Exchangeable Aluminum Content Research Articles

Modeling the impacts of extreme climate scenarios on soil acidity (pH and exchangeable aluminum) in Abbay River Basin, Ethiopia

The Abbay River Basin faces the looming threat of extreme climate events, including prolonged droughts and erratic rainfall patterns, which can significantly affect soil health and fertility. This study aimed to explore the influence of extreme climate conditions on soil pH and exchangeable aluminum, aiming to promote sustainable agricultural practices in Ethiopia. The Africa Soil Information Service (ASIS) provided datasets on soil pH and exchangeable aluminum. The European Copernicus Climate Change Data Store was used to download historical and future datasets of extreme climatic indices from 1980 to 2010 and 2015–2050, respectively. The Coupled Model Intercomparison Project Phase 6 model ensemble was used to predict future climate impacts under three shared socioeconomic scenarios: SSP1-2.6, SSP2-4.3, and SSP5-8.5. Data extraction, quality control, and clustering were conducted before analysis, and the model was validated for its accuracy and reliability in predicting soil parameter changes. An artificial neural network model was utilized to predict the effects of extreme climate indices on soil pH and exchangeable aluminum concentrations. The model was designed to accurately and reliably predict changes in soil parameters. This study compared the changes in soil pH and aluminum concentrations using paired t tests. The model's diagnostic results indicated a significant impact of extreme climate scenarios on soil pH and exchangeable aluminum. Extreme climate factors such as heavy precipitation and cooler night time temperatures significantly contribute to soil acidification and an increase in aluminum concentration. Under the SSP1-2.6 and SSP2-4.5 emission scenarios, soil pH levels are expected to increase by 8.38 % and 3.79 %, respectively. These changes in soil pH are expected to have significant impacts on the exchangeable aluminum content in the soil, with increases of 37 % and 5.38 %, respectively, under the same emission scenarios. However, the SSP5.8 scenario predicted a 45 % increase in exchangeable aluminum and a 9.36 % decrease in soil pH. Therefore, this study significantly enhances our understanding of the influence of climate change on soil health. The development of strategies to mitigate climate change impacts on agriculture in the region must consider the effects of extreme climate indices.

Evaluation of aluminum tolerance diversity in Avena sativa L. from the VIR collection

Background. Oat is an important food and feed cereal crop in Russia. The area under oats is 10 million ha worldwide, and 3 million ha in Russia. Acid soils with excessive content of exchangeable aluminum occupy almost every third hectare in the exUSSR territory. Oats are relatively resistant to unfavorable soil factors. Among cereal crops, oat is second only to rye and triticale in terms of resistance to exchangeable Al forms. Despite the crop’s high environmental plasticity, an important condition for obtaining sustainable oat yields is the development of new cultivars with resistance to adverse environmental factors, including metal toxicity and high soil acidity.The objective of this work was to search for oat cultivars resistant to soil stressors (excess of Н+ and Al3+) for use in breeding for edaphic resistance.Materials and methods. The research material included 687 oat accessions from the VIR global plant genetic resources collection. The accessions underwent laboratory evaluation of their aluminum tolerance at the initial growth and development stages using the method of measuring radicle growth after the exposure to aluminum stress. Reproducibility of the used modification of the method was mathematically proved.Results and discussion. Significant variation in the resistance to the studied stressor was observed among the accessions. The regions acting as sources of valuable aluminum resistance genes were identified for the crop. The accessions selected for their high resistance to exchangeable aluminum can be used in breeding programs to develop high-yielding oat cultivars with edaphic resistance.

