Cation Balance Research Articles

Improvement and validation of a decision support system to maintain optimal nutrient levels in crops grown in closed-loop soilless systems

To support growers in their transition towards recycling of water and fertilisers in soilless crops, an algorithm consisting of mass balance models was developed and applied via the decision support system NUTRISENSE. This algorithm is commissioned to readjust the composition of the nutrient solution (NS) supplied to plants after a chemical analysis of the drainage solution (DS), aiming to match nutrient input with crop nutrient uptake, thus maintaining the nutrient concentrations within target ranges in the root zone. The algorithm was tested in a pilot study conducted in a commercial greenhouse with tomato grown in a closed-loop soilless system and the data were further used for scenario analyses to assess its sensitivity to inaccuracies in the parameters fed to the models. The nutrient concentrations in the root solution were closer to the target levels after supplying NS readjusted using the current algorithm, thus confirming its efficiency to maintain optimal nutrient levels in the root zone of soilless crops when the DS is recycled. The scenario analysis showed that the algorithm is not sensitive to inaccuracies in input parameters related to the daily volume of NS supplied to the crop, or to the volume of available NS per plant in the soilless system. However, it was moderately sensitive to inaccurate determinations of the nutrient concentrations in the DS. Furthermore, a case study with a closed-loop soilless crop of cucumber managed with NUTRISENSE was conducted, aimed to confirm the efficiency of the algorithm to maintain optimal nutrient levels in the root environment. The case study showed that the readjustment of the nutrient supply using NUTRISENSE could successfully maintain the EC, pH and macronutrient levels within a range of ± 10% variation from the target level. Only SO42- showed a larger discrepancy than ± 10% from the target value, because the supply level of this macronutrient was not estimated directly through the current algorithm but indirectly, through the anion to cation balance. However, this problem can be easily tackled by setting a minimum level of SO42- supply as a present value in NUTRISENSE.

Melatonin promotes Al3+ compartmentalization via H+ transport and ion gradients in Malus hupehensis.

Soil acidification in apple (Malus domestica) orchards results in the release of rhizotoxic aluminum ions (Al3+) into soil. Melatonin (MT) participates in plant responses to abiotic stress; however, its role in AlCl3 stress in apple remains unknown. In this study, root application of MT (1 μM) substantially alleviated AlCl3 stress (300 μM) in Pingyi Tiancha (Malus hupehensis), which was reflected by higher fresh and dry weight, increased photosynthetic capacity, and longer and more roots compared with plants that did not receive MT treatment. MT functioned mainly by regulating vacuolar H+/Al3+ exchange and maintaining H+ homeostasis in the cytoplasm under AlCl3 stress. Transcriptome deep sequencing analysis identified the transcription factor gene SENSITIVE TO PROTON RHIZOTOXICITY 1 (MdSTOP1) was induced by both AlCl3 and MT treatments. Overexpressing MdSTOP1 in apple increased AlCl3 tolerance by enhancing vacuolar H+/Al3+ exchange and H+ efflux to the apoplast. We identified 2 transporter genes, ALUMINUM SENSITIVE 3 (MdALS3) and SODIUM HYDROGEN EXCHANGER 2 (MdNHX2), as downstream targets of MdSTOP1. MdSTOP1 interacted with the transcription factor NAM ATAF and CUC 2 (MdNAC2) to induce MdALS3 expression, which reduced Al toxicity by transferring Al3+ from the cytoplasm to the vacuole. Furthermore, MdSTOP1 and MdNAC2 coregulated MdNHX2 expression to increase H+ efflux from the vacuole to the cytoplasm to promote Al3+ compartmentalization and maintain cation balance in the vacuole. Taken together, our findings reveal an MT-STOP1 + NAC2-NHX2/ALS3-vacuolar H+/Al3+ exchange model for the alleviation of AlCl3 stress in apple, laying a foundation for practical applications of MT in agriculture.

