Effect of Saline Water on Soil Acidity, Alkalinity and Nutrients Leaching in Sandy Loamy Soil in Rwamagana Bella Flower Farm, Rwanda

The necessity to saline and sodic waters is sometimes used for irrigating agricultural activities under certain circumstances, but it is important to note that the use of these waters comes with specific considerations and limitations. One way to decrease undesirable effects of sodic waters on the physical and chemical properties of soils is to apply organic and chemical amendments within the soil. This study aimed to assess the effectiveness of saline water on soil acidity, alkalinity and nutrients leaching in sandy loamy soil at Bella flower farm, in Rwamagana District, Rwanda. The water used was from the Muhazi Lake which is classified as Class I (Saline water quality). Column leaching experiments using treated soils were then conducted under saturated conditions. The soil under experimental was first analyzed for its textural classification, soil properties and is classified as sandy loamy soil. The t-test was taken at 1%, 5% and 10% levels of statistical significance compared to control soil. The results indicated that the application of saline water to soils caused an increase in some soil nutrients like increase of Phosphorus (P), Potassium (K+), Magnesium (Mg2+), Sulphur (S), CN ratio and Sodium (Na+) and decreased soil texture, physical and chemical properties and remained soil nutrients. Consequently, the intensive addition of saline water leachates to soil in PVC pipes led to decreased of soil EC through leaching and a raiser Soluble Sodium Percentage (SSP). The rate of saline water application affected the increase accumulation of SAR and Na% in the top soil layers. The study indicated that saline water is an inefficient amendment for sandy soil with saline water irrigation. The study recommends further studies with similar topic with saline water irrigation, as it accentuated the alkalinity levels.

Alleviation of Soil Acidity and Aluminium Phytotoxicityin Acid Soils by Using Alkaline-Stabilized Biosolids

A pot experiment was catried out to study alleviation of soil acidity and Al toxicity by applying analkaline-stabilised sewage sludge product (biosolids) to an acid clay sandy loam (pH 5.7) and a strongly acidsandy loam (pH 4.5). Barley (Hondeum vulgare L. cv. Forrester) was used as a test crop and was grownin the sewage sludge-amended (33.5 t sludge DM ha-1) and unamended soils. The results showed that thealka1ine biosloids increased soil pH from 5.7 to 6.9 for the clay sandy loam and from 4.5 to 6.0 for the sandyloam. The sludge product decreased KCl-extractable Al from 0.1 to 0.0 cmol kg-1 for the former soil andfrom 4.0 to 0.1 cmol kg-1 for the latter soil. As a result, barley plants grew much better and grain yieldincreased greatly in the amended treatments compared with the unamended controls. These observationsindicate that alkaline-stabilised biosolids can be used as a liming material for remedying Al phytotoxicity instrongly acid soils by increasing soil pH and lowering Al bioavailability.

Soil Acidity： Is It a Problem in Large Scale Commercial Farms in Zimbabwe？

A study was conducted to identify the causes of low crop yield on a large scale commercial farm in Zimbabwe. Soil and water samples were collected from fields （0-60 cm） and the dam used for irrigation, respectively. Soil samples were analysed for soil fertility characteristics while the water was analysed for irrigation quality. The soils on the farm were heavy, ranging from sand loams to sand clays and fertile （〉 40 mg kgl N and 〉 20 mg kg1 available P） indicating high fertilizer utilization. It was also noted that 50% of the fields on the farm had soil pH below 5.0 despite having high basic cation （Ca = 10-18 meq% and Mg = 4-7 meq%）. A similar trend was observed down the soil profile （30-60 cm）. The soil also had extremely high concentration of iron （〉 200 ppm）, manganese （〉 400 ppm） and sulphate （〉 4000 ppm）. These findings suggest that the extreme acidity under these soils is the outcome of the exposure of pyrite to moisture and air by tillage of the land. The water used for irrigation was established to be medium saline and alkaline （pH 〉 7.6）. This pyrite induced acidity could not be neutralised by the water from the dam and the high exchangeable bases in the soil. Such problems can possibly be managed by growing tolerant crops. Soil testing on commercial farms is vital for identifying such problems in commercial farms in Zimbabwe.

