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Soil organic carbon (SOC) dynamics depend on soil properties derived from the geoclimatic conditions under which soils develop and are in many cases modified by land conversion. However, SOC stabilization and the responses of SOC to land use change are not well constrained in deeply weathered tropical soils, which are dominated by less reactive minerals than those in temperate regions. Along a gradient of geochemically distinct soil parent materials, we investigated differences in SOC stocks and SOC (Δ14C) turnover time across soil profile depth between montane tropical forest and cropland situated on flat, non‐erosive plateau landforms. We show that SOC stocks and soil Δ14C patterns do not differ significantly with land use, but that differences in SOC can be explained by the physicochemical properties of soils. More specifically, labile organo‐mineral associations in combination with exchangeable base cations were identified as the dominating controls over soil C stocks and turnover. We argue that due to their long weathering history, the investigated tropical soils do not provide enough reactive minerals for the stabilization of C input in either high input (tropical forest) or low‐input (cropland) systems. Since these soils exceeded their maximum potential for the mineral related stabilization of SOC, potential positive effects of reforestation on tropical SOC storage are most likely limited to minor differences in topsoil without major impacts on subsoil C stocks. Hence, in deeply weathered soils, increasing C inputs may lead to the accumulation of a larger readily available SOC pool, but does not contribute to long‐term SOC stabilization. [ABSTRACT FROM AUTHOR]

Quartz is one of the most common minerals in soils, mostly present in sand and silt fractions. Although quartz is basically formed of SiO2, other elements can be easily detected and assessed nowadays using a portable X-ray fluorescence (pXRF) spectrometer. Our study aims to evaluate the chemical composition of different quartz varieties, identifying their main elements, and relating them to soil attributes. Six quartz varieties (hyaline, amethyst, milky, rose, smoky, and ferriferous) were analyzed via pXRF and 13 oxides/trace elements were identified and used for quartz discrimination (Al2O3, CaO, P2O5, SiO2, Cl, Cr, Fe, K2O, Mn, Rb, S, Ti, and V). Hyaline quartz was characterized by the highest SiO2 and the lowest contents of other elements. Al2O3 was the second-highest compound present in all varieties of quartz, reaching 21,547 mg kg−1 in the smoky variety. S, P2O5, Cl, SiO2, and K2O were the main components determined by Random Forest algorithm for discriminating quartz varieties. Some elements detected may serve as a reserve of nutrients to plants to be released in soils along weathering, depending on quartz particle size, soil texture, leaching, and associated attributes. pXRF enhanced the information on chemical characterization of quartz varieties, without the generation of chemical pollutants. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the attributes of natural fertility and intrinsic fragility of the soils of Ivinhema River Basin (BHI), to subsidize agricultural development projects and environmental control and monitoring bodies. For this purpose, 62 soil samples were collected, at a depth of 0 to 20 cm, in areas of native vegetation belonging to the state of Mato Grosso do Sul - Brazil. The characteristic climate of the study area is of the humid mesothermal subtype (Cfa) without drought. The predominant vegetation is of the Cerrado type and the geological substrate is predominantly composed of the Serra Geral and Caiuá Formation. The samples were air-dried and the physical attributes (sand, silt, and clay) and chemical variables (pH H2O, CaCl2, KCl, pH, Al3+, m%, H + Al, Ca2+, Mg2+, K+, CEC, SB, V%, OC, P, Cu, Fe, Mn, and Zn) were determined according to methodologies in Embrapa's soil analysis methods manual. The data obtained were evaluated by descriptive statistics and principal component analysis. The results showed a great variety of soils inside the basin, whose natural fertility was high for the Leptsol, Regosol, and Nitisol soils, and low for the Argiluvic Plinthosol, Petroplinthic Plinthosol, and Planosol soils. The sandy soils showed lower levels of organic carbon and negative surface loads, which shows less capacity to retain cations essential to plant nutrition and less retention of environmental contaminants if any. Regarding the textural fragility of the soils of BHI, it was possible to verify the high sensitivity of the soil to erosion and susceptibility to the contamination of groundwater or infiltrated water. The data shown in research can fill the gaps of knowledge and/or for adapting conservation practices of agricultural soils that are more susceptible to erosive processes, as well as for environmental control and monitoring bodies and/or studies of area recovery and maintenance of soil fertility. [ABSTRACT FROM AUTHOR]

The current Brazilian copper (Cu) and zinc (Zn) prevention values (PV) for soil quality do not take into account the ecotoxicological impacts on soil organisms, which suggests these guiding values may not be protective of soil ecological trophic levels. This study assessed the acute (mortality) and chronic toxicity (reproduction), as well as the cumulative (bioaccumulation) potential of Cu and Zn (pseudo-total and available fractions) for earthworms Eisenia andrei in a Tropical Artificial Soil (TAS) and two tropical field soils (Oxisol and Alfisol). Toxicity data based on pseudo-total fractions were compared to PV. The Lowest Observed Effect Concentrations (LOEC) for the mortality endpoint were found at Cu and Zn concentrations higher than their PV (60 and 300 mg kg−1, respectively), regardless of the soil type. However, concentrations lower than PV reduced the reproduction of E. andrei by 20% (compared to the controls) for Cu in all tested soils (EC20s from 31.7 to 51.2 mg kg−1) and by 50% for Zn in Oxisol and Alfisol (EC50s = 225 and 283 mg kg−1, respectively). In TAS, only the EC20 (273 mg kg−1) for Zn was lower than PV. Increases of Cu in earthworm tissues occurred at concentrations higher than PV in all tested soils (LOEC values from 70 to 107 mg kg−1). The same was observed for Zn in TAS (LOEC = 497 mg kg−1), while in the field soils, the increases of Zn in earthworm tissues were lower than PV (LOEC = 131 and 259 mg kg−1 in Alfisol and Oxisol, respectively). We suggest the following: (1) The current Brazilian PV for Cu and Zn are not protective for earthworms (E. andrei) in the field soils tested; (2) PV derived from ecotoxicological assays in artificial soil cannot be representative for Brazilian field soils; (3) Using PV based on the pseudo-total fraction, without a soil-type normalizing factor, may limit the representativeness of this threshold for different soil types. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the emission factor of N2O, CH4, and the volatilization of NH3 for the combination of feces or urine with increasing doses of ammonium nitrate in tropical palisade grass pastures. The emission of greenhouse gases was assessed in eight treatments combining feces and urine with doses (75 and 150 kg of N ha−1) of ammonium nitrate, (32% N). The emission factor of N2O was 0.11, 0.19, and 0.17% for feces, urine, and 75 kg N ha−1 year−1 (as ammonium nitrate) and showed an additive linear effect when feces or urine were combined with increasing doses of N fertilizer. The emission factor of CH4 of feces (0.18 kg CH4 animal−1 year−1) was similar irrespective of combination with ammonium nitrate. The N loss by volatilized NH3 has a decreasing linear effect (p < 0.05) for the combination of feces or urine with ammonium nitrate. We concluded that N2O and CH4 emission factors of feces and urine in tropical climate conditions are lower than those reported by the IPCC. However, their N2O emission factors are sharply enhanced when combined with ammonium nitrate. These results may contribute to improvements in national and regional greenhouse gas inventories of livestock production. [ABSTRACT FROM AUTHOR]

