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Background: Soil pH is determined using a variety of methods. The key differences among them are the electrolytes and soil-tosuspension ratios. However, an optimal procedure tailored to a particular soil is required. This study, therefore, aimed to evaluate the effects of electrolytes and soil-to-suspension ratios on soil pH and to optimise pH measurement methods for acidic-coarsely textured soil. Methods: Varied standard electrolytes (water, 0.01 M CaCl2 and 1 M KCl) and soil-to-suspension ratios (1:1, 1:2.5 and 1:5 w/v) were used to measure the pH of thirty samples of acidic-coarsest textured soil. Result: Soil pH values were observed in the following order: water > 0.01 M CaCl2 > 1 M KCI. Higher soil pHs were a result of higher suspension volumes. The most optimal pH measurement method for an acidic-coarsely textured soil was obtained from the 1:2.5 soil-to-suspension ratio of 1 M KCl, which held the highest R2 (0.850), as well as the lowest root mean square error (RMSE) (0.010), indicating the most precise method. An alternative method suitable for a cost-saving laboratory was the 1:1 soilto-suspension ratio of 0.01 M CaCl2, which owned R2 of 0.766 and RMSE of 0.013, as its pH measurement was similar to those under the most optimal method. [ABSTRACT FROM AUTHOR]

This study compares soil acidity and skeletal preservation at the eighteenthcentury Fortress of Louisbourg. Soil acidity was tested in 60 individual burials using a Lusterleaf 1612 Rapitest soil pH kit. These results were then compared to skeletal preservation, coffin use, and burial depth. pH levels ranged between 4.5 (acid) to 7.5 (alkaline). There was a clear correlation between increased skeletal preservation and more neutral pH, as expected. Additionally, mortuary treatment and burial depth were also correlated with soil pH, where individuals interred in a coffin or at deeper depths saw increased soil acidity. The location of these interments in relation to homestead features and defunct lime kilns also likely influenced this pH variability. This study highlights the need to consider previous site use and mortuary practices when assessing differential skeletal preservation in complex cemetery assemblages. [ABSTRACT FROM AUTHOR]

In this work the limestone doses are estimated to correct the soil of an area of the Chianga- Huambo experimental station and aimed at obtaining ideal doses of limestone to raise the pH to a value that makes the nutrients more available to the plants, to standardize other methods of correction. Soil samples were collected from the surface to a depth of 20 cm from the experimental station. With the application of increasing doses of limestone to soil, the pH reached values of 5,79 and 5,44 in H2O and CaCl2, respectively. The experimental design was entirely random, and three evaluation periods, 30, 60 and 90 days after application in the soil. The Al 3+ ion reduced to the value of 0,2 cmol / l, whereas, the effective cation exchange capacity, sum of bases increased due to the presence of the exchange cations in the limestone. [ABSTRACT FROM AUTHOR]

Soil pH is important for controlling many soil properties. The variation in soil pH can be associated with changes in climate, soil buffering system, nitrogen deposition, and plants. However, there still lacks a comprehensive study exploring the effects of all these factors on soil pH simultaneously. Here we aimed to investigate the environmental controls on the spatial variation of soil pH in planted forests across Northern China and reveal its response to different-forms of nitrogen deposition for different species of tree plantations. We sampled 1980 soil profiles from 660 planted forest plots (3 profiles in each plot) in Northern China. We used correlation analyses and structure equation models (SEM) to explore the impacts of multiple environmental factors on soil pH. Climate (water balance, temperature) and soil inorganic carbon accounted for most variations of soil pH. Specifically, the concentration of hydrogen ions ([H+]) varied almost isometrically with soil inorganic carbon, which was also the major buffering system in this region. Nitrogen deposition affected both soil pH values and soil buffering system. Results from structure equation model indicated that nitrate nitrogen directly decreased soil pH, while ammonium nitrogen mostly affected soil pH indirectly through its impacts on soil inorganic carbon. The responses of soil pH to nitrogen deposition were species-specific, and conifer stands tended to have higher soil acidification rate than stands of other tree species. Our study provides important information for understanding mechanisms controlling the spatial pattern of soil pH in planted forests and highlights the need to develop informed policies for soil resource management under increasing threats from anthropogenic nitrogen deposition. • Climate and soil inorganic carbon dominated soil pH variations in planted forests. • Nitrogen deposition indirectly affected soil pH via impacting soil inorganic carbon. • The responses of soil pH to nitrogen deposition were species-specific. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Manure application increased soil organic matter and thus pH buffering capacity. • Manure application increased the resistance of soils to acidification. • Carboxyl protonation was main mechanism for increase in pH buffering capacity. • Carboxyl protonation led to the decrease of soil effective cation exchange capacity. Abstract Soil pH buffering capacity (pHBC) plays a crucial role in determining soil acidification rates and the amount of lime required to ameliorate soil acidity. However, it remains poorly understood how soil organic matter affects soil pHBC. Here, Alfisol and Ultisol samples from long-term fertilization experiments (control, chemical N, P, and K (NPK), manure only (M), 1/2 NPK plus 1/2 M (1/2NPKM), and NPK plus M (NPKM)) were used to investigate the effects and underlying mechanisms of manure application on the pHBC and soil resistance to acidification through simulated acidification experiments. The results indicated that the application of manure increased pHBC and the resistance of soils to acidification in both the Alfisol and Ultisol. The pHBC of the Alfisol in the M and NPKM treatments was increased by 81 and 60% compared with the control, respectively. Similarly, the pHBC of the Ultisol in the NPKM treatment was 66% higher than that of the control. The extent of protons consumption by the Alfisol followed the order: M > NPKM > 1/2NPKM > NPK ≈ control during stimulated acidification, which was consistent with their pHBC. These results suggested that manure application increased the resistance of the Alfisol to acidification by increasing soil pHBC. The protonation of organic anions from the dissociation of weakly acidic functional groups on soil organic matter to form neutral molecules was the main mechanism responsible for the increase in pHBC and soil resistance to acidification induced by manure application. During this process, some exchangebale base cations were released from negatively charged sites on organic matter into soil solution. This mechanism was confirmed by the experimental observations: the release of base cations from soils increased, while soil exchangeable base cations and effective CEC decreased as soil pH decreased. The results are of fundamental significance for understanding the role of organic matter in retarding soil acidification through long-term manure application. [ABSTRACT FROM AUTHOR]

Decomposing vertebrate cadavers release large, localized inputs of nutrients. These temporally limited resource patches affect nutrient cycling and soil organisms. The impact of decomposing cadavers on soil chemistry is relevant to soil biology, as a natural disturbance, and forensic science, to estimate the postmortem interval. However, cadaver impacts on soils are rarely studied, making it difficult to identify common patterns. We investigated the effects of decomposing pig cadavers (Sus scrofa domesticus) on soil chemistry (pH, ammonium, nitrate, nitrogen, phosphorous, potassium and carbon) over a one-year period in a spruce-dominant forest. Four treatments were applied, each with five replicates: two treatments including pig cadavers (placed on the ground and hung one metre above ground) and two controls (bare soil and bags filled with soil placed on the ground i.e. "fake pig" treatment). In the first two months (15-59 days after the start of the experiment), cadavers caused significant increases of ammonium, nitrogen, phosphorous and potassium (p<0.05) whereas nitrate significantly increased towards the end of the study (263-367 days; p<0.05). Soil pH increased significantly at first and then decreased significantly at the end of the experiment. After one year, some markers returned to basal levels (i.e. not significantly different from control plots), whereas others were still significantly different. Based on these response patterns and in comparison with previous studies, we define three categories of chemical markers that may have the potential to date the time since death: early peak markers (EPM), late peak markers (LPM) and late decrease markers (LDM). The marker categories will enhance our understanding of soil processes and can be highly useful when changes in soil chemistry are related to changes in the composition of soil organism communities. For actual casework further studies and more data are necessary to refine the marker categories along a more precise timeline and to develop a method that can be used in court. [ABSTRACT FROM AUTHOR]

