Abstract in English:

ABSTRACT The absence of quantitative limits for the diagnostic attributes that define spodic B horizons in the Brazilian Soil Classification System (SiBCS) allows the inclusion of soils in the Espodossolos (the equivalent of Spodosols or Podzols) classes that contradict the classical concepts that define the podzolization process, by including horizons with low organic carbon (Corg) content, and with alkaline pH, high sum of bases and sodic or solodic characteristics. This study aimed to propose quantitative criteria and limits to identify spodic B horizons and to contribute to the hieraquical structure of SiBCS. Morphological, physical and chemical attributes were defined after analyzing a large set of spodic B horizons of profiles classified as Espodossolos in the SiBCS available in the literature. In total, 385 spodic B horizons were identified. From this total, they were identified as following: 93 as Bs(m), 127 as Bh(m) and 165 as Bhs(m). In terms of color, the main hues were 7.5YR and 10YR, while the value and the chroma were ≥4 in Bs(m), <4 in Bh(m) and a wide variation in Bhs(m). The means and medians of the Corg contents are 7.5 and 6.7 g kg-1 for Bs(m), 19.8 and 15.1 g kg-1 for Bh(m), and 19.0 and 14.5 g kg-1 for Bhs(m). When the limit of Corg content is established as ≥3.0 g kg-1, 90 % of the spodic horizons are included in this group, with 85 % of the horizons for Corg ≥4.0 g kg-1 and 81 % of the horizons for Corg ≥5.0 g kg-1. The pH(H2O) had 94 % of the spodic B horizons with values ≤5.9. Around 48 % of the spodic B horizons have Alo and Feo data and, by calculating the equation Alo + 0.5 Feo, around 47 % of the horizons have a value ≥0.25 %. The evaluation highlighted the potential for adopting the minimum Corg ≥5.0 g kg-1 and pH(H2O) ≤5.9 as quantitative limits for defining the spodic B horizon in the SiBCS. It is also suggested to apply a lower requirement for the Corg content in spodic horizons with very low clay content that is sand texture classes, using the values of Corg ≥3.0 or ≥4.0 g kg-1 as limits. Otherwise, the minimum Corg value proposed is 5.0 g kg-1 and the types of spodic B horizons could be differentiated using a second limit of Corg, distinguishing the Bs with a content of Corg between 5.0 and 15.0 g kg-1 and Bsh ≥15.0 g kg-1.

Abstract in English:

ABSTRACT Globally, soils with gypsic horizons cover approximately 1 million km², predominantly in arid climates. The formation of pedogenic gypsum in soils has been a topic of discussion in pedological studies for some time, with gypsification representing the process responsible for secondary gypsum accumulation. Even though international classification systems acknowledge the existence of gypsic horizons, there is a paucity of documented evidence concerning their occurrence in Brazilian soils. This study aimed to identify and describe a soil with secondary gypsum accumulation in the Brazilian semiarid region, employing the established criteria for in situ identification and classification. The study was conducted on a soil profile in the semiarid region of Pernambuco State, Brazil, that is undergoing salinization. Morphological descriptions of gypsum precipitates and chemical and mineralogical analysis were evaluated for their suitability for characterizing the material. Turbidimetric methods are more suitable for gypsum determination in hypersaline soils, while thermogravimetric analysis is the most accurate method for its mineralogical identification. This study establishes the first national record of gypsification in Brazilian soils and underscores the necessity of incorporating gypsum presence criteria into the Brazilian Soil Classification System (SiBCS) for effective soil management and environmental conservation.

Abstract in English:

ABSTRACT In precision agriculture, accurate delineation of management zones and understanding spatial variability of soil properties and crop yields are critical for optimizing resource allocation and improving productivity. Spatial variability of different environmental factors (soil and plants) is evident in several studies. Associations between the texture and chemical properties of the soil and cowpea yield have been tested, but a large, unexplained variance of ranges between kriged maps is usually reported. This suggests that a deeper exploration into the soil properties of these spatial interactions may help develop our understanding on how to reduce the number of soil property maps to delineate management zones and simplify interpretation. The main objective of this study was to investigate whether factorial kriging analysis can be used as an auxiliar variable to cokriging of soil properties and cowpea yield, and what is the potential of Spatial Fuzzy c-Means associated with factorial kriging analysis to delineate management zones. This study employed factor maps and spatial clustering to classify the cowpea field in management zones based on a multivariate and geostatistical analysis using soil texture and chemical properties. From Farmer, 66 soil samples were collected at a layer of 0.00-0.20 m, at points with a regular spacing of 12 m, at Agropecuária Milênio in the municipality of Tracuateua, Pará State, to make the technology applicable to the most common data available to farmers. It also used Spatial Fuzzy c-Means to generate estimated maps. Only the kriged maps of soil properties were inefficient in delineating management zones. Factor maps and Spatial Fuzzy c-Means were efficient in delineating the two management zones. Factorial kriging analysis can be used in cokriging to estimate soil properties and the cowpea field. The proposed method is a practical tool to delineate management zones, performing better and more efficiently compared with soil multiple property maps. The optimal number of management zones for cowpea cultivation was determined to be two. This encompasses soil management, yield considerations, and site-specific choices, all aimed at mitigating the impacts of precision agriculture on high productivity.

Abstract in English:

ABSTRACT Sugar and alcohol production in Brazil comes from planting hybrids from the crossing of species belonging to the Saccharum Complex. However, little is known about the growth response of these genera to inoculation using a diazotrophic bacteria Nitrospirillum viridazoti strain BR11145, currently recommended in Brazil as an inoculant for sugarcane growth promotion. This study aimed to evaluate the initial growth of 12 sugarcane genotypes inoculated or not with the strain BR11145. After 109 days, plant growth, biomass and macronutrient accumulation were evaluated. Fresh and dry mass at the end of the trial showed a positive response to inoculation for the genotypes US72-1319, CPDAU 849678, and NG77-122 of S. spontaneum and for Fiji 10 of Miscanthus. A negative response was observed for Q45416 of Saccharum sp. The growth of S. spontaneum US72-1319 is significantly improved by the inoculation with BR11145, which leads to a high accumulation of nutrients, especially N, standing out among the genotypes tested.

Abstract in English:

ABSTRACT Atlantic Forest devastation has resulted in the search and introduction of management capable of promoting and reestablishing the quality and sustainability of the ecosystem. Agroforestry systems (AS) are recognized for many benefits due to their management. This study compares an agroforestry system macrofauna and physical and chemical soil properties to those of a secondary forest area in the Atlantic Forest biome in southeast Brazil. Agroforestry system with 8 years of establishment and the regenerating subcaducifolious tropical forest fragment with 28 years were examined. Samplings were conducted in two periods of the year (rainy and dry seasons) to evaluate physical and chemical soil fertility-associated properties, as well as soil organic matter (SOM) fractions and biological aspects (macrofauna). Higher clay content, moisture levels, basic cations, and greater values of the sorption complex, diversity indices, and uniformity in macrofauna were observed in the agroforestry plots. Agroforestry systems increased the levels of the most labile fraction of soil organic matter (SOM) compared to the forest fragment. Higher abundance, diversity indices, and evenness of fauna were observed in the agroforestry plots during both seasons. In terms of multivariate analyses, a higher correlation was observed among fauna, carbon fractions, P, K+, pH, clay, potential acidity, moisture, and temperature in the Agroforestry plots. In general, AS promoted a positive relationship between physical and chemical properties and the macrofauna community of soil invertebrates, in a similar way and sometimes superior to the forest, confirming the study hypothesis and demonstrating the efficiency of management in maintaining soil properties and, consequently, ecosystem services.