Soils interact in many ways with metal ions thereby modifying their mobility, phase distribution, plant availability, speciation, and so on. The most prominent of such interactions is sorption. In this study, we investigated the sorption of Pb, Cd, and Cu in five natural soils of Nigerian origin. A relatively sparsely used method of modelling soil-metal ion adsorption, i.e. adaptive neuro-fuzzy inference system (ANFIS), was applied comparatively with multiple linear regression (MLR) models. The isotherms were well described by Freundlich and Langmuir equations (R2 ≥ 0.95) and the kinetics by nonlinear two-stage kinetic model, TSKM (R2 ≥ 0.81). Based on the values delivered by the Langmuir equation, the maximum adsorption capacities (Qm*) were found to be in the ranges 10,000–20,000, 12,500–50,000, and 4929–35,037 µmol kg−1 for Cd, Cu, and Pb, respectively. The study revealed significant correlations between Qm* and routinely determined soil parameters such as soil organic carbon (Corg), cation exchange capacity (CEC), amorphous Fe and Mn oxides, and percentage clay content. These soil parameters, combined with operational variables (i.e. solution/soil pH, initial metal concentration (Co), and temperature), were used as input vectors in ANFIS and MLR models to predict the adsorption capacities (Qe) of the soil-metal ion systems. A total of 255 different ANFIS and 255 different MLR architectures/models were developed and compared based on three performance metrics: MAE (mean absolute error), RMSE (root mean square errors), and R2 (coefficient of determination). The best ANFIS returned MAEtest 0.134, RMSEtest 0.164, and R2test 0.76, while the best MLR returned MAEtest 0.158, RMSEtest 0.199, and R2test 0.66, indicating the predictive advantage of ANFIS over MLR. Thus, ANFIS can fairly accurately predict the adsorption capacity and/or distribution coefficient of a soil-metal ion system a priori. Nevertheless, more investigation is required to further confirm the robustness/generalisation of the proposed ANFIS. [ABSTRACT FROM AUTHOR]

Agricultural soils may become polluted by heavy metals as a result of receiving a significant amount of pollutants from different sources of land applications, such as fertilizers, animal manure, sewage sludge, pesticides, and wastewater irrigation. Given that information on the distribution of heavy metals (HMs) in the Piedemonte Llanero of Colombia is still quite limited, the main objectives of this work were to characterize the content of these elements and their potential pollution level in acidic soils under different agricultural systems. The hypothesis is to verify if the type of land use poses an environmental threat. To achieve these goals, the concentrations of seven metals were determined in the soils of three agricultural production systems: oil palm, pastures, and semi-annual crops. Soil contamination was evaluated based on the Geo-Accumulation Index (I-geo), contamination factor (CF), Pollution Load Index (PLI), and Nemerov Integrated Pollution Index (NIPI). One outstanding result was that the average concentrations of HMs in the collected topsoil samples were as follows: Mn (110.5 mg kg-1), Zn (31.93 mg kg-1), Cr (8.85 mg kg-1), Ni (11.68 mg kg-1), Cu (11.28 mg kg-1), Pb (9.42 mg kg-1) and Cd (0.21 mg kg-1). The results obtained from this study provide an estimation of the pollution status of HMs. Agricultural activities, especially the overuse of phosphate fertilizer, were the main source of nutrients across the study area. This information can become a fundamental tool to establish monitoring and follow-up processes for sustainable soil management in the Piedemonte Llanero. In conclusion, the present study highlights and provides specific information in a hyperhumid environment.

Many biogeochemical processes are modulated by dissolved organic matter (DOM), but the drivers influencing the chemodiversity of DOM compounds in Amazonian soils are poorly understood. It has also been theorized whether deforestation controls the decline of DOM. In this study, we collected soil samples from thirty sites across different regions of Brazil’s Legal Amazon, and we investigated the trade-offs among soil physical–chemical properties and DOM chemodiversity. We employed optical spectroscopy, Fourier transform ion cyclotron resonance, and multivariate analysis. Our results indicated that, despite variations in land use and soil physical–chemical properties, factors such as the deforested site, geometric mean diameter, weighted average diameter, and soil organic carbon were the main influencers of DOM chemodiversity variation. These findings highlight the importance of considering DOM chemodiversity as closely related to land use and its potential use in developing deforestation models for predicting soil quality decline in Brazil’s Legal Amazon.

Soils on many smallholder farms in Southern Africa are severely depleted in plant nutrients, in particular phosphorus (P), following years of maize monocropping with little or no fertilizer input. Past studies suggest that pigeon pea (Cajanus cajan (L.) Millsp.) may increase plant-available P. Pigeon pea is not a common crop in much of Southern Africa, and the effect of locally grown pigeon pea varieties on plant-available P is unknown. We assessed the changes in plant-available P after growing pigeon pea varieties MPPV-2, MPPV-3, and Babati White in Zambia, viz. Lixisols of Choma and Mkushi, Acrisols of Chipata and Kasama, and Arenosols of Kaoma. The selected soils were not fertilized. Baseline soils (0–20 cm), sampled after long-term maize monocropping and soils from the same fields after growing pigeon pea were collected from field trials in Kaoma, Chipata, Choma, and Mkushi and analyzed for plant-available P. Further, a greenhouse study was conducted with soils from Kasama, Choma, Kaoma, and Chipata, under which soil P was determined before and after growing pigeon pea, soybean (Dina), and maize (SC 419) without fertilizer addition. Pigeon pea under field studies had no significant (p > 0.05) effect on plant-available P in Choma, Kaoma, and Chipata. In Mkushi, pigeon pea cropping resulted in a 47.5% significant decline (p ≤ 0.05) in plant-available P, amounting to a loss of 11.2 kg ha−1. The greenhouse study showed a significant decline (p ≤ 0.001) in plant-available P after seven weeks of maize growth, while there was no significant (p > 0.05) effect on plant-available P after soybean and pigeon pea cropping. The latter was primarily due to the significantly higher P uptake associated with larger biomass production of maize after seven weeks in the greenhouse. During the initial seven weeks, pigeon pea biomass had significantly higher P concentrations than maize. Thus, P deficiency symptoms were exhibited in maize, while pigeon pea appeared healthy. However, mobilized P, calculated as the sum of plant P and soil P after cropping minus soil P before planting, was significantly lower (p ≤ 0.01) in pigeon pea compared to soybean and maize. Synthesizing field and greenhouse experiments suggests that there is a low net decline of plant-available P from soils after pigeon pea cropping. Therefore, rotation with these pigeon pea varieties could be beneficial to resource-poor farmers due to low P removal and its ability to grow in P-deficient soil.