Influence of Diatomite, Zeolite and Bentonite Clay on Agrochemical Indicators Sod-Podzolic Soil and Yield Agricultural Crops

In three-year microfield experiments on sod-podzolic light loam soil, the effect of reclamation doses (3, 6 and 12 t/ha) of siliceous rocks (diatomite, zeolite and bentonite clay) on the main agrochemical properties of the soil and crop productivity in the grain link of the crop rotation of winter wheat-spring barley-seed peas was studied. Among other positive effects, a significant effect of diatomite was found in reducing the concentration of exchangeable forms of aluminum in the soil (by 0.11 mg-eq/100 g), increasing the content of exchangeable forms of magnesium (by 0.33 mg-eq/100 g) and phosphates of soil solution (by 225%). Against the background of the influence of diatoms, barley gave the greatest increase in grain yield (by 38%) and straw (by 29%). The most significant effect of zeolite was revealed in a decrease in the actual, metabolic and hydrolytic acidity of the soil (a decrease of 1.11, 0.48 pH units and 0.33 mg-eq/100 g), as well as the concentration of exchange compounds of calcium (an increase of 17.7 mg-eq/100 g), magnesium (by 12.0 mg-eq/100 g) and potassium (by 46%). The introduction of zeolite rock contributed to the greatest increase in the yield of grain (by 32%) and straw (by 23%) of barley. The most significant influence of bentonite clay was established on the indicators of actual soil acidity (their decrease by 0.65 pH units), the content of exchangeable aluminum (decrease by 0.19 mg-eq /100 g) and phosphates of soil solution (increase by 175%). The introduction of clay contributed to the formation of the greatest increase in grain yield (by 33%) and straw (by 19%) of seed peas.

Biochar addition to tea garden soils: effects on tea fluoride uptake and accumulation

Long-term consumption of tea with high fluoride (F) content has a potential threat to human health. The application of different amounts of biochar to reduce F accumulation in tea leaves has been little studied. In this study, a pot experiment was conducted to investigate the effect of biochar amounts (0, 0.5%, 2.5%, 5.0%, 8.0%, and 10.0%, w/w) on tea F content during the tea plant growth. Changes in tea quality, soil F fraction, and soil properties caused by biochar and the relationship with tea F accumulation were also considered. The results showed that the application of biochar amendment significantly reduced water-soluble F contents in tea leaves compared to CK (without biochar), especially in the 8.0% treatment (72.55%). Overall, biochar contributed to improving tea polyphenols and caffeine, but had no significant impact on free amino acids and water leachate. Compared with CK, 5.0–10.0% biochar significantly increased soil water-soluble F content due to the substitution of F− with OH− under high pH. Additionally, biochar applied to tea garden soil was effective in decreasing the soil exchangeable aluminum (Ex-Al) content (46.37–91.90%) and increasing the soil exchangeable calcium (Ca2+) content (12.02–129.74%) compared to CK, and correlation analysis showed that this may help reduce F enrichment of tea leaves. In general, the application of 5.0–8.0% biochar can be suggested as an optimal application dose to decrease tea F contents while simultaneously improving tea quality.Graphical

RANDOM FOREST MODEL TO PREDICT THE HEIGHT OF EUCALYPTUS

Eucalyptus (Eucalyptus urograndis) production has significantly advanced over the past few years in Brazil, especially with regard to acreage and productivity. Machine learning has made significant advances in most varied fields of agrarian sciences. In this context, this study aimed to use physicochemical variables of the soil as well as climatic and dendrometric variables of eucalyptus to predict its height using the random forest algorithm. The study was conducted in the municipality of Três Lagoas, in Mato Grosso do Sul, Brazil. The original database consisted of 49 soil physicochemical variables collected at 0–0.20 m and 0.20–0.40 m, two dendrometric and four climatic variables, and one response variable related to the height of eucalyptus. A correlation matrix was applied to select variables. Furthermore, modeling was performed using the random forest algorithm, which performed well (r = 0.98, R2 = 0.96) in predicting the height of eucalyptus. Overall, the most important variables to predict the eucalyptus plant height included diameter at breast height (DBH), phosphorus content (P1), gravimetric moisture (GM1) at a soil depth between 0.00 m and 0.20 m, and exchangeable aluminum content (Al2) between 0.20 m to 0.40 m of soil.

