ABSTRACT Sandy soils pose significant challenges for nutrient management owing to their low nutrient retention capacity and the high-intensity rainfall characteristic of tropical regions. This study aimed to evaluate the effects of K fertilization timing on nutrient release from Urochloa brizantha (Hochst. ex A. Rich.) R.D. Webster residues and the subsequent impact on soybean grain yield in sandy soils. The experiment was conducted in Paraíso das Águas, Mato Grosso do Sul State, Brazil, during the 2019/2020 growing season. Treatments included two K rates applied to U. brizantha mulch (0 and 100 kg ha-1 of K; 0 and 120 kg ha-1 of K2O) and four K rates applied to soybean (0, 25, 50, and 100 kg ha-1 of K, which correspond to 0, 30, 60, and 120 ha-1 of K2O) Residue decomposition and nutrient release dynamics were monitored using litter bags collected at intervals of 0, 15, 30, 60, and 90 days. Early K application to U. brizantha significantly enhanced nutrient release, particularly K, which showed rapid release with a half-life of 16 days. Soil K was strongly stratified in the 0.00–0.05 m layer, with no evidence of substantial downward movement beyond 0.40 m within the experimental period. Instead, U. brizantha residues served as a nutrient reservoir, effectively releasing phosphorus (P) and potassium (K) to the subsequent soybean crop, aligning nutrient availability with crop demand. The highest soybean grain yield occurred, reaching 3,573 kg ha-1 especially when 100 kg ha-1 of K (120 kg ha-1 of K2O) was applied to U. brizantha and no additional K was applied to soybean; this grain yield was higher than that of to 3,176 kg ha-1, observed with direct K application to soybean without early K. These findings underscore the benefits of system-based fertilization strategies in enhancing nutrient use efficiency and sustaining crop productivity in sandy soils.
ABSTRACT Amazonian Dark Earths (ADEs), despite being a relatively minor part of Amazonian soils, are traditional choices for agricultural production by local people, which increases the potential for remobilization of Hg from these soils to aquatic environments. Therefore, considering the relevance of Hg and the general use of ADEs in the Amazon, this study aimed to evaluate the vertical distribution and the edaphic factors controlling total mercury in Amazonian Dark Earth profiles from the Madeira and Solimões River Basins to infer the relative potential for Hg retention or mobilization compared to other Amazonian soils. This study comprises ADEs sampled from the Madeira River (n = 34) and Solimões River Basins (n = 43), with depth varying between 0.20 and 0.90 m. The contents of the elements (Ca, Mg, Co, Cr, Fe, K, Mn, Ni, P, Ti, V, Zn and Zr) were determined by induced plasma optical atomic emission spectrometry. Total Hg was determined by atomic absorption spectrophotometry (AAS) with cold-vapor generation (CV-AAS). Soil classification was carried out according to the Brazilian Soil Classification System. The data show there are at least four interrelated components for Hg dynamics in ADEs: lithogenic control is indicated by immobile elements, pedogenic control by the association of Hg with iron associated with human control responsible for the deposition of ash and organic matter in soils over thousands of years, and hydromorphic control in poorly drained soils or those located in areas of periodic flooding.
ABSTRACT Open-pit gold and platinum mining is one of the main economic activities in the tropical region of the planet. However, it disturbs the ecosystem, including soil physical and chemical properties, with negative consequences for vegetation growth and recovery; therefore, it is expected that soil fertilization will have significant effects on tree growth. To evaluate the effects of soil fertility on post-mining forest in the Biogeographic Chocó (Colombia), we established an experiment with five treatments of soil fertilizer addition: N (125 kg ha-1 yr-1), P (50 kg ha-1 yr-1), K (50 kg ha-1 yr-1), NPK, and control. Generalized Linear Models (GLM) were used to evaluate the treatment effects on the relative growth rate (RGR) of trees in two size categories (small trees, 0.05 m < diameter at breast height (DBH) <0.10 m, and large trees, DBH >0.10 m) and in three dominant species (Cosmibuena grandiflora, Cespedesia spathulata and Clidemia septuplinervia) of the ecosystem. Soil N addition increased small tree RGR across the ecosystem and in the species C. grandiflora and C. spathulata. In contrast, the P and K treatments produced no detectable change in RGR for either small or large trees. At the ecosystem level, this study demonstrated that nitrogen (N) fertilization significantly enhanced tree growth. This effect was primarily driven by the response of smaller individuals, which exhibited greater sensitivity to N amendment than larger trees. Specifically, small trees of C. grandiflora and C. spathulata growing in post-mining forests of the Chocó show enhanced responsiveness to shifts in nutrient availability.