Phosphorus (P) deficiency is one of the main problems limiting crop growth in red soils of southern China. The primary objective of this study was to examine P availability as a function of soil acidity. Soils were sampled from a long-term fertilization experiment and are referred as low-P (No P fertilization) and high-P (120 kg P2O5 ha-1). Both low-P and high-P treatments were incubated adjusting soil pH to seven levels from 3.0 to 6.5 for 10, 20, 30 and 45 days. The pH, DIP, and Olsen-P were determined after each incubation period, and inorganic P fractions were measured at the end of incubation. For both low-P and high-P treatments, DIP decreased with rising pH value and increased with decreasing soil pH. Olsen-P, Ca-P (Ca2-P, Ca8-P, and Ca10-P) and Al-P increased significantly with soil pH in low-P treatment. In high-P, Olsen-P increased with pH between 3.4 and 5.0 and was stable at higher pH. Moreover, Ca-P and Al-P increased significantly but Fe-P decreased with soil pH increase. The redundancy analysis showed that Ca-P, Al-P, and pH had positive effects on Olsen-P, but Occluded-P showed a negative correlation with Olsen-P in both soils. Our results confirmed that soil P availability was influenced by pH and that the changes in DIP and Olsen-P were linked to changes of inorganic fractions from occluded to Ca- and Al-bound forms. Managing soil acidity is a key issue regarding the availability of P in red soils of China and our results suggest that at least a pH of 5.0 should be targeted. [ABSTRACT FROM AUTHOR]

The relationship between pyroxasulfone bioactivity and soil properties has not been investigated in a wide range of soils typical of western Canada. In this study, 47 soils from Saskatchewan, Manitoba and Alberta, with varying organic matter content (1.5%–22.1%), pH (5.0–7.9), and clay content (6.8%–59.4%) were used to evaluate the effect of soil properties on pyroxasulfone bioactivity and its relevance to field application rates. Bioactivity was assessed by measuring the reduction of sugar beet shoot length after 7 days in response to 0, 92, 184, and 368 µg ai kg−1pyroxasulfone concentration in soil. Multiple regression analysis showed that pyroxasulfone bioactivity was related to soil organic matter content, pH and clay content. Grouping the soils according to these properties allowed for a summarization of pyroxasulfone field application rates required to achieve bioactivity based on the magnitude of sugar beet shoot length inhibition (%). The estimated field application rates ranged from less than 120–480 g ai ha−1. [ABSTRACT FROM AUTHOR]

This paper reports the research on the physical-chemical response of silicate glasses subjected to the action of three natural soils types: acidic, neutral, and basic. The main goal of the study was to characterize the corrosion mechanisms acting upon glasses formulated with chemical compositions that are commonly found in historical glasses through an accelerated aging test that replicates natural burial. Resulting data showed a distinct and recognizable response of each glass type, with pH as the key variable for glass corrosion. Results can be of great significance to historical glass studies, especially in choosing suitable conservation strategies for archeological findings. [ABSTRACT FROM AUTHOR]

Elevated anthropogenic acid deposition can significantly affect forest ecosystem functioning by changing soil pH, nutrient balance, and chemical leaching and so on. These effects generally differ among different forests, and the dominant mechanisms for those observed responses often vary, depending on climate, soil conditions and vegetation types. Using soil monoliths (0–40 cm) from pine forest (pioneer), coniferous and broadleaved mixed forest (transitional) and broadleaved forest (mature) in southern China, we conducted a leaching experiment with acid treatments at different pH levels (control: pH ≈ 4.5; pH = 3.5; pH = 2.5). We found that pH 3.5 treatment significantly reduced dissolved organic carbon (DOC) concentrations in leachate from the pioneer forest soil. pH 2.5 treatment significantly increased concentrations of NO 3 − , SO 4 2 − , Ca 2 + , Mg 2 + , Al 3 + , Fe 3 + and DOC in leachate from the pioneer forest soil, and also concentrations of NO 3 − , SO 4 2 − , Mg 2 + , Al 3 + , Fe 3 + and DOC in leachate from the transitional forest soil. All acid treatments had no significant effects on concentrations of these chemicals in leachate from the mature forest soil. The responses can be explained by the changes in soil pH, acid neutralizing capacity (ANC) and concentrations of Al and Fe. Our results showed that acid buffering capacity of the pioneer or transitional forest soil was lower than that of the mature forest soil. Therefore preserving mature forests in southern China is important for reducing the adverse impacts of high acid deposition on stream water quality at present and into the future. [ABSTRACT FROM AUTHOR]

It is commonly believed that nitrification is the dominant process for N2O production under aerobic conditions. However, this has been challenged by recent studies on acidic soils, where denitrification has been found to dominate N2O production. Analyzing the data collected from peer-reviewed literature, we found that pH was a critical factor regulating N2O production pathways under aerobic conditions. There is a pH threshold of approx. 4.4, below which denitrification dominated N2O production and vice versa. A decrease in soil pH can significantly increase the contribution of denitrification to N2O production. Overall, this mini-review increases our understanding of N2O sources in soils under aerobic conditions. [ABSTRACT FROM AUTHOR]

Acidic deposition has resulted in the loss of available soil Ca from base-poor soils in the northeastern United States. In 1999, wollastonite (CaSiO3) was experimentally added to a watershed at the Hubbard Brook Experimental Forest in New Hampshire in an attempt to restore the base saturation of the soil to its estimated pre-acidification level. We measured the total Ca in the O horizon and the top 10 cm of mineral soil to track the fate of the added Ca. We also measured soil pH and exchangeable cations to assess the impact of the treatment on soil acidity. In the first 11 yr after treatment, Ca was transported downward through the forest floor and upper mineral soil in a progressive fashion. By Year 11, at least 650 kg ha-1 of the 1028 kg ha-1 of Ca that was added to the watershed was no longer in the O horizon or the top 10 cm of mineral soil. Soil pH and exchangeable Ca concentrations increased significantly in organic and mineral soils after treatment. Exchangeable H and Al concentrations decreased significantly. The pool of exchangeable Ca increased significantly after treatment, peaking in the O horizons 3 yr after treatment and in the upper mineral soil 7 yr after treatment. The pools of exchangeable Al and H steadily and significantly decreased through the study period. Only about 3% of the added Ca was exported from the watershed in stream water after 11 yr. Wollastonite treatment was thus an effective means of increasing available pools of Ca in this forest ecosystem. [ABSTRACT FROM AUTHOR]

The effectiveness of plantation wastes along with locally available organic materials in ameliorating acidic soil was studied by conducting an experiment with coconut husk, poultry manure, vermicompost, and compared with limestone. Application of organic amendments significantly increased the soil pH, and it was greatest in poultry manure–amended soils followed by vermicompost and coconut husk + poultry manure treatments. The relative liming efficiency was greatest for poultry manure through out the observation period of 180 days. The coconut husk alone showed the least liming effect and its liming efficiency had increased when applied in combination with poultry manure and or vermicompost. This increase in soil pH was mirrored by significant reductions in exchange acidity, exchangeable aluminum (Al3+), diethylenetriaminepentaacetic acid (DTPA)–extractable iron (Fe2+), and manganese (Mn2+) and increases in cation exchange capacity, exchangeable bases, especially calcium (Ca), and Olsen-extractable phosphorus (P) by addition of organic amendments and lime. This study indicated the potential of using coconut husk along with poultry manure for managing acidic soils in low-input agricultural systems, especially in tropical islands. [ABSTRACT FROM PUBLISHER]

One of the most important factors limiting plant growth is soil pH. The objective of this study is to determine the effectiveness of marble waste applications on neutralization of soil acidity. Marble quarry waste (MQW) and marble cutting waste (MCW) were applied to an acid soil at different rates and their effectiveness on neutralization was evaluated by a laboratory incubation test. The results showed that soil pH increased from 4.71 to 6.36 and 6.84 by applications of MCW and MQW, respectively. It was suggested that MQW and MCW could be used as soil amendments for the neutralization of acid soils and thus the negative impact of marble wastes on the environment could be reduced. [Copyright &y& Elsevier]