In the tropics, anthropogenic activities can lead to water and wind erosion, a loss of biodiversity, and a reduction in sequestered carbon, fertility, and organic matter content in the soils concerned, potentially resulting in their degradation. This study therefore aims to identify the mechanisms used by plant species to restore degraded tropical soils and plant species characteristics that are best suited to achieve this through a critical scoping review of the peer-reviewed literature. Soil restoration leads to the re-establishment of ecosystem services and an increase in soil production potential, the regeneration of biodiversity, the stopping of organic matter losses, and the creation of favorable conditions for carbon sequestration and nitrogen fixation. The choice of appropriate plant species depends on the restoration objectives to be achieved. Five key mechanisms by which plant species contribute to restore degraded tropical soils include: (1) nitrogen fixation, (2) carbon sequestration, (3) organic matter addition, (4) structure stabilization, and (5) erosion control. The main characteristics of plant species and vegetation involved in these mechanisms are (a) the capacity to form symbiotic associations with N-fixing bacteria and mycorrhizae, (b) the production of abundant root biomass releasing litter and exudates, (c) roots having a high length density, branching intensity, and depth distribution, (d) the production of an abundant and easily decomposed above ground litter, (e) the production of a vast canopy, and (f) the presence of different vegetation strata. Targeting these characteristics will contribute to acting on several mechanisms simultaneously, which will increase the chance of success in tropical soil restoration.

BACKGROUND AND OBJECTIVES: Soil is the most important basic natural resource for the support of agricultural production systems. Productivity maintenance in these ecosystems depends on their physicochemical. However, there are no significant studies on the current status of soil fertility and quality in tropical areas vulnerable to climate change and lacking management practices. The purpose of this study was to assess the physical and chemical properties of the soil to propose guidelines on soil handling and management in tropical areas.METHODS: Data on texture, macronutrients, micronutrients, and cation ratios were collected at 200 farms in the Sucre Department of Northern Colombia. Correlation analysis and principal component analysis were performed on the resulting data set, and a soil quality index was calculated.FINDING: Macronutrients N, P, K, S, Ca, Mg, and Na displayed average values of 21.65 ± 10.65 part per million, 40.35 ± 67.21 part per million, 0.46 ± 0.43 meq/100g, 7.94 ± 28.35 part per million, 15.63 ± 17.30 meq/100 g, 5.63 ± 3.58 meq/100g, 0.19 ± 0.20 meq/100g, respectively. Micronutrients Cu, Fe, Zn, and Mn displayed average values of 2.20 ± 1.66 part per million, 48.05 ± 37.87 part per million, 1.16 ± 1.26 part per million, 14.22 ± 12.24 part per million, respectively. The predominant texture among assessed soils was sandy clay loam. A significant correlation was found between (Ca/Mg) K-Ca/K, (Ca/Mg) K-Mg/K, Fe-Cu, and Ca-cation exchange capacity. The soil quality index of the soils assessed in the Department of Sucre indicates a high level of quality, which is strongly influenced by the indicators S, P, Mn (≥ 0.90) Fe, Zn, Cu, K, Na (≥ 0.80).CONCLUSION: The macronutrients displayed a deficiency of potassium. It is therefore recommended to monitor these soils and apply fertilization plans according to the needs of each assessed soil. Lastly, this study provides relevant information for proposing guidelines for crop improvement.

Sugarcane (Saccharum officinarum) is an important crop for generating fiber, biofuel and other bioproducts. Brazil is the largest sugarcane producer in the world; however, limited knowledge is available with respect to soil erosion in the sugarcane cropping system. This study reviews the soil erosion rates in sugarcane cropping and evaluates the effects of soil management and land conversion on soil erosion. Eighteen studies (using conventional tillage) reporting 43 outcomes of soil erosion rates were examined using the Scopus® database. Different methods were used to measure soil erosion yielded different soil loss rates; highest values were recorded in the natural rain method, i.e., experimental plots with a median of 28 Mg ha−1 yr−1, were obtained followed by modeling with 9.3 Mg ha−1 yr−1 and simulated rain with 2 Mg ha−1 yr−1. The median soil loss using all data (n = 43) obtained by the three methods was 7.2 Mg ha−1 yr−1. The soil type increases soil erosion; the sugarcane cropping system is practiced over the most erodible Brazilian soils (e.g., Ultisols and Oxisols) where sand fraction is dominant, particularly fine sand. Most studies focused on rainsplash and interrill erosion. However, rill, ephemeral and permanent gullies should be examined, particularly in sugarcane-cropping areas.

ABSTRACT Termites can create structures that alter the physical and chemical properties of soils. In this process, termites are selective about the soil constituents they will use to construct their mounds. Considering the common occurrence of termite mounds in Brazilian soils, this study aimed to investigate the selective action of termites in the mound building process. Samples were collected from six termite mounds and control soils (at a distance of 15 to 30 m from the termite mound) in different regions in Brazil to analyze the fine earth fraction. The content of clay fraction, organic C and Fe in pedogenic iron oxides increased in the mounds resulting in specific surface area increments. X-ray diffraction indicated a selectivity of termites by clay-sized particles such as kaolinite, gibbsite and iron oxides (hematite and goethite) rather than larger particles such as quartz. The proportion of low-crystalline iron oxides and the maghemite amount decreased in the mounds. The change of color parameters in the termite mounds was due to a combination of increase in clay fraction, organic carbon and iron oxides. The techniques used were sensitive, indicating changes and similarities between the control soils and the termite mounds.

Temperature is a key factor that influences pesticide degradation. Extrapolating degradation half-lives (DT50) measured at a given temperature to different temperatures remains challenging, especially for tropical conditions with high temperatures. In this study, the use of the standard Arrhenius equation for correcting temperature effects on pesticide degradation in soils was evaluated and its performance was compared with that of alternative Arrhenius-based equations. To do so, a database of 509 DT50 values measured between 5 and 35 °C for 32 pesticides on tropical and temperate soils was compiled for the first time through an extensive literature search. The temperature correction models were fitted to the database using linear mixed regression approaches that included soil type and compound effects. No difference in the temperature dependence of DT50 between tropical and temperate soils was detected, regardless of the model. A comparison of the prediction performances of the models showed that constant activation energy (Ea) cannot be considered valid for the whole range of temperatures. The classical Arrhenius equation with an Ea of 65.4 kJ.mol−1, as recommended by the European Food Safety Authority (EFSA), was shown to be valid for correcting the DT50 only for temperatures ranging from 5 to 20 °C. However, for temperatures greater than 20 °C, which are common in tropical environments, the median Ea was significantly lower at 10.3 kJ.mol−1. These findings suggest the need to adapt the standard temperature correction of the European pesticide risk assessment temperature procedure when it is applied in tropical settings. [ABSTRACT FROM AUTHOR]

Based on the detailed geochemical studies of 184 soil samples from Periyar River Basin (PRB), a tropical monsoon dominated river basin (5398 km2) in the southern western Ghats (WGs) of India, a baseline reference data is established. The soils are mildly acidic with sandy loam and silt loam facies in non‐monsoon to sandy loam and sandy clay loam in monsoon. The mean metal concentrations follow the upper continental crust and world shale values. The Geoaccumulation index (Igeo) shows unpolluted to moderately polluted category, except for Cu, Zn, and Ba, while Enrichment Factor (EF) indicates no to minor enrichment for all elements. Contamination factor (Cf) indicates low to considerable contamination for V, Rb, Sr, Ni, and low to very high contamination for Cu, Zn, and Ba. Three significant components are extracted by Principal Component Analysis (PCA), explaining 78.09% and 74.10% of the total variance for monsoon and non‐monsoon seasons. Ti, Al, Fe, Ca, Na, K, V, Cr, Ni, Sr, and Ba exhibited common source of origin while anthropogenic origin is identified for Zn and Cu. The study will provide valuable information into the pedological characteristics of WGs river basins. [ABSTRACT FROM AUTHOR]

