Acid Sulfate Soils Research Articles

KARAKTERISTIK TANAH SULFAT MASAM DAN PENGELOLAANNYA UNTUK LAHAN PERTANIAN

Acid sulfate soils are quite abundant in Indonesia, and some have been used for agricultural land. The main problem with this soil is the presence of pyrite compounds (FeS2). The oxidation of these compounds causes the soil to become acidic, metals and bases dissolve so that the soil becomes poor and the life of aquatic biota affected by the drainage water is disturbed. The oxidized soil, if flooded again, causes an increase in ferrous iron ions and hydrogen sulfide which can poison plants, therefore management of acid sulfate soils needs to be carried out so that the soil has characteristics that can support plant growth. Some soil management actions that can be taken are controlling the activity of microorganisms in the oxidation and reduction processes of pyrite, providing amelioration materials and fertilization, land management and water management.

Exploring the Impact of Biochar‐Dolomite Application at Different Pyrolysis Temperatures on Acid Sulfate Soil Properties

ABSTRACTThe use of biochar as a soil amendment for acid soil, particularly acid sulfate soil, has garnered significant interest due to its capacity to improve soil properties, which is further accentuated when combined with dolomite. However, the extent to which the magnitude and direction of this effect vary with biochar produced at different pyrolysis temperatures remains uncertain. We conducted an incubation by mixing soil with dolomite and biochar types derived from Melastoma malabathricum (MMBC) and Dicranopteris linearis (DLBC) at three temperatures (300, 500, and 700°C). The incorporation of dolomite with both biochar types led to significant improvements in soil pH, available P, available Fe, exchangeable K, and exchangeable Ca compared to soil amended with dolomite only. These enhancements were likely attributed to the release of alkalinity, which further raised soil pH, as well as the direct dissolution of P, K, and Ca from the biochar. Moreover, the reduced Fe availability was likely due to the complexation of Fe onto surface functional groups of biochar. Furthermore, these improvements surpassed the effect of the initial feedstock and became increasingly pronounced with higher pyrolysis temperatures. However, an antagonistic effect of dolomite and biochar co‐incorporation was observed, particularly in the relative reduction of soil exchangeable Mg with both biochar types, and a decrease in the soil available N with MMBC produced at 300 and 500°C compared to dolomite addition alone, which could be due to the adsorption of Mg and N onto biochar surface. The results indicate that concurrent application of dolomite and biochar can change the acid sulfate soil properties to varying magnitudes and in different directions, largely regulated by the characteristics of biochar as well as the probable interplay with dolomite. Consequently, selecting the appropriate biochar that aligns with the desired soil properties is crucial in managing dolomite‐treated acid sulfate soil.

Changes in Acid-Sulfate Soil Characteristics with Biochar from Various Materials and their Effect on IR-Zinc Production

Changes in Acid-Sulfate Soil Characteristics with Biochar from Various Materials and their Effect on IR-Zinc Production

Fe toxicity tolerance is advantageous in rice growth recovery after Fe stress alleviation

AbstractBackgroundFe toxicity often inhibits rice growth on acid sulfate soils in tropical coastal lowlands. Previous studies in plant physiology and breeding have focused on high‐Fe stress, but not on growth recovery after stress alleviation.AimsThe objective of this study was to elucidate the morphophysiological characteristics in rice growth recovery from high‐Fe stress.MethodsWe evaluated the seedling growths of Taichung65 (T65) (Fe toxicity‐tolerant) and Ciherang (susceptible) in hydroponic culture, during the period of high‐Fe stress (250 mg Fe2+ L−1 for 12 or 18 days) and after stress alleviation.ResultsThe plant growth rate during recovery was negatively correlated with the leaf bronzing score (damage symptoms due to Fe toxicity) at the end of high‐Fe stress, which in turn was negatively correlated with the shoot Fe concentration. After 18‐day stress, T65 showed greater growth recovery than Ciherang, attributable to its higher net assimilation rate, higher transpiration rate (water uptake/green leaf area), and greater increase in total root length during recovery. In particular, T65 showed vigorous lateral root development in nodal roots that emerged during the stress period and vigorous growth of nodal roots that emerged during recovery.ConclusionsOur results suggest that tolerance to high‐Fe stress confers an advantage in growth recovery. It is likely that tolerance to Fe toxicity contributes not only to the maintenance of green leaf area at the end of stress but also to quick root growth recovery, leading to vigorous water uptake and high photoassimilation capacity after stress alleviation.