The effect of mineral fertilizers and liming on the properties of sod-podzolic soils and the productivity of legume-grass mixture in the conditions of the Komi Republic

The research was carried out in 1998-2018 in the conditions of the Komi Republic. Under study was the effectiveness of single application (1983) of lime doses (1.0; 2.0; 2.5 h. a.) and the systematic use of mineral fertilizers (N60P75K75) against the background of lime effect in the cultivation of perennial grass mixtures (meadow clover, meadow timothy and cocksfoot). High efficiency was shown by liming at doses of 2.0 and 2.5 h. a., the effect remained for 35 years since their introduction to the soil. Thus, in 2018, the exchange acidity was 4.5-4.8 pHKCl (the initial 4.1-4.2 pHKCl). A similar decrease was observed in the hydrolytic acidity and the content of exchangeable aluminum in the soil. The amount of humus by 2018 increased to 1.7-1.8 % (the initial 1.4-1.5 %). The average yield of perennial grasses during soil liming at doses of 2.0 and 2.5 h .a. was 24.0-25.1 t/ha of green mass (5.3-5.5 t/ha of good quality dry matter), which is 52.8-59.8 % higher than the variant without fertilizers (15.7 green mass and 3.7 t/ha of dry matter). In the variant with the systematic use of NPK, the exchange acid content of the soil and the humus content remained at the initial level, the amount of the mobile forms of phosphorus and potassium increased to 198 and 121 mg/kg of soil (the initial 42 and 62 mg/kg). The average annual yield of grasses was 25.3 t/ha of green mass (5.4 t/ha dry matter) and was 61.1 and 45.9 % higher than the control. Against the background of the aftereffect of lime flour, the effect of NPK on soil properties was similar to the effect of non-fertilizing cultivation, with the exception of a significant increase in the availability of mobile forms of phosphorus and potassium – up to 254-288 and 148-166 mg/kg, respectively. A high yield of green mass of 28.1-30.7 t/ha (6.4-6.7 t/ha dry matter) was obtained, exceeding the control by 78.9-95.5 %. In these variants, grass mixture of high quality was obtained: the content of crude protein – 13.8-13.9 %; dry matter – 21.8-21.9 %; the content of total phosphorus – 0.92-0.94 %; potassium – 2.93-2.95 % and calcium – 0.79-0.81 %. The amount of nitrates in the feed did not exceed the MPC (147-149 mg/kg dry matter). Long-term studies on sod-podzolic poorly cultivated soil showed that the optimal method for the cultivation of long-term legume-cereal grass mixture was the use of lime flour (2.0 and 2.5 h .a.) and the annual use of N60P75K75.

Chemical changes in soil with use of pelletized organomineral fertilizer made from biosolids and sugarcane filter cake

Soil fertility has become an interconnected aspect of modern agriculture, incorporating factors such as nutrient availability from soil, and its revision has become necessary for ensuring sustainability. Therefore, to understand the solubility of nutrients from organomineral fertilizers pelleted with biosolids and sugarcane filter cake, and to evaluate the resulting chemical changes in soil from its use, an experiment was performed in a completely randomized design. The experiment was done with four replicates in a 3 × 5 +1 factorial scheme, using three fertilizer sources (mineral fertilizer, organomineral fertilizer pelletized with biosolids, and organomineral fertilizer pelletized with the filter cake); five doses (60%, 80%, 100%, 120%, and 140% of the recommended dose of fertilization for corn); and an additional control treatment (absence of fertilization). The formulation of the organomineral fertilizers was 5-17-10 with 10% total organic carbon. All fertilizer sources were packed in a microfiber cloth positioned 1 cm below the surface of the soil and incubated for 60 days. Subsequent evaluation of chemical attributes: pH H2O (1:2.5); pH SMP (Shoemaker-McLean-Pratt); and the content of exchangeable aluminum, phosphorus, potassium, calcium, magnesium, silica, and organic matter within the soil was done. Organomineral fertilizers pelleted with biosolids or filter cake do not acidify the soil, but they were found to reduce aluminum saturation and promote a slow release of nutrients, which allowed a more balanced base in the soil. This then ensured a better balance of nutrients, with greater cation exchange capacity, base sums, and base saturation. The use of these fertilizers can contribute to stabilizing the pH of the soil with fewer applications of acidity correctives

