Cation Saturation Research Articles

Soil solution composition affects microstructure of tropical saline alluvial soils in semi-arid environment

The remediation of soils stressed by salinity improves soil quality for food production. However, information on how remediation techniques affect microstructural stability/elasticity and resistance is lacking. Hence, the objective of this study was to characterize the microstructure of saline alluvial soils from a semi-arid environment, and to evaluate how the techniques of leaching soil and Na+ substitution by other cations affect the microstructure strength and elasticity evaluated by rheological techniques. Homogenized soil of sixteen horizons of four salinized soil profiles (an Abruptic Solonetz, a Eutric Gleysol, and two Hypereutric Planosols) were collected in Northeast of Brazil. Each horizon was analyzed separately in a completely randomized design, with three replications. The treatments corresponded to soils saturated with 1 × 10−4 mol m−3 of KCl (+K), CaCl2 (+Ca) or MgCl2 (+Mg), leaching of salts (LS) by successive leaching with alcohol 60%, and untreated soil (control). The soils were submitted to an amplitude sweep test with controlled strain in a compact modular rheometer. The obtained variables were strain and stress at the end of the linear viscoelastic interval (LVR) (γLVR and τLVR, respectively), strain (γYP) and stress (G’YP) at the yield point, shear stress (τmax), and integral Z (Iz). The rheological properties varied greatly between the horizons of the same soil profile. The LS increased γLVR compared to control, while the saturation with cations caused reduction in γLVR, especially in soils of higher clay content. The saturation with saline solution increased γYP and Iz, with greater effect in + K treatment. Both leaching of salts and cation saturation increased soil shear strength at the end of the LVR and at the yield point. Leaching of salts caused destabilization of soil microstructure, which is an important finding that needs to be addressed by measures accompanying remediation of salinized soils to maintain soil physical quality.

The cationization of synthetic polymers in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry: Investigations of the salt-to-analyte ratio.

Matrix-assisted laser desorption/ionization (MALDI) is a soft ionization technique that when used to analyze synthetic polymer analytes often requires the addition of a metal cationization agent (herein termed the "salt"). The choice of both the matrix and the cationization agent needs to be taken into account when considering the polymer under study; different polymers have shown different affinities toward different cationization agents, and their selectivity can change as the matrix changes. Salt-to-analyte ratio (S/A) plots are used in this work to investigate the effect of the quantity of cationization agent employed in the analysis of a poly (methylmethacrylate) (PMMA) analyte with different MALDI matrices. The point at which analyte signal stops increasing with the added cationization agent is termed the "cation saturation point," and it was found to occur around a S/A of 1. When the analyte signal after this point remains constant, it is termed an "ideal case." The "non-ideal case" occurs when the analyte signal decreases after the cation saturation point. The amount of matrix present (measured as the matrix-to-analyte molar ratio, M/A) and the use of different counterions for the salt are also found to affect the intensity of the analyte signal. In non-ideal cases, changes in the counterion or an increase in the M/A are found to increase the analyte signal, often converting an initially observed non-ideal case into an ideal case. Several experiments attempting to uncover the reason for observation of the non-ideal S/A behavior are also described.

Quantification of Mixed-Layer Clays in Multiple Saturation States Using NEWMOD2: Implications for the Potassium Uplift Hypothesis in the SE United States