New Fertilization Approach Improves Okra (Abelmoschus Esculentus L. Moench) Production on Acidic and Degraded Soil in Cameroon

Soil acidity, combined with high aluminum toxicity, is one of the major problems limiting agricultural productivity. The objective of this work was to improve growth and yields of okra on acidic and degraded soil in the Center region, Cameroon, using an innovative fertilization approach and lime material. The soil is ferralitic, very acidic, with aluminum toxicity and significant imbalance in the (Ca/Mg/K) ratio of (55/15/30). Seven fertilization treatments were applied: Control without fertilizer; arbuscular mycorrhizal fungi (AMF); AMF+50% poultry manure (AMF+½ PM); mineral fertilizers with cation balance at 100% (MF100 %); AMF+50% mineral fertilizers (AMF+50 % MF); poultry manure at 50%+50 % mineral fertilizers (MF50%+½ PM) and poultry manure (PM). Two varieties of okra were used (Kirikou F1 and Local). The experimental design was a split-plot with two factors. Considering MF, an innovative Ca/Mg/K ratio of 68/23/9 was applied. The results showed that the applied fertilizers had a significant effect on the agronomic parameters of okra with MF50%+½ PM followed by PM and MF100% as the best treatments. An average increase in fresh yield from 111% to 1840% over the control was recorded and the best symbiotic parameters were observed at the AMF treatment associated with the Local variety. This variety responds better to organic matter intake while Kirikou F1 is more favorable to chemical fertilizer addition.

Nutritional standards through Integrated Differential Diagnosis (IDD) in pomegranate (Punica granatum L.)

The foliar analysis is a useful tool to detect the nutritional status of plants, predict future problems in the reproductive cycles of fruit production and implement preventive and corrective measures to achieve a mineral balance in fruit trees, obtaining higher productivity. There is little information available on nutrient sufficiency ranges in pomegranate leaf and the literature reported differs due to diverse cultivation practices, cultivars, and agroecological conditions. Therefore, the objective of this work was to determine the mineral content of ‘Wonderful’ pomegranate leaves for each the nutritional elements and the cation balance, and to establish the nutritional standards using Integrated Differential Diagnosis (IDD). The mineral content of the pomegranate leaves was determined and based on the results, nutritional standards for macro elements, cation balance and microelements were generated through the IDD, which evaluate whether there are mineral and/or physiological imbalances. The macro elements in the cultivation of the pomegranate were the following: NO3 3747.5 µg g-1, Total Nitrogen 1.35%, P 0.14%, K 0.88%, Ca 1.65%, Mg 0.19%, Na 0.006%. For the cation balance, the optimal values ​​were: (Ca+Mg)/K 4.48 mEq 100 g-1, Ca/(K+Mg) 2.13 mEq 100 g-1, Mg/(K+Ca) 0.16 mEq 100 g-1, Ca/Mg 5.06 mEq 100 g-1, K/Mg 1.36 mEq 100 g-1. Finally, the optimal values ​​for the microelements were: Fe 59.5 µg g-1, Mn 31.4 µg g-1, Zn 6.3 µg g-1, Cu 6.1 µg g-1. The values ​​obtained for the micro and macro elements were like those reported. In the case of cation balance and foliar nitrate content, they have not been previously reported. The IDD is a promising and effective auxiliary tool to characterize the nutritional status of pomegranate trees and, in turn, an alternative to conventional methods of nutritional diagnosis with the advantage of establishing a nutritional deficiency (soil-plant relationship) or a physiological imbalance (relation plant - climate) for this crop.

Environmental conditions and plant physiology modulate Cu phytotoxicity in field-contaminated soils

Foliar Cu concentration has been widely used as a biomarker of plant growth in phytotoxicity bioassays. This relation has helped find plant processes altered by Cu in dose-response experiments (a bivariate approach). However, when plants are grown in field conditions, their responses can vary in function of multiple variables, such as the environment, plant physiology, and other elements in plant (plant ionome). These sources of variability are commonly unreported, which could limit bioassays’ utility. Thus, the present study aimed to assess and integrate the mentioned sources of variability on Cu phytotoxicity. Lettuce was used as plant model. Lettuces were grown in growth chambers with contrasting light and air humidity conditions and on two different field-contaminated soils (sandy and loamy soils). Results showed that environmental conditions significantly affected foliar Cu and plant growth, but this effect differed in the two studied soils. Foliar Cu was not a good biomarker of plant growth. In contrast, integrating the potential phytotoxicity effect with the plant's nutritional status allowed a better understanding of plant growth. We remarked on using a structural equation modeling approach (SEM) to integrate plant physiology and plant ionome as moderators of plant growth. Results showed that plant growth was primarily related to plant nutritional status rather than Cu phytotoxicity. Also, the foliar Cu concentration would affect plant nutritional status due to photosynthesis-related plant processes and cation balance. Finally, this research invites to state and include sources of variability when assessing phytotoxicity. This way, it is possible to advance toward understanding complex linked processes occurring in field conditions.