Ecologically safe device technologies of road covering with the using technogenic materials

The influence of nepheline sludge on the soil of a roadside strip when used in the device of road coverings is studied. Chemical analysis of soil samples taken from the roadside strip of a highway constructed using a base made of nepheline sludge was performed. It is shown that the change in the content of calcium-the main element of the sludge at a distance from 5 to 100 m from the road did not exceed its value in the background sample, and the content of exchangeable aluminum in the soil of the analyzed areas was at a very low level-less than 0.5 mg/kg and practically did not affect its content in the soil at all sampling points from 0 to 150 m from the road. Based on the conducted ecotoxicity studies using single-and dicotyledonous plants, the possibility of using nepheline sludge as a component of road covering in the form of a nepheline-crushed stone mixture has been established and the absence of toxicity in the analyzed soil samples at various distances from the roadside strip has been proved.

The effect of biochar, lime and ash on maize yield in a long-term field trial in a Ultisol in the humid tropics

A multi-season field trial was carried out to investigate the effect of the amendment of biochar, lime, ash and washed biochar on the growth of maize. A degraded, strongly acidic Ultisol (pHKCl 3.60), with a relatively high exchangeable aluminium content (2.4 cmolc/kg) and a low exchangeable calcium content (0.99 cmolc/kg), was used. Soil was treated once at the beginning of the field trial and crop growth was monitored over seven planting seasons (PS). All treatments increased maize yield. The average increases were; seven times for biochar, five times for lime, five times for washed biochar and eight times for ash treatment, when compared to the control across all PS. The effect of biochar, lime and ash treatments on maize yield were sustained over the seven PS. Soil pHKCl was significantly increased (p < 0.05 level) following the addition of all of the amendment materials. All treatments significantly reduced the concentration of Al3+ when compared to the control (p < 0.05), with the lowest concentrations for the lime and ash treatments. The ash treatment also increased the concentration of macronutrients (K, P and Mg) to the greatest extent. Results showed that there was a clear liming effect at play. The better performance of biochar compared to lime, despite lime having the highest pH and the lowest Al3+ concentration, can be explained by the additional K, Mg and P the biochar adds to the soil. Results also showed a clear nutrient addition effect where ash added the most nutrients. Overall, this work supports the fact that small scale farmers in Indonesia should produce biochar from their waste agricultural materials. Doing so not only provides an increase in crop productivity, but also sequesters carbon resulting in the best overall environmental benefit.

Improvement effects of quicklime and calcium magnesium phosphate fertilizer on acidified soil cultivating Codonopsis tangshen.

To solve the problem of soil acidification in the cultivation of Codonopsis tangshen, laboratory experiments were carried out to investigate C. tangshen seed germination, seedling growth and soil exchangeable acid, microbial community structure after applying quicklime (QL) and calcium magnesium phosphate fertilizer (CMP). The results showed that QL and CMP treatments significantly improved the survival rate of C. tangshen seedlings from 147.7% to 326.7% and from 270.1% to 311.2%, respectively. The maximum increase rates of the height of C. tangshen seedlings were 516.7% and 546.3%, and that of root length were 798.0% and 679.2% in the treatments of QL and CMP, respectively. 1‰-4‰ QL or CMP treatments increased the relative chlorophyll content, antioxidant enzyme activity and the content of soluble protein of C. tangshen seedlings, decreased the content of malondialdehyde and superoxide anion radical of seedlings, increased soil pH by 0.88-2.02 units and 0.23-1.19 units, and decreased the exchangeable aluminum content in soil by 53.0%-95.3% and 17.6%-81.3%, respectively. Soil bacterial and actinomycetic abundances were significantly higher in 2‰-4‰ QL or CMP treatments than that in the control. Soil fungal abundance was significantly lower in the QL treatment of 2‰ and CMP treatment of 4‰. 1‰-4‰ QL or CMP treatments significantly increased fresh weight of C. tangshen tubers by 40.5%-78.5% and 28.4%-78.8%, respectively. In conclusion, the suitable quantity of QL and CMP for acidified soil (pH=4.12, ρb=1.15 g·cm-3, tillage layer=15 cm) amendment were 1.73-3.45 t·hm-2 and 3.45-6.90 t·hm-2, and QL and CMP amendment could fit the optimum soil pH (5.5-6.5) for the growth of C. tangshen seedlings.