Concepts of soil chemistry were established, in the main, for agricultural soils with a fine texture and near-neutral pH. These concepts often need to be modified when considering acidic forest soils. For example, studies conducted in northeastern US forests challenged the idea of a universal positive relationship between base saturation ( Bsat), effective cation exchange capacity ( CECe) and pH. The objective of this study was to measure soil chemistry variables in Podzols of southwestern Canada and determine their interrelationships as well as the potential influence of surface-active iron ( Fe) and aluminium ( Al) species. We measured exchangeable cation concentration in each pedogenic horizon and investigated their relation to pH, soil organic carbon, silt and clay and pyrophosphate-extractable, oxalate-extractable and dithionite-extractable Al and Fe. We found that the chemistry of the forest floor was different from that of the mineral soil because of the limited extent of mixing between the two layers. In the forest floor, biological cycling maintained a large Bsat and large calcium saturation but a low pH. In the subsoil, pH had a positive correlation with Bsat but a negative correlation with CECe. The formation of organo-mineral complexes between soil organic matter and short-range order Al and Fe phases could explain the anomalous relationship between pH and CECe. This study provides new insight into mechanisms controlling forest soil chemical properties and should hence contribute to our ability to manage forests for long-term productivity. Résumé Les concepts de la chimie du sol ont été développés pour la plupart dans des sols agricoles de texture fine et pH proche de la neutralité. Ces concepts doivent souvent être modifiés lorsque les sols forestiers acides sont considérés. Par exemple, des études conduites dans les forêts du nord-est des Etats-Unis ont remis en question le caractère universel de la corrélation positive entre le taux de saturation (Bsat), la capacité d'échange cationique effective (CECe) et le pH. L'objectif de ce travail était de mesurer les paramètres courants de la chimie du sol dans des podzols du sud-ouest canadien afin d'établir leur interrelation ainsi que l'influence potentielle des espèces minérales réactives de fer (Fe) et d'aluminium (Al). A ces fins, nous avons mesuré la concentration de cations échangeables dans chaque horizon pédogénétique et avons étudié sa relation avec le pH, le carbone organique du sol, les limons et argiles, et le Fe et Al extraits par le pyrophosphate, l'oxalate et le citrate-bicarbonate-dithionite. Les résultats montrent que la composition chimique de l'horizon organique est très différente par rapport au sol minéral. Ceci s'explique par le faible taux de transfert entre les deux couches. Dans l'horizon organique, le phénomène de recyclage biologique maintient une forte Bsat et forte saturation en calcium, mais un pH faible. Dans les horizons du sous-sol, le pH est corrélé de manière positive avec la Bsat mais de manière négative avec la CECe. La formation de complexes organo-minéraux entre la matière organique du sol et les minéraux de Fe et Al mal cristallisés pourraient être á l'origine de la relation surprenante entre le pH et la CECe. Cette étude fournit de nouveaux éléments quand aux mécanismes régissant les propriétés chimiques des sols forestiers et devrait ainsi contribuer á améliorer notre capacité de gestion de la forêt pour une productivité durable. [ABSTRACT FROM AUTHOR]

Acid mine drainage ( AMD) barrens result from destruction of vegetation within AMD flow paths. When exposed to air, soluble iron in AMD undergoes oxidation and hydrolysis to form ferric iron (oxyhydr)oxides which accumulate on soil surfaces. A restoration experiment was conducted at a 50-year-old AMD barrens created by discharge from an abandoned underground coal mine. The objective was to determine whether vegetation could be established by altering rather than removing surface layers of acidic precipitates at a site representative of other mining-degraded areas. Three zones in the barrens were identified based on moisture content, pH (2.7-3.3), and thickness of precipitates (0-35 cm). Our hypothesis was that application of the same reclamation method to all zones would fail to sustain >70% vegetative cover in each zone after four growing seasons. The method consisted of applying 11 t/ha lime and 27 or 54 t/ha compost before rototilling (top 15 cm) and mulching with oat straw containing viable seeds for a nurse crop. Lime-only plots were included for comparison, and all amended plots were sown with a mine reclamation seed mix. Oats, sown species, and indigenous species dominated cover in the first, second, and fourth growing seasons, respectively. In the fourth year following reclamation, compost-amended plots had >70% cover and improved soil properties in all three zones, providing evidence to reject our hypothesis. Vegetative restoration of AMD barrens did not require removal of highly acidic precipitates, since they could be transformed at low-cost into a medium that supports indigenous plants. [ABSTRACT FROM AUTHOR]

Background and Aims: Crop residues are important for the redistribution of alkalinity within soils. A net increase in pH following residue addition to soil is typically reported. However, effects are inconsistent in the field due to confounding soil processes and agronomic practises. Methods: A column experiment investigated the effects of canola, chickpea and wheat residues, differing in alkalinity content and C:N ratio, on soil pH changes in a Podosol (Podzol; initial pH 4.5) and Tenosol (Cambisol; initial pH 6.2) under field conditions. Results: Residues (10 g dry matter kg soil; 0-10 cm) increased soil pH, and temporal changes in alkalinity depended on the residue and soil type. Alkalinity was generated via abiotic association reactions between H and added organic matter and via ammonification and decarboxylation processes during decomposition. Alkalinity from canola and chickpea residues moved down the soil profile (10-30 cm) and was attributed to nitrate immobilisation and organic anion decomposition by soil microbes. Conclusions: The application of residues to acid and moderately acid soils increased the pH of both topsoil and subsoils, which persisted over 26 months. Maximal increase of pH observed at 3 months was correlated with the concentration of excess cations in the residues. [ABSTRACT FROM AUTHOR]

Various crop residues were applied to a strongly acidic tea garden soil to investigate their performance in ameliorating soil acidity. A laboratory study found the performance of crop residues on soil acid amelioration was mainly determined by the combined effect of nitrogen (N) transformation, cation exchange, and ash alkalinity. Nitrogen transformation was varied for different crop residues added, but followed N regulation, resulting in an adverse liming effect. It was assumed that during the release of ash alkalinity, cations replaced soil exchangeable acidity in soil solution, which largely diminished the liming effect of ash alkalinity. That was why soil pH was highly correlated with N transformation process. Furthermore, soil pH was positively correlated with carbon (C)/N ratios of crop residues both in low-level treatment (R2= 0.955) and in high-level treatment (R2= 0.981). Therefore, crop residues with relative high C/N ratios were considered to be more suitable for long-term pH adjustment of tea garden soils. [ABSTRACT FROM AUTHOR]

Soil acidity and aluminum toxicity are considered the most damaging soil conditions affecting the growth of most crops. This paper reviews the results of tests of pH, exchangeable acidity and the mobile aluminum (Al) concentration in profiles of pseudogley soils from the Čačak--Kraljevo Basin. For these purposes, 102 soil pits were dug in 2009 in several sites around the Čačak--Kraljevo Basin. The tests encompassed 54 field, 28 meadow, and 20 forest soil samples. Samples of soil in a disturbed state were taken from the Ah and Eg horizons (102 samples), from the B1tg horizon in 39 field, 24 meadow and 15 forest pits (a total of 78 samples) and from the B2tg horizon in 14 field, 11 meadow, and 4 forest pits (a total of 29 samples). The mean pH values (1 M KCl) of the tested soil profiles were 4.28, 3.90 and 3.80 for the Ah, Eg and B1tg horizons, respectively. The soil pH of the forest samples was lower than those in the meadow and arable land samples (mean values of 4.06, 3.97 and 3.85 for arable land, meadow and forest samples, respectively). The soil acidification was especially intensive in the deep horizons; thus, 27 (Ah), 77 (Eg) and 87 % (B1tg) of the soil samples had a pH value below 4.0. The mean values of the total exchangeable acidity (TEA) were 1.55, 2.33 and 3.40 meq (100 g) -1 for the Ah, Eg and B1tg horizons, respectively. The TEA values in the forest soils were considerably higher (3.39 meq (100 g)-1) than those in the arable and meadow soils (1.96 and 1.93 meq (100 g)-1, respectively). The mean mobile Al contents of the tested soil samples were 11.02, 19.58 and 28.33 mg Al (100 g) -1 for the Ah, Eg and B1tg horizons, respectively. According to the pH and TEA values, mobile Al was considerably higher in the forest soils (a mean value of 26.08 mg Al (100 g) -1) than in the arable and meadow soils (mean values of 16.85 and 16.00 mg Al (100 g)-1, respectively). The Eg and B1tg horizons of the forest soil had especially high mobile Al contents (mean values of 28.50 and 32.95 mg Al (100 g)-1, respectively). High levels of mobile Al were especially frequent in the forest soils, with 35 (Ah), 85.0 (Eg) and 93.3 % (B1tg) of the tested samples ranging above 10 mg Al (100 g)-1. [ABSTRACT FROM AUTHOR]

