Hydrogen peroxide is not a good reagent for the removal of soil organic matter

Organic matter (OM) is the most important cementing agent of soil particles. Soils containing high amount of OM (like the limestone soil from Leyte in the picture below) generally have good aggregation (i.e. the sand, silt and clay particles are glued together by the OM). Removal of OM using chemical reagents is thus an important pretreatment in textural or particle size analysis as well as in the evaluation of soil mineralogy, cation exchange capacity, and surface area.

Soil in Leyte having a dark surface horizon due to OM 

Hydrogen peroxide (H2O2) which was first used in 1923 by G.W. Robinson to destroy soil organic matter, is the most widely used chemical reagent for removing OM in soil laboratories worldwide. However, there have been some scientific reports indicating that it may not be a good reagent for that purpose due to some unwanted effects on the mineral soil particles. In the Philippines, it is not also easy to procure large volumes of hydrogen peroxide since it requires clearance from the Philippine National Police.

Robert Mikutta and colleagues from the Institute of Soil Science and Plant Nutrition of the University of Halle-Wittenberg, Germany in a study published in the Soil Science Society of American Journal, Vol. 69 (2005), compared the performance of the three most accepted reagents for OM removal: hydrogen peroxide, sodium hypochlorite (NaOCl), and disodium peroxodisulfate (Na2S2O8).

The old soil mineralogy lab at the Univ Halle-Wittenberg

They found that: 1) removal of OM from soil is mostly incomplete with efficiency of removal varying with reaction conditions and sample properties; 2) sodium hypochlorite and disodium peroxodisulfate are generally more effective in removing OM compared with hydrogen peroxide; 3) alkaline conditions and additives favoring dispersion and/or decomposition of OM such as sodium pyrophosphate, are crucial for OM removal; and 4) OM removal can be little in soils containing high amounts of clay-sized minerals like Fe oxides, poorly crystalline Fe and Al phases, and expanding clay types.

The authors also found that the use of hydrogen peroxide to remove OM should be avoided for the determination of mineral particle properties since the treatment may promote organic-assisted dissolution of poorly crystalline minerals at low pH, disintegration of expandable clay minerals, and transformation of vermiculite into mica-like products due to ammonium (NH4+) fixation.

Clay collection for mineralogical analysis 

They concluded that sodium hypochlorite and disodium peroxodisulfate are less harmful for soil minerals than hydrogen peroxide; prolonged heating to 40 degrees Celsius during any pretreatment may transform poorly crystalline minerals into more crystalline ones; and sodium hypochlorite can be used at 25 degrees Celsius and can thus prevent heat-induced soil mineral changes.

Simply put: sodium hypochlorite is better than hydrogen peroxide in removing OM from soil samples.

Reference

Mikutta R, Kleber M, Kaiser K and Jahn R. 2005. Organic matter removal from soil using hydrogen peroxide, sodium hypochlorite, and disodium peroxodisulfate. Soil Science Society of America Journal 69: 120-135.

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.

The Physical Environment of Mt. Pangasugan, Leyte, Philippines

Geology

Mt. Pangasugan is generally built up by andesitic and basaltic pyroclastic rocks (referred to as Pangasugan formation) which are mostly of Quaternary and Tertiary origin. This rock formation is characterized by weak consolidation, lithologic discontinuities, abundance of rock outcrops, and shearing due to the occurrence of the Philippine fault line approximately at the center of the mountain range. Minor earthquakes are relatively frequent in the area. All these geological characteristics indicate that the area is unstable.

Geomorphology

The morphology of Mt. Pangasugan is largely the result of the combined effects of volcanism, erosion, faulting and tectonic uplift. Mt. Pangasuagn rises abruptly from the narrow alluvial coastal plain along the Camotes Sea into a vertical wall-like rock mass with a maximum height of about 1100 m above sea level (asl). The air distance between the sea level and the peak of the mountain is less than 3 km. This short distance suggests extremely high erosion energy potential which is visible in the form of waterfalls particularly during periods of high rainfall. The west-facing slope of the mountain is deeply dissected by several short parallel streams that empty into the Camotes Sea. The V-shaped valleys, which indicate youthful stage, coupled by the unconsolidated nature of the rock material, cause widespread landslides during typhoon periods.

Climate

The climate of the area is a humid tropical monsoon climate with no pronounced maximum rain period and no dry season (Type 4 of the Coronas climatic classification). It has an average annual rainfall ranging from 2600 mm in the coastal lowland, to more than 3000 mm at higher elevations. Average temperature in the plain is 27 degrees Celsius which decreases by an average of 0.6 degree Celsius per 100 m rise in elevation (i.e. at 500 m elevation, the average temperature is 24 degrees Celsius). Two types of monsoon winds tremendously influence the over-all climate of the area. From June to October, a southwest monsoon (Habagat) occurs which enhances rainfall in the area (western side of mountain). From November to February, the northeast monsoon (Amihan) follows which generally coincides with cyclonic disturbances thereby bringing plenty of rain particularly to the eastern side of the mountain range.

Pedology

The soils of the mountain can be grouped into four: the old soils in the mountain footslopes (approximately below 200m asl), the mature soils in the mountain midslopes (approximately between 200 and 400m asl), the young soils in the upper slopes (approximately above 400m asl) and the undeveloped soils in very steep slopes.The old soils (Ultisols) are deep, clayey, acidic and infertile. They are relatively stable although landslides may occur. The mature soils (Alfisols) are generally fertile and productive. The young soils in the upper slopes (Andisols) result from the fast weathering of andesitic rocks. They have excellent physical condition but are acidic and generally low in phosphorus. Because of their weak profile development and amorphous clay mineralogy, these soils are unstable and prone to landslides and erosion. The undeveloped soils on steep slopes (Inceptisols and Entisols) have low productivity due to their shallow profile, abundance of rock fragments and steep slopes. They are also prone to erosion.