Background: C:N:P homeostasis in plants guarantees optimal levels of these nutrients in plant metabolism. H However, one of the causes to the effects of deficit irrigation is the loss of C:N:P homeostasis in leaves and stems that causes reduction in the growth of sugarcane. Being able to measure the impact of water deficit on C:N:P homeostasis in plants from the stoichiometric ratios of the concentrations of these nutrients in leaves and stems. This loss causes a decrease in nutritional efficiency, but can be mitigated with the use of silicon. Silicon favors the homeostasis of these nutrients and crop productivity. The magnitude of this benefit depends on the absorption of Si by the plant and Si availability in the soil, which varies with the type of soil used. Thus, this study aims to evaluate whether the application of Si via fertigation is efficient in increasing the absorption of Si and whether it is capable of modifying the homeostatic balance of C:N:P of the plant, causing an increase in nutritional efficiency and consequently in the production of biomass in leaves and stems of sugarcane ratoon cultivated with deficient and adequate irrigations in different tropical soils. Results: Water deficit caused biological losses in concentrations and accumulation of C, N, and P, and reduced the nutrient use efficiency and biomass production of sugarcane plants cultivated in three tropical soils due to disturbances in the stoichiometric homeostasis of C:N:P. The application of Si increased the concentration and accumulation of Si, C, N, and P and their use efficiency and reduced the biological damage caused by water deficit due to the modification of homeostatic balance of C:N:P by ensuring sustainability of the production of sugarcane biomass in tropical soils. However, the intensity of attenuation of such deleterious effects stood out in plants cultivated in Eutrophic Red Oxisols. Si contributed biologically by improving the performance of sugarcane ratoon with an adequate irrigation due to the optimization of stoichiometric ratios of C:N:P; increased the accumulation and the use efficiency of C, N, and P, and promoted production gains in biomass of sugarcane in three tropical soils. Conclusion: Our study shows that fertigation with Si can mitigate the deleterious effects of deficient irrigation or potentiate the beneficial effects using an adequate irrigation system due to the induction of a new stoichiometric homeostasis of C:N:P, which in turn improves the nutritional efficiency of sugarcane cultivated in tropical soils. [ABSTRACT FROM AUTHOR]

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Calcium (Ca) and potassium (K) are essential nutrients for plant growth but the antagonistic effect between these nutrients may reduce crop yield. A two–year field trial was carried out in a loamy sand soil to evaluate cassava response to Ca (0, 50, 100, and 200 kg ha−1, as ground limestone, GL) and K (0, 50, 100, and 200 kg K 2 O ha−1, as potassium chloride, KCl). Calcium addition, especially 200 kg Ca ha−1, adversely affected soil K availability with more pronounced on water–soluble K than on exchangeable and non–exchangeable K from day–7 onwards. Both Ca and K had no antagonistic impact on cassava. However, growth and yield responded positively to K more promptly than to Ca. Combined rates, except 100 kg Ca ha−1 with no K fertilizer, significantly increased fresh tuber yield by 7.6–41.1 % over the control. To gain the highest fresh tuber yield by adding 200 kg Ca ha−1, 200 kg K 2 O ha−1 must be implemented. This light–textured soil was physically preferable for cassava tuberization, and the optimum yield can be achieved by proper Ca and K fertilization. [ABSTRACT FROM AUTHOR]

Arabica coffee (Coffea arabica) is cultivated throughout the tropics and is essential to local economies. Globally, most Arabica coffee is farmed in high-density monocultures despite evidence that agroforestry systems with shade trees can increase resiliency of coffee productivity and associated livelihoods. Open questions remain, however, on how Arabica coffee farm management affects local soil properties, especially soil microbial communities which are vital to plant productivity. To test if Arabica coffee soil microbiomes respond to farm management across geographies, we collected soil samples at coffee farms in Colombia and El Salvador that differed in management system (sun grown vs. shade grown) and soil samples in Peru that varied in agroforestry systems (native vs. non-native shade tree species). From these soils, we sequenced microbial DNA on an Illumina MiSeq to identify bacterial and fungal community diversity and composition. We found that each country had distinct soil microbial communities, and we describe their microbial profiles. In El Salvador and Colombia, both bacterial and fungal community composition differed between sun and shade systems, while alpha diversity of bacterial communities was only lower in El Salvador sun grown Arabica coffee soils. Within Peru agroforestry systems, bacterial and fungal composition differed between farms with non-native shade trees (Eucalyptus grandis and Pinus tecunumanii) and native shade trees (dominated by Inga spp.), but alpha diversity was not statistically different between agroforestry systems. Across all farms, composite microbial association networks showed similar topology, but distinctions in connectors and hub taxa, showcasing regional differences in potentially key microbial taxa. Our findings indicate that aboveground Arabica coffee farm management impacts belowground microbial biodiversity. A better understanding of these relationships can assist us in predicting how Arabica coffee production will be impacted by farm management changes and is essential for understanding the resilience of coffee farms. • Coffee growing countries can have distinct soil microbial taxa. • Coffee farm management impacts soil microbial community composition and diversity. • Shade tree species above coffee can impact microbial communities. • Sun grown coffee alters both bacterial and fungal soil communities. [ABSTRACT FROM AUTHOR]

The Atlantic Forest exhibits remarkable floristic diversity over short distances, and when combined with altitude, it results in variations in soil biological properties and hydrological dynamics. This study aimed to quantify the distribution pattern of soil biological properties along a small topographic gradient and identify how these properties are related to soil chemical, physical, and topographical attributes in an Atlantic Forest fragment in Brazil. Plots were established along hillslope positions varying from 100 to 180 m of altitude. Soil biological characterization was performed at a depth of 0.0–0.10 m in both summer and winter seasons. The lowland showed higher microbial biomass nitrogen in summer (57.28 ± 5.57 μg g−1 soil) and higher anaerobically mineralizable nitrogen in summer and winter (42.70 ± 2.14 mg kg−1 and 41.06 ± 3.37 mg kg−1, respectively). The midland showed lower microbial biomass carbon, enzymatic activity, and soil moisture in both seasons, and higher metabolic coefficients in summer. Soil chemical properties exerted a greater influence on the variability of biological properties in both seasons. The land slope conditioned lower microbial activity and organic cycling in the midland. Soil biological properties were affected by seasonality. Even a small altitudinal gradient (up to 100 m) in the Sea of Hills regions of the Atlantic Forest can lead to significant changes in soil biological and chemical attributes.

