, 2000).

a) Solution K. This is the K dissolved in the soil solution. It is the form of K that is readily available to plants and soil microorganisms and also is the form of K most subject to leaching losses. It varies in amount from 2 to 5 mg/liter K but can be dramatically changed by the addition of k fertilizers to the soil.

b) Exchangeable K. This is the form of soil K that is adsorbed on the surfaces of soil colloids. It is readily exchanged with other cations in the soil solution and is also readily available to plants. Some authors combine exchangeable K and solution K into one form called readily available form of K which comprises only 1 to 2 percent of soil K. This is also dependent on the CEC of the soil.

c) Nonexchangeable K. This is the portion of soil K that is fixed or held between adjacent layers of 2:1 clay minerals particularly vermiculite and smectite clay minerals. This is continually released to the exchangeable form when levels of exchangeable and soil solution K drops due to plant uptake and leaching losses.

d) Mineral K. This is the K that is part of the crystal structure of primary minerals such as muscovite, biotite, and feldspars. It is the most abundant and accounts for 90 to 98 percent of soil K. It is unavailable to plants and can only be released to the soil solution upon weathering of the minerals.

Leaching is the major cause of loss of K in the soil. Leaching of soil solution K is greatly dependent on the CEC of the soil and thus is influenced by the amount and type of clay and the SOM content of the soil. Soils with higher CEC like clayey soils have greater ability to hold K and thus have lower leaching losses than sandy soils with low CEC. Excess application of K-fertilizers can also enhance leaching losses especially under conditions of high rainfall.

Another form of leaching loss of K (and other nutrients) which is often overlooked is the one that occurs from the leaves of the plants. This can cause substantial nutrient loss exceeding seven times the amount in the standing crop in the case of K. Nutrients are leached from the leaves in the order K>N>P although this would also depend on the nutrient status and leaf morphology. Anything that reduces the water contact with leaves like smooth cuticle, erect leaves, etc. also reduces leaching losses (Chapin, 1980).

References
Chapin, F.S. III., 1980. The mineral nutrition of wild plants. Ann. Rev. Ecol. Syst. 11:233-260.
Marschner, H. 1995. Mineral Nutrition of Higher Plants. 2nd ed., Academic Press, London.
Sparks, D.L. 2000. Bioavailability of soil potassium. In:  In: Handbook of soil Science (M.E. Sumner, ed.). CRC Press, Boca Raton, pp: D38-D53.

Highly weathered soils from Visayas, Philippines

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 that soil composition will with time move towards the residua system composed of SiO2, Al2O3, Fe2O3, and H2O. In the USDA Soil Taxonomy, the highly weathered soils belong to the Ultisols and Oxisols orders. In the World Reference Base, these soils belong to the reference soil groups Alisols, Acrisols, and Ferralsols. These soils possess nutritional problems for crop growth and thus are a problem for agriculture.

(Beinroth, F.H. 1982.Geoderma 27(1982)-1-73; Chesworth, W. 1973. J. Soil Science 24: 69-81; Jackson, M.L. et al. 1948. J. Physical and Colloidal Chemistry 52: 1237-1260).  

Below are photos of the important highly weathered soils from Leyte, Negros and Samar islands in the Visayas. 

This is an Oxisol that formed from ultrabasic rock in Salcedo, Eastern Samar

The widespread red soil (Ultisol) in the volcanic area of Central Negros

An Ultisol on pre-weathered sediments from basalt in Silago, Southern Leyte

An Ultisol formed on pre-weathered sediments from basalt in Biliran, Leyte

The widespread soil from basalt on the lower slopes of Mt. Pangasugan, Baybay, Leyte

Response of Abaca (Musa textilis Née) to shade, irrigation and fertilization

Abaca plants

Abaca (Musa textilis Née), a relative of the edible banana (Musa acuminata and Musa balbisiana), is a native to the Philippines. It is grown primarily for its fibers which are utilized by the pulp, cordage and fiber craft industries. Studies have shown that the specific tensile strength of abaca fiber is comparable to or even higher than that of fiberglass (Bledzki et al., 2007;Sinon, 2008).

Dr. Marlito Bande and co-workers, in a paper to be published in the international journal Industrial Crops and Products 42:70– 77, reported on the optimum light, nutrient and water requirements of abaca to attain optimum yield. They also discussed how these parameters affect fiber recovery and fiber quality under field conditions. 