Surface Amendments Can Ameliorate Subsoil Acidity in Tea Garden Soils of High-Rainfall Environments

Strongly acidic soils （pH 〈 5.0） are detrimental to tea （Camellia sinensis） production and quality. Little information exists on the ability of surface amendments to ameliorate subsoil acidity in the tea garden soils. A 120-d glasshouse column leaching experiment was conducted using commonly available soil ameliorants. Alkaline slag （AS） and organic residues, pig manure （PM） and rapeseed cake （RC） differing in ash alkalinity and C/N ratio were incorporated alone and in combination into the surface （0-15 cm） of soil columns （10 cm internal diameter x 50 cm long） packed with soil from the acidic soil layer （15-30 cm） of an Ultisol （initial pH -- 4.4）. During the 120-d experiment, the soil columns were watered （about 127 mm over 9 applications） according to the long-term mean annual rainfall （1 143 mm） and the leachates were collected and analyzed. At the end of the experiment, soil columns were partitioned into various depths and the chemical properties of soil were measured. The PM with a higher C/N ratio increased subsoil pH, whereas the RC with a lower C/N ratio decreased subsoil pH. However, combined amendments had a greater ability to reduce subsoil acidity than either of the amendments alone. The increases in pH of the subsoil were mainly ascribed to decreased base cation concentrations and the decomposition of organic anions present in dissolved organic carbon （DOC） and immobilization of nitrate that had been leached down from the amended layer. A significant （P 〈 0.05） correlation between alkalinity production （reduced exchangeable acidity - N-cycle alkalinity） and alkalinity balance （net alkalinity production - N-cycle alkalinity） was observed at the end of the experiment. Additionally, combined amendments significantly increased （P ~ 0.05） subsoil cation concentrations and decreased subsoil A1 saturation （P 〈 0.05）. Combined applications of AS with organic amendments to surface soils are effective in reducing subsoil acidity in high-rainfall areas. Further investigations under field conditions and over longer timeframes are needed to fully understand their practical effectiveness in ameliorating acidity of deeper soil layers under naturally occurring leaching regimes.

Acidity Regimes of Soils Under Different Vegetations in the Changbai Mountains Region

The acidity regimes of representative soils on the north slope of the Changbai Mountains were examined through determinations of PH and pCa of the soil paste as well as in-site determinations. For soils under broad-leaf forest or broad-leaf-Korean pine forest, the pH decreased from the litter to lower layers gradually until it did not change or decreased further slightly. For soils under coniferous forest or Ermans birch forest,there was a minimum in pH at a depth of 3～6 cm where the content of humus was high. The pCa increased gradually from the soil surface downward to a constant value. The lime potential (pH-0.5pCa) showed a similar trend as the PH in its distribution. For a given soil, the measured pH value of the thick paste, ranging from 4.5 to 5.5, was lower by about 0.5 units than the value determined by the conventional method with a water to soil ratio of 5:1. The PH determined in site was even lower. It was found that there was a fairly close relationship between soil acidity and the type of vegetation. The pH showed a trend of decreasing from soils under broad-leaf forest through broad-leaf-conifer mixed forest and coniferous forest to Ermans birch forest, and the pCa showed an opposite trend in variation.

Succession of Soil Acidity Quality and its Influence on Soil Phosphorus Types

Succession rules of soil acidity quality of larch plantations in first rotation at different development stages, succession rules of soil acidity quality of young stand of larch plantations in second rotation and the relationship between soil acidity and various forms of organic phosphorus and inorganic phosphorus were studied in mountainous area of eastern part of Northeastern China. The results showed that active acidity (pH value) inrhizosphere soil decreased continually with stand age increasing from young stand, half-mature stand, near mature stand to mature stand, but active acidity (pH value) in non-rhizosphere soil, exchange acidity, exchangeable aluminium, total hydrolytic acidity, and the ratio of exchange acidity and total hydrolytic acidity in rhizosphere soil and in non-rhizosphere soil increased apparently; total organic P, moderately resistant organic P, and highly resistant organic P in soil decreased at all age stages in larch plantations when soil acidity added. For rhizosphere soil of all stands of larch plantations at different development stages,there was positive correlation between Ca-P (except in young stand), Al-P(except in half-mature stand), Fe-P (except in near mature stand and mature stand), O-P (except in young stand), and soil active acidity,respectively; For rhizosphere soil, there was negative correlation between Ca-P (except in half-mature stand), Al-P(except in young stand), O-P, and exchange acidity, exchangeable aluminium, there was also negative correlation between Ca-P, Al-P(except in young stand and half-mature stand), Fe-P, O-P, and total hydrolytic acidity respectively. For rhizosphere soil, the correlation coefficient between Ca-P, O-P and total hydrolytic aciditydecreased, respectively, as stand ages up and that between Fe-P and exchange acidity,exchangeable aluminium increased, respectively, as stand ages grew. For non-rhizosphere soil, there was not significant correlation between soil acidity and various forms of inorganic phosphorus and organic phosphorus,respectively.