ABSTRACT Nitrogen (N) losses from soil through volatilization are influenced by multiple factors, including the amount and source of nitrogen fertilizer applied, crop type, intrinsic soil characteristics, and environmental conditions. The study aimed to quantify ammonia (N-NH3) volatilization in relation to the method of nitrogen application, either split or single-rate, on annual ryegrass (Lolium multiflorum Lam.) pasture in an integrated crop-livestock system. The trial was conducted on a Humic Cambisol in Southern Brazil during the fall and winter seasons of 2022 and 2023. The treatments were: N-0 – no nitrogen fertilization; N-split – fertilization with 200 kg ha-1 of N as urea split into four applications (50 kg ha-1 at tillering and three subsequent applications of 50 kg ha-1); and N-single – fertilization with 200 kg ha-1 of N as urea applied in a single rate at the ryegrass tillering stage. Ammonia volatilization was assessed using static semi-open collectors and quantified by colorimetry. Losses due to volatilization were monitored for 14 days after each N application and summed over 56-day period. In both years, during the first evaluation, the N-single treatment caused the greatest losses but did not differ significantly from split fertilization (N-split). However, in the subsequent three evaluations, the highest volatilization losses were observed with N-split. Regarding the total accumulated losses of N-NH3 over 56 days, the values in the first year were 375, 810, and 345 g ha-1 for N-0, N-split, and N-single, respectively. In the second year, the losses were 808, 1963, and 900 g ha-1 of N-NH3 for N-0, N-split, and N-single. Splitting nitrogen fertilization resulted in greater N losses through volatilization than a single application at tilling; however, the losses remained below 1 % of the applied N. Despite these differences in volatilization, split nitrogen fertilization produced ryegrass forage yields equivalent to those obtained with the single-rate application. Split N fertilization increased NH3 losses compared to single-dose application in ryegrass, yet yields were equivalent, and losses remained below 1 % of the applied N.
ABSTRACT João de Deus karst cavity is located at Lagoa dos Patos, northern Minas Gerais, Brazil and was previously occupied by humans. This study advances the pedogenetic interpretation of Archaeo-Anthrosols with results and discussions about the finding of the first cavity in a carbonate karst environment whose soil exhibits strong pedality in Brazilian territory. Analytical approach, including macroscopic and microscopic observations, and physical, chemical, mineralogical, and pedostratigraphic analyses, provides the empirical basis for reconstructing soil formation and transformation over time. Six pedostratigraphic units were distinguished, supporting the recognition of three discrete phases of human occupation and successive inputs. We propose a six-phase polygenetic model for this cave soil, emphasizing the evolutionary pathways of ped formation and the incorporation of archaeological materials into the profile. Carbonation, gleization, and bioturbation emerge as the dominant pedogenetic processes shaping all pedostratigraphic units under hydromorphic conditions within the cavity, mediated by biological and anthropic contributions. Radiocarbon dating is compared between a pedostratigraphic level of the João de Deus cavity and two regional archaeological contexts: the open-air Caixa D’Água site in Buritizeiro, on the left bank of the São Francisco River, and the Bibocas II quartzitic shelter in the upper-middle São Francisco basin. The identification of ceramic microfragments in two units and the temporal proximity indicated by radiocarbon assays suggest that plant domestication and ceramic production in Central Brazil may have begun earlier than typically acknowledged in the archaeological literature.