They showed that abaca planted under 50% shade had significantly (p < 0.01) higher fiber yield than those planted under the other shade/light treatments (30% and 40% of full sunlight using polypropylene shade nets) since the plants pseudostem under such treatment were longer, bigger and heavier.They revealed that the combination of irrigation and fertilization further enhanced fiber yield to as much as 41% but this was not enough to offset the effects of shade on the performance of the plant which significantly (p < 0.01) increased fiber yield to as much as 165%. Shade and irrigation–fertilizer application had no significant effect on fiber fineness and tensile strength. 

They concluded that 50% shade is the optimum requirement of abaca to achieve an optimum machine stripped fiber yield of 135.04± 4.31 g/plant without affecting fiber quality for industrial purposes.

The study which was conducted in Ormoc, Leyte, Philippines was funded by the German Research Foundation (DFG).

References

Bande MM, J Grenz, VB Asio, and J Sauerborn. 2013. Fiber yield and quality of abaca (Musa textilis var. Laylay) grown under different shade conditions, water and nutrient management. Industrial Crops and Products 42:70–77.

Bledzki AK, AA Mamun, O Faruk. 2007. Abaca fibre reinforced PP composites and expansion with jute and flax fibre PP composites. eXPRESS Polymer Letters 1 (11), 755–762.

Sinon FG. 2008. Optimization of stripping technologies for the production of high quality abaca fiber. Dissertation, Universität Hohenheim, Stuttgart, Germany

Ethnopedology: the study of local soil knowledge

“There is a need to integrate science and local knowledge. Both are vital and can be brought together only by participation” emphasized Prof. Dr. Franz Heidhues in his concluding remarks during the International Scientific Conference on Sustainable Land Use and Rural Development in Mountain Areas held at the University of Hohenheim, Germany on 16-18 April 2012. As can be seen from the figure below, scientific knowledge becomes more relevant when it is combined with local knowledge (Barrios and Trejo, 2003).

Precision & relevance of scientific and local knowledge  

Ethnopedology is the study of the local knowledge on soil and land systems of rural populations, from the most traditional to the modern. Ethnopedological research covers a wide diversity of topics centered around four main issues: (1) the formalization of local soil and land knowledge into classification schemes; (2) the comparison of local and technical soil classifications; (3) the analysis of local land evaluation systems; and (4) the assessment of agro-ecological management practices (Barrera-Bassols and Zinck, 2003; Barrios and Trejo, 2003). It encompasses many aspects, including indigenous perceptions and explanations of soil properties and soil processes, soil classifications, soil management, and knowledge of soil–plant interrelationships (Talawar, 1996).

In a recent study conducted in Vietnam and Thailand and presented in the above-mentioned scientific conference in Hohenheim, Dr. Gerhard Clemens and co-workers found, among other things, that: 1) Farmers classify their soils first of all according to soil color; 2) Farmers are able to describe soil properties and features. They also know the local factors affecting their soil; 3) Local soil classification is not consistent but the predominant soils can be efficiently identified using local soil knowledge.

An old farmer sharing some traditional knowledge 

Our own research in the degraded lands of Parasanon, Pinabacdao, Samar showed that the sweetpotato farmers possess a local knowledge system with regards to the nature of the soil and that of their sweetpotato crop. The demographic traits of the farmers clearly differed but they adhered to the same knowledge system regarding the attributes of the soil in their locality and the growth condition of their sweetpotato plants. Using their native dialect, the farmers have a soil classification scheme based on textural characteristics; they have also certain indicators of soil fertility and plant health. Moreover, the farmers know of certain problems concerning their soil or crop but they are not detracted by these because of their experience in finding ways to circumvent the situation (Pardales et al., 2001).

There has been an increasing research interest in local soil knowledge in recent years. This is the result of a greater recognition that the knowledge of people who have been interacting with their soils for a long time can offer many insights about the sustainable management of tropical soils (Barrios and Trejo, 2003).

References

Barrios E and MT Trejo. 2003. Geoderma 111: 217-231
Barrera-Bassols N and JA Zinck 2003. Geoderma 111: 171-195
Clemens G, U Schuler, BL Vinh, H Hagel, and K Stahr. 2012. International Scientific Conference on Sustainable land use and Rural Development in Mountainous Areas, University of Hohenheim, Stuttgart, 16-18 April 2012
Heidhues F. 2012. Conclusions. International Scientific Conference on Sustainable land use and Rural Development in Mountainous Areas, University of Hohenheim, Stuttgart, 16-18 April 2012.
Pardales JR, VB Asio, AB Tulin and DM Campilan. 2001. Project Report, UPWARD-CIP, Laguna.
Talawar, S., 1996. Research paper #2.Department of Anthropology, University of Georgia, Athens, USA.