Influence of Soil pH, Organic Matter, and Clay Content on Environmentally Available Lead in Soils: A Case Study in Muncie, Indiana, USA

Due to historical and ongoing industrial practices, lead contamination in urban soils presents substantial health risks, primarily due to its capacity to readily migrate from the soil to humans. This research focused on the influence of soil pH, organic matter, and clay content on extractable lead amounts. Sixty-four soil samples from Muncie, Indiana, were analyzed, revealing that the examined factors accounted for 21.71% of the Pb mg/Kg-dry variable variance (p −0.4, p < 0.001), with XRD and FTIR analyses confirming the binding affinity of clay minerals with lead. In contrast, no significant relationships were found between Pb concentrations and soil pH (r = 0.07;p = 0.59) or organic matter content (r = 0.12;p = 0.34). Elucidating the interactions between lead, clay minerals, and other soil constituents is crucial for addressing lead-contaminated soils and reducing environmental and health impacts.

Characteristics of Soluble and Exchangeable Acidity inan Extremely Acidified Acid Sulfate Soil

An extremely acidified acid sulfate soil (ASS) was investigated to characterize its soluble and exchangeableacidity. The results showed that soluble acidity of a sample determined by titration with a KOH solutionwas much significantly greater than that indicated by pH measured using a PH meter, particularly for theextremely acidic soil samples. This is because the total soluble acidity of the extremely acidic soil sampleswas mainly composed of various soluble Al and Fe species, possibly in forms of Al sulfate complexes (e.g.,AISO4) and ferrous Fe (Fe2+). It is therefore suggested not to use pH alone as an indicator of soluble acidityin ASS, particularly for extremely acidic ASS. It is also likely that AISO4+ actively pericipated in cationexchange reactions. It appears that the possible involvement of this Al sulfate canon in the canon adsorptionhas significant effect on increasing the amount of acidity being adsorbed by the soils.

Differential Expression of Iron Deficiency Responsive Rice Genes under Low Phosphorus and Iron Toxicity Conditions and Association of OsIRO3 with Yield in Acidic Soils

With the hypothesis that iron(Fe) deficiency responsive genes may play a role in Fe toxicity conditions,we studied five such genes OsNAS1,OsNAS3,OsIRO2,OsIRO3 and OsYSL16 across six contrasting rice genotypes for expression under high Fe and low phosphorus(P) conditions,and sequence polymorphism.Genotypes Sahbhagi Dhan,Chakhao Poirieton and Shasharang were high yielders with no bronzing symptom visible under Fe toxic field conditions,and BAM350 and BAM811 were low yielders but did not show bronzing symptoms.Hydroponic screening revealed that the number of crown roots and root length can be traits for consideration for identifying Fe toxicity tolerance in rice genotypes.Fe contents in rice roots and shoots of a high-yielding genotype KMR3 showing leaf bronzing were significantly high.In response to 24 h high Fe stress,the expression levels of OsNAS3 were up-regulated in all genotypes except KMR3.In response to 48 h high Fe stress,the expression levels of OsNAS1 were3-fold higher in tolerant Shasharang,whereas in KMR3,it was significantly down-regulated.Even in response to 7 d excess Fe stress,the transcript abundances of OsIRO2 and OsNAS3 were contrasting in genotypes Shasharang and KMR3.This suggested that the reported Fe deficiency genes had a role in Fe toxicity and that in genotype KMR3 under excess Fe stress,there was disruption of metal homeostasis.Under the 48 h low P conditions,OsIRO2 and OsYSL16 were significantly up-regulated in Fe tolerant genotype Shasharang and in low P tolerant genotype Chakhao Poirieton,respectively.In silico sequence analysis across 3 024 rice genotypes revealed polymorphism for 4 genes.Sequencing across OsIRO3and OsNAS3 revealed nucleotide polymorphism between tolerant and susceptible genotypes for Fe toxicity.Non-synonymous single nucleotide polymorphisms and insertion/deletions(InDels) differing in tolerant and susceptible genotypes were identified.A marker targeting 25-bp InDel in OsIRO3,when run on a diverse panel of 43 rice genotypes and a biparental population,was associated with superior performance for yield under acidic lowland field conditions.This study highlights the potential of one of the vital genes involved in Fe homeostasis as a genic target for improving rice yield in acidic soils.