Increased sugarcane productivity and environmental improvement in acid sulfate soils: A win–win system

AbstractThis paper describes a sugarcane farming system on acid sulfate soils (ASS) in coastal, eastern Australia which has improved crop production, increased carbon sequestration, enhanced soil health and controlled drainage discharge to estuaries. The farming system has evolved as a collaboration between innovative sugarcane farmers, researchers and government agencies. The collaboration started when discharge from the farmed coastal floodplain ASS acidified an entire estuary in eastern Australia, wiping out all gilled and benthic organisms for 18 months. The event produced major conflicts between fishers, farmers, the community, entrained researchers and local and state governments. It led to a major initiative to develop sugarcane farming systems which enhanced environmental benefits and increased crop production. Such a win–win system has applicability to other locations with variable resource use conflicts. The system of cane land management adopted on the Tweed site is described.

Soil remediation and nano-biosilica: a potential combination to improve the environmental quality of brackishwater aquaculture ponds affected by acid sulfate soils.

The successful management of ASS-affected brackishwater aquaculture ponds necessitates overcoming associated environmental limitations. This study investigated the potential application of nano-biosilica from rice husk ash (RHA) and soil remediation techniques to improve the environmental quality of ASS-affected brackishwater ponds. The study followed a completely randomized design (CRD) with four treatments and three replicates. The treatments comprised applying soil remediation, nano-biosilica fertilizer, and their combination. The study generally revealed that the combination of soil remediation technique and RHA-driven nano-biosilica improved the water quality of ASS-affected brackishwater ponds. Soil remediation improved water quality by reducing acidity levels. However, excessive lime application as an integral part of the remediation might release acidity and toxic metals into water, potentially increasing calcium-phosphorus fixation. Despite liming potential negative consequences, if mixed with nano-biosilica could increase diatom-phytoplankton growth by reducing dissolved Al and Fe levels while boosting P and Si availability. Liming could also help boost diatom photosynthesis and inhibit unwanted algae blooms by decreasing water turbidity and increasing sunlight penetration. This study emphasized that the effectiveness of nano-biosilica in promoting diatom growth depends on appropriate nitrogen (N) and phosphorus (P) concentrations and ratios, which should not be a limiting factor. However, the required N/P concentration and ratio are only met if the remediation method is effectively implemented. The combination of nano-biosilica and soil remediation treatment maintained SiO2 concentrations above the average natural seawater concentration; however, availability may be limited due to complexes containing Ca, Al, Mg, and Fe. Regularly applying cost-effective nano-biosilica fertilizer in combination with N and P fertilizers is recommended to enhance water remediation efficiency by boosting Si availability and decreasing the toxicity of dissolved toxic metal ions.

Antimony sorption to schwertmannite in acid sulfate environments

Schwertmannite is a poorly-crystalline Fe(III) oxyhydroxysulfate mineral that may control Sb(V) mobility in acid sulfate environments, including acid mine drainage and acid sulfate soils. However, the mechanisms that govern uptake of aqueous Sb(V) by schwertmannite in such environments are poorly understood. To address this issue, we examined Sb(V) sorption to schwertmannite across a range of environmentally-relevant Sb(V) loadings at pH 3 in sulfate-rich solutions. Antimony K-edge extended X-ray absorption fine structure (EXAFS) spectroscopy revealed that Sb(V) sorption (at all loadings) involved edge and double-corner sharing linkages between SbVO6 and FeIIIO6 octahedra. The coordination numbers for these linkages indicate that sorption occurred by Sb(V) incorporation into the schwertmannite structure via heterovalent Sb(V)-for-Fe(III) substitution. As such, Sb(V) sorption to schwertmannite was not limited by the abundance of surface complexation sites and was strongly resistant to desorption when exposed to 0.1 M PO43-. Sorption of Sb(V) also conferred increased stability to schwertmannite, based on changes in the schwertmannite dissolution rate during extraction with an acidic ammonium oxalate solution. This study provides new insights into Sb(V) sorption to schwertmannite in acid sulfate environments, and highlights the role that schwertmannite can play in immobilizing Sb(V) within its crystal structure.