Earthworms: the most important soil and ecosystem engineers

Earthworms are thought to be the most ancient soil animals having started colonizing terrestrial environments about 600 million years ago (Spain and Lavelle 2001). They are the most predominant soil fauna except in dry and cold climates. Earthworms are semiaquatic animals which extract water continuously from the surrounding soil inorder to maintain their cuticle in a moist state to facilitate gas exchange. Thus moisture status is a major limitation to earthworm activities and distribution.

Spain and Lavelle (2001) reported that since earthworms live in direct and continuous contact with the soil matrix and the soil solution, their presistence, propagation and activity are greatly affected by the chemical (pH, dissolved ions) characteristics of the soil. Based on their sensitivity to soil pH, earthworms are grouped into acidophilic species (able to thrive below pH 6 such as in organic forest litter), neutrophilic species (they prefer soil pH 6 to 7) and basophilic species (prefer basic soils).

Three ecological types of earthworms (Spain and Lavelle, 2001)

a) Epigeics. Earthworm of this type live in the litter layers and thus are effective compost-makers. However, they have no or little effects on soil structure.

b) Anecics. These are earthworms that feed on the surface littler that they mixe with soil but spend most of the time in galleries they create within the soil. They are
also able to translocate considerable amount of leaf-litter into the soil.

c) Endogeics. Earthworms of this type live and feed within the soil. Among the earthworm types, the endogeics are the major agent of soil aggregation.

Effects of earthworms on soil properties

Earthworm burrows are known to have high continuity in both horizontal and vertical directions and thus greatly influences water and air movement in the soil. Earthworms influence the physical and chemical soil properties in many ways by burrowing, casting, feeding and propagating. According to Emmerling et al. (2002) earthworms are the most important ecosystem engineers (organisms that may modify or create their habitat and thus influence availability of resources to other species and soil properties) in arable soil due to their lasting effects on soil physical and biochemical properties.

In an interesting laboratory study to assess the impact of ecologically different earthworm species on soil water characteristics, such as soil tension, water content, and water infiltration rate, Ernst et al. (2009) exposed three earthworm species (Lumbricus rubellus, Aporrectodea caliginosa, Lumbricus terrestris) in soil columns (diameter 30 cm, height 50 cm) for 100 days with a total fresh earthworm biomass of 22.7 ± 0.4 g per column, each in duplicate. Each column was added with 30 g of sieved and rewetted horse manure placed on the soil surface as a food source. Precipitation events (10 mm) were simulated at day 28 and day 64.

Results revealed that ecologically different earthworms modify soil water characteristics in different ways. The anecic L. terrestris and the endogeic A. caliginosa showed the tendency to enhance the drying of the topsoil and subsoil. Their intensive and deep burrowing activity seemed to enhance the exchange of water vapor due to a better aeration in the soil. In contrast, the epigeic L. rubellus tended to enhance the storage of soil moisture in the topsoil, which might be linked to lower rates of litter loss from soil surface and thus a thicker litter layer remaining. A. caliginosa led to considerable higher water infiltration rates and faster water discharges in the subsoil, relative to the other species, probably due to a high soil dwelling activity.

Vermiculture

The term "vermiculture" refers to the cultivation of epigeic earthworms grown in an organic matter substrate with no soil. Rearing soil dwelling earthworms undercontrolled conditions requires an understanding of their needs. Many earthworm species can exhibit a degree of plasticity in behavior, so general maintenance does not necessarily require extremely large containers. L. terrestris for example does not need access to a vertical borrow and can be bred in pots which may be only a few cm in depth (Butt, 2009).

References

Butt, KR. 2009. Collection and rearing of earthworms. Workshop Kommission III der DBG, 20-21.03.2009, Trier, Germany

Emmerling, C, M Schlotter, A. Hartmann, and E. Kandeler. 2002. Functional diversity of soil organisms- a review of recent research activities in Germany. JPNSS 165:
408-420.

Ernst G, D Felten, M Vohland, and C Emmerling. 2009. European Journal of Soil Biology 45: 207-213.

Lavelle, P. and A.V. Spain. 2001. Soil Ecology. Kluwer Academic Publishers. Dordrecht, 654p
Photo source:

L. FitzPatrick at http://blog.southtownstar.com/

The role of mycorrhiza in the mineral nutrition of plants

Mycorrhiza is the association between fungi and the roots of higher plants. The term was introduced by the German scientist A.B. Frank in 1885 (Mengel and Kirkby, 2001). Mycorrhiza is considered as the most widespread association between microorganisms and higher plants. On a global scale, between 86% and 94% of plants are mycorrhizal (Brundrett 2009). All Gymnosperms as well as 83% and 79% of dicotyledonous and monocotyledonous plants, respectively, are mychorrhizal (Marschner 1995). Nonmycorrhizal plants can be found in stressed soil environments (very dry or saline, waterlogged, severely disturbed as in mining areas, infertile) or even in very fertile soils. Mycorrhizas (or mycorrhizae) are absent under all environmental conditions in the Cruciferae and Chenopodiaceae (Marschner, 1995). Generally, in root-fungus association the fungus is strongly or wholly dependent on the higher plant, whereas the plant may or may not benefit from the association. It is not also essential for plant survival except in some plants like orchids. Mycorrhizal associations are therefore either mutualistic, neutral, or parasitic depending on the circumstances although mutualism is the dominant type.