Characterization of Acidity in Acid Sulphate Soils of Kerala

The acidity characteristics of acid sulphate soils of Kuttanad, Kerala, were studied in detail by collecting surface, profile and subsurface soil samples from 20 locations of six soil series viz., Ambalapuzha, Purakkad, Thotapally, Thuravur, Kallara and - Thakazhi that belonged to acid sulphate soils. The soils were extremely acidic showing a range of pH （H：O） varying from 2.5 to 5.2. Lowest pH was recorded by Thakazhi series and the highest by Thotapally. The potential acidity of soils ranged from 14.71 cmol.kg-1 to 110.5 cmol-kg1 with Thakazhi series showing the highest value. The contribution of hydrolytic acidity to potential acidity ranged from 70.2% to 97.2%. In all soil series, exchangeable A13＋ was greater than exchangeable H~. A significant correlation was observed among pH （KCI）, pH （H20） and pH （CaCI2） in all series.

Reduction of N2O emissions by DMPP depends on the interactions of nitrogen sources(digestate vs. urea) with soil properties

The inhibition of nitrification by mixing nitrification inhibitors(NI)with fertilizers is emerging as an effective method to reduce fertilizer-induced nitrous oxide(N_(2)O)emissions.The additive 3,4-dimethylpyrazole phosphate(DMPP)apparently inhibits ammonia oxidizing bacteria(AOB)more than ammonia oxidizing archaea(AOA),which dominate the nitrification in alkaline and acid soil,respectively.However,the efficacy of DMPP in terms of nitrogen sources interacting with soil properties remains unclear.We therefore conducted a microcosm experiment using three typical Chinese agricultural soils with contrasting pH values(fluvo-aquic soil,black soil and red soil),which were fertilized with either digestate or urea in conjunction with a range of DMPP concentrations.In the alkaline fluvo-aquic soil,fertilization with either urea or digestate induced a peak in N_(2)O emission(60μg N kg^(-1)d^(-1))coinciding with the rapid nitrification within 3 d following fertilization.DMPP almost eliminated this peak in N_(2)O emission,reducing it by nearly 90%,despite the fact that the nitrification rate was only reduced by 50%.In the acid black soil,only the digestate induced an N_(2)O emission that increased gradually,reaching its maximum(20μg N kg^(-1)d^(-1))after 5–7 d.The nitrification rate and N_(2)O emission were both marginally reduced by DMPP in the black soil,and the N_(2)O yield(N_(2)O-N per NO2–+NO3–-N produced)was exceptionally high at 3.5%,suggesting that the digestate induced heterotrophic denitrification.In the acid red soil,the N_(2)O emission spiked in the digestate and urea treatments at 50 and 10μg N kg^(-1)d^(-1),respectively,and DMPP reduced the rates substantially by nearly 70%.Compared with 0.5%DMPP,the higher concentrations of DMPP(1.0 to 1.5%)did not exert a significantly(P<0.05)better inhibition effect on the N_(2)O emissions in these soils(either with digestate or urea).This study highlights the importance of matching the nitrogen sources,soil properties and NIs to achieve a high efficiency of N_(2)O emission reduction.