Soil pH buffering capacity, described here as lime buffer capacity (LBC), is a fundamental soil property needed to estimate the change in soil pH after a known quantity of acidity or alkalinity is added to soil. Its rapid determination can be useful for many purposes, for example, estimating the lime needed to raise pH or acid needed to lower pH to a desired level. The objective of the present study was to evaluate the statistical relationship developed in previous studies between LBC from 30-min equilibration with Ca(OH)2 (LBC30) and LBC from 5-d equilibration with Ca(OH)2 (LBCeq) on a larger set of soils from Georgia. Five days was considered adequate time for true pH equilibrium and obtaining a true LBC. Eighty-seven soils from Georgia were treated with Ca(OH)2 using standard procedures for both equilibrium times, and the statistical relationship between the two LBCs were developed. The relationship developed in the first study was further tested in a second incubation of 67 soils to determine its accuracy in achieving a target pHCaCl2 of 6.0. The data from the second incubation indicated that the target pH was exceeded by an average of 0.11 pH units and that the average pH spread around the acquired pH was ±0.1 pH unit. The results suggest that the prediction of soil pH buffering capacity based on the proposed protocols will be sufficiently accurate for making agricultural lime application recommendations. [ABSTRACT FROM AUTHOR]

The relative tolerance to soil acidity of four annual legumes—biserrula (Biserrula pelecinus), French serradella (Ornithopus sativa), bladder clover (Trifolium spumosum) and arrowleaf clover (T. versiculosum)—was compared to the more widely grown annual legume species, subterranean clover (T. subterraneum). The pH of a Red Kandosol was adjusted with lime to achieve five pH levels ranging from 4.2 to 5.8 in CaCl2. All species were inoculated with an appropriate rhizobia strain and half the treatments received additional mineral nitrogen (N). Shoot weights of all species increased with liming. The pH value required to achieve 90% of maximum herbage yield without N application was c. 4.96–4.98 with 9.3% exchangeable aluminium (Al) for arrowleaf clover, biserrula, French serradella and subterranean clover, but significantly higher at c. 5.3 and only 4.0% exchangeable Al for bladder clover. Root nodule number was insensitive to liming for all species except subterranean clover, which showed a large increase in root nodule number with lime. Comparisons of the percentage reduction in shoot dry weight at the lowest soil pH (4.2), relative to the respective maximum yields with lime in the absence of applied N, showed subterranean clover (39.1%) was the most tolerant species to low pH, followed by French serradella (44.4%), arrowleaf clover (45.2%), biserrula (56.2%) and bladder clover (63.8%). [ABSTRACT FROM PUBLISHER]

Soil acidity and aluminum toxicity are considered most damaging soil conditions affecting the growth of most crops. This paper reviews the results of tests of pH, exchangeable acidity and mobile aluminum (Al) concentration in profiles of pseudogley soils from Čačak--Kraljevo basin. For that purpose, 102 soil pits were dug in 2009 in several sites around Čačak--Kraljevo basin. The tests encompassed 54 field, 28 meadow, and 20 forest soil samples. Samples of soil in the disturbed state were taken from the Ah and Eg horizons (102 samples), from the B1tg horizon in 39 field, 24 meadow and 15 forest pits (a total of 78 samples) and from the B2tg horizon in 14 field, 11 meadow, and 4 forest pits (a total of 29 samples). Mean pH values (1M KCl) of the tested soil profiles were 4.28, 3.90 and 3.80 for the Ah, Eg and B1tg horizons, respectively. Soil pH of forest samples was lower than those in meadow and arable land samples (mean values of 4.06, 3.97 and 3.85 for arable land, meadow and forest samples, respectively). Soil acidification was especially intensive in deep horizons, as 27% (Ah), 77% (Eg) and 87% (B1tg) soil samples had the pH value below 4.0. Mean values of total exchangeable acidity (TEA) were 1.55, 2.33 and 3.40 meq 100 g-1 for the Ah, Eg and B1tg horizons, respectively. The TEA values in forest soils were considerably higher (3.39 meq 100 g-1) than those in arable soils and meadow soils (1.96 and 1.93, respectively). Mean mobile Al contents of tested soil samples were 11.02, 19.58 and 28.33 mg Al 100 g-1 for the Ah, Eg and B1tg horizons, respectively. According to the pH and TEA values, mobile Al was considerably higher in the forest soils (the mean value of 26.08 mg Al 100 g-1) than in the arable soils and meadow soils (the mean values of 16.85 and 16.00 mg Al 100 g-10, respectively). The Eg and B1tg horizons of the forest soil had especially high mobile Al contents (the mean values of 28.50 and 32.95 mg Al 100 g-1, respectively). High levels of mobile Al were especially frequent in the forest soils, with 35% (Ah), 85.0% (Eg) and 93.3% (B1tg) of the tested samples ranging above 10 mg Al 100 g-1. [ABSTRACT FROM AUTHOR]

Abstract: One of the most influential factors determining the growth and composition of soil bacterial communities is pH. However, soil pH is often correlated with many other factors, including nutrient availability and plant community, and causality among factors is not easily determined. If soil pH is directly influencing the bacterial community, this must lead to a bacterial community growth optimised for the in situ pH. Using one set of Iberian soils (46 soils covering pH 4.2–7.3) and one set of UK grassland soils (16 soils covering pH 3.3–7.5) we measured the pH-optima for the growth of bacterial communities. Bacterial growth was estimated by the leucine incorporation method. The pH-optima for bacterial growth were positively correlated with soil pH, demonstrating its direct influence on the soil bacterial community. We found that the pH from a water extraction better matched the bacterial growth optimum compared with salt extractions of soil. Furthermore, we also showed a more subtle pattern between bacterial pH growth optima and soil pH. While closely matched at neutral pHs, pH-optima became higher than the in situ pH in more acid soils, resulting in a difference of about one pH-unit at the low-pH end. We propose that an explanation for the pattern is an interaction between increasing overall bacterial growth with higher pHs and the unimodal pH-response for growth of bacterial communities. [Copyright &y& Elsevier]

The Rhizobium sp. strain PR389 was isolated from the root nodules of (Willd.) Ohwi, which grows in acidic (pH 4.6) yellow soil of the Jinyun Mountains of Beibei, Chongqing, China. While rhizobia generally have a pH range of 6.5-7.5 for optimum growth, strain PR389 grew in a liquid yeast extract - mannitol agar medium at pH 4.6, as well as in a pH 4.1 soil suspension, suggesting acid tolerance in this specific strain of rhizobium . However, at pH 4.6, the lag phase before vigorous growth was 40 h compared with 4 h under neutral conditions (pH 7.0). For PR389, the generation time after the lag phase remained the same at different pH levels despite the different durations of the lag phase. Except in the pH 4.4 treatment, the pH of the culturing media increased from 4.6, 4.8, 5.0, and 5.5 to neutral and slightly alkaline after 70 h of culture. Chloramphenicol was added to determine if protein production was involved in the increasing pH process. Chloramphenicol significantly inhibited PR389 growth under acid stress but had little effect under neutral conditions. Proton flux measured during a short acid shock (pH 3.8) revealed that this strain has an intrinsic ability to prevent H+ from entering cells when compared with acid-sensitive rhizobia. We propose that the mechanism for acid tolerance in PR389 involves both intracellular and extracellular processes. When the extracellular pH is lower than pH 4.4, the cell membrane blocks hydrogen from entering the cell. When the pH exceeds 4.4, the rhizobium strain has the ability to raise the extracellular pH, thereby, potentially decreasing the toxicity of aluminum in acid soil. [ABSTRACT FROM AUTHOR]

Forages are important throughout the south-east USA for livestock production and wildlife habitat. However, little is known about how forage species commonly grown in this region influence soil-quality indicators. The objectives of this research were to determine short-term response of soil water-stable aggregates (WSA) and density of fungal hyphae (DFH) to: (i) forage species or mixtures grown at identical soil pH levels and (ii) forage species or mixtures grown at field-state versus adjusted soil pH levels. Nine warm-season species (sole crop) and eleven cool-season sole crop or legume-grass mixtures were grown under protected culture in southern coastal plain soil microcosms. Levels of WSA and DFH, and plant shoot and root biomass were evaluated after two 12-week experimental growth periods in both field-state and adjusted-pH soil. Both warm- and cool-season forage species significantly altered short-term responses of WSA and DFH levels; these responses differed when the soil pH was adjusted from the field state with lime addition. The short-term responses of both WSA and DFH to lime addition in coastal plain soil were negative only when certain forage species were grown, and no response was detected for the control. It appeared that differences in plant shoot and root developmental characteristics played a key role in soil WSA and DFH responses to the species studied. Further long-term studies are needed to understand how these relationships are expressed in more variable environments over expanded time frames. [ABSTRACT FROM AUTHOR]