Abstract in English:

ABSTRACT Soil saturated hydraulic conductivity (Ksat) and steady-state infiltration rate (SSIR) are essential and necessary soil properties for different geoscience applications. Values of these hydraulic properties for the Brazilian territory are difficult to access and are dispersed in research efforts carried out around the country. This study developed an easy-to-manipulate, freely accessible database of soil saturated hydraulic conductivity, comprising field and laboratory analyses, and steady-state infiltration rates for Brazilian soils. This database was named Ksat-SSIR-DB. One analysis of the Ksat-SSIR-DB aimed to evaluate its coverage in Brazilian territory and in different soil groups. Average values of these hydraulic properties were also presented for textural classes, with values compared to those reported in international literature, and for other groupings, such as soil class, land use class, and porosity class. The variability of Ksat data in these groupings and in their combinations were also analyzed. The Ksat-SSIR-DB showed broad national coverage, comprising a total of 2,579 records, corresponding to 409 sampling sites, with Ksat and/or SSIR data and other associated soil information. A significant difference was observed between Ksat values for the vast majority of Brazilian clayey and very clayey soils compared to soils from the same textural groups from temperate regions. The two groupings that presented the lowest variability in terms of Ksat standard deviation values were the combination of textural classes with soil classes at the second category level of SiBCS (Brazilian Soil Classification System), and porosity classes with soil classes at the second category level of SiBCS. The Ksat-SSIR-DB has enormous potential for developing and testing Ksat pedotransfer functions in Brazilian soils, serving as a reference source for different geoenvironmental applications and, in particular, for modeling land surface processes. It is open access and can be accessed at https://www.sgb.gov.br/ksat-ssir-dbbase-de-dados-de-condutividade-hidraulica-saturada-e-de-taxa-de-infiltracao-basica-emsolos-brasileiros, which also includes the python script for data analysis.

Abstract in English:

ABSTRACT Santa Catarina State, in the South region of Brazil, has 713 thousand hectares of pine forests. Harvesting operations of this species can degrade the soil, especially when carried out on very wet soil. However, there is little information on the impact of pine harvesting on the physical properties of the soil in this region. This study aimed to evaluate the impact of Pinus taeda L. harvesting on the physical properties of a Nitossolo Bruno distrófico típico. Two areas were selected for the evaluations: a 17-year-old planted pine forest and a harvested forest area. Soil samples were collected from 0.40-m-depth soil pits in the 0.00-0.10, 0.10-0.20, and 0.20-0.40 m layers to evaluate soil bulk density, porosity (total, macro, and micro), aggregate stability, penetration resistance, field capacity, permanent wilting point, available water, aeration capacity, and saturated hydraulic conductivity. There was modification between the two areas in properties related to porosity, aeration, water retention, hydraulic conductivity, penetration resistance, and aggregate stability. Macroporosity and aeration capacity remained above the limit of 0.10 m3 m-3, even with intense machine traffic at harvest. In the pine harvesting area, hydraulic conductivity was higher and penetration resistance was lower in the deepest layer. Before and after forest harvesting, penetration resistance was less than 3.5 MPa in all the layers evaluated, a value considered not to be restrictive to root growth and development. The mean aggregate diameter in the harvested forest area is 7 % lower compared to the pine forest area in the 0.00-0.10 m layer and 12 % lower compared to the 0.10-0.20 m layer. Therefore, mechanized harvesting of pine in the tree-length system led to little modification of the physical properties of the Nitossolo Bruno in the Planalto Sul (Southern Plateau) region of Santa Catarina.

Abstract in English:

ABSTRACT Grasses of the Brachiaria genus are widely used as cover crops in no-tillage areas of the Brazilian Cerrado. This study aimed to evaluate the ability of six Brachiaria cultivars to produce shoot and root biomass, and the potential of the root system to grow through a 0.01 m thick wax layer with 1.5 MPa penetration resistance. The plants were grown in PVC columns with a diameter of 0.1 m and a height of 0.7 m. The column was divided into an upper part measuring 0.25 m (top) and a lower part measuring 0.45 m (bottom). The wax layer was positioned between the two parts of the column as a physical barrier to be perforated by the roots. The columns were filled with peaty substrate. The Brachiaria cultivars used were: Brachiaria brizantha cv. BRS Piatã, Brachiaria decumbens cv. Basilisk, Brachiaria brizantha cv. BRS Paiaguás, Brachiaria ruziziensis cv. Ruziziensis, Brachiaria brizantha cv. Xaraés and Brachiaria brizantha cv. Marandu. The Ruziziensis cultivar accumulated a high root dry mass, but the Xaraés cultivar presented the highest wax layer perforation capacity (80 %). Decumbens is the species with the lowest wax layer perforation capacity (10 %). Brachiaria species and cultivars demonstrated differences in their responses to high root penetration ability, which can be used for recommended different species of Brachiaria in different proposes used changes in shoot, leaves, and root dry matter and the distribution of roots in the soil column profile. Xaraés cultivar has potential to be used as a management strategy in soil recovery for degraded lands with mechanical impedance.