Genetic improvement of legume roots for adaption to acid soils

Acid soils occupy approximately 50% of potentially arable lands.Improving crop productivity in acid soils,therefore,will be crucial for ensuring food security and agricultural sustainability.High soil acidity often coexists with phosphorus(P) deficiency and aluminum(Al) toxicity,a combination that severely impedes crop growth and yield across wide areas.As roots explore soil for the nutrients and water required for plant growth and development,they also sense and respond to below-ground stresses.Within the terrestrial context of widespread P deficiency and Al toxicity pressures,plants,particularly roots,have evolved a variety of mechanisms for adapting to these stresses.As legumes,soybean(Glycine max) plants may acquire nitrogen(N) through symbiotic nitrogen fixation(SNF),an adaptation that can be useful for mitigating excessive N fertilizer use,either directly as leguminous crop participants in rotation and intercropping systems,or secondarily as green manure cover crops.In this review,we investigate legumes,especially soybean,for recent advances in our understanding of root-based mechanisms linked with root architecture modification,exudation and symbiosis,together with associated genetic and molecular strategies in adaptation to individual and/or interacting P and Al conditions in acid soils.We propose that breeding legume cultivars with superior nutrient efficiency and/or Al tolerance traits through genetic selection might become a potentially powerful strategy for producing crop varieties capable of maintaining or improving yields in more stressful soil conditions subjected to increasingly challenging environmental conditions.

Effects of Microbial Fertilizers in Improving Acidic Tobacco-planting Soil and Tobacco Leaf Quality

[Objectives]This study was conducted to improve acidic soil and enhance the quality of tobacco leaves.[Methods]The effects of different microbial fertilizers on improving acidic tobacco-planting soil and tobacco leaf quality were investigated through plot experiments.[Results]The application of microbial fertilizers could improve the pH value of acidic soil,and composite microbial agent A showed the best application effect.The application of bio-organic fertilizer was beneficial to improving the contents of available phosphorus and available boron in acidic soil.The application of composite microbial agent A was beneficial to improving the contents of available phosphorus and available potassium in acidic soil,and could promote the growth of tobacco plants and improve the economic traits of flue-cured tobacco and the coordination of chemical components in tobacco leaves.The application of composite microbial agent B led to a downward trend in the content of available boron in acidic soil.The application of composite microbial agent B could promote the absorption of nutrients by tobacco plants,and improve their disease resistance and the quality of tobacco leaves.Due to the differences in functional microorganisms contained,the application effects of different microbial fertilizers in improving acidic tobacco-planting soil and improving tobacco leaf quality varied.Overall,the application of microbial fertilizers could increase soil pH,activate soil nutrients,promote tobacco growth,enhance disease resistance,increase tobacco output value,and improve tobacco quality.Microbial fertilizers have good application prospects in improving acidic soil and improving tobacco quality.[Conclusions]The application of microbial fertilizers to improve acidic tobacco-planting soil can ensure the normal growth and development of tobacco plants and the improvement of tobacco leaf quality,achieving high-quality and sustainable development of Zhaotong tobacco.

Calcium-Magnesium Ca/Mg Ratios and Their Agronomic Implications for the Optimization of Phosphate Fertilization in Rainfed Rice Farming on Acidic Ferralsol in the Forest Zone of Ivory Coast

This study is a contribution to improving rice productivity on acidic plateau soils of the tropical rainforest zone. It is based on taking into account the cationic balances of the soil in order to optimize the phosphorus (P) nutrition of rice on these acidic soils, where this nutrient constitutes a limiting factor for agricultural production. Three (3) pot trials were conducted in Adiopodoumé in the forested south of Côte d’Ivoire. The interactive effects of calcium carbonate (0, 25, 50 and 75 kg Ca ha−1) and magnesium sulfate (0, 25, 50 and 75 kg Mg ha−1) were evaluated on the response of NERICA 5 rice at doses 0, 25, 50 and 75 kg P ha−1 of natural phosphate from Togo, applied only once at the start of the experiment. Additional fertilizers of nitrogen (N) (100 kg N ha−1) and potassium (K) (50 kg KCl ha−1) were added to each of the tests in a split-plot device. The test results revealed a paddy production potential of approximately 3 to 5 t⋅ha−1 for NERICA 5 on an acidic soil, under the effect of the interaction of P, Ca and Mg. The quadratic response of rice yield to the doses of these fertilizers would be more dependent on their balance, itself influenced by Ca nutrition. For the sustainability and maintenance of rice production in agro-ecology studied, it was recommended doses of 38 kg Ca ha−1, 34 kg Mg ha−1 in a Ca/Mg ratio (1/1) with intakes of 41 kg P ha−1, overall in a ratio 1/1/1 (P/Ca/Mg) more favorable to the availability of free iron considered a guiding element of mineral nutrition. Thus, these promising results should be confirmed in a real environment for better management of the fertilization of rice cultivated on acidic plateau soils in Côte d’Ivoire.