CHANGES IN CHEMICAL PROPERTIES BY USE AND MANAGEMENT OF AN OXISOL IN THE AMAZON BIOME

ABSTRACT The proper soil use and management are essential for a sustainable production, thus the pursuit for systems that minimize damages to the environment and improve soil fertility is continuous. The objective of this study was to evaluate changes in soil fertility by the use and management of an Oxisol (Latossolo Vermelho-amarelo, SiBCS) in the Amazon biome. The soil uses and management systems evaluated were native forest, native pasture, minimum tillage system and conventional tillage system. The chemical atributes of the soil layers 0.00-0.10, 0.10-0.20, 0.20-0.30 and 0.30-0.40 m were evaluated. The soil pH (CaCl2) and the contents of organic matter, available phosphorus and exchangeable potassium, calcium, magnesium and aluminum were evaluated and the saturation by Al, effective cation exchange capacity and soil potential were determined. The highest pH values were found in the native pasture area, and the highest exchangeable aluminum contents were found in the layers 0.00-0.10 and 0.10-0.20 m of the conventional tillage system. The highest phosphorus availability was found in the layer 0.00-0.10 m of the native forest area. The highest potassium availability was found in the minimum tillage system. The lowest calcium and magnesium values were found in the layers 0.00-0.10 and 0.10-0.20 m of the conventional tillage system. The highest soil organic matter content was found in the layer 0.00-0.10 m of the native forest area. The nutrient availability for plants decreases in soils managed using the conventional tillage system. Soil uses and management systems of little soil disturbance are recommended to minimize environmental degradation in the Amazon biome.

Soil Factors Related to the Severity of Clubroot in Rio de Janeiro, Brazil.

Soil pH and calcium levels are determining factors in the success or failure of managing clubroot during the cultivation of Brassica spp. The aim of the present study was to evaluate the influence of soil attributes in tropical regions on the development of roots and clubroot and the accumulation of biomass and nutrients in cauliflower. One hundred and fifty-one samples of soil and plants were collected from 16 family farms that have a history of more than 50 years of regular cauliflower cultivation in Nova Friburgo, Rio de Janeiro, Brazil. Chemical and physical analyses were performed on the soil samples, and the severity of clubroot and the accumulation of biomass and macronutrients in individual plants and plant tissues. Clustering and main principal component analyses were performed on the data. The disease occurred on all farms, but with different intensities. A direct relationship was observed for the soil attributes (acidity and exchangeable aluminum content in particular) with the percentage of roots with clubroot and with the accumulation of biomass and macronutrients in the different plant organs. To reduce losses from clubroot in weathered soils, practices should aim to reduce the pathogen's inoculum potential and improve the physical and chemical conditions of the soil, which would favor root development of the plants.

English

Many researches have performed on gypsum application to correct high exchangeable aluminum content in acidic soils, especially in subsurface. Although, they have found increases in the exchangeable calcium and sulfur contents, exchangeable aluminum has not been decreased. The exchangeable aluminum buffering by organic matter may contribute to non-significant reduction in exchangeable acidity. The objective of this study was to evaluate the effect of mineral gypsum on the aluminum compartments of Hardsetting Ultisol and monitor the capacity of gypsum to provide exchangeable calcium and sulfur in subsurface. Increasing amounts of mineral gypsum (0, 2, 4, 6, and 8 Mg ha-1) were applied with broadcast at the field. The experimental design consisted of randomized block with four replicates. Aluminum compartments (Al-organic matter, Al-amorphous and Al-crystalline) were evaluated at 0 and 15 days after gypsum application and the exchangeable calcium and sulfur contents were evaluated at 0, 15, 64 and 90 days. The evaluations were performed in three different layers. Gypsum application increased the exchangeable calcium and sulfur contents in subsurface and did not reduce the exchangeable aluminum content. Al-organic matter in the surface layers decreased along the incubation time and application gypsum. Al-amorphous in the subsurface layers increased with the increased amounts of gypsum. Al-crystalline decreased as soil depth increased. The exchangeable aluminum buffering in surface layers was performed by Al-organic matter and, in subsurface, by Al-crystalline. Key words: Aluminum compartments, aluminum fractionation, soil acidity, soil pH, exchangeable calcium.