Soil Characteristics and Pedoclimatic Evaluation of Rainfed Sorghum (Sorghum bicolor (L.) Moench) in the Mayo-Lemié Division, South-Western Chad

In recent decades, many regions in the Chad Republic in Central Africa have experienced a continuous decline in agricultural yields. In order to determine the main factors leading to this decline in yields and mainly Sorghum yields, this study was conducted in South-Western Chad, in the Sudano-Sahelian environment. Three soil profiles of variable depths, namely, M1, M2, and M3, were dug along a toposequence, respectively, in the footslope, mid-slope, and the upslope. Soil samples collected from each horizon in the three soil profiles were labelled and sent to laboratories for mineralogical, geochemical, and physicochemical analyses. For land evaluation, climatic characteristics are divided into rating groups with respect to the crop and its climatic requirements. Parametric values were attributed to each soil characteristic for soil evaluation and the land index calculated. The main minerals identified in the studied soils are quartz, K-feldspars, plagioclase, kaolinite, smectite, illite, associated to traces of anatase, sepiolite, calcite, and interstratified minerals. In all the analyzed samples, silicon content is very high. It is closely followed by aluminum, iron, and potassium. The presence of kaolinite and smectite suggests that monosiallitisation is a crystallochemical processes acting at the bottom of profile towards bisiallitisation. All samples collected from the three soil profile horizons are mainly sandy and globally poor in nutrients. The pedoclimatic assessment of Sorghum cultivation reveals that the studied soils are marginally to moderately suitable for the production of Sorghum due to soil texture, wetness, and soil fertility. The decline in yields is related to low base saturation, in line with low exchange base content in the studied soils. These limitations could be solved by restoration of the cation balance through fertilization and liming, combining organic inputs with mineral fertilizer, and the realization of channels for the drainage of water at the base of the soil sequence.

Phosphorus fertilization affects cation balance in cool-season grasses associated with grass tetany

Magnet Italian ryegrass (Lolium multiflorum L.), HiMag tall fescue (Festuca arundinacea Schreb.), and Mgwell orchardgrass (Dactylis glomerata L.) are the first cultivars bred for higher magnesium uptake (high-Mg) to reduce grass tetany risk for ruminants. The experiment was conducted to evaluate whether magnesium (Mg) uptake efficiency by high-Mg cultivars is limited to specific phosphorus (P) levels, and to optimize P level for individual selections of high-Mg grasses in nutrient culture. The high-Mg cultivars were compared with two existing commercial cultivars viz., Tachiwase and Waseyutaka, of Italian ryegrass, Kentucky-31 (Ky-31) and Fawn of tall fescue, and Akimidori and Okamidori of orchardgrass, respectively. One-month aged seedlings were grown in controlled conditions with three P treatments of 0.1, 1, and 5 mM for 10 days and nutrient contents were determined. Increasing P fertilization increased shoot weights of the grasses. Shoot potassium (K) content of the high-Mg cultivars was lower than the commercial cultivars. In contrast, the high-Mg cultivars were consistently higher in shoot calcium (Ca) and Mg contents when compared to the commercial cultivars, irrespective of species, over P fertilization. While the shoot Mg and Ca contents increased, the K content and K/(Ca + Mg) decreased with increasing P fertilization, regardless of cultivars. Across the P levels, the high-Mg cultivars always showed a K/(Ca + Mg) value lower than 2.2, a safer value for grass tetany in ruminants. Irrespective of grass species, increasing P level reduced the K/(Ca + Mg) and the value became lowest at 5 mM P level. The highest relative range for shoot Mg content was obtained in 5 mM P level for Italian ryegrass (37.6%), tall fescue (30.1%), and orchardgrass (47.9%). Our results indicate the effectiveness of using 5 mM P level for screening high-Mg cool-season grass seedlings.