ABSTRACT Sambaquis are Brazilian archaeological sites whose matrix is predominantly composed of shells, accumulated and mixed with various kinds of debris. They are formed by the anthropogenic deposition of mollusk exoskeletons, plant remains, charcoal, tools, and ceramics, among other marks of human intervention. These shell mounds usually have overlying soils with dark-colored horizons rich in organic matter and high in fertility, called Archaeological Dark Earths (ADE). One of the oldest and most significant records of sambaquis in Brazil, known and studied since the 19th century, is Porto da Mina in Quatipuru (PA). Although it represents a long-term human occupation site, no pedoarchaeological investigation has been undertaken there to date. To fill this gap, we conducted a pedogeochemical, mineralogical, and chronological characterization of this site, aiming to understand its genesis, properties, classification, and the geochemical distribution of key elements associated with anthropogenic activity. Soil samples were collected in genetic horizons and submitted to physical and chemical analyses, P fractionation, X-ray diffraction, radiocarbon dating (14C), sulfuric digestion, selective dissolution with dithionite citrate bicarbonate and ammonium oxalate, and microchemical characterization with SEM coupled to EDS of the silt and clay fractions. The geochemical distribution of P, K, Ca, Mn, Fe, Al, Si, and Ti in the shell mound area was also evaluated. The cumulative soil formation in the Porto da Mina shell mound is well-defined by superimposed layers indicating the dynamics of occupation, abandonment, and reoccupation of the site by human groups. The predominant form of inorganic P in this soil is P-Ca, with the highest values associated with enriched organic matter horizons, which is paradoxical given the humid tropical climate. Also, the soil still possesses a large reserve of primary biogenic apatite, and the presence of hydroxyapatite, halite, and calcite in the clay fraction. Neoformed 2:1 clay minerals were also observed in the soil. The carbon dating ranged from 4920 ± 30 to 500 ± 30 years BP, and indicates long intervals of site abandonment, up to 200 years. Inconsistencies with previous carbon dating indicate a possible inversion of layers due to active pedobioturbation. The geochemical distribution of the elements at the archaeological site indicated higher contents in areas closer to the main depositional mound and localized points of lower concentration for, P, and Mn.
ABSTRACT Shell middens, known in Brazil as Sambaquis, are anthropogenic formations composed mainly of shells, along with food debris, terrestrial fauna remains, fish bones, lithic artifacts, and, occasionally, human burials. These sites occur in specific areas of the Brazilian coast and in the Amazonian floodplains. This study presents a pedoarchaeological investigation aimed at understanding soil formation processes in shell middens along the southern coast of Espírito Santo State, Brazil, and providing contributions to the classification of Brazilian anthropic soils. We performed standard chemical and physical analyses, X-ray fluorescence, X-ray diffraction, micromorphology, electron microprobe analysis, and radiocarbon dating. The soils of the Rio Preto 1 Sambaqui are poorly developed, directly formed over shell deposits, and influenced by both ancient human activities and post-depositional pedogenetic processes. The main factors driving pedogenesis include parent material, biological activity, topography, and past anthropogenic impacts. Identified pedogenetic processes are melanization, organic matter stabilization and translocation, lessivage, and induced cementation. Rio Preto 1 is currently the oldest known sambaqui on the southern coast of Espírito Santo, dating back over 6,000 years BP. Due to its fragility and historical significance, urgent conservation measures are needed to safeguard this archaeological heritage site.
ABSTRACT Anthropogenic soils provide key evidence for understanding how past human societies transformed landscapes and generated long-term environmental changes. This study aimed to analyse the human influence on the formation of anthropogenic soils in the lower basin of the Uruguay River, with special emphasis on the Cañada Saldaña site (Soriano, Uruguay) during the late Holocene. The main objective is to characterize the area geomorphologically and determine whether the Anthrosols found correspond to metagenetic or neogenetic types, thus contributing to the knowledge of pre-Hispanic human practices of the anthropization of the environment. The methodology used is based on a geoarchaeological approach, combining sedimentological, geochemical, and granulometric analysis. Four test pits and two boreholes were carried out in the elevated structures on land and in adjacent landscape units (beach ridges and wetlands). The results indicate that the Cañada Saldaña mound has a mixed genesis, combining contributions from in situ activities and transport of material from the wetland. The presence of several burials within the mound suggests recurrent use of the space for funerary purposes, which could explain the incorporation of additional parental material. It is concluded that the formation of elevated sites in the region is driven by diverse processes, with coexisting structures of constructive, mixed, and in situ disturbance origin. This emphasizes the need to apply precise methodologies to understand the variability of the formation processes of archaeological sites in the lower basin of the Uruguay River.