The extent to which pretransplant colonization of seedlings with the arbuscular mycorrhizal fungus (AMF) Schenck and Smith emend. Koske could enhance the post-transplant growth of two cultivars of (Lam.) de Wit (cv. K-8 and cv. K-636) in Al- and Mn-rich acid soils was evaluated in a greenhouse. Arbuscular mycorrhizal colonization measured at the end of the experiment was significantly stimulated by inoculation in both cultivars at all pH levels tested, although colonization was most stimulated if cv. K-8 was grown in the Al-rich soil at the lowest pH. Symbiotic effectiveness measured as P content of pinnules was significantly suppressed in both cultivars if they were grown at the lowest pH. Symbiotic effectiveness measured as pinnule P content and shoot biomass yield was enhanced in both cultivars by liming. The trends in effectiveness were similar in both cultivars, but cultivar effect was significant in the Mn-rich Oxisol (Wahaiawa soil) but not in the Al-rich Ultisol (Leilehua soil). The tolerance of the cultivars to acid soil toxicity in the Wahiawa soil varied with the pretransplant mycorrhizal status of their seedlings. The effect of pretransplant colonization of seedlings was to eliminate the differences in the tolerance of the cultivars to acid soil toxicity. Our data suggest that AMF could offset some of the growth reduction associated with soil acidity and that host genotype could play a role in this regard. [ABSTRACT FROM AUTHOR]

Abstract: On acid soils, no-tillage farmers are often advised to apply lime to the soil surface without incorporation by tillage. As such, it can take a number of years before the subsoil acidity is decreased. However, no-tillage seeders vary in the level of soil disturbance caused during seed placement. The consequence of such variations in soil disturbance for the effectiveness of lime in no-tillage cropping has not been explored. Our objectives were (i) to determine if the liming effect could be accelerated by increasing the rate of lime and level of soil disturbance during no-tillage seeding, and (ii) evaluate the effect of no-tillage seeding method, rate of lime and soil pH on yield of wheat, barley, canola and lupins. Three trials, each with a factorial design consisting of four seeding methods and four lime rates, were established in 1999 and continued until 2005. The soil had a texture contrast with about 15–20cm of sand over yellow sandy clay loam and the initial pH (CaCl2) at both 0–10 and 10–20cm was between 4.5 and 4.7. The four seeding treatments were: low disturbance zero-till disc openers (ZT), higher disturbance no-tillage tines with narrow knife-points (NT), higher disturbance full cut seeding with sweeps (FC) for the first three years followed by ZT from then on, and FC for the first year followed by NT thereafter. The four lime rates were 0, 1, 2 and 4tha−1. The liming effect was more rapid with the higher disturbance seeding of NT, FCZT and FCNT, compared with ZT; the seeding effect on soil pH diminished with time and was not detected in the subsoil after four years. Higher rates of lime increased this effect and there was no interaction between seeding method and lime rate. This indicated that soil pH under the different seeding methods responded in a similar manner to increased lime. Nonetheless, significant positive linear regressions were found between yield and soil pH for wheat and barley and a negative relationship for lupins. Canola showed no response to soil pH, possibly because establishment was affected by seeding method, and soil pH was not low enough to elicit a response. The ZT seeding method gave lower yields than the other methods for canola and lupins in some years, but had no effect on wheat and barley yields. Higher disturbance at the time of no-till seeding can, therefore, accelerate the liming effect, making earlier economic gains possible. [Copyright &y& Elsevier]

The red soil region in China is very important to agriculture. However, soil aluminum (Al) toxicity often occurs as a result of the high soil acidity. In a long-term experiment, we analyzed soil samples to determine the effect of fertilization on soil acidity and potential Al toxicity. The results showed that after 12 years of utilization, Al toxicity occurred in the soil of the control plot. Chemical fertilizer further decreased soil pH and intensified Al toxicity. However, rice straw effectively improved soil pH and ameliorated soil Al toxicity from 0 to 50 cm deep, which may be attributed to the accumulated soil organic matter (SOM) and the decomposition of the rice straw. Corresponding to the lower Al content in soil, peanut crops grew healthier with greater yields in the rice straw plot, indicating that returning crop stalks to the field should be a feasible fertilization strategy in the region. [ABSTRACT FROM AUTHOR]

The mechanisms by which organic materials affect soil pH are not fully understood. This study for the first time compared the short-term effect of various model organic compounds on pH change of two soils differing in initial pH (Podosol of pH 4.4 and Tenosol of pH 6.1). Eight organic compounds, representing common compounds in plant residues, were selected based on the number and type of chemical functional groups. The addition of organic acids (acetic, malic, citric, and benzoic acid) reduced soil pH immediately due to H dissociation. The magnitude of pH decrease depended on the rate of application, degree of dissociation of the acids, and initial soil pH. During a subsequent incubation, pH was slowly restored as these compounds were decomposed. The degree to which pH was restored was reduced with increasing addition rate. The production of H ions was increased with increasing rate of acid addition and decreased over time. When potassium citrate (organic anion) was added, soil pH increased due to H consumption upon decomposition. Compounds with amine groups (glucosamine hydrochloride) and less easily decomposable compounds (phenol) did not significantly alter pH during 16-day shaking. Changes in pH after glucose addition were relatively small compared with other compounds and were not expected because hydroxyl chemical groups of glucose are neutral. The present study demonstrated that the addition of model organic compounds to soil caused soil pH to increase, decrease, or remains unaffected. The extent and direction of pH change was dependent on the chemical functional group, addition rate, decomposition, and the initial soil pH. [ABSTRACT FROM AUTHOR]

Background: The divergent glacial histories of southern and northern Europe affect present-day species diversity at coarsegrained scales in these two regions, but do these effects also penetrate to the more fine-grained scales of local communities? Methodology/Principal Findings: We carried out a cross-scale analysis to address this question for vascular plants in two mountain regions, the Alps in southern Europe and the Scandes in northern Europe, using environmentally paired vegetation plots in the two regions (n = 403 in each region) to quantify four diversity components: (i) total number of species occurring in a region (total γ-diversity), (ii) number of species that could occur in a target plot after environmental filtering (habitat-specific γ-diversity), (iii) pair-wise species compositional turnover between plots (plot-to-plot b-diversity) and (iv) number of species present per plot (plot a-diversity). We found strong region effects on total γ-diversity, habitatspecific γ-diversity and plot-to-plot b-diversity, with a greater diversity in the Alps even towards distances smaller than 50 m between plots. In contrast, there was a slightly greater plot a-diversity in the Scandes, but with a tendency towards contrasting region effects on high and low soil-acidity plots. Conclusions/Significance: We conclude that there are strong regional differences between coarse-grained (landscape- to regional-scale) diversity components of the flora in the Alps and the Scandes mountain ranges, but that these differences do not necessarily penetrate to the finest-grained (plot-scale) diversity component, at least not on acidic soils. Our findings are consistent with the contrasting regional Quaternary histories, but we also consider alternative explanatory models. Notably, ecological sorting and habitat connectivity may play a role in the unexpected limited or reversed region effect on plot adiversity, and may also affect the larger-scale diversity components. For instance, plot connectivity and/or selection for high dispersal ability may increase plot a-diversity and compensate for low total γ-diversity. [ABSTRACT FROM AUTHOR]

Abstract: Coal fly ash can be used to ameliorate productivity constraints in agricultural soils, but their efficacy still remains highly variable. To ascertain the capacity of Class F fly ashes to modify pH of acidic soils, and their effects on the yield and uptake of molybdenum (Mo) and selenium (Se) by canola (Brassica napus L.), we applied two acidic and two alkaline Class F ashes at rates equivalent to 0, 12, 36, and 108Mg/ha to the top layer (0–10cm) of 100cm long intact cores of acidic sandy clay and clay loam soils. Only the alkaline ash which had the highest calcium carbonate equivalent (2.43%) increased the pH of the top 10cm of the sandy clay soil. However, this ash was also highly saline and when applied at ⩾36Mg/ha it increased the electrical conductivity in the top soil layer. Increases in soil pH as a result of alkaline ash addition also elevated concentrations of Se in the plant shoot. The ashes with high concentrations of Mo and Se generally increased uptake of these elements in the plant shoot and/or seed. When these ashes were applied at 108Mg/ha they increased the concentrations of these elements in the treated topsoil. [ABSTRACT FROM AUTHOR]