Long Term Trends of Base Cation Budgets of Forests in the UK to Inform Sustainable Harvesting Practices

There is growing concern in the UK that available base cation pools in soil are declining due to the combined effects of acid deposition and forest harvesting. To help inform the issue, elemental mass balances for calcium (Ca), magnesium (Mg) and potassium (K) were calculated using more than 10-years (10–24 years) of data from the UK’s ICP Forest Intensive Monitoring Network (Level II) of plots, covering a range of soil types and three tree species—oak, Scots pine and Sitka spruce. Out of the ten sites investigated, small negative Ca balances were observed at three sites and negative K balances on two sites, all on acid geology and nutrient poor soils, which were previously heavily acidified due to acid deposition. There is sufficient Ca and K in the soil exchangeable pool to sustain forest growth on these sites, however, if the present rate of Ca and K loss continues forest health and productivity are likely to be threatened within a few forest rotations. Magnesium showed a positive balance at all but one site, partly sustained by marine deposition. Base cation budgets were significantly (p < 0.01) positively related to soil exchangeable cations and soil base saturation status. Six of the sites showed an increasingly statistically significant positive cation balance with time, attributed to a decline in leaching linked to recovery from acidification. This included the three sites with negative Ca balance, although Ca remained in deficit. One site (Alice Holt) exhibited a decreasing cation balance, driven by a continued significant decline in base cation deposition thought to be related to pollutant emission control. The results were used to simulate the impact of different forest biomass harvesting scenarios involving the removal of brown (extracted after needle drop) or green (extracted before needle drop) brash. Podzols and deep peats were found to be the most vulnerable to brash harvesting causing Ca and K imbalance, but problems also occurred on brown earths. Impacts were greatest for the extraction of green brash from higher productivity stands. Base cation balance calculations remain highly uncertain due to the restricted nature of available measurements and wide variation of some estimates, particularly inputs from mineral weathering. More data are required to check and improve model predictions to better guide forest harvesting practice and ensure sustainable forest management.

Vermiculite enriched by Fe(III) oxides as a novel adsorbent for toxic metals removal

Expanded vermiculite (EV) was modified by deposition of different spinel ferrite composites on the outer surface of EV 2:1 layers in order to improve its adsorptive properties. Modifications were made by deposition of: magnetite, manganese ferrite, cobalt ferrite and chromium oxide/hematite. The characterization of modified materials was performed by: scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET) methodology, X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), magnetization measurements, as well as determination of cation exchange capacity (CEC) and pH point of zero charge (pHPZC). Obtained samples were used as adsorbents for Pb2+, Ni2+and Cd2+ ions from an aqueous solution in a batch system. Results showed that adsorption capacity was strongly dependent on physical and chemical changes induced by specific chemical modification. Hydrothermally produced manganese and cobalt ferrites caused significant surface changes and altered the interlayer cation balance. Among the others, EV-Mn/Co-ferrite(s) samples possessed the highest adsorption capacity towards Ni2+ (33.06 mg g-1), along with an increase of the CEC. Freundlich's adsorption isotherm model provided the best fit of obtained experimental data, while kinetic studies showed that the adsorption rate follows the pseudo second-order model, implying heterogeneous adsorbents surface. Thermodynamic and kinetic parameters indicated that the mechanism of cations removal efficacy was dominantly followed by the ion exchange. This study confirmed that doped ferrites, produced by solvothermal method, improve surface properties of EV and increase adsorption potentials towards heavy metals.

Remineralization of a Dystric Ferralsol Using Basalt and Tephra Dusts, Effective Microorganisms Manure and NPK 20-10-10 for Radish (Raphanus sativus) Production in Bamougoum (Cameroon Western Highlands)

This paper studies the effect of basalt and tephra dusts, as alternatives to chemical fertilizers, on soil fertility and Radish (Raphanus sativus) production. The experiment was conducted in the field and in the laboratory in the years 2017 and 2018 on two separate plots so as to annul residual effects of fertilizers). The experimental design in the field was a randomized complete block design (56 m2 ), including five treatments and three replications: control (T0), basalt dust (T1), tephra dust (T2), effective micro-organism (EM) fertilizer (T3) and NPK 20-10-10 (T4). The main results show the following decreasing trend based on yield: T1>T3>T0>T4>T2. The best yields appear in T1 and T3 probably because they supplied the highest levels of soil nutrients to match the needs of the crops. Although T2 plants performed poorly, soil properties like pH.H2O (6.14 to 6.49), sum of exchangeable bases, base saturation, available phosphorus and cation balance were improved after tephra treatment. T2 plants might have performed poorly due to intrinsic properties of the tephra dust like low availability of trace elements compared to T1 and T3. T4 plants show the highest number of leaves, leaf area index and plant height. The Fe, Mn, Cu and Zn levels in bulbs and leaves will not pose danger of toxicity to human upon consumption and could serve as nutrient supplement for children and expectant mothers. The most profitable treatment is T1 permitting to recommend the popularization of basalt dust for radish cultivation as an alternative to chemical fertilizers.