ABSTRACT Amazonian Dark Earths (ADEs) are archaeological soils with darkened anthropic horizons, fragments of charcoal ceramics, and enriched in P, Ca2+, Mg2+, Mn, Zn, and organic matter. They mainly occur in Terra Firme, adjacent to river banks, rarely being recorded in Várzeas. The Solimões River remains practically unexplored in ADE studies. To fill this gap, seven ADE soil profiles were studied in this unexplored region, five in Terra Firme and two in Várzea areas, between São Paulo de Olivença and Amaturá (Alto Solimões, Amazonas). Morphological, physical, and chemical analyses were carried out, complemented by P-form extraction and radiocarbon dating. The morphology of the dark surface shows the abundance of pyrogenic charcoal and ceramics. The high chemical status is confirmed by high levels of P, Ca2+, Mg2+, Mn, Zn, Sum of Bases, CEC, and TOC. There is a marked illuviation of clay, accompanied by OM, P and Ca2+, with increasing P contents underground. The P fractions reveal a predominance of P-Ca for the anthropic horizons in Várzeas, whereas P-Al and P-Fe dominate the anthropic horizons of Terra Firme, with few exceptions. The radiocarbon ages of the Terra Firme ADEs in Alto Solimões range from 1190 – 1410 years BP (younger) to 2500-2870 years BP (older), indicating an ancient Late Holocene occupation of drained soils along river banks. In contrast, Várzea ADEs range from 920 to 1270 years BP, indicating a later occupation period after the settlement of adjacent Terra Firme (uplands). Although we present only a provisional account based on a few sites, we postulate that the first settlers in Alto Solimões occupied the Terra Firme area adjacent to the main rivers and later diversified into the Várzeas (floodplains). This pattern of a complementary Várzea-Terra Firme ADE continuum is recurring throughout the Amazonas-Solimões system, as revealed by the new archaeological sites analyzed. The ADEs of Upper Solimões Várzeas show greater chemical fertility than Terra Firme areas. Similar to the Middle Amazon Valley, but they form unusual mounds not observed in the Middle Amazon, suggesting that different floodplain hydrological regimes account for these features. Phosphorus-Ca forms are the primary source of P, which are progressively transformed into P-Al and P-Fe forms with advancing pedogenesis in the most acidic environments of Terra Firme. The unprecedented presence of anthropogenic landforms in the Alto Solimões floodplains demands a more comprehensive investigation of the region to uncover the pre-Colombian cultural occupation and chronology in a key area of the Amazon Basin.
ABSTRACT The environmental persistence of plastics, their slow degradation and constant fragmentation pose risks to soil health. Microplastic (MP) contamination is already a real global environmental issue, with increasing evidence of its widespread presence in all terrestrial ecosystems, affecting physical and chemical properties, microbial communities, and pedogenetic processes. Soil serves as a significant sink for MPs, primarily through agricultural practices, landfills, waste mismanagement, wastewater treatment and atmospheric deposition. Furthermore, plastics can contribute to the formation of "rocks" (e.g., plastiglomerates and antropoquinas) that could redefine soil classification systems. Existing classification frameworks, including the World Reference Base for Soil Resources, Australian Soil Classification, U.S. Soil Taxonomy, and Brazilian Soil Classification System (SiBCS), differ in how they address the presence of plastics, highlighting a lack of consensus in recognizing anthropogenic artifacts within soils. Despite its increasing prevalence, plastics are often overlooked in soil classification systems, prompting the need for new qualifiers. Furthermore, advancements in detection and quantification methods, such as Soil Spectroscopy and Digital Soil Mapping, are essential to improve our understanding of MP behavior in soil matrices. Pedologists play a crucial role in quantifying MP impacts, developing soil management strategies, and contributing to global environmental policy. Addressing soil MP pollution requires international cooperation, transdisciplinary research, and robust methodological approaches to safeguard soil ecosystems and human health. Research on soil MP pollution has the potential to alter our understanding of human influence on soil properties and functions, with implications for the genesis and classification of Anthroposols. This review highlights important aspects of this phenomenon, with a greater focus on the Brazilian context. Soil scientists are encouraged to pay attention to this matter and contribute to filling current knowledge gaps.