Abstract: Branched glycerol dialkyl glycerol tetraether (GDGT) lipids occur in soils worldwide and are presumed to be produced by soil bacteria. They form the base of the MBT/CBT proxy (methylation of branched tetraethers/cyclisation of branched tetraethers) for palaeoclimate reconstruction. The degree of cyclisation and methylation, expressed in the CBT and MBT indices, has been shown to relate to soil pH, and to both temperature and soil pH, respectively. To evaluate the direct impact of soil pH on the abundance and distribution of branched GDGTs, either present as core lipids or derived from intact polar lipids (IPLs), long term (>45years) soil pH manipulation plots, with a pH range of 4.5–7.5, were analyzed. The CBT index values of both core and IPL-derived branched GDGTs was significantly (r 2 =0.93, P =0.0004 and r 2 =0.93, P =0.0005, respectively) linearly related to actual soil pH, confirming the direct influence of pH on the distribution of branched GDGT. In contrast, the MBT index was only influenced to a minor extent by the changes in soil pH. Branched GDGT abundances decreased with increasing soil pH, supporting the idea that Acidobacteria may be a possible source of these orphan membrane lipids. [Copyright &y& Elsevier]

The persistence of fenazaquin (4-t-butylphenylethyl quinazolin-4-yl ether) was studied in three different soils, namely, Gangetic alluvial (pH 6.9), laterite (pH 5.3), and terai (pH 5.1) soil and in water at three different pH values (4.0, 7.0, and 9.2) under laboratory-simulated condition and samples were analyzed upto 60 days at regular intervals. Fenazaquin was applied at 5 and 10 µg g-1 for each soil and at 0.2 and 0.4 µg mL-1 to each water sample. Dissipation of fenazaquin in soil and water followed first-order kinetics irrespective of any treatments. The half-life of fenazaquin was found in the range of 47-64 days in soils and 3.49-37.6 days in water irrespective of dose. The persistence of fenazaquin in soil significantly increased in the order of Gangetic alluvial soil (pH 6.9) > laterite soil (pH 5.3) > terai soil (pH 5.1), whereas in water the trend of persistence was pH 9.2 ≥ pH 7.0 > pH 4.0. The dissipation of fenazaquin in soil and water was found to be dependent on pH irrespective of doses. [ABSTRACT FROM AUTHOR]

Abstract: The chemical composition of fruit belonging to ‘Barbara’ and ‘Daniela’ myrtle cultivars was monitored during development from fruit-set to an over-ripe stage (July–January), with the aim to identify a reliable maturity index. Acidity, pH, reducing and total sugars, phenols, tannins, anthocyans, carbon dioxide and ethylene production rates were monitored over two different year seasons. Titratable acidity decreased during maturation, with significant differences due to cultivar and year of observation. Reducing sugars increased in both cultivars approximately sevenfold from fruit set to complete maturation. Total sugar content increased similarly ranging from 1.43% and 1.41% at fruit set to 8.28% and 7.56% at maturation for ‘Barbara’ and ‘Daniela’, respectively. Total phenols and tannins occurred at high levels after fruit set and declined during development. Anthocyans levels increased, in both cultivars, according to a sigmoid curve. The pattern of respiration rate showed a gradual decline in both cultivars ranging from 365.81 and 396.42mgkg−1 h−1 to 79.98 and 52.27mgkg−1 h−1, respectively for ‘Barbara’ and ‘Daniela’ in 2006. A peak of variable size was observed in October–November period. Small increases in ethylene production have been detected during fruit development ranging from 130.57 and 269.14μLkg−1 h−1 measured at the onset of development to 13.04 and 19.36μLkg−1 h−1 measured at harvest for ‘Barbara’ and ‘Daniela’, respectively. [Copyright &y& Elsevier]

Habitats with soil pH < 4 and Ca < 100 ppm, such as pocosins, Sphagnum bogs and heathlands, would appear inimical to land-snail biodiversity. Nevertheless, a survey of 1,356 sites, c. 1/2 million individuals and over 240 species (c. 1/5 of the continental fauna) across North America shows that c. 10% of species appear to favour such highly or moderately acidic sites, spread from subtropical forests of the Gulf of Mexico coast to the arctic tundra. Nonmetric multidimensional scaling ordination of faunas from 292 sites that support at least five co-occurring species documents that the principal axis of compositional variation in highly and moderately acidic habitats is significantly (P < 0.0005) correlated with latitude, while the second axis is significantly (P < 0.0005) correlated with moisture level. Composition was found to vary continuously along both axes, implying that discrete acidophilic communities are not present. While highly and moderately acidic sites were shown to have significantly (P < 0.000000005) lower richness and abundance compared with neutral/calcareous habitats, even the most acidic sites still typically supported 5–10 species. Abundance distributions in highly acidic habitats were found to be more uneven those of neutral/calcareous sites. The greater richness of the North American acidophilic land snail fauna compared with that in Europe has allowed communities to display replacement-driven compositional turnover. These results demonstrate that it is vitally important for biodiversity surveys of North American land snails not to ignore acidic habitats, because they harbour an important and surprisingly diverse fauna. [ABSTRACT FROM PUBLISHER]

This work was carried out aiming to evaluate the effect of thidiazuron (TDZ) on the quality of Gala' apples stored under controlled atmosphere (CA) conditions. Plants were sprayed at full bloom with TDZ at 0, 10, 20, or 40g ha-1 (a.i.). Harvested fruits were then stored in CA with 1.0+2.5, 1.5+2.5 and 1.5+5.0 (kPa O2+kPa *CO2), both at 0.5°C. In addition, the partial pressure of 1.5kPa of O2+2.5kPa of CO2 was also evaluated at -0.5°C. Higher flesh firmness and titratable acidity was obtained by applying 20 or 40g ha-1 TDZ. Furthermore, these TDZ doses decreased the respiration rate as well as the occurrence of flesh breakdown, mealiness and decay The application of TDZ at doses ranging from 20 to 40g ha-1 maintains higher fruit quality for up to 8 months under CA. In addition, the storage of Gala' apples under CA with 1.0Pa O2+2.5kPa CO2 at 0.5°C results in higher flesh firmness and titratable acidity. Moreover, this CA condition reduces the incidence of flesh breakdown, mealiness and postharvest decay in 'Gala' apple fruits. [ABSTRACT FROM AUTHOR]

1. Low pH inhibits microbial conditioning of leaf-litter, which forms the principal energy input to many headwater streams. This reduces food quality and availability for the shredder assemblage, thereby creating a potential bottleneck in the flux of energy and biomass through acidified food webs. 2. We explored the consequences of acidity on the well-characterised community of Broadstone Stream in southeast England, by quantifying the physiological condition (protein and lipid content) of three dominant shredder species ( Leuctra nigra, L. hippopus and Nemurella pictetii) and relating this to changes in the numerical abundance and biomass of invertebrates across a longitudinal pH gradient (5.3–6.5). 3. Total taxon richness increased with pH, as did shredder diversity. The acid-tolerant stonefly, L. nigra, exhibited a positive correlation between pH and protein content, but its abundance was suppressed in the less acid reaches. These results suggest that the impacts of environmental stressors might be manifested differently at the population (i.e. numerical and biomass abundance) versus the physiological (i.e. protein content of individuals) levels of organisation. Body composition of L. hippopus and N. pictetii did not exhibit any significant relationship with stream pH in the field. 4. The survey data were corroborated with a laboratory rearing experiment using N. pictetii, in which survival rate, growth rate, and protein and lipid content of individuals were measured in stream water of differing pH and acid versus circumneutral microbial conditioning regimes. Acid-conditioned leaves were associated with increased mortality and reduced protein content in consumers’ tissues, with acid water also having the latter effect. 5. Our results suggest that biochemical constraints within key taxa might create energy flux bottlenecks in detrital-based food webs, and that this could ultimately determine the productivity of the entire system. Hence assays of the body composition of macroinvertebrates could be an effective new tool that complements population level studies of the impacts of stressors in fresh waters. [ABSTRACT FROM AUTHOR]