Abstract in English:

ABSTRACT Stress transfers inside the soil during the traveling process of agricultural machinery, and the bonding of soil particles during this process is the main cause of soil compaction. In this study, the discrete element method was used to simulate the different responses of stress transfer and particle bonding in the soil under different times of tire passes in the tire-soil interaction process of agricultural machinery operation. It was found that from 1 to 8 passes, the increase in the times of tire passing caused the soil stress to transfer from the depth of 0.20 to 0.70 m, with the maximum stress reaching 27.36 kPa. The number of force chains between soil particles increased gradually with the increase in the times of tire passing, and the number of force chains risen from 12,058 to 14,515. This indicated that there was an inextricable link between tire passes and the formation of cumulative compaction in soil. The results of this study verified the validity of the DEM model based on PFC3D, providing a theoretical basis for the subsequent research on soil mechanical compaction technology for mitigating soil compaction caused by agricultural machinery and equipment.

Abstract in English:

ABSTRACT Organic fertilization with tobacco powder compost produced via solid-state fermentation (SSF) is a recent practice that needs to be evaluated through research. This study aimed to evaluate the effect of two nitrogen sources – tobacco powder compost or mineral fertilizer (NPK) – and of compost doses on N use and loss in an immediate and residual way in a wheat/corn crop succession in a subtropical Argissolo. The wheat/corn crop succession was established after three successive fertilizer applications with different doses of the compost and of NPK. The following treatments were evaluated: control without application of the compost or mineral fertilizer (C0); mineral fertilization (NPK); and three doses of tobacco powder compost calculated to supply half (C50), the same amount (C100), and double (C200) the N applied via mineral NPK fertilization. To evaluate the residual effect of the fertilizer applications, the C50, C100, C200, and NPK treatments gave rise to additional treatments that did not receive more fertilization: rC50, rC100, rC200, and rNPK, respectively. The C0 generated an additional treatment that came to receive compost, identified as C0-C100. Yield and N accumulation in the aerial part of wheat and corn and N2O emission were evaluated throughout the two crop periods. Compost, in comparison to NPK, maintained the grain yield of wheat (3.0 vs2.5 Mg ha-1) and of corn (10.2 vs 9.5 Mg ha-1) and increased N accumulation in the wheat plants (96 vs 68 kg ha-1) and corn plants (191 vs 164 kg ha-1). Compost increased cumulative N2O emissions by up to three times compared to NPK (6.84 vs 1.93 kg N-N2O ha1 yr1). Increasing the compost dose increased cumulative N2O emissions by 52 % (9.36 vs 6.16 ha-1 yr-1); however, it did not change the emission factor (EF) of N2O, the yield-scaled emission, or N use efficiency. The compost residual effect increased wheat yield up to 93 % and corn yield up to 102 %, whereas no residual effect was observed from NPK. Compost applied on the previous crops did not affect N2O emissions in wheat or in corn; consequently, a residual effect did not impact the EF of N2O. Therefore, tobacco powder compost has the potential to replace mineral fertilization in wheat and in corn. Considering its residual effect is an important strategy to optimize its use and mitigate N2O emissions to the atmosphere.

Abstract in English:

ABSTRACT Different cultivation methods directly affect the quality of medicinal materials, to gain insights into the effects of different type of mulching on the quality of Notopterygium franchetii root medicinal materials, farmland experiments were conducted in the Qinghai-Tibet Plateau. We subjected two-year-old Notopterygium franchetii seedling to five mulching treatments: no mulching (CK, control), coarse sand mulching (CM), grassy mulching (GM), stalk mulching (SM), and plastic mulching (PM). Following these treatments, we determined the moisture content, pH, NPK contents, and enzymeatic activity of the soil, and morphological indexes and content of the main components of root. Stalk mulching and PM increased the main root biomass by increasing its ground diameter and reduced branched root biomass by reducing the number of branched roots produced. Grassy mulching increased the root biomass by promoting main root elongation. Mulching increased the total content of the six main root components, with the most significant change obtained with GM, but the pattern of change of the different components varied among the mulch treatments. Contents of NPK were significantly higher than in the control with GM, but decreased with PM. Coarse sand mulching and PM significantly reduced the activities of urease and sucrase, and SM significantly increased the activities of urease, catalase and sucrase, but significantly decreased that of phosphatase. Furthermore, GM significantly increased phosphatase and sucrase activities, while CM significantly decreased urease and sucrase activities. Various soil enzymes and its pH promote main root bioaccumulation by increasing the root ground diameter or main root length. Sucrase activity promoted the accumulation of ferulic acid, psoralen, and notopterol content, and inhibited the accumulation of chlorogenic acid and nodakenin. Elevated soil water content promoted the accumulation of ferulic acid, notopterol and nodakenin, and inhibited isoimperatorin accumulation. Hence, NPK, pH, and various enzymes have different effects on the accumulation of major components in the root. The effect of mulching is closely linked to root growth and distribution, as well as to the soil environment. Various soil factors affect the quality of medicinal materials differently and, ultimately, can work together to form an equilibrium state that benefit the accumulation of main root biomass and main components with medicinal interest in Notopterygium franchetii.

Abstract in English:

ABSTRACT Modern runner-type peanut cultivars have high yield potential, but little is still known about the dynamics of nutrient uptake by these cultivars and whether nutrient uptake differs between maturity groups. This study evaluated the growth, nutrient uptake, and nutrient removal of runner-type peanut cultivars with early and late maturity. The study was conducted in the field in the 2021/2022 season, in a sandy soil environment in southeastern Brazil. Treatments consisted of runner-type peanut cultivars (early and late maturity) and the phenological stage of sampling (V4/V5, R2/R3, R4, R5, R6, R7, and R8). Average pod yields were 4.0 and 5.9 Mg ha-1 for the early and late-maturity cultivars, respectively. Uptake of P, Cu, and Zn was linearly increased until stage R8. Nitrogen uptake continued until stage R7 for the early-maturity cultivars and stage R8 for the late-maturity cultivar. Potassium and B uptake did not increase after stages R5 and R6, respectively. For all other nutrients, maximum uptake occurred between stages R3 and R7. Leaf contents of all nutrients were within the sufficiency range, except Fe, which was higher than needed. Maximum macronutrient uptake (late-maturity cultivar) rates were 300, 28, 215, 76, 31, and 19 kg ha-1 for N, P, K, Ca, Mg, and S, respectively, and the maximum micronutrient uptake rates were 2350, 95, 391, 659, and 414 g ha-1 for Fe, Cu, Zn, Mn, and B, respectively. Maximum macronutrient removal rates were 210, 20, 48, 15, 7, and 12 kg ha-1 for N, P, K, Ca, Mg, and S, respectively, and the maximum micronutrient removal rates were 967, 59, 236, 153, and 136 g ha-1 for Fe, Cu, Zn, Mn, and B, respectively. Late-maturity cultivar had higher biomass production and greater uptake of all nutrients except K and Fe. The uptake of K and Fe was the same for both maturity groups.

Abstract in English:

ABSTRACT Cashew tree (Anacardium occidentale L.) is a fruit species widely cultivated in Brazil, but the interest in evaluating this plant nutritional status is very recent, to the point there is still no defined diagnostic leaf. This study aimed to define the leaves that reflect the nutritional status of dwarf cashews. Leaf samples were collected from a productive orchard established with four dwarf cashew clones: ‘CCP 76’, ‘BRS 189’, ‘BRS 226’, and ‘BRS 265’. Leaf sampling was performed over four consecutive years, at the beginning of the flowering season and the emergence of inflorescences with floral buds. Sampling was carried out from the first to the sixth fully expanded (mature) leaf, from the inflorescence towards the base of the branch. Total leaf content of macronutrients, micronutrients, and Na were quantified. Multi-element index variables were obtained using Compositional Nutrient Diagnosis (CND) methodology, and total leaf concentrations were correlated with cashew nut yields. The pair of leaves closest to the base of the branch, 5th and 6th leaves, showed a balanced index of nutrients, including N, K, Ca, S, Mn, and Zn. These leaves were also positively correlated with cashew nut yield and exhibited lower coefficients of variation for most of the analyzed nutrients. Thereby, the 5th and 6th leaves are recommended as diagnostic leaves for evaluating the nutritional status of dwarf cashews.