The prevalence and practice of soil balancing among organic corn farmers

AbstractThe scientific community and most mainstream agriculturalists typically design fertilizer recommendations to provide a ‘sufficient level of available nutrients’ to meet the annual N, P and K requirements of common field crops. Soil balancing is another approach to managing soil fertility that focuses on the levels of Ca, Mg and K to achieve a desired base cation saturation ratio (BCSR). Soil balancing is believed to be practiced frequently by organic and other alternative farmers but is viewed skeptically by conventional agricultural scientists due to a lack of support for the idea in the published scientific literature. This study represents a pioneering effort to collect systematic data on the extent of soil balancing, how it is practiced and the types of outcomes reported by organic farmers. Our survey of over 850 farmers who grow certified organic corn in Indiana, Michigan, Ohio and Pennsylvania found that over half report using a soil-balancing approach based on BCSR. Their practice of soil balancing frequently includes more than management of base cations, but also uses a wide range of soil amendment products (such as purchased organic NPK fertilizers, micronutrients, microbial stimulants and soil inoculants) other than those applied specifically for cation balance. Farms that rely on vegetable and dairy production for most of their income, and Amish farmers who rely on horses for fieldwork, were more likely to report using a soil-balancing program. Self-described soil balancers perceived positive agronomic outcomes from the use of a BCSR program, including improvements in soil physical and biological properties and improved crop health and quality. Although farmers in our study report extensive use and positive perceived outcomes from soil-balancing methods, the scientific research literature has been unable to reproduce evidence that manipulating soil base cation levels has any systematic effect on crop yield. Future research could consider the interacting effects of BCSR with other field management practices to more closely approximate the actual practices of farmers.

Soil chemical properties affecting soybean yield on a nationwide scale in Japan

ABSTRACT Wide-area surveys have been conducted on a prefectural or regional scale in Japan for revealing soil chemical properties affecting soybean yield. However, they vary by region and thus, the common chemical factors through Japan remain unclear. This study aims to identify the soil chemical properties involved in soybean yield based on field data in various prefectures throughout Japan. We collected datasets of the topsoil chemical properties and soybean yields at 228 sampling points from 16 prefectures in Japan over the period of 2015–2017. The data sampling was conducted on two fields with different yield levels, namely high- and low-yield groups, which were managed by the same cooperating farmers in each point. We regarded the two fields at each point as a pair for a pairwise comparison. The average yield of the high- and low-yield groups was 3.1 t ha−1 and 2.5 t ha−1, respectively. The p-values of the pairwise comparison results were calculated via the Wilcoxon signed rank test. The differences of the exchangeable Mg (p= 0.040), and the Mg/K (p= 0.027) and Ca/Mg (p= 0.007) ratio between the high-yield and low-yield groups were statistically significant, whereas the other variables were not significant. The exchangeable Mg and Mg/K ratio were negatively related to yield, while the Ca/Mg ratio was positively related. The results suggested that excessive Mg for K or Ca adversely affects the soybean yield. As far as we know, there have been few reports focusing on the relation between the exchangeable cation, especially for the cation balance, and soybean yield. Our results may help researchers and producers deepen their understanding of the relationship between soil chemical properties and soybean yield.

Sophie Carenco

Sophie Carenco

What is the role of putrescine accumulated under potassium deficiency?

Biomarker metabolites are of increasing interest in crops since they open avenues for precision agriculture, whereby nutritional needs and stresses can be monitored optimally. Putrescine has the potential to be a useful biomarker to reveal potassium (K+ ) deficiency. In fact, although this diamine has also been observed to increase during other stresses such as drought, cold or heavy metals, respective changes are comparably low. Due to its multifaceted biochemical properties, several roles for putrescine under K+ deficiency have been suggested, such as cation balance, antioxidant, reactive oxygen species mediated signalling, osmolyte or pH regulator. However, the specific association of putrescine build-up with low K+ availability in plants remains poorly understood, and possible regulatory roles must be consistent with putrescine concentration found in plant tissues. We hypothesize that the massive increase of putrescine upon K+ starvation plays an adaptive role. A distinction of putrescine function from that of other polyamines (spermine, spermidine) may be based either on its specificity or (which is probably more relevant under K+ deficiency) on a very high attainable concentration of putrescine, which far exceeds those for spermidine and spermine. putrescine and its catabolites appear to possess a strong potential in controlling cellular K+ and Ca2+ , and mitochondria and chloroplasts bioenergetics under K+ stress.