Recently, non-destructive in-situ tests have emerged that can predict the resilient modulus (MR) of materials that make up railway sidewalk layers in an agile and low-cost manner. These are in contrast to laboratory tests that require more infrastructure and are more time-consuming to perform. However, few studies have been directed to the resilient behavior compared to in-situ and laboratory tests for soils classified as tropical. This paper aims to determine the relationship between the estimated modulus of elasticity (ELWD) and the estimated resilient modulus (MR) from the repeated load triaxial test (RLT) for use in tropical soil railway subsoils. The samples of subgrade soils belong to a railway stretch in Brazil, present in the states of São Paulo-SP and Minas Gerais-MG, which has large circulation of minerals and commodities. The soils are classified as lateritic and non-lateritic according to the Brazilian Miniature, Compacted, Tropical (MCT) methodology, in addition to grain size, compaction, LWD and RLT tests. It is noted that the modulus of elasticity (ELWD) tends to decrease according to the increase in strain obtained in LWD. For soils classified as lateritic, as the soil moisture increases the ratio between the moduli obtained by RLT and LWD tend to increase. However, non-lateritic soils have the opposite performance, i.e., the ratio between the modulus of the tests decreases with increasing moisture. In this study, the LWD test is a possible viable alternative with good accuracy and effectiveness for geotechnical investigations in tropical soils.

Despite the increasing adoption of proximal sensors worldwide, rare works have coupled proximal with remotely sensed data to spatially predict soil properties. This study evaluated the contribution of proximal and remotely sensed data to predict soil texture and available contents of micronutrients using portable X-ray fluorescence (pXRF) spectrometry, magnetic susceptibility (MS), and terrain attributes (TA) via random forest algorithm. Samples were collected in Brazil from soils with high, moderate, and low weathering degrees (Oxisols, Ultisols, Inceptisols, respectively), and analyzed by pXRF and MS and for texture and available micronutrients. Seventeen TA were generated from a digital elevation model of 12.5 m spatial resolution. Predictions were made via: (i) TA; (ii) TA + pXRF; (iii) TA + MS; (iv) TA + MS + pXRF; (v) MS + pXRF; and (vi) pXRF; and validated via root mean square error (RMSE) and coefficient of determination (R2). The best predictions were achieved by: pXRF dataset alone for available Cu (R² = 0.80) and clay (R2 = 0.67) content; MS + pXRF dataset for available Fe (R2 = 0.68) and sand (R2 = 0.69) content; TA + pXRF + MS dataset for available Mn (R2 = 0.87) content. PXRF data were key to the best predictions. Soil property maps created from these predictions supported the adoption of sustainable soil management practices. [ABSTRACT FROM AUTHOR]

Due to the urban expansion of large cities, the characterization of the soils that are being used for civil construction is very significant: roads, bridges, and buildings. For this reason, in this study, soil from the Guabirotuba formation in Brazil is physically and mechanically characterized. The results show that it is predominantly silty soil but contains clay minerals that make it expansive. In addition, its geological origin shows it is in a normally consolidated state. Finally, the resistance of the soil in its natural and compacted state shows values below 500 kPa, which makes it a soil with low mechanical resistance, but which could be improved with chemical stabilization and geopolymerization techniques. [ABSTRACT FROM AUTHOR]

Tropical regions hold one third of the world's soil organic carbon, but few experiments have warmed tropical soils in situ. The vulnerability of these soils to climate change-induced losses is uncertain with many hypothesizing these soils would be less sensitive to climate change because already-high temperatures in tropical systems might limit microbial sensitivity or due to increased mineral protection of organic carbon in highly weathered tropical soils. Here we present the results of a deep soil (0–100 cm) warming experiment in a tropical Andisol. Andisols can store large, persistent pools of soil carbon that are protected from decomposition by poorly and non-crystalline minerals (PNCM). In 20 cm depth intervals, we measured key soil properties including carbon, nitrogen, pH, PNCM, bacterial and fungal richness along with temperature, moisture, and CO2 production. Over a year of soil warming, CO2 production significantly increased by 50–300% per degree of warming, but only in the top 40 cm of the soil profile in contrast to the results of other deep soil warming experiments. Multimodal analysis supported our hypothesis that high concentrations of PNCM was the primary driver of the lack of CO2 response, followed by high relative soil moisture and low bacterial richness, which may be a proxy for organic carbon availability. The lack of elevated CO2 production in response to warming suggests a limited positive feedback to climate change in Andisols driven by their strong mineral protection of organic matter. Therefore, Andisols should be considered high priority restoration or protection areas when considering the management of soil carbon stocks as part of climate action. [ABSTRACT FROM AUTHOR]

Silicon (Si) is known to have multiple beneficial effects on crops. Most plant-available Si in soils is provided through litter decomposition and subsequent phytolith dissolution, especially in strongly desilicated tropical soils. The importance of Si cycling in tropical soil-plant systems raised the question if oil-palm cultivation, the oil palm being a Si-accumulating crop, alters Si cycling. As Si accumulates in plant tissue, we hypothesized that i) Si is stored in the aboveground biomass of oil palms with time, and that ii) the system might lose considerable amounts of Si every year through fruit-bunch harvest. To test these hypotheses, we sampled leaflets, the rachis, fruit-bunch stalk, fruit pulp, kernels and frond bases from mature oil palms planted on well-drained and temporarily flooded riparian smallholder oil-palm plantations (n = 4 each) in lowland Sumatra, Indonesia. We quantified Si concentrations of these oil-palm parts by NaCO3 extraction. We further estimated Si storage in the total above-ground biomass of the oil palms, Si return to soils through decomposing pruned palm fronds, and Si losses from the system through harvest, to assess if Si return to soils via pruned palm fronds sufficed for maintaining Si cycling in the system, or if any measures are needed to compensate for Si export through fruit-bunch harvest. At all sites, leaflets of oil-palm fronds had a significantly higher (p ≤ 0.05) mean Si concentration (≥ 1 wt. %) than the rachis, frond base, fruit-bunch stalk, fruit pulp and kernel (≤ 0.5 wt. %). All analysed oilpalm parts had a Si/Ca weight ratio ≥ 1, except for the rachis. At well-drained sites, mean Si concentrations in leaflets increased with palm-frond age (R² = 0.98). Estimates of Si storage in the total above-ground biomass of oil palms, Si return to soils through decomposing pruned palm fronds, and Si losses through harvest were similar at well-drained and riparian sites: a single palm tree could store about 4 - 5 kg of Si in its total above-ground biomass, a smallholder oil-palm plantation of 1 hectare could store about 550 kg of Si in the palm trees' aboveground biomass. Pruned palm fronds were estimated to return 110 - 131 kg of Si per hectare to topsoils each year. Fruit-bunch harvest corresponded to an annual Si export of 32 - 72 kg Si per hectare in 2015 and 2018. Thus, on smallholder plantations in our study area, more Si can be returned to soils through pruned palm fronds than is lost through fruit-bunch harvest. Greater Si losses would occur if oil-palm stems were removed from plantations prior to replanting. Therefore, it is advisable to leave oil-palm stems on the plantations e.g., by distributing chipped stem parts across the plantation at the end of a plantation cycle (~25 years). This would return about 550 kg ha-1 Si stored in the palm trees' above-ground biomass to the soils. [ABSTRACT FROM AUTHOR]