Abstract in English:

ABSTRACT Lime applications are used in acid soils to correct pH and eliminate Al3+ toxicity in crops. The lime rates are determined based on the estimated soil potential acidity (H+Al), using soil incubations with calcium carbonate (CaCO3) for 180 days, being a time-consuming and laborious process. An alternative method with calcium hydroxide [Ca(OH)2] for 96 h incubation may efficiently estimate H+Al, but it needs further studies. Also, soils from specific regions in southern Brazil have high organic matter (SOM) contents (>5 %), medium clay contents (20-40 %), and are stony, lacking research to improve liming recommendations. The study aimed to determine potential acidity and adjust lime rates for acidity correction in medium-textured soils with high SOM and stoniness in the Serra Gaúcha region (RS), Brazil, and to test the efficiency of the short incubation alternative method. For this purpose, 20 native forest soils were sampled in the 0.00-0.20 m layer. Samples were dried, sieved, and subjected to short and long incubations. The H+Al values obtained through the incubations were compared with the Manual de calagem e adubação para os Estados do Rio Grande do Sul e de Santa Catarina (CQFS-RS/SC, 2016) equation. The H+Al values estimated by CQFS-RS/SC were lower than those determined by the long incubation, indicating lime rates ranging from 2.0 to 5.1 Mg ha-1 lower than in the long incubation. The short incubation showed a positive correlation (0.93***) with the long incubation. The potential acidity for soil water pH 6.5 can be obtained by long [H+Al (cmolc dm-3) = 1354.9e-0.855TSM] and short [H+Al (cmolc dm-3) = 3763.8e-1.086TSM] incubations, in which TSM is the Tampão Santa Maria index. On average, 34 % of the soil volume was composed of rock fragments (>2 mm). We recommend adjusting the limestone rates for soils with stoniness, considering only the percentage of soil in the diagnostic layer (SDL%).

Abstract in English:

ABSTRACT Although the hydrological importance of water infiltration into the soil and surface runoff is well known, manual measurement of these processes, especially at the plot and hillslope scales, is laborious and requires a trained team. This study aimed to develop prototypes with the tipping bucket principle for the automatic monitoring of surface runoff at a plot scale (14.5 × 3 m). In total, 18 prototypes were built and installed in an experiment with different soil covers. Aspects of the construction, calibration, operation and maintenance of the prototypes were reported in this study. Prototypes showed a satisfactory ability to monitor surface runoff with flow rates up to ~80 L min-1. The devices have an adjustable resolution of up to 5 L pulse-1, and they are inexpensive, easy to construct and simple to maintain. Although designed for a specific plot size (43.5 m2), the equipment can be adapted to smaller or larger plots by adjusting the volume of the tipping chambers. The proposed systems allow greater practicality in conducting experiments to monitor water loss through surface runoff at the plot scale and provide more detailed recordings of information.

Abstract in English:

ABSTRACT Soil erosion in tropical environments causes environmental, social and economic damage. Canephora coffee crops are impacted by soil erosion and testing alternatives to mitigate this damage is a current need. This study aimed to evaluate the losses of sediment, organic carbon, nutrients and surface runoff caused by water erosion in between-rows spacing of Coffea canephora Pierre ex A. Froehner plants in management with and without cover crops, and the effect of the intensity of rains on sediment loss and the surface runoff. The management practices tested in between-rows spacing of coffee plants were: ES - exposed soil after manual weeding with a hoe; CC1- soil covered by palisadegrass [Urochloa brizantha (Hochst. ex A.Rich.) R.D.Webster] and nutsedge grass (Cyperus rotundus L.); and CC2- soil covered with purslane plant (Portulaca oleracea L.). Nine experimental plots were installed to measure losses of sediment, organic carbon, nutrients and surface runoff in the periods from September/2021 to March/2022 and from September to December/2022. The CC1 and CC2 reduced losses of sediment, organic carbon, nutrients and the volume of surface runoff from 37 to 86 % compared to ES. The increase in volume and rainfall intensities increased sediment loss and the surface runoff linearly, being more intense in ES management. The maintenance of the cover crops in between-rows spacing of coffee plants proved to be advantageous for mitigating losses of sediment, organic carbon, nutrients and surface runoff caused by water erosion, contributing to soil conservation and the sustainability of canephora coffee production.