Impact of soil and water quality on the sustainable management of mangrove-compatible brackishwater aquaculture practices in Indonesia

The widespread degradation of mangroves has been attributed to their conversion into other land uses and purposes, most notably their destruction to construct extensive brackishwater aquaculture ponds. This study investigated the relationship between environmental factors and management alternatives for an integrated mangrove-aquaculture system in Derawan Island District, Berau Regency, East Kalimantan Province, Indonesia. The study collected a total of 56 soil and water samples from around 50 ha to assess environmental limiting factors for integrated mangrove-brackishwater aquaculture management. The measured soil quality variables included field pH (pHF), pH of hydrogen peroxide extract (pHFOX), peroxide oxidizable sulfur (SPOS), pyrite (FeS2), organic matter (OM), nitrogen-total (N-TOT), iron (Fe), and aluminum (Al). Water quality variables included salinity, temperature, pH, dissolved oxygen (DO), different forms of nitrogen (NH3–ammonia, NO3–nitrate, and NO2–nitrite), phosphate (PO4), Fe, and total organic matter (TOM). The study employed a hydrological restoration approach to suggest a mangrove-friendly aquaculture pond design and layout. The study generally showed that Acid Sulfate Soils (ASS) significantly restricted the existing mixed-mangrove aquaculture pond management by negatively impacting water quality. This study highlights that, given the characteristics of ASS-affected aquaculture ponds, reducing pond size for shrimp culture (mangrove-to-pond ratio of 80% and 20%) will simplify managing ASS environmental limiting factors through cost-effective remediation techniques and a Balanced Fertilization Strategy (BFS). The reduced shrimp pond size will also provide direct opportunities for mangrove restoration and allow effective hydrological restoration. The economic benefit of the proposed pond design and management model focuses on diversifying production units which include shrimp aquaculture ponds, milkfish or tilapia culture in the peripheral canals of the mangrove compartment, juvenile shrimp production, and periodic harvest from the primary pond canal. The study findings are particularly applicable to ponds that have already been built in ASS to improve productivity in addition to supporting the mangrove rehabilitation program. Converting mangrove and ASS-affected land is not advisable for constructing new aquaculture ponds.

Pengaruh Pupuk Cair terhadap pH, Fe-larut, dan C-organik di Tanah Sulfat Masam Desa Danda Jaya

One of the challenges of acid sulfate soil is the high Fe content in the soil, thus effective processing is needed to address its toxicity. The purpose of this study was to determine the changes in soil pH, Fe solubility, and organic-C from liquid fertilizer in acid sulfate soil in Danda Jaya Village, as well as to determine the relationship between soluble Fe and soil pH, organic-C and soil pH, and soluble-Fe. This research was structured using a descriptive method by comparing the application of liquid fertilizer with a control. The study was conducted in the Chemistry, Physics, and Biology Laboratory of the Soil Department, Faculty of Agriculture, Lambung Mangkurat University. The results of the study showed that the application of liquid fertilizer was able to increase pH and organic-C and decrease Fe solubility. Additionally, there was a correlation between soluble-Fe and pH with a coefficient of -0,95, a correlation between organic-C and pH with a coefficient of 0,91, and a correlation between organic-C and soluble-Fe with a coefficient of -0.89. Furthermore, the equation for the relationships was soil pH = -0.002 soluble-Fe + 5.958, Soil pH = 0.30 organic-C + 4,43, and soluble Fe = -154.92 organic-C + 830.15.