Groups of mycorrhizas

Two mycorrhizal groups according to how the fungal mycelium relates to the root structure:
a) Endomycorrhizas. The fungi live inside the cortical cells of the roots and also grow intercellularly. The best known type is the vesicular-arbuscular mycorrhiza (VAM). This is widespread in cultivated soils.
b) Ectomycorrhizas. This group of mycorrhiza occurs mainly on roots of woody plants and only occasionally on herbaceous and graminaceous perennial plants. Some temperate tree species like beech, oak, spruce and pine cannot survive without ectomycorrhiza (Schachtschabel et al., 1998). They form a sheath or mantle of fungal mycelium over the surface of fine roots. The hyphae penetrate into the intercellular spaces of the root cortex and it extends outward into the soil.

Role of mycorrhizas in the mineral nutrition of host plants

Mycorrhizas are very important in the uptake of nutrients such as P, N, K, Cu, Zn and Ca by plants especially in soils low in these nutrients. Since P is the most limiting nutrient in tropical soils, mycorrhizas are vital for improving P nutrition particularly for cultivated plants. External hyphae can absorb and translocate P to the host from soil outside the root depletion zone. The thin mycorrhizal hyphae (2-4 μm in diameter) are able to penetrate soil pores not accessible to the root hairs which are about five times larger than the hyphae (Kirkby and Mengel, 2001). For example, studies have shown that the heavily mycorrhizal root of cassava enables it to grow well in phosphate-deficient soils where other crops fail (Wild, 1993). Also, a long-term study at the National Abaca Research Center at VSU (Armecin and Geneston-Asio, 2004) has provided the first clear evidence that abaca plant (Musa textilis) is mycorrhizal although colonization was relatively low (18-22%). In alkaline soils, mycorrhiza can prevent iron and manganese deficiencies. Mycorrhizas are also known to protect the plant from soil borne pathogens.

Recently, Lambers et al. (2010) reported that terrestrial plants (except epiphytes, parasites and carnivorous species) acquire most mineral nutrients from the soil primarily via two pathways: 1) direct absorption through the roots, and 2) indirect absorption through symbiotic mycorrhizal fungi. The majority of plants can take up phosphorus via both pathways but depend primarily on mycorrhizal fungi to acquire phosphorus.

References

Armecin RB and LG Asio. 2004. Effects of vesicular-arbuscular mycorrhizal fungi inoculation on Abaca (Musa textilis). Unpublished research report. NARC, VSU, Baybay, Leyte.
Brundrett, M. 2009. Plant and Soil 320: 37-77.
Lambers H, MC Brundrett MC, JA Raven and SD Hopper. 2010. Plant and Soil 334:11-31.
Marschner, H. 1995. Mineral Nutrition of Higher Plants. 2nd ed., Academic Press, London.
Mengel, K. and E.A. Kirkby. 2001. Principles of Plant Nutrition (5thed.). Kluwer Academic Publishers, Dordrecht, 849pp.
Schactschabel P., H.P. Blume, G. Brümmer, K.H. Hartge and U. Schwertmann. 1998. Lehrbuch der Bodenkunde (14th ed.). Ferdinand Enke Verlag, Stuttgart, 494pp.
Wild, A 1993. Soils and the Environment. Cambridge University Press, Cambridge, 287pp.

Photo Sources:
1. G. Quinn at http://www.finegardening.com/
2. Nathan Brandt, Iowa State University Extension News at http://www.extension.iostate.edu/

Soil degradation in the Philippines

Soil degradation is a severe global problem of modern times. About six (6) million hectares of agricultural land worldwide become unproductive every year due to the various soil degradation processes. The problem is much more serious in tropical than in temperate areas since tropical soils are generally more prone to degradation because of the nature of their properties (e.g. they are more weathered) and the prevalent climatic conditions. Countries in Asia and Africa that depend upon agriculture as the engine of economic growth are believed to suffer the greatest impact of soil degradation. In the Philippines, soil degradation is one of the most serious ecological problems today. The National Action Plan (NAP) for 2004 to 2010 identified soil degradation as a major threat to food security in the country. NAP reported that about 5.2 million hectares are seriously degraded resulting in a 30 to 50% reduction in soil productivity.