ABSTRACT The critical soil test value (CSTV) of phosphorus (P) is defined by the relationship between relative crop yield (%) and soil P availability and is essential to guide fertilization decisions. However, CSTVs may vary depending on the diagnostic soil layer, crop type, and the Mathametical model used, highlighting the importance of refining their estimation. This study aimed to evaluate whether the subsurface layer (0.10–0.20 m) improves the diagnosis of P availability under different fertilization strategies and to re-estimate CSTVs for the Center-South region of Paraná, Brazil, by integrating new field trials with existing regional datasets and comparing multiple models. Relative yield and Mehlich-1 extractable P data were fitted to five models: Cate and Nelson (1965), modified ALCC, Mitscherlich, linear-plateau, and quadratic-plateau. Field trials were conducted in Oxisols (Humic Hapludox - Latossolos) with medium and high soil test P (STP) levels. Data were grouped by soil layer (0.00–0.20, 0.00–0.10, and 0.10–0.20 m) and crop season (summer and winter). In a second analysis, regional data were grouped by soil layer and crop type (summer + winter, summer, and winter), and all models were adjusted to 90 % of maximum relative yield. The field trials showed limited model fit due to high P availability in the surface layer, which was sufficient to sustain high yields even without P fertilization for four years. The Cate and Nelson model yielded CSTVs of 3.7 mg dm-3 for the 0.00–0.20 m layer and 0.9 mg dm-3 for the 0.10–0.20 m layer, both adequate for maintaining crop productivity. In the regional analysis, all models provided statistically significant fits, though numerical differences were not statistically significant due to overlapping 95 % confidence intervals. Estimated CSTVs ranged from 7.4–13.5 mg dm-3 (summer + winter), 6.6–19.0 mg dm-3 (summer), and 5.5–12.5 mg dm-3 (winter), encompassing the regional threshold of 8 mg dm-3. Plateau models tended to estimate higher CSTVs for summer crops, while ALCC and Mitscherlich were more aligned with winter crop requirements, with Mitscherlich showing the best performance for winter crops in both 0.00–0.10 and 0.00–0.20 m layers. These results support the use of the 0.10–0.20 m layer as a diagnostic depth under no-till systems and highlight the need for standardized model selection and expanded regional datasets to refine CSTV estimates and enhance the efficiency of P fertilization strategies.
ABSTRACT The extreme climatic event in southern Brazil underscores the hydro-sedimentological vulnerability of agricultural headwater catchments within the Jacuí River Basin. This article describes the hydrological and erosive processes that took place between April 29 and 30, 2024, in the Guarda Mor River experimental catchment (18.5 km2), located at the interface between the Basaltic Plateau and the Central Depression regions of Rio Grande do Sul. The hydrological event was monitored based on rainfall, streamflow, and suspended sediment concentration to characterize runoff generation and sediment transport. In addition, topographic and geospatial surveys were conducted to characterize hillslope erosion processes and morphological changes in the stream channel. The study of the behavior of this event allows for a more precise understanding of local water dynamics, enabling stakeholders to anticipate flood risks, manage water resources more efficiently, and design targeted conservation strategies. Over a 31-hour period, 435 mm of rainfall were recorded, resulting in multiple streamflow peaks, with the highest reaching approximately 700 m3 s-1, and an estimated suspended sediment yield of around 12,365 Mg. Numerous diffuse and concentrated erosion processes occurred simultaneously and extensively, aggravated by local geomorphological, pedological, and land-use characteristics. The results underscore the importance of hydrological monitoring in headwater catchments and the adoption of practices to control and reduce surface runoff. These findings are particularly relevant for the Southern region of Brazil, which is characterized by intensive agricultural activity, complex topography, and a high frequency of extreme weather events, including intense rainfall and prolonged droughts. In this context, headwater catchments play a critical role in regulating water flow, sediment transport, and nutrient cycling across larger river basins.