Effects of Calcium and Magnesium on Phosphorus Availability in Ferralsols and Rice Production in Forest Zones of Côte d’Ivoire

Phosphorus bioavailability has long been a recurring problem in tropical acid soils. A pot experiment was carried out during three (3) successive rice production cycles at Adiopodoumé to evaluate the response of the NERICA 5 rice accession to various doses of calcium, magnesium and phosphorous. The experiment was conducted using a randomized split-plot design. The interactive effects of calcium carbonate (0, 25, 50 and 75 kg·Ca·ha-1) and magnesium sulfate (0, 25, 50 and 75 kg·Mg·ha-1) and Togo natural phosphate (0, 25, 50 and 75 kg·P·ha-1) were determined at each production cycle. The results showed that single-dose natural phosphate supplementation for three cropping cycles resulted in an average enrichment of around 2 mg·P·kg-1 after each trial following its continuous dissolution, with an increase in DSP (33.31% to 70.52%). The study revealed one strategy for managing and enhancing native P with cations and another for exogenous P: there would be a synergy of Ca/Mg on native P, whereas an antagonism would characterize the two parameters in phosphate fertilization.

Role of Low-Molecule-Weight Organic Acids and Their Salts in Regulating Soil pH

The process of organic materials increasing soil pH has not yet been fully understood. This study examined the role of cations and organic anions in regulating soil pH using organic compounds. Calcareous soil, acid soil, and paddy soil were incubated with different simple organic compounds, pH was determined periodically and CO2 emission was also measured. Mixing organic acids with the soil caused an instant decrease of soil pH. The magnitude of pH decrease depended on the initial soil acidity and dissociation degree of the acids. Decomposition of organic acids could only recover the soil pH to about its original level. Mixing organic salts with soil caused an instant increase of soil pH. Decomposition of organic salts of sodium resulted in a steady increase of soil pH, with final soil pH being about 2.7-3.2 pH units over the control. Organic salts with the same anions （citrate） but different cations led to different magnitudes of pH increase, while those having the same cations but different anions led to very similar pH increases. Organic salts of sodium and sodium carbonate caused very similar pH increases of soil when they were added to the acid soil at equimolar concentrations of Na^＋. The results suggested that cations played a central role in regulating soil pH. Decarboxylation might only consume a limited number of protons. Conversion of organic salts into inorganic salts （carbonate） was possibly responsible for pH increase during their decomposition, suggesting that only those plant residues containing high excess base cations could actually increase soil pH.

Soil pH Management across Spatially Variable Soils

Knowledge and management of soil pH, particularly soil acidity across spatially variable soils is important, although this is greatly ignored by farmers. The objective of the study was to evaluate in-field spatial variability of soil pH, and compare the efficiency of managing soil pH through site-specific method vs. uniform lime application. The study was conducted on three sites with study sites I and II （23°50＇ S; 29°40＇ E）, and study sites IIl （23°59＇ S; 28°52＇ E） adjacent to each other in the semi-arid regions of the Limpopo Province, South Africa. Soil samples were taken in four replicates from geo-referenced locations on a regular grid of 30 m. Soils were analyzed for pH, and SMP buffer pH. Soil maps were produced with Geographic Information System （GIS） software, and soil pH datasets were interpolated using a geostatistical tool of inverse distance weighing （IDW）. Soil pH in the fields varied from 3.93 to 7.00. An excess amount of lime as high as 30 t/ha under uniform lime application were recorded. These recommendations were in excess on field areas that needed little or no lime applications. Again, there was an under applications of lime as much as 35 t/ha for uniform liming applications. This under- and over-recommendations of lime based on average soil pH values suggests that uniform soil acidity correction and soil pH management strategy is not an appropriate strategy to be adopted in these fields with spatially variable soils. The field can be divided into lime application zones of （1） high rates of lime, （2） low rates of lime and （3） areas that requires no lime at all so that lime rates are applied per zone. A key to site-specific soil acidity correction with lime is to reach ideal soil pH for the crop in all parts of the field.