AbstractQuantification of mineral assemblages in near-surface Earth materials is a challenge because of the often abundant and highly variable crystalline and chemical nature of discrete clay minerals. Further adding to this challenge is the occurrence of mixed-layer clay minerals, which is complicated because of the numerous possible combinations of clay layer types, as defined by their relative proportions and the ordering schemes. The problem of ensuring accurate quantification is important to understanding landscape evolution because mineral abundances have a large influence on ecosystem function. X-ray diffraction analysis of the variable cation-saturated clay fraction in soil and regolith from the Calhoun Critical Zone observatory near Clinton, South Carolina, USA, was coupled with modeling using NEWMOD2 to show that mixed-layer clays are often dominant components in the mineral assemblages. Deep samples in the profile (>6.5 m) contain mixed-layer kaolinite/smectite, kaolinite/illite-like, kaolinite-vermiculite, illite-like/biotite, and illite-like/vermiculite species (with ‘illite-like’ defined herein as Fe-oxidized 2:1 layer structure with a negative layer charge of ~0.75 per unit formula, i.e. weathered biotite). The 2:1 layers in the mixed-layer structures are proposed to serve as exchange sites for K+, which is known to cycle seasonally between plant biomass and subsurface weathering horizons. Forested landscapes have a greater number of 2:1 layer types than cultivated landscapes. Of two nearby cultivated sites, the one higher in landscape position has fewer 2:1 layer types. Bulk potassium concentrations for the forested and two cultivated sites show the greatest abundances in the surface forested site and lowest abundance in the surface upland cultivated site. These observations suggest that landscape use and landscape position are factors controlling the mixed-layer mineral assemblages in Kanhapludults typical of the S.E. United States Piedmont. These mixed-layer clays are key components of the proposed mechanism for K+ uplift concepts, whereby subsurface cation storage may occur in the interlayer sites (with increased negative 2:1 layer charge) during wetter reduced conditions of the winter season and as biomass decay releases cation nutrients. Cation release from the mixed-layer clays (by decreased 2:1 layer charge) occurs under drier oxidized conditions during the growing seasons as biota utilize cation nutrients. The types and abundances of mixed layers also reflect long-term geologic factors including dissolution/alteration of primary feldspar and biotite and the subsequent transformation and dissolution/precipitation reactions that operate within the soil horizons. Thus, the resulting mixed-layer clay mineral assemblages are often complex and heterogeneous at every depth within a profile and across landscapes. X-ray diffraction (XRD) assessment, using multiple cation saturation state and modeling, is essential for quantifying the clay mineral assemblage and pools for cation nutrients, such as potassium, in the critical zone.

Effect of Lime and Phosphorus Fertilizer on Soybean [<i>Glycine max L</i>. (Merrill)] Grain Yield and Yield Components at Mettu in South Western Ethiopia

Soil acidity and poor soil fertility are regarded as crop productivity limiting factors particularly in south western Ethiopia. Acidic soils limit the productive potential of crops because of low availability of basic cations and excess of hydrogen and aluminium in exchangeable forms. At the study area, soil acidity is a well-known problem limiting crop productivity. This, study was conducted to determine the effect of lime and phosphorus fertilizers on soybean yields and to explore the best treatments that can maximize the productivity of soybean. Factorial combinations of five lime levels (0, 1.41, 2.82, 4.23 and 5.64 t ha^-1) and four P levels (0, 10, 20 and 30kg P ha^-1) were laid out in Randomized Complete Block Design (RCBD) with three replications. Data on yield and yield components, were collected and analyzed using SAS version 9.3 software. Treatment means were compared at 5% level of significance using List Significant Different Test. The results revealed that Lime x phosphorus interactions were significant (p<0.01) for some yield and yield components. Findings showed that the application of phosphorus (30Kg/ha) significantly increased the plant height (67.03 cm), number of pods per plant (49), number of seeds per plant (77.67) above ground biomass (6160Kg/ha) and the grain yield (1828.44 Kg/ha). A combined application of phosphorous at 30 kg/ha and lime at 5.64 t ha^-1 had good response in reclaiming the soil and fostering the crop productivity, which is statically at pars with 4.23 lime t/ha and 30 P kg/ha. Study concluded that application of lime with phosphorus proved to be superior with respect to grain yield as well as other yield and growth parameters of soybean. The result of this study verified that application of lime and Phosphorus improved yield and yield related traits of soybean crop. In conclusion further study should be conducted to determine the response of different maturity group of soybean varieties to appropriate rates or combination of lime and phosphorus fertilizers which can maximize the productivity of the crop and reduce soil acidity problem in the study area and finally, the study should be conducted across different acid soil and the agricultural extension suggest the farmers as they apply lime based on the concentration of acid saturation cation until the best combination of lime and phosphorus will be determined.