Guava is one of the most important fruits in the Brazilian export market. The objective of this work was to evaluate the effects of liming and phosphorus (P) sources on micronutrients content in guava seedlings. The experimental design was completely randomized in a factorial scheme (2 × 3 × 3) comprising two dolomite limestone rates (0 and 5 Mg ha−1), three soil types (Typical Red Oxisol, Typical Yellow Oxisol, and Typical Yellow Ultisol), and three P sources (Arad rock phosphate, thermophosphate 'Yoorin,' and triple superphosphate) at 150 mg kg−1, with three replicates. Boron [B], copper [Cu], zinc [Zn], iron [Fe], and manganese [Mn] concentrations in guava seedling leaves and stems were affected by liming, by the P source, and by the soil type. Limestone and P sources altered the B, Cu, Zn, Fe, and Mn concentrations in leaves and stems of guava seedlings in each of the three evaluated soil types. Due to its low solubility, and regardless of soil type and liming, Arad rock phosphate was less effective than triple super phosphate as a P source for guava seedlings. [ABSTRACT FROM AUTHOR]

This technical note presents the results of two static load tests performed in a root micropile installed in a tropical lateritic soil profile. The tests were executed 6 years apart in order to investigate for signs of ageing effects in the pile side shear resistance and load settlement behaviour. Despite the measurements indicated an increase in the side shear capacity of the first soil layer, the results did not show clear signs of ageing effects, which occurrence was analysed considering different mechanisms. Soil suction possibly contributes to the differences between the tests, which should be carefully monitored for future studies of ageing effects in piles installed in unsaturated tropical sites. [ABSTRACT FROM AUTHOR]

The main factor that causes soil degradation is water erosion. The characteristics, in relation to geology, geomorphology, soils and climate, are conditioning factors of the erosive processes at work. Anthropic intervention, on this substrate of the physical environment, modifies the ways in which erosive forces act. Among the laboratory tests that directly quantify soil erodibility, we have the Inderbitzen test. In this work, the use of the Inderbitzen assay in research in Brazil is studied, they present criticisms of the original model of the assay and equipment and procedures are developed in order to mitigate the variation in the results of the assays. For the study, three soils from the Cerrado of Goiás were selected, being from the metropolitan region of Goiânia. The soils have a different pedological texture and origin, being: Dystrophic RED LATOSOL (Soil 1), Dystrophic HABIC CAMBISSOL Ta (Soil 2) and Ortical QUARTZARENIC NEOSOL (Soil 3). Modifications to the Inderbitzen assay procedures and equipment were proposed, which caused good precision and repeatability. the results found. In Soils 2 and 3 there was little variation in soil loss due to the void index. For Solo 1, on the other hand, it showed a significant increase in soil loss with the increase in the void index. [ABSTRACT FROM AUTHOR]

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Background: Micronutrient deficiency is currently the major cause of declining productivity in rice‐growing countries, including Thailand. A pot experiment was conducted to determine limiting micronutrients (Fe, Mn, Zn, and Cu) for Khao Dawk Mali 105 (KDML 105) rice, in four soil types. Soil micronutrient speciation and in‐soil extracts were examined to identify the species controlling the availability to the plant and the efficiency of soil extract to assess the availability indices of multi‐micronutrients for KDML 105 rice. Results: Micronutrients in the studied soils were in the order Fe > Mn > Cu > Zn, mostly in stable forms accounting for 96.8%–99.7%, 81.3%–96.5%, 95.6%–97.6%, and 83.3%–98.0%, respectively, and in available fractions of only 0.32%–3.2%, 3.55%–18.66%, 2.44%–4.42%, and 2.03%–16.74% respectively. The omitted Fe had the greatest effect on limiting the rice grain yield with a significant reduction of 24.12%–46.46%, whereas the omitted Zn had the least effect. To assess the availability for KDML 105 rice, DTPApH 7.3 was the most suitable multipurpose extractant for Fe, Mn, and Cu, while HCl was superior to other extractants for Zn. All oxide fractions were responsible for supplying available Fe, Mn, and Cu, while Zn was generated from the organic and exchangeable fractions. Conclusions: The yield of KDML 105 rice can be increased by adding each of these micronutrients but yield magnitude was different depending upon their deficient levels in soils. The oxide‐bonded micronutrients were the species controlling its availability and DTPApH 7.3 was suggested as the multipurpose extractant for micronutrient availability indices indicators. [ABSTRACT FROM AUTHOR]

The flow of water in mining waste may cause serious environmental impacts associated with acid-rock drainage. In relatively dry climates, dry soil covers have been considered as feasible alternatives to minimise such effects. The objective of this paper is to evaluate the influence of the hydrological cycle and soil type on the performance of dry cover systems, considering the tropical conditions found in Brazil's central-west region. Numerical analyzes of four different cover systems composed of tropical soils were performed using the Finite Element Method. Among the proposed arrangements, three use a soil that presents a bimodal soil-water characteristic curve and the fourth system employs a unimodal soil. The thicknesses of intermediate materials were varied and different representative precipitation parameters were considered for a period of one year. The results obtained were compared in terms of the internal flow and the capacity of the cover to store water. The results indicate that bimodal soils may not be ideal materials and require specific compaction conditions to reduce the volume of macropores. Unimodal tropical soils presented adequate response as store-and-release materials. The use of an intermediate layer acting as a capillary barrier did not offer significant improvement to the cover systems evaluated. [ABSTRACT FROM AUTHOR]

Since human settlement approximately 2,000 years ago, Pacific Island nutrient cycles have been increasingly modified. Modern agricultural intensification has resulted in further changes in the island nutrient flows. Country scale agricultural land nutrient (nitrogen, phosphorus, and potassium) budgeting in Tonga, Fiji, Samoa, Kiribati, and Tuvalu were calculated from FAO country statistic data (1964-2018). Nutrient input data from birds, atmospheric dust, and rainfall and human waste were calculated from literature values. Overall, there are nutrient imbalances in all countries and agricultural lands are exporting nitrogen, phosphorus, and potassium. The budgeting calculations did not consider nutrient losses via erosion, leaching and run-off or denitrification, and the net nutrient fluxes may well be greater than reported. The use of animal and human waste would help off-set nutrient imbalances, but additional macroand micro-nutrients would need to be added for balanced plant nutrition and soil carbon sequestration. While increasing fertiliser inputs will improve the nutrient balance and potential primary productivity, trade-offs such as nutrient losses will need to be considered. Improving nutrient budgets would need a farming systems approach, whereby the use of cover crops, crop rotations and legumes would augment the fertiliser applications. [ABSTRACT FROM AUTHOR]

Soil degradation is a process resulting from the management adopted by the industrial agriculture, that configures an ecological and social crisis. In this context, agroecology as a movement, science, and practice, values diversification of food production respecting the edaphoclimatic conditions of the ecosystems. The agroecological practices demand methods that help farmers assess the health of their soils. Pfeiffer Chromatography is a simple and low-cost diagnostic tool. This article aimed to understand the soil health status in four land uses (agroforestry system, banana with green manure, fallow area, and forest fragment) in a certified biodynamic farm, located in the state of São Paulo, Brazil. The results obtained, in a qualitative and quantitative way, allow us to affirm that the soils of forest fragment area and agroforestry system were the healthiest. The chromatography was an efficient method for analyzing the health of tropical soils, with potential for use by family farmers. [ABSTRACT FROM AUTHOR]