Stability and transformation of jarosite and Al-substituted jarosite in an acid sulfate paddy soil under laboratory and field conditions

Jarosite, a prominent mineral in oxidised acid sulfate soil, is known to sorb and incorporate a variety of elements, including Al. However, to understand the role that jarosite plays in regulating element cycles, it is crucial to understand the stability and transformation pathways of jarosite in an acid sulfate soil under dynamic biogeochemical conditions. In this study, we observed the transformation of unsubstituted jarosite and Al-substituted jarosite, collectively referred to as ‘jarosite’, in an acid-sulfate rice paddy topsoil and subsoil from Thailand. Jarosite was incubated in flooded paddy topsoils and subsoils for up to sixteen weeks, both in laboratory mesocosms and in the field, using bags made of polyethylene terephthalate mesh. One set of mesh bags contained jarosite that was not mixed with any other minerals, and referred to as ‘pure mineral’ incubations. Mineral transformations occurred under the influence of the soil porewater only and were primarily followed by X-ray diffraction analysis. A parallel set of mesh bags contained soil with 57Fe-labelled jarosite enrichment (Fe enriched in soil by a factor of 1.3 but 57Fe enrichment factor of 12.5–13.6), which allowed jarosite transformation to occur in close association with the soil matrix. Mineral transformations in 57Fe-jarosite-enriched soil were followed using 57Fe Mössbauer spectroscopy. In laboratory mesocosms and in the field, jarosite transformed most quickly in topsoil, whereas jarosite underwent limited transformation in subsoils, especially in laboratory mesocosms where Fe reduction was slow. The chemical environment around the jarosite affected the outcome of the transformation processes. Crystalline Fe oxyhydroxides, such as goethite, dominated the products in mesh bags where jarosite was not mixed with soil, whereas short-range-ordered or non-mineral Fe phases, such as Fe(II) sorbed to mineral surfaces or complexed with organic ligands, were dominant transformation products of jarosite when mixed in soil. Furthermore, Al substitution in jarosite caused contrasting effects in mesh bags containing pure minerals or mineral-enriched soil. Aluminium substitution slowed the transformation of jarosite in pure mineral mesh bags, but Al-substituted and unsubstituted jarosite showed similar transformation rates and pathways when incubated as a mixture with soil. The contrasting rate of transformation in topsoil and subsoil, the contrasting products of transformation in pure mineral mesh bags and 57Fe-jarosite-enriched soil, and the contrasting effect of Al substitution in pure mesh bags or jarosite-enriched soil, all demonstrate that the rate and products of jarosite transformation are defined by a balance between competitive transformation pathways that affect the transforming minerals.

The Potential of Agricultural Waste Compost to Elevate Growth and Rice Production with the SRI Method in Acid Sulfate Soils

The Potential of Agricultural Waste Compost to Elevate Growth and Rice Production with the SRI Method in Acid Sulfate Soils

Diagnostics of Acid Sulfate Soils in a Coal Mining Area of the Taiga Zone

Technogenic soils result from the oxidation and hydrolysis of minerals in rocks extracted from mining areas and brought to the surface. Diagnostics of such soils involve a set of detailed tests, which can be both time-consuming and costly. In this study, the pH of sulfate soils in the Kizel Coal Basin (Perm krai, Russia) was determined using hydrogen peroxide. Particularly, the soils affected by runoff from rock dumps, outflow, and mine water discharge were examined. The findings showed pH-H2O2 below 2.5 in certain horizons, indicating the presence of sulfides. Additionally, the soils exhibited significantly higher levels of mobile sulfur and iron, total sulfur, and sulfates, ranging from tens to hundreds of times above the background content. XRD analysis revealed that the soils contained goethite and jarosite, thereby confirming the efficacy of pH determination with hydrogen peroxide for the prompt diagnostics of acid sulfate soils.