Agricultural crop influences availability of nickel in the rhizosphere; a study on base cation saturations, Ni dosages and crop succession

Nickel availability in the soil is altered mainly by pH, which can indirectly be changed by base saturation (BS). The objective was to evaluate the effect of consecutive plants growth on Ni availability and enzymatic activities in the rhizosphere. It was evaluated the interaction between BS ratios (50% and 70%) and Ni application rates (0, 0.1, 0.5, 1.0, and 10.0 mg dm−3 of soil) on the availability of Ni in the rhizosphere. Two agricultural crops were grown in succession (soybean and sunflower). The effects of Ni rates and BS ratios on the activity of the urease and dehydrogenase in the soil were evaluated. Ni distribution in the bulk soil fractions was also investigated by Ni sequential extraction. The objective was to evaluate the effect of consecutive plants growth on Ni availability and enzymatic activities in the rhizosphere. It was observed the Ni availability was higher in the rhizosphere than bulk soil. The plant species have a large influence on the enzymatic activities in the rhizosphere. Urease activity was higher in the rhizosphere with BS70 under soybean growth, whereas for sunflower, BS50 lead to the highest urease activity, in all rates. The dehydrogenase activity was greater with BS70, regardless of plant species. The extractants Mehlich-1, Mehlich-3, and diethylenetriamine penta acetic acid (DTPA) showed comparable ability to estimate the available Ni fraction in the rhizosphere with a significant correlation with Ni accumulation in the grains. The Ni sequential extraction results showed the predominant effect of pH on the availability of Ni in bulk soil. Ni bound to organic matter (OM) was the fraction that showed the greatest BS influence. In soil under BS50, up to 20% of total Ni in the soil was bound to OM. Increasing Ni application rates to the soil increased the exchangeable fraction of Ni in the bulk soil up to 36-fold, but did not cause toxicity for either crops. Collectively, the results showed that nickel availability in rhizosphere affected urease and dehydrogenase activities, Ni uptake, and plant growth-related responses to different extents. Our work suggests that the rhizosphere should be evaluated for Ni monitoring in Ni-supplied agricultural areas.

Soil influences on uptake and transfer of pharmaceuticals from sewage sludge amended soils to spinach

Sewage sludge from wastewater treatment plants, which may contain various contaminants including pharmaceuticals, is often used as a soil amendment. These contaminants may subsequently be taken up by plants. In the present study we examined uptake of select pharmaceuticals from sewage sludge applied to soils by spinach plants. Seven soils were amended with sewage sludge from two wastewater treatment plants (A and B). Concentrations of compounds in plant tissues (roots and leaves) of spinach planted 45 days in these soils under greenhouse conditions were evaluated after harvest. The largest bioaccumulation in the roots and leaves was observed for sertraline (bioaccumulation factors (BAF) of 3.3–37.9 and 1–13.4, respectively), tramadol (1.3–10.0 and 4.8–30.0), and carbamazepine (2.2–17.2 and 6.1–48.8) and its metabolite carbamazepine 10,11-epoxide (not-quantified to 7.3 and 9.3–96.7). Elevated bioaccumulation in spinach roots was also identified for telmisartan (3.0–20.3) and miconazole (4.3–15.1), and leaves for metoprolol acid (not-quantified to 24.3). BAF values resulting from application of sludge B were similar to or moderately higher than BAFs from sludge A. The BAF values of carbamazepine and carbamazepine 10,11-epoxide in all tissues were negatively correlated with soil cation exchange capacity (CEC). This negative correlation between BAF and CEC was also observed for tramadol (A-roots and B-leaves), citalopram (B-roots), and telmisartan (B-roots) or between BAF and clay content for metoprolol acid (A-leaves and B-roots), tramadol (B-roots and A-leaves) and venlafaxine (B-roots). However, in the case of some other compounds (i.e. sertraline, amitriptyline, mirtazapine, metoprolol), uptake and the subsequent translocation and transformation from 3 soils of a higher pH and base cation saturation (Stagnic Chernozem Siltic, Haplic Chernozem and Greyic Phaeozem) significantly differed from 4 soils with a lower pH and base cation saturation (Haplic Luvisol, Haplic Cambisol, Dystric Cambisol and Arenosol Epieutric). Such observations proved strong compound dependent influences of soil conditions on various compounds bioaccumulations in plants and necessity of studying these processes always in diverse soils.

Ecological Processes Shaping Bulk Soil and Rhizosphere Microbiome Assembly in a Long-Term Amazon Forest-to-Agriculture Conversion.