Thoughts on acidification of soils by nitrogen and sulfur fertilizers

AbstractSome crops, like blueberries, require a pH of 4 to 5. Irrigation of acid‐loving crops with alkaline water can raise pH and cause micronutrient deficiencies. Diseases like citrus greening (Huanglongbing) are more severe at higher soil pH values. Application of acidifying fertilizers to lower soil pH may therefore benefit crop growth in such instances and release calcium from calcareous soils to remove sodium. Therefore, a good understanding of the processes involved and the amount of acidification from various fertilizer materials is needed. We show with an anion–cation balance of recent plant uptake data that the alkalinity released from plant uptake of nutrients alone gave a value of 2 kg CaCO3 equivalents of alkalinity per kilogram of N uptake, in close agreement with Association of Official Analytical Chemists values of 1.8. We also provide equations and calculations and a summary table that allows a user to compare the acidifying capacity of commonly available N and S fertilizers.

Gypsum Amendment to Soil and Plants Affected by Sodic Alkaline Industrial Wastewater Irrigation in Urban Agriculture of Ouagadougou, Burkina Faso

Low-quality water such as sodic alkaline industrial wastewater is often used to irrigate crops of intensively managed urban gardening systems in the semi-arid tropics to help meet the fresh food demands of a rapidly increasing city population. An on-farm experiment was established to examine the effects of sodium (Na) and bicarbonate (HCO3−)-loaded industrial wastewater on soil and crops on the one hand, and to determine melioration effects on soil condition and plant development on the other hand. To ameliorate the sodified soil, fine-powdered gypsum (CaSO4) was applied as soil amendment onto the upper soil (0–20 cm) before sowing of crops. Depending on soil pH and exchangeable sodium percentage (ESP), which reflected the level of soil degradation (SDL), two different amounts of gypsum were applied: 6.8 t ha−1 in moderate and 10 t ha−1 in high SDL plots. Subsequently rainfed maize (Zea mays L.) and irrigated spinach (Spinacia oleracea L.) under two irrigation water qualities (clean and wastewater) were cultivated. Chemical and physical soil parameters, as well as plant root density (RLD), crop yield and concentrations of major plant nutrients and Na were determined. The results showed that gypsum application reduced soil pH on average below 8 and reduced ESP below 18%. Furthermore, gypsum-treated soils showed a significant reduction of sodium absorption rate (SAR) from 14.0 to 7.9 and aggregate stability was increased from 44.2 to 51.2%. This in return diminished Na concentration in plant tissues up to 80% and significantly increased RLD of maize. Overall, calcium (Ca) addition through the gypsum amendment changed the soil cation balance by increasing the Ca:Mg ratio from 3.5 to 7.8, which likely influenced the complex interactions between competing cations at the exchange surfaces of the soil and cation uptake by plant roots.

Effects of whole-tree harvesting on soil, soil water and tree growth – A dynamic modelling exercise in four long-term experiments

Whole tree harvesting (WTH) following final felling of productive forests is increasingly promoted as a method to extract biomass for energy purposes. Despite its importance, there is a limited number of experimental studies investigating the impacts of WTH on forest ecosystem sustainability. Modelling studies have previously been carried out to complement and explain empirical observations from four long-term WTH experiments in Sweden. The literature shows a significant discrepancy between these studies, and open questions remain as to the fate of the base cations that are not removed in the absence of WTH. This study uses the integrated ecosystem model ForSAFE, which simulate a forest ecosystem’s biogeochemical processes and the feedbacks between these processes, to trace the fate of base cations for the said four long-term WTH experiments. The study shows that the model generally captures the observed effects of WTH on the stocks of base cations in the biomass and in the soil. The modelled results were also used to map how the base cations removed through WTH would otherwise (if left at the site) have been distributed in the ecosystem. The results indicate that the soil organic pool may be more important to the long-term base cation balance than the exchangeable pool, and should receive more attention in future research.