The effect of soil acidity on root and rhizosheath development in wheat and barley seedlings was investigated in an acid Ferrosol soil to which various amounts of lime (CaCO3) were applied to modify soil Al concentrations (pH (CaCl2): 4.22 to 5.35 and Al (CaCl2 extract): 17.7 to 0.4 mg kg−1 soil; respectively), and Ferrosol soil from an adjacent location at the same site which had a higher Al concentration (pH 4.19; 29.2 mg kg−1 Al). The cereal lines were selected on the basis of differences in their rate of root growth, Al-resistance and root hair morphology. Root morphology was assessed after 7 days of growth. The length of fine (mainly lateral) roots of Al-sensitive genotypes was more sensitive to soil Al concentrations than that of the coarse (mainly primary) roots. The experiments demonstrated that even where root growth was protected by expression of the TaALMT1 gene for Al-resistance, root-soil contact was diminished by soil acidity because root hair length (in many lines), and root hair density and rhizosheath formation (all lines) were adversely affected by soil acidity. In the case of Al-sensitive lines, fine root growth and rhizosheath mass were reduced over much the same range of soil Al concentrations (i.e. >3–6 mg kg−1 Al). Although Al-resistant lines could maintain fine root length under these conditions, they were similarly unable to maintain rhizosheath mass. This finding may help to explain why Al-resistant wheats which yield relatively well in deep acid soils, may also benefit from application of lime to the surface layers of the soil. [ABSTRACT FROM AUTHOR]

Recently, sugar maple (Acer saccharum Marsh.) decline in northeastern North America has been regarded as a major factor structuring hardwood forests by favouring American beech (Fagus grandifolia Ehrh.) in the understory of maple-dominated stands. To determine whether soil fertility differences associated with sugar maple decline may have promoted the expansion of American beech, we explored the relationships between the soil base status and the sapling and tree strata density and composition, using data from 426 permanent sample plots distributed throughout Quebec. Our results indicate that American beech is currently expanding in the sugar maple range of Quebec. The abundance and proportion of American beech in the sapling stratum are mainly associated with the proportion of American beech in the tree stratum, the relative basal area of dead sugar maple trees, and the base status of soils. In accordance with the many studies reporting on the high sensitivity of sugar maple to the acid–base status of soils and the decline of the sugar maple population, this study supports the hypothesis that soil base cation depletion, caused in part by atmospheric acid deposition, is among the main factors involved in the present-day expansion of American beech over a large area in Quebec. [ABSTRACT FROM AUTHOR]

Abstract: The contamination of the topsoil of 262 woody habitats around a former lead smelter in the North of France was assessed. In this urbanized and industrialized area, these kinds of habitats comprise of hedges, groves, small woods, anthropogenic creations and one large forest. Except for the latter, which is 3km away, these woody habitat soils often present a high anthropization degree (a significant amount of pebbles and stones related to human activities) with a high metal contamination. In the studied woody habitat topsoils, Cd, Pb and Zn concentrations largely exceeded those of agricultural topsoils located in the same environmental context. Therefore, atmospheric emissions from the smelter are not the only cause of the high contamination of the woody habitat soils. This last one is related to the nature and the contamination level of deposit in relation with human activities (rubbles, slag, soils, etc). With regard to the results obtained with chemical extractions, the mobility of Cd, Pb and Zn in these soils is also greater than in agricultural soils. In the forest, pollutant solubility is increased by soil acidic pH. The variability of the physico-chemical parameters and the high metal contamination of the topsoils are the main characteristics of the woody habitats located around the former smelter. Although never taken into account during risk assessment, the disturbance of these environmental components could have important biogeochemical impacts (nutrients and metal cycles). Moreover, any modification of the soils'' use could potentially cause mobilization and transfer of the pollutants to the biosphere. Six years after the closure of the smelter, and as social and economic pressures considerably increase in this area, the study of these peculiar ecosystems is necessary to understand and predict the bioavailability, transfer, bioaccumulation and effects of pollutants in food chains. [Copyright &y& Elsevier]

A combination of the pH-dependent leaching test CEN/TS 14429 and geochemical modelling (LeachXS©-ORCHESTRA) was used to evaluate the partitioning of major, minor and trace elements in relation to their phosphorus retention capability, the release of non-nutrient constituents, their reduction of soil acidity and their organic matter retention. One Australian soil sample and two different soil amendments (Red Lime and Alkaloam) were studied. The pH-dependent leaching test showed that the acid neutralization capacity and the phosphorus retention of the soil were improved, respectively, by a factor of two to five and by a factor of two to ten after addition of these amendments. The amendments improved retention of dissolved organic matter (by a factor of 3–10) and did not increase leachability of undesired contaminants. The partitioning as obtained from modelling between free and dissolved organic-carbon-bound metals provides insight into the potential for uptake (bioavailability). This partitioning is very pH-dependent and therefore testing and associated chemical speciation modelling provide valuable information for judging traditional soil improvers and soil amendments, including the waste-derived soil amendments Alkaloam and Red Lime. [ABSTRACT FROM AUTHOR]

Abstract: The effect of chickpea processing (i.e. defatting, isoelectric precipitation vs ultrafiltration/diafiltration) on the composition, protein recovery and antinutritional factors of protein concentrates was studied for two varieties (Mylese and Xena). Defatting did not affect significantly the content of antinutritional factors in the flours. However, production of concentrates from defatted flours by isoelectric precipitation resulted in higher phosphorous and phenolic contents compared to the concentrates produced by the same process using the full fat flours as starting material, while trypsin inhibitor content was not affected. When processed by ultrafiltration/diafiltration, protein concentrates produced from defatted flour showed a slightly lower trypsin inhibitor content than the ones produced from full fat flours in most cases, while the inverse was true for the phosphorous content, and for the phenolic content; this effect was a function of chickpea variety. Overall, UF pH 9/DF pH 6 resulted in concentrates with the lowest phosphorous content, while isoelectric precipitation and UF pH 9/DF pH 9 resulted in concentrates with lower phenolic content compared to the ones produced by UF pH 9/DF pH 6; for both processes the trypsin inhibitor content of the concentrates remained high. Industrial relevance: Chickpea production is one of the major agricultural sectors of significant importance to Canada. Although chickpeas are grown in Canada for export, very little is exported in the value-added or processed form. Development of new extraction technologies and value-added products such as the ones presented in this paper is of interest for Canada since it would have a significant impact on the growth of the industry domestically, thus, creating opportunities to strengthen rural development in Canada. Successful implementation of these technologies would make interested Canadian companies viable competitors in the global plant protein production industry and would put Canada in a good position to enjoy a large share of this market both locally and internationally. More specifically, we are the first research group to compare the use of isoelectric precipitation and ultrafiltration/diafiltration for the production of chickpea protein concentrates from full fat and defatted flours of Kabuli and Desi chickpea variety, and to quantify the effect of these processes on the composition and on the antinutritional factors (i.e. phytic acid, total phenolics and trypsin inhibitors) of the resulting concentrates. Overall, it was observed that isoelectric precipitation was effective to an extent in producing concentrates with low phosphorous and phenolic contents. UF pH 9/DF pH 9 was also effective to an extent in producing concentrates with low phenolic content, while UF pH 9/DF pH 6 was more efficient in producing concentrates with low phosphorous content. High-quality chickpea protein concentrates with improved nutritional properties and good functional properties could beneficially be combined with other protein sources, such as soy protein, or be used in the formulation of foods, such as meat analogues, dairy, and bakery products. [Copyright &y& Elsevier]

We used a combination of 16S rRNA gene clone library surveys, quantitative PCR (qPCR) analysis, and fluorescent in situ hybridization to investigate the diversity, abundance, and distribution of members of candidate division SR1 in multiple habitats. Using SR1-specific 16S rRNA gene primers, we identified multiple novel SR1 lineages in four different anaerobic environments: sediments from Zodletone Spring, a sulfide- and sulfur-rich spring in southwestern Oklahoma; inner layers of microbial mats obtained from Sperm Pool, a high-temperature, low-pH pool (55°C, pH 2.5) in Yellowstone National Park; fresh bovine ruminal contents; and anaerobic freshwater pond sediments (Duck Pond) in Norman, Oklahoma. qPCR analysis indicated that SRi members constitute a small fraction (<0.01%) of the microbial communities in Duck Pond and ruminal samples but constitute a significant fraction (11.6 and 48.7%) of the total number of bacterial 16S rRNA genes in Zodletone Spring and the inner layers of Sperm Pool microbial mat samples, respectively. By using SR1-specific fluorescent probes, filamentous cells were identified as the sole SR1 morphotype in all environments examined, with the exception of Sperm Pool, where a second bacillus morphotype was also identified. Using a full-cycle 16S rRNA approach, we show that each of these two morphotypes corresponds to a specific phylogenetic lineage identified in the Sperm Pool clone library. This work greatly expands the intralineage phylogenetic diversity within candidate division SR1 and provides valuable quantification and visualization tools that could be used for investigating the ecological roles, dynamics, and genomics of this as-yet-uncultured bacterial phylum. [ABSTRACT FROM AUTHOR]