Forest-to-agriculture conversion has been identified as a major threat to soil biodiversity and soil processes resilience, although the consequences of long-term land use change to microbial community assembly and ecological processes have been often neglected. Here, we combined metagenomic approach with a large environmental dataset, to (i) identify the microbial assembly patterns and, (ii) to evaluate the ecological processes governing microbial assembly, in bulk soil and soybean rhizosphere, along a long-term forest-to-agriculture conversion chronosequence, in Eastern Amazon. We hypothesized that (i) microbial communities in bulk soil and rhizosphere have different assembly patterns and (ii) the weight of the four ecological processes governing assembly differs between bulk soil and rhizosphere and along the chronosequence in the same fraction. Community assembly in bulk soil fitted most the zero-sum multinomial (ZSM) neutral-based model, regardless of time. Low to intermediate dispersal was observed. Decreasing influence of abiotic factors was counterbalanced by increasing influence of biotic factors, as the chronosequence advanced. Undominated ecological processes of dispersal limitation and variable selection governing community assembly were observed in this soil fraction. For soybean rhizosphere, community assembly fitted most the lognormal niche-based model in all chronosequence areas. High dispersal and an increasing influence of abiotic factors coupled with a decreasing influence of biotic factors were found along the chronosequence. Thus, we found a dominant role of dispersal process governing microbial assembly with a secondary effect of homogeneous selection process, mainly driven by decreasing aluminum and increased cations saturation in soil solution, due to long-term no-till cropping. Together, our results indicate that long-term no-till lead community abundances in bulk soil to be in a transient and conditional state, while for soybean rhizosphere, community abundances reach a periodic and permanent distribution state. Dominant dispersal process in rhizosphere, coupled with homogeneous selection, brings evidences that soybean root system selects microbial taxa via trade-offs in order to keep functional resilience of soil processes.

Metal cation saturation on montmorillonites facilitates the adsorption of DNA via cation bridging

Extracellular DNA (eDNA) is widely present in soil, with potential ecological impacts. Metal cations are naturally present on the surface of soil clay minerals, although the adsorption mechanism of eDNA on clay minerals saturated with metal cations is still not fully understood. The research investigated the adsorption of eDNA, using salmon sperm DNA as a representative, on metal cation (Na+, Ca2+, and Fe3+)-saturated montmorillonites (Mt). Metal cation-saturated Mt have higher adsorption capacities for DNA. Compared with Mt (3500 mg⋅kg−1), the amounts of DNA adsorption on metal cation-saturated Mt (pH = 7.0) were increased by 0.74–5.38 times, and followed the descending order of Fe-Mt > Na-Mt > Ca-Mt > Mt. A temperature of 25 °C was found to be more suitable than 15 and 35 °C for DNA adsorption, while an increasing pH value (3.0–9.0) reduced DNA adsorption on Mt and metal cation-saturated Mt. Microscopic and spectroscopic analyses, together with a model computation technique, confirmed that metal cations saturated on the surface of Mt work like a “cation bridge” linking oxygen atoms in the phosphate groups of DNA and the negatively charged moieties of Mt, which were predominantly bound through electrostatic forces, thus, facilitating DNA adsorption at pH > 5. The results of this investigation provide valuable insight into eDNA adsorption on soil clay minerals and the transport and fate of eDNA in the natural soil environment.

Characterization and Classification of Soils of the Terra da Esperança Settlement Project in Chapada do Apodi, Brazil

Soil characterization and pedological classification are essential to define its main potentials and restrictions. The objective of this work was to classify the morphological, physical, chemical, and pedological attributes of soils of the Terra da Esperan&amp;ccedil;a Settlement Project (TESP) in Chapada do Apodi, Brazil, and find the most sensitive attributes for distinguishing them using multivariate analysis. The research was carried out in the TESP, in the municipality of Governor Dix-Sept Rosado, state of Rio Grande do Norte, Brazil. Ten sites were chosen to open representative soil profiles: Native Forest Area 1 (NFA1), 2 (NFA2), and 3 (NFA3), Collective Area with Native Forest (CNF), Agroecological Area (AEA), Cashew crop Area (CCA) Collective Area with Pasture 1 (CAP1), and 2 (CAP2), Permanent Preservation Area (PPA), and Cajaraneira (Spondia sp.) Orchard Area (COA). Disturbed and undisturbed soil samples were collected and subjected to physical and chemical analysis for soil classification. The soils classes found were: Cambissolo Haplico Carbonatico vertissolico (NFA1), Cambissolo Haplico Carbonatico tipico (CNF, and AEA), Cambissolo Haplico Ta Eutrofico tipico (CAP2, NFA2, and COA), Cambissolo Haplico Ta Eutrofico vertissolico (NFA3), Argissolo Vermelho Distrofico latossolico (CCA), Chernossolo Rendzico Ortico saprolitico (CAP1), and Neossolo Fluvico Ta Eutrofico tipico (PPA). The material of origin of the soils contributed to the presence of a calcic horizon in the profiles NFA1, CNF, AEA, CCA (Cambissolos), and CAP1 (Chernossolos). The textural class of the soils varied from sand to clay. The Argissolo (CCA) presented acid character, high aluminum saturation, low base saturation, dystrophic character, and low cation exchange capacity, forming horizons with chemical limitations, due to its latossolico character. The most sensitive attributes for distinguishing the soil classes were related to the source material, which directly influenced the soil physical (silt and clay) and chemical (acidity, salinity, nutrient availability, and clay activity) attributes.