Surface applied lime dynamics and base saturation index in a consolidated no-tillage area

The aim of this study was to evaluate the behavior of chemical properties and crop yields during five years after liming, in a consolidated no-tillage system area and indicate a base saturation index to serve as a criterion for recommendation. The experiment was conducted in a randomized complete block design with four repetitions, being the treatments the five lime doses (0, 2.4, 4.8, 7.2 and 9.6 Mg ha-1) applied and maintained on the soil surface. Soil chemical properties were evaluated in eight soil sampling, in the layers 0 to 0.025; 0.025 to 0.05; 0.05 to 0.10; 0.10 to 0.15; 0.15 to 0.20 and 0.20 to 0.40 m, besides crop grain yield (wheat, soybean and corn) and black oat dry matter yield, totaling five years of evaluation. The surface liming in no-tillage system increased the exchangeable magnesium and calcium contents, base saturation and soil pH and reduced the exchangeable aluminum content. The cumulative grain yield (six crops) and black oat dry matter yield (three crops) was not influenced by liming. These results suggested, from this study conditions, that the value of 50% of base saturation should be adopted as a criterion for liming for crops implanted under consolidated no-tillage systems.

CHARACTERISTICS OF RICE SOILS FROM THE TIDAL FLAT AREAS OF MUSI BANYUASIN, SOUTH SUMATRA

Tidal flats in the Musi Banyuasin region that cover more than 200,000 ha are the largest area for agricultural development in South Sumatra Province. Only about a half of this has been used for tidal swamp rice fields, therefore, the other half needs to be developed. To obtain a better understanding of their properties for appropriate soil management, soil characteristics of the area need to be studied. To characterize the soil, thirty-four soil samples from seven soil profiles were analyzed for their chemical and mineralogical composition at the laboratories of the Center for Soil and Agroclimate Research and Development. The results indicate that soils from the tidal flat areas have an aquic soil moisture regime, the upper parts of the soils are mostly ripe, and most of the pedons show the presence of sulfidic materials below 65 cm of the mineral soil surface. The soils are classified as Sulfic Endoaquept (P1, P2), Histic Sulfaquent (P3), Typic Sulfaquept (P4), Fluvaquentic Endoaquept (P5), and Sulfic Hydraquent (P6, P7). Mineral composition of the sand fraction is dominated by quartz, while the clay minerals consist of predominantly kaolinite, mixed with small amount of smectite, illite, quartz, and crystoballite. Organic carbon content is high to very high, potential phosphate content of most pedons ranges from very low to medium, while potential potassium content varies from very low to medium in the upper layers and medium to very high in the bottom layers. Phosphate retention of topsoil sample varies from 56 to 97%, and is positively correlated (r2 = 0.73) with aluminum from amorphous materials. Exchangeable cations are dominated by Mg cation, and in all pedons cation exchange capacity values are medium to very high, and seem to be influenced by organic carbon. Specific chemical properties, particularly soil pH and content of exchangeable aluminum exhibit a significant change about 1-2 months after soil samples were taken from the field. Theoretically, interaction between good water management and fertilizer application are among the choices of management to make these soils productive.