Physical qualities of acid sulfate soil: its limitations and implications for oil palm production

ABSTRACT Global demand has pressured the extension of oil palm production areas in Thailand to acid sulfate soils. Besides their severe acidity and nutrient imbalance, the soil physical quality is expected to restrict production. This research defined the critical physical limitations of acid sulfate soils for oil palm production. The soil parameters of physical quality were assessed, covering 32 points in both the topsoil (Ap) and subsoil horizons. These parameters consisted of penetration resistance in the wet and dry seasons, saturated hydraulic conductivity (Ksat), bulk density (BD), the water characteristic curve, available water capacity (AWCA), available water content (AWCO), infiltration, and the S-index (a single indicator of soil physical quality derived from the parameters of the van Genuchten equation). The results showed critical physical quality constraints, particularly concerning the S-index and water shortage. The poor physical quality was more distributed in the Ap horizon (S-index = 0.024) than in the subsoil (S-index = 0.033). The penetration resistance was moderately restricted (3.26 Mpa) to the plant roots only in the dry season. Corresponding to the S-index data, the Ap horizon had a lower AWCA (0.21) than the subsoil (0.30). Most negative AWCO values in the subsoils (78%) during the wet season suggested a severe water shortage for oil palm production. Further research is needed to refine a specific partial drainage technique under oil palm canopies, focusing on the air-water balance system.

Assessing the productive potential of high-yielding rice varieties on acid sulfate soils in the tidal swampland of Central Kalimantan

Abstract Tidal swampland holds significant agricultural potential including cultivating rice. Farmers in these regions typically cultivate local rice varieties. Breeding rice techniques have led to the development of superior rice well-suited to thrive in tidal swamplands. This research was conducted on acid sulfate soil within a tidal swampland located in Terusan Karya Village, Kapuas Regency, Central Kalimantan, during the 2021 dry season. The study employed a completely randomized block design with two replications. The experimental treatments comprised nine high-yielding rice varieties: Inpari IR Nutri Zinc, Cakrabuana Agritan, Inpari 3, Inpari 32, Inpari 42, Inpari 47, Inpara 2, Inpara 8, and Inpara 10. The parameters were observed, including plant height, panicle number per hill, panicle length, and grain yield. The high-yielding varieties of rice planted in acid sulfate tidal swamplands exhibit varying growth and yield performances. Grain yields of rice ranged from 5.45 to 7.30 t ha−1 of dry-milled grain. The highest grain yield was shown by Inpari 3 (7.30 t ha−1) and Inpari 32 (7.04 t ha−1). High heritability values are indicated by the traits of dry harvest and milled grains, while wide variability is shown by characters such as plant height, panicle length, grain dry harvest, and dry milled.

Formulation of soil ameliorant material based on humic and silica to reduce Fe concentration in acid sulfate soils and improve rice growth

Abstract Applying soil ameliorants can suppress the Iron (Fe) toxicity of paddy cultivation in acid-sulfate soils. Humic materials can interact with Fe and Al metal ions to form chelates so that their solubility decreases. Silica plays a role in reducing the uptake of Fe and Al, reducing the Fe content on the surface of rice roots by increasing the oxidizing strength of rice roots. The research aim was to study the effect of ameliorant material formulation based on humate and silica on decreasing the Fe content in acid sulfate soils and increasing the growth of rice plants. The research was conducted in the Greenhouse, Swampland Agricultural Research Institute, Banjarbaru, from March to October 2022. The experimental design was randomized complete block factorial with the following treatments: Factor 1. Formula of soil ameliorant (F0 = 100% agricultural lime, F1 = 30% humate manufacturer+30% rice husk ash+40% agricultural lime, F2=30% water hyacinth humate+30% rice husk ash+40% agricultural lime, F3=30% water hyacinth humate+30% rice husk biochar + 40% agricultural lime, F4 = 30% humate manufacturer+30% rice husk biochar+40% agricultural lime), Factor 2. Dosage of soil ameliorant (D1 = 1 t/ha, D2 = 2 t/ha, D3 = 4 t/ha). Parameters observed were soil Fe content, available P and soil pH, plant height, and number of rice tillers every two weeks. The results showed that the formula F3, namely 30% water hyacinth humic acid + 30% rice husk biochar + 40% agricultural lime, was capable of decreasing soil Fe levels from 540ppm (F0) to 422 ppm and increasing soil pH from 4.23 (F0) to 4.48 and availability of P from 27 ppm (F0) to 55.20 ppm in acid sulfate soils. In addition, the formula can also increase the growth of rice plants. Improvements in soil chemical properties and plant growth are expected to increase the productivity of Inpara 8 rice plants in acid-sulfate soils.