Effect of long-term organic and mineral fertilisation on selected physico-chemical soil properties in rye monoculture and five-year crop rotation

Abstract The research was carried out continuously since 1923 in a permanent fertilisation experiment at the Experimental Station of SGGW in Skierniewice. The objective of the research was to determine the effect of long-term fertilisation (Ca, CaNPK, NPK) and crop rotation systems (rye monoculture without fertilisation with manure and five-field rotation with legume crop and manure fertilisation) on selected physical and chemical soil properties. Long-term fertilisation caused various degrees of change in many physio-chemical properties in three soil horizons (Ap, Eet, Bt): pH in KCl, cation exchange capacity, total exchangeable bases, base saturation, content of carbon, nitrogen and mineral forms of nitrogen (NO3, NH4) as well as the carbon-nitrogen ratio. The combined manure and mineral fertilisation increased the sorption capacity, total exchangeable bases, base cation saturation and total content of C and N in comparison to organic or mineral fertilisation. As a result of lime application, an increase in these parameters was determined with the exception of total contents of carbon and nitrogen, showing no differences or a decrease. A positive effect was confirmed in five-field crop rotation, which improves physicochemical soil properties in comparison to cereal monoculture. The C:N ratio narrows down with growing depth because more nitrogen than carbon migrates down the soil profile.

Amazon forest-to-agriculture conversion alters rhizosphere microbiome composition while functions are kept.

The conversion of native forest to agriculture is the main cause of microbial biodiversity loss in Amazon soils. In order to better understand this effect, we used metagenomics to investigate microbial patterns and functions in bulk soil and rhizosphere of soybean, in a long-term forest-to-agriculture conversion. Long-term forest-to-agriculture led to microbial homogenization and loss of diversity in both bulk soil and rhizosphere, mainly driven by decreasing aluminum concentration and increased cations saturation in soil, due to liming and fertilization in long-term no-till cropping. Data revealed that long-term no-till cropping culminated in a decrease in Acidobacteria, Actinobacteria and Proteobacteria abundances. However, α- and β-Proteobacteria abundances were higher in the rhizosphere than in bulk soil, regardless of the time after forest-to-agriculture conversion. Changes in functional potential occurred predominantly in bulk soil, with decreases in functions related to potassium metabolism and virulence, disease and defense, while functions related to nucleic acids metabolism increased. Functions in the soybean rhizosphere remained stable, except for those related to potassium metabolism, which decreased after 20-year no-till cropping. Together, our results show that the soybean root system selects microbial taxa via trade-offs, to maintain functional resilience in the rhizosphere microbiome over time.

Assessment and suggestions for improvement of soils with different uses in a sector of Montesinho Natural Park, Portugal

The main objective of this study is to evaluate the quality of four soils with distinct uses and managements (pasture, cereal, chestnut and oak) to check whether their use is appropriate and propose improvements. The investigation took place at Vilar de Ossos, a sector of Montesinho Natural Park in northeast Portugal. Results were obtained from field work and laboratory analyses of more than 25 parameters (textural analysis, nitrogen, phosphorous and potassium contents, cation exchange capacity and cation saturation percentage, pH, organic matter, stoniness, useful soil depth, drainage, etc.). An estimation of erosion was also made following the universal soil loss equation. Pasture and oak registered low values on soil erosion while cereal and chestnut had medium values in the same parameter. With the data obtained, we made soil evaluations according to the Agrologic Classes and the Riquier Bramao and Cornet systems. Results indicate that only chestnut soil had low qualities for farming, and that cereal soils needed a change of use. Finally, based on the assessments, recommendations to improve soil quality have been made. For the pasture soil, the proposal is to put the focus on the nutritional values. In the cereal soil, conservation tillage is proposed. In the chestnut soil, stopping the current plowing technique is suggested and, in the oak soil, which is a natural soil, the proposal is to leave it in its current state.