Geogenic Pollution of Groundwater Quality in Gampaha District, Sri Lanka: A Case Study of Groundwater Acidification from Rathupaswala

Over recent decades, Gampaha district, Sri Lanka, has experienced significant urbanisation and industrial growth, increasing groundwater demand due to limited and polluted surface water resources. In 2013, a community uprising in Rathupaswala, a village in Gampaha district, accused a latex glove manufacturing factory of causing groundwater acidity (pH < 4). This study evaluates the spatial and temporal changes in geochemical parameters across three transects in the southern part of Gampaha district to 1) assess the impact of geological formations on groundwater;2) compare temporal variations in groundwater;and 3) explain acidification via a geochemical model. Seventy-two sample locations were tested for pH, electrical conductivity (EC), and anion concentrations (sulphate, nitrate, chloride and fluoride). Depth to the water table and distance from the sea were measured to study variations across sandy, peaty, lateritic, and crystalline aquifers. Results showed pH readings around 7 for sandy and crystalline aquifers, below 7 for peaty aquifers, and below 5 for lateritic aquifers, with significant water table fluctuations near Rathupaswala area. Principal component analysis revealed three principal components (PCs) explaining 86.0% of the variance. PC1 (40.6%) correlated with pH, EC, and sulphate (saltwater intrusion), while PC2 (32.0%) correlated with nitrates and depth to the water table (anthropogenic nutrient pollution). A geochemical transport model indicated a cone of depression recharged by acidic groundwater from peat-soil aquifers, leading to acidic groundwater in Rathupaswala area. Previous attributions of acidic pH to the over-exploitation of groundwater by the latex factory have been reevaluated;the results suggest natural acidification from prolonged water-rock interactions with iron-rich lateritic aquifers. Groundwater pH is influenced by local climate, geology, topography, and drainage systems. It is recommended that similar water-rock interaction conditions may be present throughout the wet zone of Sri Lanka, warranting detailed studies to confirm this hypothesis.

Evaluation of Soil pHs in 30 Districts of AI-Madinah AI-Munawarah Province, KSA

The pH values of soils collected from 30 different districts of Al-Madinah Al-Munawarah province were measured using an Electric pH meter. The pH values revealed （27%） a slight to （60%） medium alkalinity ranged between： 7.17-9.45 （pH 8.13 ± 0.13） The alkalinity is attributed to scanty rainfall and deep underground waters as well as deposition of high air pollution contents at Al-Madinah Al-Munawarah. Such soil alkalinity is not optimum to growth of arable/lea-grassland but only for limited cultivation i.e. date palms in comparison with Northwestern and Southwestern sectors of KSA. It is recommended to carry out similar soil evaluation of other parts of KSA involving more measurements i.e. ionic concentration, nutrient levels, micro-flora and to laundry these lands to lower soil＇spHs and to increase its fertility.

Aluminum Soil Chemistry: Influence on Soil Health and Forest Ecosystem Productivity

Soil aluminum phytotoxicity has been a major research area since the inception of modern soil science. Acid soils, which typically manifest plant aluminum toxicity, are frequently dedicated to food production, thus yield and quality reductions influence food security. This manuscript reviews our modern understanding of 1) soil aluminum hydrolysis and polymerization, 2) aluminum complexation with inorganic and organic anions, 3) aluminum interference with vital plant physiological processes, 4) aluminum and forest ecosystem productivity, and 5) demonstrates the software simulation of aluminum reactivity and its role in predicting soil behavior. The manuscript also provides a perspective for future soil-aluminum research critical to maintaining food security and food quality.