Characteristics of pipestems from acid sulfate soils of Finland and Australia

AbstractThis study describes iron (Fe) pipestems formed around and within root channels during the development of a homogeneous unripe sulfidic sediment into a ripe soil where redox‐ or pH‐active elements segregate. Pipestems and adjacent soil material samples were characterised by chemical and mineralogical analyses and scanning electron microscopy (SEM) associated with energy dispersive spectroscopy (EDS). Pipestems occurred at 60–190 cm and at 30–130 cm in a young Finnish soil and a more mature Australian soil, respectively, while sulfidic materials were found below 170–180 cm. The pipestems consisted of mineral grains cemented together by Fe precipitate. There was an up to 24‐fold enrichment of Fe and an up to 13‐fold enrichment of sulfur (S) in the Finnish pipestems compared to the adjacent soil material, whereas the corresponding enrichment in the Australian soil was up to 27‐fold for Fe and up to 8‐fold for S. In the Australian pipestem matrices, the Fe concentration was as high as 40% compared to 14% in the Finnish ones. It was estimated that about 70 ton ha−1 S had been mobilised from the sulfidic material in the Finnish soil at the depth of 50–150 cm. Part of S has leached out but a substantial amount remained in the soil constituting the stock of retained acidity. Almost all pipestems contained a new solid phase precipitated within the former cortex cells of the plant roots. In the Finnish samples, this precipitate consisted of jarosite and schwertmannite. After oxidative exhaustion of sulfidic material in the surrounding soil, these metastable minerals are gradually hydrolysed, associated with leaching of S. In the mature Australian soil, most of these minerals had already been transformed to goethite. Pipestems formed after roots in unripe soil are sites for synthesis and hydrolysis of minerals and serve as routes for atmospheric oxygen into the reduced subsoil and for soluble reaction products to exit the soil. Pipestems have an important role in the ripening of the soil profile.

The first documented and characterized Norwegian acid sulfate soils

AbstractAcid sulfate soils (ASS) containing hypersulfidic material (pH >4) can, when drained, transform to ASS with a thionic horizon (pH <4), which can cause environmental effects due to the formation of sulfuric acid and the consequent mobilization and leaching of metals and acid into waterways, as well as cause geotechnical problems. Yet, the occurrence of ASS has till now not been a topic of research in Norway. The present pilot study was carried out on an area along the northern coast of Norway. Thirty‐nine localities were sampled and analysed near Alta. Of these, six were classified as ASS with either hypersulfidic or parahypersulfidic material. ASS is not as widespread as within the Baltic Sea area, but the analyses document the occurrence of ASS with hypersulfidic material with high acidifying potential in certain areas if oxidized. This pilot study shows that ASS occurs in specific areas. Three localities with documented ASS were studied in greater detail. Here, sections were excavated and analysed to help with the understanding of the geological context of these occurrences. In this way, the geological prerequisites considered of importance of soils with ASS with hypersulfidic material are outlined. The prerequisites for ASS occurrence that evolved during this study include young, marine, fine‐grained deposits and a low relief environment subjected to episodic sedimentation but otherwise calm water and little water exchange. The results are a starting point for further studies of ASS occurrences along the Norwegian coast.