Sorption of citalopram, irbesartan and fexofenadine in soils: Estimation of sorption coefficients from soil properties

The sorption of 3 pharmaceuticals, which may exist in 4 different forms depending on the solution pH (irbesartan in cationic, neutral and anionic, fexofenadine in cationic, zwitter-ionic and anionic, and citalopram cationic and neutral), in seven different soils was studied. The measured sorption isotherms were described by Freundlich equations, and the sorption coefficients, KF (for the fixed n exponent for each compound), were related to the soil properties to derive relationships for estimating the sorption coefficients from the soil properties (i.e., pedotransfer rules).The largest sorption was obtained for citalopram (average KF value for n = 1 was 1838 cm3 g−1) followed by fexofenadine (KF = 35.1 cm3/n μg1−1/n g−1, n = 1.19) and irbesartan (KF = 3.96 cm3/n μg1−1/n g−1, n = 1.10). The behavior of citalopram (CIT) in soils was different than the behaviors of irbesartan (IRB) and fexofenadine (FEX). Different trends were documented according to the correlation coefficients between the KF values for different compounds (RIRB,FEX = 0.895, p-value<0.01; RIRB,CIT = −0.835, p-value<0.05; RFEX,CIT = −0.759, p-value<0.05) and by the reverse relationships between the KF values and soil properties in the pedotransfer functions. While the KF value for citalopram was positively related to base cation saturation (BCS) or sorption complex saturation (SCS) and negatively correlated to the organic carbon content (Cox), the KF values of irbesartan and fexofenadine were negatively related to BCS, SCS or the clay content and positively related to Cox. The best estimates were obtained by combining BCS and Cox for citalopram (R2 = 93.4), SCS and Cox for irbesartan (R2 = 96.3), and clay content and Cox for fexofenadine (R2 = 82.9).

Historical perspective of soil balancing theory and identifying knowledge gaps: A review

The common philosophies that contextualize soil test results and fertilizer recommendations are sufficiency level of available nutrients, buildup and maintenance, and basic cation saturation ratio (BCSR). The BCSR approach postulates maintaining an ideal ratio of basic cation saturations on the soil exchange sites to maximize crop yields. The practice of adding amendments to alter the ratios of basic cation saturations in soils is called “soil balancing.” While the scientific community disregards this theory, some farmers, crop consultants, and commercial soil‐testing laboratories still use BCSR to guide their fertilizer recommendations. Earn 1 CEU in Soil &amp; Water Management by reading this article and taking the quiz at www.certifiedcropadviser.org/education/classroom/classes/537.

Agro-ecological implications of forest and agroforestry systems conversion to cereal-based farming systems in the White Nile Basin, Ethiopia

ABSTRACTThe Afromontane forests of southwest Ethiopia are high in endemism and biodiversity. However, the increasing human population and expansion of agricultural land have led to deforestation. We evaluated the effects of land use change on species composition, species diversity and soil fertility. Woody and herbaceous plant species were recorded in natural forest, agroforestry and cropland at different altitudes, using 15 plots with three replicates. A total of 90 soil samples were taken. In total, 77 woody and herbaceous species have been recorded. The selective felling of trees and shrubs in the agroforestry system to favor coffee growth through enhanced light penetration also favors grass and herb diversity. A Factor Analysis based on the soil characteristics shows a gradient in soil fertility from both forests and agroforestry to croplands. The bulk density, pH, organic C, total N, available P, cation exchange capacity and base cations saturation of the forest soil are equivalent with that of agroforestry. However, forests and agroforestry are significantly different from croplands regarding those soil characteristics. Therefore, this study suggests that the agroforestry practices are important for keeping biodiversity and soil fertility at levels which are similar to the natural forest.

Effect of basic cation saturation ratios in soil on yield of annual ryegrass (Lolium multiflorum L.)