ABSTRACT The combination of farming dairy effluent (FDE) with mitigating agents’ nitrogen (N) losses to the environment, such as zeolites, dicyandiamide (DCD), and biochar, may reduce losses and improve N availability to plants. A field experiment was conducted in an Argiudol of the Pampa region, Argentina, to evaluate N use efficiency and associated losses following FDE application. On a natural grassland with a predominance of ryegrass (Lolium multiflorum) and the presence in smaller quantities of fescue (Festuca sp.), alfalfa (Medicago sativa), and white clover (Trifolium repens). The treatments included application of FDE, FDE plus zeolite (Zeo), FDE plus dicyandiamide (DCD), FDE plus biochar (BC), and a control untreated soil (C), each with three replicates. A uniform application of 11 L m-2 of effluent (eq to 250 kg of N ha-1) was performed, and nitrous oxide (N₂O) emissions, ammonia (NH₃) volatilization, soil and atmospheric temperature, and water-filled pore space were monitored up to three months. Overall, N₂O emissions were low across all treatments, reaching a maximum of 18.4 µg m2 h-1 of N-N2O. Zeo and BC significantly reduced N₂O emissions by 63.1 and 63.8 %, respectively, compared with FDE alone. Furthermore, BC reduced NH₃ volatilization by 55.5 % relative to FDE, highlighting its strong potential to mitigate total N losses. Regarding pasture performance, the highest greenness index was observed in the BC treatment, followed by intermediate values in FDE, DCD, and Zeo, and the lowest in the control. Under our study conditions, with particularly low rainfall and high temperatures, the mitigating effects of DCD and Zeo appeared to be limited. In contrast, the combination of FDE and BC emerged as the most effective strategy to reduce N losses and enhance pasture quality. Furthermore, environmental conditions play a key role in determining the efficacy of mitigation strategies to curb N losses.
ABSTRACT In tropical and subtropical agricultural no-till (NT), lime and nitrogen (N) fertilizers are surface-applied. The pH increase from liming can enhance ammonia (NH3) volatilization. This study aimed to quantify NH3 losses from NT areas treated with different N fertilizers and lime rates and assess the effects on topsoil pH. Field experiments were conducted on clayey soil (Latossolo Vermelho distroférrico típico). The experimental design was a randomized complete block design with a 4 × 4 factorial split-plot arrangement and four replications. Main plots received four rates of dolomitic limestone (0, 2.6, 5.4, and 8.1 Mg ha-1) and subplots received four N fertilizers. Nitrogen fertilizers were: conventional urea (46 % N), urea coated with copper (Cu) and boron (B) (Ur-Cu+B; 0.15 % Cu, 0.4 % B, and 44 % N), NBPT-treated urea (Ur-NBPT, 46 % N and 0.53 % NBPT), and ammonium sulfate (AMS, 21 % N and 22 % sulfur). Nitrogen fertilizers were applied during two second-crop corn growing seasons, at 24 and 36 months after liming. Soil pH in the 0.00-0.05 m layer was determined at the end of the experiment. The increase in soil pH due to liming enhanced NH3-N volatilization losses, regardless of the N fertilizer used. Ammonia volatilization losses ranged from 16 to 32 % in urea plots, 12 to 31 % in Ur-Cu+B plots, 7 to 19 % in Ur-NBPT plots, and 0.2 to 5 % in AMS plots treated with lime rates of 0 to 8.1 Mg ha-1, respectively. For every 1 Mg ha-1 of applied lime, NH3-N volatilization increased by 1.7 to 2.2 % in Ur plots, 1.6 to 5.1 % in Ur-Cu+B plots, 1.3 to 1.5 % in Ur-NBPT plots, and 0.7 to 0.9 % in AMS plots. These results highlight the need to adjust N management after liming, with ammonium-based fertilizers (e.g., AMS) or stabilized urea sources (e.g., Ur-NBPT) being more effective mitigation strategies than urea or Ur-Cu+B in reducing NH3 volatilization under surface-limed no-till conditions.