References

Asio V.B.1996. Characteristics, weathering, formation and degradation of soils from volcanic rocks in Leyte, Philippines. Hohenheimer Bodenkundliche Hefte 33, Stuttgart, Germany, 290pp.

Quimio, J.M., V.B. Asio, J.M. Alkuino, B.B. Dargantes and P.S. Muga. 1997. Initial Environmental Examination of the Leyte-Mindanao Interconnection Project. NPC, Quezon City, 151pp.

Biological nitrogen fixation in corn

Corn (Zea mays L.) can establish rhizospheric or endophytic associations with various nitrogen-fixing bacteria (diazotrophs) such as Azospirillum, Klebsiella, Pantoea, Herbaspirillum, Bacillus, Rhizobium etli and Burkholderia. Most of these diazotrophs can grow in the intercellular tissue of plants without causing any disease.

Biological nitrogen fixation (BNF) is the biological process by which nitrogen (N2) in the atmosphere is converted to ammonia by an enzyme called nitrogenase. The screening of plant genotypes for their enhanced ability to acquire nitrogen by BNF can reduce the use of expensive nitrogen fertilizers in several important crops like sugarcane, rice, wheat and corn. It can greatly benefit particularly the poor farmers of developing countries.

In a recent study aimed to quantify the symbiotic biological nitrogen fixing activity of a range of commercial corn cultivars, Montanez et al. (2009) demonstrated that corn cultivars obtain significant nitrogen from BNF, the level of which varied with corn cultivar and nitrogen fertilization level. The study showed that some cultivars were more sensitive than others to nitrogen application and that 15N isotope dilution method is a useful tool to screen and select corn cultivars with any potential BNF.

Reference

Montanez A, Abreu C, Gill PR, Hardarson G, and Sicardi M. 2009. Biological nitrogen fixation in maize (Zea mays L.) by 15N isotope dilution and identification of associated culturable diazotrophs. Biology and Fertility of Soils 45: 253-263

Invitation to the 13th Scientific Conference of PSSST on 27-28 May 2010

The Philippine Society of Soil Science and Technology (PSSST) will hold the 13th Annual Meeting and Scientific Conference in Puerto Princesa City, Palawan, on 27-28 May 2010. Following is the formal announcement by the PSSST President Constancia G. Mangao.

PHILIPPINE SOCIETY OF SOIL SCIENCE AND TECHNOLOGY, INC. c/o BUREAU OF SOILS AND WATER MANAGEMENT
Elliptical Road corner Visayas Avenue, Diliman

February 16, 2010

Dear Fellow PSSST Members:

The Philippine Society of Soil Science and Technology, Inc. (PSSST), a duly recognized non-stock, non-profit professional society registered with the Securities and Exchange Commission, will hold its 13th Annual Meeting and Scientific Conference on May 27-28, 2010. This will be an important gathering of the members of the Society and interested professionals to share the latest developments and findings in soil science and technology.

In line with the conference’s theme, Soil and Water Management Approaches for Climate Change Mitigation and Adaptation, Puerto Princesa City, Palawan was chosen as the venue. Puerto Princesa City is a first class city with breath-taking sights, pristine sand beaches, lush rainforests, water falls, and beautiful islands with spectacular limestone karst landscape in its underground river, a significant habitat for biodiversity conservation. The city instituted environmental protection measures against the spoilers of nature.

We believe that you are an important partner to deal with in promoting soil technologies in the country. In this regard, we are inviting you to attend and actively participate in this annual meeting and scientific conference. The registration fee is six thousand six hundred fifty pesos (Php 6,650.00) which is inclusive of food and accommodation, attendance to scientific sessions, and symposium kits. Transportation and post conference tour are excluded in the registration fee.

Attached is the final announcement for your reference. For further details, please contact Dr. Virginia M. Padilla (vmpadilla02@yahoo.com/0919-66-8609) or Dr. Constancio A. Asis, Jr. (asis_tony@yahoo.com /09077441188).

Thank you very much. Very truly yours,

CONSTANCIA G. MANGAO
President

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

Effects of Lantana camara on soil properties and neighboring plants

Lantana camara Linn, locally called Utot-utot, Koronitas or Kantotoy in the Philippines, is a shrub which originated from tropical America. It is considered as one of the worst invasive plant species and is a noxious weed in many parts of the world.

The plant is known to suppress the regeneration of neighboring plants through allelopathic effects (by releasing volatile and non-volatile chemicals from its tissues and residues). The spread of Lantana is aided by the characteristic of its leaves which is somewhat poisonous to animals while its fruit is a delicacy for many birds which distribute the seeds (Wikipedia).

In a recent study published in Geoderma journal, Ling Fan and co-workers evaluated the chemical and microbiological properties of the soil underneath the canopy of Lantana camara as well as the soil away from it. They also investigated the effect of Lantana on the growth of three neighboring plant species (ryegrass, mungbean, and radish).

Results revealed that the soils underneath the canopy of Lantana had higher pH, total N, total P, available N and available P than the soils on the edge of the canopy and 2-5 m away from the Lantana plant. Soil respiration, enzyme activities, and microbial biomass N and P were higher in the soils underneath the canopy of Lantana than that away from it.

The study showed that Lantana camara improved soil fertility, accelerated N and P cycles, utilized carbon substrate more effectively, had higher functional diversity and did not inhibit the growth of the neighboring plant species.

Reference
Ling Fan, Yan Chen, Jian-gang Yuan and Zhong-yi Yang. 2010. The effect of Lantana camara Linn invasion on soil chemical and microbiological properties and plant biomass accumulation in southern China. Geoderma 154: 370-378.