Effect of basic cation saturation ratios in soil on yield of annual ryegrass (Lolium multiflorum L.)

Effect of basic cation saturation ratios on the Mg, K and Ca content of annual ryegrass (Lolium multiflorum L.)

Effect of basic cation saturation ratios on the Mg, K and Ca content of annual ryegrass (Lolium multiflorum L.)

Historical Perspective of Soil Balancing Theory and Identifying Knowledge Gaps: A Review

Core Ideas A soil with an ideal basic cation saturation ratio (BCSR) is said to maximize crop yields. Previous studies concluded higher crop yields are possible over a wide range of ratios. Scientific community generally disregards BCSR theory. Soil balancing effects on weeds, soils, and crop quality are critical knowledge gaps. The common philosophies that contextualize soil test results and fertilizer recommendations are sufficiency level of available nutrients (SLAN), buildup and maintenance, and basic cation saturation ratio (BCSR). The BCSR approach postulates maintaining an ideal ratio of basic cation (Ca2+, Mg2+, and K+) saturations on the soil exchange sites to maximize crop yields. The practice of adding amendments to alter the ratios of basic cation saturations in soils is called “soil balancing.” Bear, Graham, and Albrecht promoted this concept, with each suggesting a desired saturation ratio of Ca:Mg:K for optimum crop yields. Several researchers have tried to validate this theory with both greenhouse and field experiments but could not conclude that an ideal cation saturation ratio existed and found that crop yields were similar across a wide range of ratios. While the scientific community disregards this theory, some farmers, crop consultants, and commercial soil‐testing laboratories still use BCSR to guide their fertilizer recommendations. It is believed that soil balancing effectively controls weeds, insects, and pests and improves overall soil health for better plant growth, ultimately producing better crop yields. Some even argue that soil balancing improves nutritional quality of the harvested crop. However, contemporary research to objectively demonstrate such perceived benefits of practicing soil balancing is missing. This review presents a holistic overview of soil balancing, presents a literature review on BCSR, and identifies knowledge gaps, which need to be addressed to better understand the merits and limitations of soil balancing.

Alterações na fertilidade de um solo sob diferentes usos na região de Brasnorte - MT

A conversão da cobertura vegetal natural provoca alterações nas propriedades químicas do solo, de forma a melhorá-las ou degradá-las. Este estudo teve como objetivo avaliar as modificações nas propriedades químicas do solo sob diferentes coberturas vegetais, tendo como referência a Floresta Secundária, bioma Cerrado. A pesquisa foi realizada no município de Brasnorte - MT, analisando os sistemas: Floresta Secundária (FS); cultivo de Teca (Tectona grandis) de 19 anos, 16 anos, 13 anos e 8 anos; e Pastagem (PA). Foi utilizado o delineamento em blocos casualizados em esquema fatorial, com as coletas das amostras de solo em três profundidades (0 - 5, 5 - 10 e 10 - 20 cm) e, posteriormente, feitas as análises químicas. A retirada da vegetação nativa para implantação de cultivo de Teca e de Pastagem alterou as propriedades químicas do solo. O solo sob a Floresta Secundária apresentou os maiores teores de Ca2+, K+ e de P, os maiores valores de soma de bases, de capacidade de troca de cátions e de saturação por bases na camada de 0 - 5 cm. Os solos sob a Pastagem e sob o cultivo de Teca com 13 anos apresentaram os maiores teores de COT na camada de 0 - 5 cm, em razão da matéria orgânica formada nos dois casos.

Assessment of the maximum allowed acid deposition load at current stage in China

Soil acidification caused by acid deposition has been significant in some forests in southern China. We present an approach for assessing the current stage maximum allowed load (SML) of acid deposition for terrestrial system in the country. The main idea was that soil base cation exchange as a finite buffer to acidity was included in the soil acidity mass balance calculation at current acidification stage. We calculated the SML for five forests in southern China. The usual critical loads for the same forests were also calculated by the steady state mass balance model for comparison. The results showed that the SML is a more tolerant limit than the critical load for the forests with soils not acidified seriously at current stage. However, the SML become a more stringent limit to acid deposition when the forest soils have acidified seriously to very low base cation saturation. In this case the SML assessment is beneficial for the soils recovering from a serious acidified state. Based on a national scale database, the SML mapping for non-agricultural soil system in China was carried out.