Abstract in English:

ABSTRACT Wetlands provide important ecosystem services, including climate regulation through carbon sequestration and water storage. Identifying and protecting wetlands is a potentially significant opportunity for current global mitigation efforts. Cerrado wetlands commonly contain carbon-rich soils (peat); however, these environments have been neglected due to lack of knowledge on their characteristics and behaviors. Obtaining data in remote regions using a detailed sampling approach to characterize the organic carbon accumulation in these environments is extremely necessary. In this study, soil samples from 40 points of a peat-wetland (173.16 ha) in the Urucuia River watershed (Minas Gerais, Brazil) were analyzed every 0.20 m up to 1.20 m of depth. Their chemical and physico-hydraulic properties were studied to quantify organic carbon storage under different land covers. In addition, the influence of organic carbon accumulation on soil water storage in a dry period was also investigated. Considering the contribution of each vegetation type, the (weighted) average for the wetland stocks was 321.91 Mg ha-1 of carbon at full depth, whereby vereda (462.59 Mg ha-1) and gallery forest (447.63 Mg ha-1) were the biggest stockers compared to wet grassland (267.22 Mg ha-1), pasture (123.46 Mg ha-1), and Cerrado stricto sensu (57.77 Mg ha-1). Also, the study area holds 677.38 mm of water, with the following water depths: 831.32 mm for gallery forest, 780.42 mm for vereda, 693.63 mm for wet grassland, 297.59 mm for pasture, and 220.33 mm for Cerrado stricto sensu. The total organic carbon mass and stored water volume were respectively 55,741.94 Mg and 1,155,635.21 m3, respectively. A significant correlation between organic carbon and water stored was found (0.73), highlighting the role organic matter plays in water storage, whereby the latter is under greater influence and can be explained by layer depth rather than vegetation type. However, surface layers show evidence of a degradation process that may be linked to the lowering of the water level due to subsurface lateral flow, either through the indirect use of their soils and/or through the input of mineral material (erosion process). The study data highlight that riparian zones of the Cerrado biome must be protected to maintain their ecosystem services.

Abstract in English:

ABSTRACT Soils polluted by potentially toxic elements (PTEs) pose a high risk to human health and must be remediated. Applying biochar to such soils can reduce metal bioavailability and phytotoxicity, improving phytoremediation techniques. This study aimed to assess the effects of rice straw biochar (RSB) on mitigating metal stress and accumulation of Si, Cd, Pb, and Zn in corn plants grown in soil contaminated by metallurgy slag. Soil in pots was amended with RSB rates equivalent to 0, 5, 10, 20, and 30 Mg ha-1 and grown with corn for 45 days. Chlorophyll fluorescence, photosynthetic pigment contents, and gas exchange parameters were evaluated as PTEs toxicity indicators. The RSB rates significantly increased Si uptake while reducing Cd, Pb, and Zn accumulation in corn shoots. The addition of 30 Mg ha-1 RSB promoted 18, 34, and 37 % reductions for Zn, Cd, and Pb in the plants, respectively. Photosynthetic rate, transpiration, and stomatal conductance increased by 68, 67, and 55 %, while chlorophyll a, b, and carotenoid contents increased by 77, 57, and 42 %, correspondingly. Chlorophyll fluorescence measurements showed a linear and positive relationship between photosystem II energy consumption efficiency (Fv/Fm) and RSB rates. The combined use of RSB and corn can effectively phytoattenuate Cd, Pb, and Zn contamination by enhancing biomass and improving maize tolerance to PTE stress. This sustainable and cost-effective strategy offers environmental and health benefits while generating income for stakeholders in resource-limited areas.