CHARACTERISTICS OF RICE SOILS FROM THE TIDAL FLAT AREAS OF MUSI BANYUASIN, SOUTH SUMATRA

Tidal flats in the Musi Banyuasin region that cover more than 200,000 ha are the largest area for agricultural development in South Sumatra Province. Only about a half of this has been used for tidal swamp rice fields, therefore, the other half needs to be developed. To obtain a better understanding of their properties for appropriate soil management, soil characteristics of the area need to be studied. To characterize the soil, thirty-four soil samples from seven soil profiles were analyzed for their chemical and mineralogical composition at the laboratories of the Center for Soil and Agroclimate Research and Development. The results indicate that soils from the tidal flat areas have an aquic soil moisture regime, the upper parts of the soils are mostly ripe, and most of the pedons show the presence of sulfidic materials below 65 cm of the mineral soil surface. The soils are classified as Sulfic Endoaquept (P1, P2), Histic Sulfaquent (P3), Typic Sulfaquept (P4), Fluvaquentic Endoaquept (P5), and Sulfic Hydraquent (P6, P7). Mineral composition of the sand fraction is dominated by quartz, while the clay minerals consist of predominantly kaolinite, mixed with small amount of smectite, illite, quartz, and crystoballite. Organic carbon content is high to very high, potential phosphate content of most pedons ranges from very low to medium, while potential potassium content varies from very low to medium in the upper layers and medium to very high in the bottom layers. Phosphate retention of topsoil sample varies from 56 to 97%, and is positively correlated (r2 = 0.73) with aluminum from amorphous materials. Exchangeable cations are dominated by Mg cation, and in all pedons cation exchange capacity values are medium to very high, and seem to be influenced by organic carbon. Specific chemical properties, particularly soil pH and content of exchangeable aluminum exhibit a significant change about 1-2 months after soil samples were taken from the field. Theoretically, interaction between good water management and fertilizer application are among the choices of management to make these soils productive.

Novel solution injection technology for in-situ leaching of weathered crust elution-deposited rare earth ores

Weathered crust elution-deposited rare earth ores are rich in the middle and heavy rare earths. The present study investigated the content of exchangeable aluminum and the exchangeable rare earth in the different layer of orebody and the partitioning of rare earth was determined as well to understand the mode of occurrence of rare earth. Furthermore, the swelling of clay minerals from different layers was investigated. The results shown that, in completely weathered layer and partly weathered layer, the content of exchangeable rare earth was more than 0.06% and the content of exchangeable aluminum was below 0.02%. However, in humic layer, the content of exchangeable rare earth was below 0.015% and the exchangeable aluminum was more than 0.03%. In the weathered crust elution deposited rare earth ore, the exchangeable aluminum is mainly found in the humic layer, whereas the rare earth elements are abundant in the completely weathered layer and partly weathered layer and the rare earth in humic layer belong to light rare earth group. Additionally, the swelling of clay minerals in humic layer was ranged between 2.5% and 2.7%, which were higher than the swelling of clay minerals in completely weathered layer and partly weathered layer. Based on these findings, a novel in-situ leaching technology of weathered crust elution-deposited rare earth ores is proposed. The leaching agents were directly injected into the completely weathered layer without infiltrating through the humic layer. Avoiding the humic layer, only the completely weathered layer and partly weathered layer were leached. According to this method, the exchangeable aluminum in the rare earth leaching solution can be decreased and the purity of rare earth product can be improved. Meanwhile, the ammonium chloride was alternatively applied to leach rare earth and the choices of available leaching reagents were broadened.

Genesis and Classification of Soils Containing Carbonates in a Toposequence of the Bambuí Group