Amelioration of salt‐affected soil using combined amendments for synergistic effects: Impacts and management implications

AbstractSaline acid sulphate soils are commonly ameliorated using traditional amendments like lime and cow manure. Biochar, derived from crop residues, is another potential remedy for this type of soil. Their combined use may create synergistic effects, necessitating further investigation. This study aims to assess the combined impacts of biochar with traditional amendments on soil quality, properties and rice yield. A field experiment was established with six treatments: no‐amendment (control), lime, cow manure, biochar, combined lime and biochar, and combined cow manure and biochar with rice (Oryza sativa) planted in four replicates. The study revealed that the effects of these amendments on soil properties were driven by their inherent characteristics and secondary processes, such as neutralization. Combining biochar with lime significantly increased soil pH (6.2), and exchangeable calcium (648.6 cmol(+) kg−1), while reducing exchangeable aluminium (11.83 cmol(+) kg−1) and iron (37.5 cmol(+) kg−1), compared to the control. Meanwhile, combining biochar with cow manure notably enhanced Mehlich‐1 phosphorous (3.4 mg kg−1), organic carbon (4.99%), ammonium (27.0 mg kg−1) and cation exchange capacity (17.2 cmol(+) kg−1). Biochar combined with cow manure exhibited greater synergetic effects on soil quality than when combined with lime. Consequently, these combinations improved the soil quality index, which exhibited a strong correlation with rice yield and biomass when its value was below 0.4. This finding indicates that these combinations exhibit insignificant synergistic effects on rice yield and growth. Further research is needed to elucidate these findings and explore the optimal application rates concerning soil properties for improved management practices.

Selecting Phosphorus-Solubilizing Strains of Purple Nonsulfur Bacteria Isolated From Pineapple Cultivated Acid Sulfate Soils

The presence of acid sulfate soils is such an obstacle for pineapple cultivation in Vietnam due to their low pH, high toxicity and poor nutrient availability, especially phosphorus (P), which is immobilized by cations in the soils. Therefore, the study occurred to select purple nonsulfur bacteria (PNSB) strains that can solubilize P under toxic and acidic conditions. There were 33 strains that can tolerate the acidic condition, and they were selected and tested for viability and P solubilization under conditions containing Al3+, Fe2+, and Mn2+ toxins. Four strains, including W15, W39, W42 and W48 suffered from growth inhibition by Al3+, Fe2+ and Mn2+ less than the other strains under both microaerobic light and aerobic dark conditions (ML and AD conditions). In addition, there were four strains (W15, W25, W42 and W48) solubilizing Al-P well (21.4-25.2 mg L-1), two strains (W23 and W42) solubilizing Fe-P well (15.9-17.3 mg L-1), and two strains (W17 and W42) solubilizing Ca-P well (23.0-36.4 mg L-1) under both ML and AD conditions. Ultimately, there were five strains selected (W17, W23, W25, W42 and W48) and identified as Rhodopseudomonas palustris strain W17 and W23, Cereibacter sphaeroides strain W23, W42 and W48 based on the 16S rRNA technique. The selected strains also produced ALA, EPS and siderophores at 1.31-2.19 mg L-1, 0.78-1.89 mg L-1, and 16.2-55.6%, respectively. Therefore, these strains were promising in providing nutrients for pineapples in the form of biofertilizer.

Chemical Characterization of Soils from Kole Land Ecosystem of Thrissur District, Kerala, India

Chemical characteristics of acid sulphate soils (Kole) of Thrissur district were done after the flood in 2018, in order to access the fertility and productivity of the soil. A total of 25 random samples were collected from different locations of AEU 6 in Thrissur district and its chemical characterization and mapping were done. Soils of Kole lands of Thrissur district were ultra to moderately acid in reaction (3.31 to 6.42) with an average pH of 4.98 and with medium to high organic carbon content (1.17 to 4.41 %) and 92 per cent of soil samples were high in available nitrogen which was resulted due to the presence of more organic matter and clay. Forty percent of soils were low in available phosphorus content. Almost 80 per cent of soil samples showed sufficiency in potassium content. Among the secondary nutrients, calcium and sulphur were sufficient while 52 per cent of soil samples showed deficiency in available magnesium. Among the micro nutrient content in collected soil samples, available Fe, Mn and Zn were high and no Zn deficiency was noticed. Cation exchange capacity ranged from 7.57 to 22.01 cmol (+) kg-1 with a mean content of 13.92 cmol (+) kg-1. The present study on mapping and primary characterisation form the base for further detailed study of Kole land ecosystem of Thrissur district in post flood scenerio.