ABSTRACT Integrating ancestral agricultural techniques into modern practices is essential to developing sustainable, resilient food systems in environments constrained by limited natural resources. This study investigated the Anthrosols of the Atacama Desert, analyzing how traditional populations managed and transformed local soils to enable sustainable agriculture under extreme arid conditions. To this end, samples of cultivated and natural soils were collected in six villages in the province of El Loa, characterizing their granulometry, the content of organic matter, macro and micronutrients, electrical conductivity and soluble anions, besides the mineralogy of the clay fraction by X-ray diffractometry. Statistical analyses (Kruskal-Wallis and Kendall tests) were used to evaluate differences and correlations between the parameters studied. Based on the study of cultivated soils, the results indicate that these Anthrosols underwent three distinct processes of anthrosolization: (1) the construction of terraces with selected materials, involving the removal of larger gravels and the concentration of finer particles, providing more favorable agricultural conditions; (2) irrigation management with Andean meltwater, enriching soils with Na, Ca, and Mg, while maintaining pH range without inducing salinization; and (3) the addition of animal manure, significantly increasing the organic matter and nitrogen contents compared to adjacent reference desert soils. Particle size analysis revealed a higher content of fine particles in cultivated soils (CS) compared to non-cultivated soils (NCS), resulting in greater water retention and improved soil structure. Chemical analysis indicated higher pH, cation exchange capacity, and base saturation values in CS, while phosphorus levels remained similar between CS and NCS, suggesting a high regional natural background of volcanic materials. The mineralogy of the clay fraction evidenced the presence of 2:1 (illite, smectite) and 1:1 (kaolinite) minerals, in addition to the formation of secondary carbonates in some CS, probably associated with irrigation practices. These Anthrosols, as ancestrally built and managed, represent valuable archaeological records of agricultural knowledge and have the potential to support long-term, sustainable cultivation strategies in arid environments subject to water scarcity and adverse climate conditions.
ABSTRACT For a comprehensive and global evaluation of soils, it is essential to define common diagnostic properties among classification or interpretative systems. Specifically, in soil taxonomy, the Brazilian Soil Classification System (SiBCS) adopts analytical methods that differ from those used in international systems such as the World Reference Base for Soil Resources (WRB) and the Soil Taxonomy (ST). In the chemical properties, differences are observed in the determination of exchangeable basic cations and potential acidity (H+Al), as well as derived properties such as the sum of bases (SB), cation exchange capacity (CECpH7), and base saturation (V). This study aimed to: (i) to compare the values of H+Al, SB, CEC, and V in Brazilian soils determined by different analytical methods; (ii) to propose regression models to harmonize values of the properties obtained through different analytical procedures; and (iii) to compare the threshold values of diagnostic properties used as classification criteria in the SiBCS with those adopted by WRB and ST. A representative database of Brazilian soils published in the Brazilian Soil Data Repository (SoilData) was used, comprising 2,217 samples from surface horizons and 3,726 from subsurface horizons. Values of SB, CEC, and V for surface and subsurface horizons, obtained using the methods applied in the SiBCS, were lower than those determined by the WRB and ST methods. The difference in the estimated V values was below 5 %, which falls within the analytical error range. Thus, the SiBCS criteria of V ≥50 % for identifying eutrophic character and >65 % for defining a chernozemic A horizon were found to be high, and they tend to underestimate several Brazilian soil classes, particularly those classified as Chernossolos, as well as the misclassification of anthropic and other soils modified by agricultural practices. It is proposed that the SiBCS adopt thresholds similar to those used in WRB and ST for base saturation, or alternatively, apply regression equations to improve correspondence among the systems.