BACKGROUND AND OBJECTIVES: Soil is the most important basic natural resource for the support of agricultural production systems. Productivity maintenance in these ecosystems depends on their physicochemical. However, there are no significant studies on the current status of soil fertility and quality in tropical areas vulnerable to climate change and lacking management practices. The purpose of this study was to assess the physical and chemical properties of the soil to propose guidelines on soil handling and management in tropical areas. METHODS: Data on texture, macronutrients, micronutrients, and cation ratios were collected at 200 farms in the Sucre Department of Northern Colombia. Correlation analysis and principal component analysis were performed on the resulting data set, and a soil quality index was calculated. FINDINGS: Macronutrients N, P, K, S, Ca, Mg, and Na displayed average values of 21.65 ± 10.65 part per million, 40.35 ± 67.21 part per million, 0.46 ± 0.43 meq/100g, 7.94 ± 28.35 part per million, 15.63 ± 17.30 meq/100 g, 5.63 ± 3.58 meq/100g, 0.19 ± 0.20 meq/100g, respectively. Micronutrients Cu, Fe, Zn, and Mn displayed average values of 2.20 ± 1.66 part per million, 48.05 ± 37.87 part per million, 1.16 ± 1.26 part per million, 14.22 ± 12.24 part per million, respectively. The predominant texture among assessed soils was sandy clay loam. A significant correlation was found between (Ca/Mg) K-Ca/K, (Ca/Mg) K-Mg/K, Fe-Cu, and Cacation exchange capacity. The soil quality index of the soils assessed in the Department of Sucre indicates a high level of quality, which is strongly influenced by the indicators S, P, Mn (= 0.90) Fe, Zn, Cu, K, Na (= 0.80). CONCLUSION: The macronutrients displayed a deficiency of potassium. It is therefore recommended to monitor these soils and apply fertilization plans according to the needs of each assessed soil. Lastly, this study provides relevant information for proposing guidelines for crop improvement. [ABSTRACT FROM AUTHOR]

Little is known about nematode communities related to Costa Rican crops, which limits the efforts to offer adequate responses to producers interested in soil conservation. The objective of this work was to describe nematode fauna of pineapple plantations in the northern plains of Costa Rica as an example of how agronomical management practices can influence nematode diversity. The abundance of families (or genera) of the nematode communities in soil samples of 15 pineapple plantations and 11 patches of forests or tree plantations near them was calculated. Forty-three families were identified, 39 families in forest, 36 in tree plantations, and 35 in pineapple plantations. Helicotylenchus was the most abundant genus in pineapple, while Discocriconemella dominated in forests and tree plantations. Non-metric multidimensional scaling and redundancy analysis showed few differences but revealed that forests and tree plantations correlated with organic matter, Ca, Mg, and with Discocriconemella. Meanwhile, pineapple plantations correlated with exchangeable acidity, K, and with abundance of Mesocriconema. Basal index was significantly lower in forest and tree plantations while the Structure index was higher. Other calculated indexes (Plant-parasitic index, Maturity index, Channel index, Enrichment index, and Metabolic Footprints) did not show any statistical differences among land uses. Most statistical differences were found at the nematode genus level. [ABSTRACT FROM AUTHOR]

There is a variation in the depth of subsurface horizon of Planosols in semi-arid region, which may influence the agricultural potential and affect food production. The general aim of this study was to identify potentialities and limitations of two Planosols as a function of subsurface horizon depth. The adjacent profiles P1 and P2 were studied in Pentecoste (Ceará, Brazil). Morphological, physical, and chemical analyses were done aiming at soil characterization. Soil bulk density (BD), porosity, and penetration resistance (PR) were analyzed in a completely randomized split-plot design with four replicates to compare P1 and P2 and the horizons Ap and Btf. Btf was found at 62cm depth in P1 and at 18 cm depth in P2. Indicatives of water saturation were more evident in P2. The profile P1 showed lower hardness and higher friability, as well as higher acidity in subsurface (pHH2O from 4.4 to 4.7) and higher aluminum content (1.2cmolc kg-1). Both profiles were eutrophic and showed low contents of organic carbon (1.5 to 8.5g kg-1) and phosphorus (0.9 to 3.9mg kg-1). The sodium percentage in CEC was 9.1% in P1 and 5.5% in P2. Water retention increases in Btf compared with Ap was 7.3% in P2 and 2.7% in P1. Both profiles showed increase in BD in Btf, reaching 1.7g cm-3, while PR was higher in P2 (1.5 MPa). There are potentialities and limitations common to both soil profiles, but P1 has more physical potentialities and more chemical limitations than P2.

Abstract The objective of this work was to determine pedotransfer functions to predict water retention at the -33 and -1500 kPa matric potentials of soils under Cerrado, in the south of the state of Mato Grosso, Brazil. Samples (n=156) were collected for model calibration (n=124) and validation (n=32). A stepwise multiple regression was used to determine pedotransfer functions. Willmott’s index of agreement, root-mean-square error, Pearson’s correlation coefficient, and the confidence index were used to evaluate the performance of the functions and to compare them with those described in the literature. The most efficient variables to estimate water retention were: microporosity, total sand, and clay at -33 kPa; and total sand, silt and clay at -1500 kPa. The regional pedotransfer functions explained more than 94% of water retention variance in the studied soils. The reliability of the functions to predict water retention increased, at -33 kPa, with the use of the structural property microporosity and, at -1500 kPa, with the use of granulometric parameters. The studied regional pedotransfer functions predict water retention at the -33 and -1500 kPa matric potentials of soils under Cerrado, in southern Mato Grosso, better than the functions described in the literature.

Tropical soils play a critical role in the global biogeochemical cycles and are essential for maintaining the Earth's carbon balance. Understanding the dynamics of dissolved organic matter (DOM) is paramount due to its implications for ecosystem functioning and nutrient cycling. This study comprehensively evaluated the origin, distribution, and composition of DOM and inorganic solutes in Brazilian tropical agricultural soils. Multiple analytical techniques were utilized to assess DOM from soil profiles (0–100 cm depth) across a spectrum of land uses, including a native Atlantic Forest, a degraded pasture, as well as intensive grazing, extensive grazing, and silvopastoral systems. Inorganic elements were quantified to assess the coupling between the organic and inorganic biogeochemical cycles. The dominance of C 4 carbon in topsoil layers suggested substantial contributions of organic matter from grasses to the soil organic matter pool. However, with increased depth, C 3 carbon inputs became more prominent, indicating the influence of forest vegetation that existed prior to the implementation of agricultural managements. DOM concentrations decreased with soil depth due to reduced carbon inputs, sorption to minerals, or oxidation. DOM composition did not show significant changes among different land use and managements. Lignin was identified as the primary contributor to oxidized DOM with increasing soil depth. The composition of DOM exhibited a shift from more aromatic and higher molecular weight compounds in topsoil layers to smaller, more aliphatic compounds in subsoil layers. Our key findings revealed that aliphatic compounds, particularly fatty acids, tend to accumulate in deeper soil layers. This phenomenon was consistent in pastures dominated by grasses but not in soils near treed vegetation. Overseeding (from C 3 plants) did not significantly impact DOM compositions, emphasizing the persistence of C 4 plants in these systems. The presence of inorganic elements in soil water extracts showed minimal impact on DOM dynamics, suggesting decoupled organic and inorganic biogeochemical cycles in tropical pasturelands. [Display omitted] • DOM in topsoil layers showed high C 4 contributions, while subsoil layers showed higher C 3 inputs. • Aromatic compounds became oxidized with increasing soil depth. • Fatty acids were produced by lignin oxidation or selectively preserved in subsoil layers. • Inorganic solutes might not play a major role in soil biogeochemistry. [ABSTRACT FROM AUTHOR]