The Bambui Group, formed from siliciclastic sediments deposited on an extensive epicontinental platform at the end of the Neoproterozoic era, is characterized by limestones with fine to very fine texture. Limestone-derived soils in the southeast of Tocantins state, Brazil, are less notorious than similar soils in other regions of Brazil and their characterization could contribute to the Brazilian System for Soil Classification (SiBCS). Given that little is known of these soils, despitetheir agricultural potential, the objective of this study was to characterize their properties and the processes leading to soil of genesis, and also contribute to developing the Brazilian System of Soil Classification (SiBCS). Soils profiles were located on the summit (P1), shoulder (P2), backslope (P3), and footslope (P4) of a toposequence in the municipality of Lavandeira, Tocantins. Morphological, physical, chemical, and mineralogical properties of the profiles were determined. The soils were classified as: P1 - Chernossolo Rendzico Litico tipico (Lithic Haplustolls); P2 - Cambissolo Haplico Ta Eutrofico leptico hipocarbonatico (Lithic Haplustolls); P3 - Cambissolo Haplico Carbonatico leptico (Lithic Haplustepts); and P4 - Luvissolo Haplico Ortico tipico (Typic Rhodustalfs). All the profiles showed high contents of silt, calcium, and magnesium, which resulted in high pH and low exchangeable aluminum content. Base saturation and calcium carbonate equivalent contents were also high, and the horizons showed dark colors due to high organic matter content, which contained humin as the dominant fraction. Mineralogical analysis of the clay fraction indicated predominance of hydroxy-interlayered vermiculite, followed by illite, kaolinite, and quartz, whereas the sand fraction exhibited reflections characteristic of the quartz mineral. Given P4 contents of calcium carbonate equivalent above 50 g kg-1 and the relevance of this feature for agriculture, we propose the inclusion of hypocarbonate as a criterion for classification of Luvissolos Haplicos Orticos at the subgroup level.

The impact of introduced and indigenous woody plants on change of selected soil chemical properties in the arboretum Mlyňany

DOI: 10.15414/afz.2015.18.02.44–48 Received 17. December 2014 ǀ Accepted 08. November 2014ǀ Available online 29. June 2015 In this work has been studied the impact of changed vegetation on selected soil chemical characteristics of Stagni-Haplic Luvisol in the Arboretum Mlyňany. Soil samples from A horizons were collected under growths of anthropogenically introduced (cherry laurel and Jeffrey pine) and indigenous (Norway spruce, common yew and oak-hornbeam) tree species. Since the original vegetation in Arboretum was oak-hornbeam forest, the soil under rest of that forest was used as control. Obtained results suggest that anthropogenic change of vegetation highly significantly affected the soil chemizm in A horizons under both, indigenous and introduced tree species. Cherry laurels and Jeffrey pines (their litter, root exudates) had the most significant effect on changes of studied soil chemical properties compared to the soil under original oak-hornbeam forest. The most affected were values of sum of base cations, base saturation, content of available phosphorus and exchangeable aluminum.

Effects of rumen digesta on the physico-chemical properties of soil in Nsukka, South eastern Nigeria

In tropical and subtropical areas, the importance of organic manure in improving soil physico-chemical properties and crop production for food security cannot be overemphasized. A study was conducted during 2012/2013 crop years, to investigate the effects of rumen digesta on the physical and chemical properties of soil in Nsukka, Enugu State, Nigeria. Soil samples were collected from Opi, Nsukka and treated to four rates of rumen digesta (viz. 0, 50, 100, and 150 gkg -1 soils). Physical and chemical properties of the soil were determined pre and post-experiment. The results obtained revealed that rumen digesta significantly (p = 0.05) increased the mean weight diameter (0.49 to 1.75 mm), aggregate stability (54.7% to 75.3%), soil pH (3.8 to 7.8), total nitrogen (0.01% to 0.02%), exchangeable sodium and potassium (0.22 to 4.39 cmolkg -1 for Na + and 0.30 to 4.31 cmolkg -1 for K + ), CEC (7.2 to 14.9 cmolkg -1 ) and organic matter content (0.97% to 4.29%). It had no significant effect on the texture, micro-aggregate (measured as dispersion ratio), exchangeable calcium and magnesium content of the soils. The study found significant reduction in the exchangeable aluminum (1.5 to 0.0 cmolkg -1 ) and hydrogen (3.7 to 2.2 cmolkg -1 ) contents of the soils. Farmers can therefore improve the physical and chemical properties of soils by using rumen digesta as an alternative liming material. Keywords : Rumen digesta, soil properties, fertilizer use, Nsukka-Nigeria