ABSTRACT In the Moatize mine, tree species have been used for the coal minesoil restoration for more than 10 years. Nevertheless, the effects of such revegetation on chemical and physical properties of Moatize minesoils remain unknown. Here we present a pioneering 10.6-year chronosequence study aiming to monitor Moatize minesoils fertility, organic carbon stocks, and porosity, as well as interrelations of these properties. Furthermore, a natural (unmined) soil was sampled for comparison to provide insights into the reintegration of minesoils into the environment. We hypothesized that the fertility, organic carbon stocks, and physical properties of the minesoils improve with increasing restoration time but remain inferior to those of the unmined soil, likely due to the short revegetation period (10.6 years). The study was carried out in the Moatize coal mining area in Mozambique. In 2023, soil samples were collected from the 0.00−0.10 m layer in three 100 m transects, totaling 12 replicates per site, and chemical and physical properties were determined. Minesoils exhibited similar and strong acidity (pH <5.0) until 1.4 years, while from 5.3 to 10.6 years, they exhibited intermediate (5.14) and moderate (6.14) soil pH. Soil organic carbon stocks doubled in minesoils between the initial (until 1.4 years) and the final phase of evaluation (10.6 years). The positive effect of revegetation is also evident in the increase in macroporosity of the minesoils over time. The minesoil with 10.6 years of restoration presented properties very close to those of the unmined soil. However, we reinforce the need to monitor these minesoil properties in the long term to certify the successful integration of the mined land into the landscape.
ABSTRACT In southern Bahia, Brazil, cocoa trees (Theobroma cacao L.) are grown in soils with varied physical properties. As many orchards in the region have surpassed their productive lifespan, renewal is crucial for increasing productivity. However, there is limited understanding of how soil physical properties affect the productivity of renovated cocoa orchards. This study aimed to assess the relationship between soil physical properties and cocoa productivity in no-till renovated orchards. The research was conducted across 15 field trials on cocoa farms in southern Bahia. Cocoa yield was monitored from 2019 to 2022 (4th to 7th year post-establishment), while soil physical properties—granulometry, porosity, bulk density, soil penetration resistance, and volumetric water content (at field capacity, permanent wilting point, and available water)—were measured in 2019 as baseline in three soil layers: 0.00–0.10, 0.10–0.20, and 0.20–0.40 m. Data were subjected to univariate and multivariate statistical analyses. In all layers, yield was significantly correlated (p<0.05) with silt content (r = −0.29 to −0.31), silt/clay ratio (r = −0.23 to −0.27), field capacity (r = 0.24 to 0.34), permanent wilting point (r = 0.23 to 0.26), and available water (r = 0.22 to 0.24). Principal Component Analysis showed that yield was positively associated with field capacity and permanent wilting point, and negatively related to soil resistance to penetration and bulk density in the surface layers. Hierarchical cluster analysis grouped the 90 plots into four productivity classes: G1 (74 %, 2,758 kg ha-1), G2 (58 %, 1,878 kg ha-1), G3 (37 %, 1,557 kg ha-1), and G4 (17 %, 792 kg ha-1). Tukey’s HSD test (p<0.05) revealed that the higher-yielding groups (G1 and G2) had significantly lower silt content and silt/clay ratios compared to the lowest-yielding group (G4). Overall, cocoa yield was constrained by excessive soil penetration resistance in surface layers and by high silt content and silt/clay ratios across all layers, while balanced sandy-clay textures with improved aeration and water retention favored higher productivity. These results corroborate previous studies recommending cocoa cultivation in soils with lower silt content, due to its association with compaction, drainage limitations, and reduced water retention. The findings highlight the importance of considering soil physical properties, particularly granulometry, as a criterion for selecting priority areas for orchard renewal, thereby contributing to high-yielding and climate-resilient crops.