With an increase in the generation of sewage sludge, there comes a demand for disposal methods for it, and agricultural use is a sustainable alternative. However, there are gaps regarding emerging pollutants, especially in the pharmaceutical class. Nimesulide - an anti-inflammatory pharmaceutical recently associated with liver damage and banned in some European countries - is among the most consumed pharmaceuticals in Brazil hence can be found in wastewater and, therefore, in sewage sludge used for agriculture at ng L−1 concentrations. The objective of this research was to evaluate the toxicity of the anti-inflammatory pharmaceutical nimesulide through toxicity tests using the organism Enchytraeus crypticus in both natural and artificial soils, adopting concentrations about studies carried out with other anti-inflammatory drugs on seeds in the soil. In this work, the toxicity of nimesulide was evaluated in natural tropical soil sampled in São Paulo – Brazil, and in tropical artificial soil. The invertebrate E. crypticus was exposed to nimesulide nominal concentrations of 200; 340; 578; 982 and 1670 mg nimesulide kg−1 of dry soil and the reproduction test was performed according to ISO 16.387 (2014) standard, with 5 replicates per concentration. The results obtained through reproduction testing with E. crypticus in each concentration presented were EC50 values of 699 and 759 mg nimesulide Kg−1 dry soil, respectively for both natural and artificial soil. The Tukey test showed no significant difference between the soils, however. Finally, this study suggests that the anti-inflammatory drug nimesulide displays a toxicological effect on the reproduction of soil fauna organisms in high concentrations. Therefore, stresses the importance of identifying and monitoring unknown concentrations of this emerging pollutant in the environment. • The organism Enchytraeus crypticus as a bioindicator of pharmaceutical toxicity in soil • There was no significant difference in nimesulide toxicity to E. crypticus in natural and tropical artificial soil. • Reproduction of E. crypticus decreases with increasing anti-inflammatory concentrations. • Low toxicity of nimesulide at high concentrations in artificial soil [ABSTRACT FROM AUTHOR]

• Usefulness of varied proximal sensors to study tropical soil minerals was tested. • Representative soil classes and parent materials of tropical regions were studied. • Proximal sensor data help characterize tropical soil mineralogy. • Accurate predictions of contents of clay-sized minerals were achieved. • pXRF outperformed Vis-NIR for predictions of most clay-sized minerals. Proximal sensors combined with X-ray diffraction (XRD) have optimized soil characterization, but scarce studies have focused on predicting the contents of minerals under this scope. The objectives herein were to: a) use the portable X-ray fluorescence (pXRF) spectrometry, diffuse reflectance spectroscopy in the range of visible and near-infrared (Vis-NIR), magnetic susceptibility (χ) and XRD to characterize the mineralogy of soils derived from representative Brazilian soil parent materials, and b) create models to quantify the minerals obtained via XRD. Twenty-two soil profiles developed from gabbro, gneiss, quartzite, mineral and organic sediments were described with 53 soil horizons sampled. Each sample had the sand, silt and clay fractions separated and analyzed with XRD, pXRF, χ, and Vis-NIR. Models were created using the Random Forest algorithm permuting the following predictor variables (separately and combined): pXRF, parent material (PM), χ, soil texture (sand, silt, and clay content), and Vis-NIR. Models' accuracy was calculated using the leave-one-out cross-validation method. Si, Al, Fe, Ca, K, and Ti contents obtained by pXRF and the χ discriminated the soil particle size fractions according to the parent material. XRD analysis allowed the evaluation of the pedogenetic development of soils and their relation to the respective parent material. The best models for mineral contents were found for hematite (Hm) (1 0 4)+(Gt) (1 3 0) (R2 = 0.85), Hm (1 1 0) + Mh (1 3 1) (R2 = 0.76), kaolinite (Kt) (0 0 1) (R2 = 0.73), Kt (0 0 2) (R2 = 0.80), mica (Mc) (0 0 1) (R2 = 0.77), and Mc (0 2 0) + Kt (0 2 0) (R2 = 0.81). Clay mineralogy content was accurately modeled using only pXRF and parent material data. This approach can facilitate and speed up detailed soil mineralogy characterization. Further studies are encouraged to model the content of minerals found in the sand and silt fractions of soils with diverse mineralogy via proximal sensors and using larger data sets. [ABSTRACT FROM AUTHOR]

Quartz is one of the most common minerals in soils, mostly present in sand and silt fractions. Although quartz is basically formed of SiO2, other elements can be easily detected and assessed nowadays using a portable X-ray fluorescence (pXRF) spectrometer. Our study aims to evaluate the chemical composition of different quartz varieties, identifying their main elements, and relating them to soil attributes. Six quartz varieties (hyaline, amethyst, milky, rose, smoky, and ferriferous) were analyzed via pXRF and 13 oxides/trace elements were identified and used for quartz discrimination (Al2O3, CaO, P2O5, SiO2, Cl, Cr, Fe, K2O, Mn, Rb, S, Ti, and V). Hyaline quartz was characterized by the highest SiO2 and the lowest contents of other elements. Al2O3 was the second-highest compound present in all varieties of quartz, reaching 21,547 mg kg−1 in the smoky variety. S, P2O5, Cl, SiO2, and K2O were the main components determined by Random Forest algorithm for discriminating quartz varieties. Some elements detected may serve as a reserve of nutrients to plants to be released in soils along weathering, depending on quartz particle size, soil texture, leaching, and associated attributes. pXRF enhanced the information on chemical characterization of quartz varieties, without the generation of chemical pollutants.

We present experimental observations and a conceptual model for understanding the compression and swelling characteristics of Old Alluvium (OA) from San Juan, Puerto Rico. Prior studies have classified OA as a transported, in situ weathered tropical soil whose intact macrostructure comprises a cemented, pseudo-silt with a mixture of quartz grains and aggregated clay particles. The aggregates include mixtures of kaolinite and smectite coated by Fe-oxides. The Fe-oxides also act as cementing agents between the particles. This study describes results from a series of high-pressure (up to 63 MPa) incremental consolidation tests. Breakdown of the clay aggregates and cemented structure is observed through changes in the compression properties, significant swelling during unloading, and an extraordinary reduction (i.e., by three orders of magnitude) in the coefficient of consolidation. These experimental observations are explained by a combination of mechanical processes, comminution and breakdown of cementing bonds, and physicochemical changes linking pore fluid in the intra- and inter-aggregate pore space. These processes alter the fundamental particle size distribution and macro-porosity of the soil and activate the swelling potential of the smectites concealed by the Fe-oxides coating in the intact material. The experimental observations provide the basis for the formulation of a constitutive model to describe macroscopic compression and swelling behavior of Old Alluvium and offer a framework to understand the response of piedmont transported residual soils found elsewhere. [ABSTRACT FROM AUTHOR]