Soil acidity in the Argentine Pampas: Effects of land use and management

Soil acidification restricts crop yield in many regions. Our objective was to estimate what effect land use has had on soil acidity in the Pampean Region of Argentina. Sampling paired sites under contrasting land uses indicated that soils under trees had lower pH and much higher levels of exchangeable and total acidity than uncultivated controls under graminaceous vegetation up to 0.75 m depth. Cultivated soils did not present acidification as compared to controls. The meta-analysis of all available comparisons between agricultural soils and non-cultivated controls indicated that when agriculture advanced on soils that previously were under savanna-forest vegetation, pH increases of the topsoil occurred. Conversely, in soil previously under grassland, agriculture resulted in only minimum pH changes. The cation balance of cultivated soils was positive from 1870 to 2010. Only the potassium balance became negative since 1990 but its losses were compensated by the positive calcium, magnesium and sodium balances. The amount of protons produced by the agricultural use of soils increased exponentially from the 1970s due to the excess cation in an increasing crop production and a greater nitrogen fertilizer use. Conversely, the loss of organic matter from cultivated soils consumed protons, resulting in a negative proton balance in 140 years of cultivation, becoming positive only in recent years. In summary, trees produced a strong increase of soil acidity in Pampean soils, with a minimal effect of agriculture. Acidification under tree seems to be related to the alteration of the carbon cycle and is not permanent. The present proton budget would acidify cropped Pampean soils not buffered by carbonates.

Band Gap Engineering from Cation Balance: The Case of Lanthanide Oxysulfide Nanoparticles

Among the inorganic compounds, many oxides and sulfides are known to be semiconductors. At the crossroads of these two families, oxysulfide MxOySz compounds were much less investigated because they are scarce in nature and complex to synthesize. Amongst them, lanthanide oxysulfide Ln2O2S (Ln = lanthanide) are indirect bandgap semiconductors, with wide gaps, except Ce2O2S. (Gd,Ce)2O2S anisotropic nanoparticles with hexagonal structure were obtained over the whole composition range and exhibit colors varying from white to brown with increasing Ce concentration. Bandgap engineering is thus possible, from 4.7 eV for Gd2O2S, to 2.1 eV for Gd0.6Ce1.4O2S, while the structure is preserved with a slight lattice expansion. Surprisingly, due to the limited thickness of the lamellar nanoparticles, the bandgap of the nanoparticles is direct as validated by density functional theory on slabs. The fine control of the bandgap over a wide range, solely triggered by the cation ratio, is rarely described in the literature and highly promising for further development of this class of compounds. We propose a multi-regime mechanism to rationalize the bandgap engineering over the whole composition range. This should inspire the design of other bimetallic nanoscaled compounds, in particular in the field of visible light photocatalysis.

Arsenite phytoextraction and its influence on selected nutritional elements in one-year-old tree species

Trees have long been recognized as promising for arsenic phytoremediation, however, the most suitable traits of various tree species are still under examination. Therefore, the aim of the studies was to investigate the uptake and accumulation capabilities of As(III) by one-year-old trees from of species (Acer platanoides L., Betula pendula Roth., Quercus robur L., Ulmus laevis Pall) using hydroponic culture. A further aim was to analyse the influence of As(III) on the content of selected nutritional minerals, such as B, Ca, K, Mg, Na and Si.The highest accumulation of As(III) was detected in A. platanoides (BCF=2.16) and Q. robur (BCF=2.69). In A. platanoides >80% of total As(III) of the whole plant was accumulated in its stem while its TF was 10.8. Q. robur TF was 0.1 and it accumulated As(III) predominantly in its roots – >85% of total As(III) of whole the plant. The high As(III) accumulation capabilities of A. platanoides and its location predominantly in the stem classify this tree species as a hyperaccumulator and a good candidate for As(III) phytoextraction while Q. robur would be more suitable for phytostabilization and eco-restoration.As(III) uptake also caused alteration in the content of nutritional minerals. Decreased levels of B and Si were detected in the roots of most trees exposed to As(III) indicating the competition between these elements in the uptake process. In A. platanoides stems a high accumulation of As(III) resulted in a significant decrease of Si content in all the studied organs, suggesting that As(III) was transported from root to shoot predominantly by Si transporters.As(III) also led to a general alteration in the level of other macronutrients – e.g. an increase in the level of Na and K. The reactions varied between tree species and organs. Hence, As(III) uptake and accumulation results in a deterioration of cation balance and homeostasis, which could be one of the factors affecting the vitality of the examined trees.