Abstract: Benzaldehyde lyase from Pseudomonas fluorescens (BAL, EC 4.1.2.38) is a versatile catalyst for stereoselective carboligations. Nevertheless, rather inconsistent data about its biochemical properties are reported in literature. In this study, the dependency of BAL activity on ionic strength, pH, and concentration of DMSO was for the first time systematically investigated and interpreted. It was found that the activity of BAL strongly depends on all three parameters, and a correlation exists between the dependency on pH and DMSO concentration. This correlation could be explained by an interaction of DMSO with an ionic amino acid in the catalytic site. A model-based analysis indicated that the pKa of this residue shifts to the alkaline milieu upon addition of DMSO. Consequently, the optimum pH also shifts to alkaline values when DMSO is present. Potentiometric experiments confirmed that the pKa can most probably be attributed to Glu50 which governs the activity increase of BAL on the acidic limb of its pH-activity profile. With these findings, the apparently contradicting data from literature become comprehensible and optimal reaction conditions for synthesis can easily be deduced. [Copyright &y& Elsevier]

Abstract  Carbon paste electrode modified with aminated Mobil Catalytic Material Number 41 (MCM-41) was prepared and used for immobilization of K3[Fe(CN)6] in acidic medium, and then electrochemical behavior of modified electrode containing ferricyanide was studied in detail, including pH-dependence and scan rate effect. Cyclic voltammetry studies showed that the electrode reaction is a surface-controlled process at the scan rate range from 5 to 60 mV s−1. Also, the electrocatalytic behavior of modified electrode toward the reduction of H2O2 is reported and the effect of pH on catalytic peak current was discussed. According to experimental results, with increasing solution pH, the catalytic effect of this modified electrode is decreased. Catalytic reduction current of H2O2 increases linearly with its concentration. It has been demonstrated that ferricyanide immobilized on the aminated MCM-41 is a stable catalyst for the electrocatalytic reduction of H2O2. [ABSTRACT FROM AUTHOR]

Abstract: Fenton reaction is thought to play an important role in wood degradation by brown-rot fungi. In this context, the effect of oxalic acid and pH on iron reduction by a biomimetic fungal chelator and on the adsorption/desorption of iron to/from wood was investigated. The results presented in this work indicate that at pH 2.0 and 4.5 and in the presence of oxalic acid, the phenolate chelator 2,3-dihydroxybenzoic acid (2,3-DHBA) is capable of reducing ferric iron only when the iron is complexed with oxalate to form Fe3+-mono-oxalate (Fe(C2O4)+). Within the pH range tested in this work, this complex formation occurs when the oxalate:Fe3+ molar ratio is less than 20 (pH 2.0) or less than 10 (pH 4.5). When aqueous ferric iron was passed through a column packed with milled red spruce (Picea rubens) wood equilibrated at pH 2.0 and 4.5, it was observed that ferric iron binds to wood at pH 4.5 but not at pH 2.0, and the bound iron could then be released by application of oxalic acid at pH 4.5. The release of bound iron was dependent on the amount of oxalic acid applied in the column. When the amount of oxalate was at least 20-fold greater than the amount of iron bound to the wood, all bound iron was released. When Fe–oxalate complexes were applied to the milled wood column equilibrated in the pH range of 2–4.5, iron from Fe–oxalate complexes was bound to the wood only when the pH was 3.6 or higher and the oxalate:Fe3+ molar ratio was less than 10. When 2,3-DHBA was evaluated for its ability to release iron bound to the milled wood, it was found that 2,3-DHBA possessed a greater affinity for ferric iron than the wood as 2,3-DHBA was capable of releasing the ferric iron bound to the wood in the pH range 3.6–5.5. These results further the understanding of the mechanisms employed by brown-rot fungi in wood biodegradation processes. [Copyright &y& Elsevier]

Abstract: Marine tidal inundation was partially restored to a severely degraded tropical acid sulfate soil landscape after having been excluded for over 30 years. The effects on soil acidity and iron-sulfide mineral reformation were investigated by comparing the geochemistry of soils before and after five years of regular tidal inundation. The soil pH increased by 2–3 units and titratable actual acidity (TAA) decreased by ∼40–50 μmol H+ g−1 within former sulfuric horizons. Relict acidity remained at depth (>1 m) in the underlying sulfidic horizons. δ 34S data indicate that tidal inundation caused exchange of marine solutes within former sulfuric horizons, but not within underlying sulfidic material. There was considerable reformation of pyrite within former sulfuric horizons after tidal inundation with reduced inorganic sulfur increasing by ∼60 µmol g−1. Acid-volatile sulfide also accumulated, but mainly near the soil surface (up to 16 µmol g−1). Reduction of Fe(III) minerals strongly influences the geochemistry of the tidally inundated soils. After tidal inundation the soil pH and Eh closely followed the iron redox couple and there was non-sulfidic solid-phase Fe(II) up to 600 µmol g−1. There was also substantial diagenetic enrichment of poorly crystalline Fe-oxides near the soil surface following tidal inundation, with reactive Fe spanning 400–1800 µmol g−1. While the decreases in soil acidity documented here are likely due to a combination of marine alkalinity inputs and reduction of both Fe and SO4 2−, the relative importance of each process remains to be determined. This study demonstrates that marine tidal inundation can be an effective landscape-scale strategy for ameliorating severe acidity associated with drained acid sulfate soils. [Copyright &y& Elsevier]

Abstract: Two laboratory-scale systems were set up (i) composting (without earthworms) and (ii) vermicomposting (with earthworms) and were monitored for 60 days after pre-composting. The physico-chemical parameters (pH, C/N, organic matter, and ash content) showed similar evolution in both systems except a higher in the initial vermicomposts. However, principle component analysis (PCA) of enzymatic activities and community level physiological profiles revealed differences in the functional response of microbial communities in compost and vermicompost during maturation. Dehydrogenase activity and bacterial counts indicated a steady decrease in biological activity and population during composting, whereas vermicomposting exhibited higher activity on day 30 and a reduction in bacterial counts on day 10. PCA of denatured gradient gel electrophoresis (DGGE) profiles showed divergent dynamics of bacterial communities in two processes. These results indicated differences in the functional response and genetic structure of microbial community in composts and vermicomposts despite similar changes in their physico-chemical parameters. [Copyright &y& Elsevier]

This article reviews a number of studies over the last decades, which may contribute to a more coherent understanding of the complicated thermal behaviour of β-lactoglobulin during heat treatments at pH>6.8. Many research papers on β-lacto-globulin ignore studies published before the digital period, which means that useful information from the past has been lost or is repeated. In this review results of former studies are compared with recent research data in order to get a more complete and consistent overview over the temperature range up to 150°C. All results indicate that the dissociation and conformational changes are reversible after heat treatments up to 60°C. Irreversible modifications of monomers appear between 60 and 70°C, starting as a slight conformational change, called the “molten globule state”. Increased exposure of thiol groups at temperatures between 65 and 75°C causes small oligomers mainly by oxidation of the thiols. Thiol/disulphide exchange reactions dominate between 75 and 85°C (at pH>7.0), and aspecific non-covalent aggregation induces larger aggregates. The formation of large aggregates is prevented at temperatures between 85 and 105°C, followed by fast cooling. Unfolding of residual structures of β-lactoglobulin is observed above 125°C, possibly induced by the chemical breakdown of disulphide bonds. [Copyright &y& Elsevier]

We examined a low pH effect on root growth of Atractylodes lancea, a Chinese traditional medicinal plant, and accumulation of the major active compound, β-eudesmol. Our results have shown that low pH increases root hair density and root dry weight, but reduces the length of the main root. More acidic pH stimulates production of β-eudesmol in A. lancea roots. [ABSTRACT FROM AUTHOR]