A degraded upland in Leyte

Soil degradation is defined as the process which lowers the current or future capacity of the soil to produce goods or services. It implies a long-term decline in soil productivity and its environment-moderating capacity. The concept of soil degradation was first used by Kostychiev and Korchinski in 1888 to describe a natural soil change. Since natural degradation is slow, the present concept of soil degradation according to the Global Assessment of Soil Degradation (GLASOD) focuses on a human-induced process. Soil degradation occurs because of drastic changes or disruption in the normal processes of soil formation due to human activities.

A degraded upland covered with Imperata (cogon) grass in Samar

In a review paper on the problem of soil degradation in the Philippines published in the Annals of Tropical Research vol. 31, we (Asio et al. 2009) revealed that soil erosion is the most widespread process of soil degradation and is also the most studied in the country. Other important but less studied soil degradation processes include loss of nutrients and organic matter, salinization, acidification, pollution, compaction, and subsidence. 

A degraded upland in Bukidnon

Studies reviewed have shown that the widespread degraded upland soils possess chemical and physical constraints for crop growth like acidic or calcareous pH, low organic matter and nutrient contents, shallow solum, presence of toxic substances, and compaction. The major factors that cause soil degradation include deforestation, overgrazing, agricultural practices, industrial activities, mining, and waste disposal. Deforestation is the main cause of soil degradation in Asia and South America while overgrazing is the main factor in the dryland areas of Australia, Africa, Europe, and Asia.

The typical degraded land in Cagayan Valley due to deforestation & overgrazing 

There is a need for more data on the physical and socio-economic characteristics of degraded lands to aid in the formulation of appropriate soil management strategies to support biodiesel production in these unproductive lands which are now being promoted by the Philippine government. Also, there is the danger that the use of the degraded lands for intensive and long-term biodiesel production without the appropriate soil management would cause further soil deterioration and thus aggravate the ecological problems that are now occurring.

Reference

Asio VB, Jahn R, Perez FO, Navarrete IA, and Abit SM Jr. 2009. A review of soil degradation in the Philippines. Annals of Tropical Research 31: 69-94

Note: All photos are owned by the author.

Response of corn to chicken dung and rice hull ash application and mycorrhizal fungi inoculation

By Luz Geneston-Asio, Central Analytical Services Lab, VSU, Baybay, Leyte

The use of locally available and cheap organic fertilizers like chicken dung and rice hull ash which have the ability to increase crop yield and at the same time improve soil quality is becoming popular among farmers in many places in the Philippines. In addition, considering that the world demand for corn as food and feed is projected to greatly increase in the coming decades, there is a need to explore the use of such materials for corn production.

We evaluated the growth and yield responses of corn to chicken dung and rice hull ash application a well as to mycorrhizal fungi inoculation. The experiment was laid out in a split-plot in Randomized Complete Block Design consisting of three replications. Vesicular-arbuscular mycorrhizal (VAM) inoculation served as the main plot while application of fertilizer was designated as the subplot. The fertilizer treatments included the following: To-control, T1-inorganic fertilizer (60-60-60 kg/ha N, P205, K20), T2-chicken dung alone (60 kg/ha N), T3-chicken dung (as in T2) + 30 kg/ha rice hull ash. The experimental area had an alluvial clay loam soil with pH of 5.8 and moderate fertility status.

Results showed that VAM inoculation significantly increased the total N but not the total P, K, and Ca contents of the tissue of corn plant. However, VAM inoculation did not significantly affect the grain yield and the agronomic characteristics of corn. In contrast, fertilization using inorganic fertilizer, chicken dung or chicken dung plus rice hull ash enhanced the early tasseling and silking but not emergence and maturity of corn. The application of fertilizers significantly increased plant height as well as the fresh stover yield compared to the control plants.

The inorganic fertilizer, chicken dung, and chicken dung plus rice hull ash significantly increased the number of ears per plant, ear length, number of grains per ear, weight of 1000 seeds, grain yield and harvest index. The use of chicken dung combined with rice hull ash for corn production is a good substitute for the inorganic fertilizer in increasing corn grain yield. (Above photo shows VAM infection in the root of corn from this study).

Reference

Luz Geneston-Asio and Alfredo B. Escasinas. 2006. Response of corn to chicken dung and rice hull ash application and mycorrhizal fungi inoculation. Annals of Tropical Research 26: 23-36