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Black wattle is a tree native to Australia and commercially planted in South Africa and Brazil. Replacement of exported nutrients by wood and bark harvesting, associated with the maintenance of harvest residues, increases productivity, thus maintaining production sustainability. Here, we review recent advances in soil nutrient dynamics, harvest residue management (HRM), and soil organic matter in black wattle plantations. Over the 7–11-year cycle of black wattle, N is the most exported macronutrient (458–1509 kg ha− 1), followed by K (200–766 kg ha− 1), Ca (270–717 kg ha− 1), Mg (62–128 kg ha− 1), S (29–57 kg ha− 1) and P (16–40 kg ha− 1). The average increase in bark yield to 20 kg P ha− 1 applications on sandy soils was 2.7–2.9 t ha− 1 and on clay soils from 2.8 to 8.7 t ha− 1. Sandy soils with low K are more responsive to fertilizer, and rates must consider the K content and cation exchange capacity. Ca and Mg addition responses are more likely when in the topsoil they are in low concentrations (< 0.75 and 0.41 cmolc dm− 3, respectively). Micronutrient fertilization reduces the occurrence of gummosis caused by Phytophthora spp, and B deficiency is the most common and can be supplied by fertilization or foliar application (1 g B L− 1). Few studies have evaluated the impact of black wattle HRM on soil organic matter (SOM) and its effects on production. However, conserving SOM should be considered an essential practice for the sustainability of black wattle production. [ABSTRACT FROM AUTHOR]

Cotton (Gossypium hirsutum L.) is responsive to boron (B) fertilization when there is low soil availability, but the best source and rate to be used and whether this response is dependent on soil texture are still unknown. This study aimed to adjust boron fertilization for cotton as a function of the production environment and B source used. Two field experiments were conducted in the 2020/2021 season in Chapadão do Sul, MS (clayey soil—adequate B content) and Dracena, SP (sandy soil—low B content), Brazil. Treatments consisted of B sources (ulexite [low solubility], borax pentahydrate [BP] [intermediate solubility], and boric acid [BA] [high solubility]), and B rates (0, 1, 2, 4, and 6 kg ha−1) applied to the soil at 25 days after plant emergence. In sandy soil with low B content, application of 2 (high and medium solubility sources) and 4 kg B ha−1 (low solubility source) improved fiber yield between 10% (210 kg ha−1 fiber) and 28% (555 kg ha−1), respectively, as well as micronaire index, strength, elongation, uniformity, and short fibers. Application of B greater than 4 kg ha−1 via soluble sources reduced (between 9% (175 kg ha−1)—BP and 14% (257 kg ha−1)—BA) fiber yield only in sandy soil. When B content in the soil is adequate, B fertilization did not improve yield, but increased fiber strength (4%—1.1 g tex−1) and reduced the short fiber index (16%) by applying 1 kg B ha−1, regardless of the source used. The highest fiber yields were obtained with leaf B contents between 12 and 17 mg kg−1 (sandy soil) and 25 and 27 mg kg−1 (clayey soil). We recommend applying 2 kg B ha−1 (solubility sources) and 4 kg B ha−1 (low solubility source) in sandy soils with low B content to improve yield and fiber quality, and 1 kg B ha−1 in clayey soil with adequate B content to improve fiber quality and replace B amounts removed through harvesting. Core Ideas: Boron fertilization in sandy soils increased fiber yield by 210–555 kg ha−1.There are no effects of B fertilization in clayey soils on fiber yield, but there are improvements in fiber quality.Rates greater than 4 kg ha−1 of B via soluble sources reduce fiber yield in sandy soils.Cotton grown in clayey soil is more resistant to B toxicity. [ABSTRACT FROM AUTHOR]

Aims: We aimed to understand how eucalypt forests planted in highly weathered natural low fertile soils of the Brazilian Cerrado would benefit from the use of limestone (+ L) and phosphogypsum (+ G) applied banded or broadcast and incorporated or non-incorporated. Methods: The treatments applied here can be grouped into three, as follows: Group 1 – consists of three treatments that did not receive any limestone or phosphogypsum (control); Group 2 – consists of four treatments with + L only (different ways of applying + L); and Group 3 – consisting of two treatments including + L + G combined (different ways of applying + L + G). Results: The + L banded (Ba) and incorporated (I) (+ LBaI – Group 2) provided the greatest residual effect on soil chemical characteristics, increasing Ca2+ and Mg2+ availability and decreasing exchangeable and active acidity, regardless of the soil type. Consequently, an increase of 39.4% (~ 91.4 m3 ha−1) and 16.7% (~ 47 m3 ha−1) of eucalypt wood volume was obtained in the sandy and clay soils, respectively, when compared to the controls. However, when + L and + G were combined (Group 3) it increased S-SO42− concentrations, improving root development in the deeper layers. This resulted in the highest eucalypt productions with 58% (122.7 m3 ha−1) and 29% (94.7 m3 ha−1) more wood than the control in the sandy and clay soils, respectively. Conclusions: The application of + L and + G increased wood production of eucalypt planted forests in highly weathered and low fertile tropical soils due to better plant nutrition and soil amelioration. [ABSTRACT FROM AUTHOR]

The agricultural frontier in Brazil advances mainly in areas of sandy soils, where the management of soil fertility is still a challenge, including the practice of liming. Limestone dissolution was investigated under varying doses (0–40 t ha−1) in soil samples with a wide range of textural gradients (5%–74% clay). In view of textural variations and limestone rates, the objective was to generate information regarding pH, the residual liming effect, and exchangeable calcium (Ca) and magnesium (Mg) levels, including under overliming conditions. Throughout the textural gradient, the pH was between 4.2 and 8.5. On more sandy soils (5%–18% clay), overheating (pH > 7) was obtained with ~ 2 t ha−1 of limestone. On clayey soils (37%–74% clay), a similar effect was obtained with ~ 10 t ha−1 of limestone, indicating the marked difference in the acid buffering capacity of these soils. In addition, the equilibrium pH in the context of overliming in sandy soil was higher (8.2) compared with clayey soils (7.8). The residual liming effect was greater in sandy soils due to the lower potential acidity. Regardless of the soil texture, the Ca/Mg ratio increased in the context of overliming. Liming must be carefully applied and requires proper recommendations, especially on sandy soils, avoiding pH ≥ 6.5, a condition that is not suitable for most crops. [ABSTRACT FROM AUTHOR]

The occurrence of lateritic soils with clayey texture, unsaturated, and with high porosity is common in Brazil. When subjected to an increase in moisture (loss of suction) in the more superficial layers, such soils end up altering their stress–strain behaviors, which are complex, culminating in countless geotechnical uncertainties. A phenomenon referred to as collapse is attributed to materials subjected to variation in saturation that entail significant differential settlements. Considering this situation, following the implementation of the Geotechnical Engineering Experimental Field located in the state of Rio Grande do Sul, Brazil, a broad study involving laboratory tests (granulometry, x-ray diffraction, water retention curve, confined compression, direct shear (natural and inundated condition), and consolidated drained triaxial compression tests) and field tests (SPT and static pile load tests) was carried out in the natural moisture and inundated conditions to assess the conditions of saturation and loss of suction in such materials. The results indicated that the shear strength of the soil was linked to the suction, having an 81.34% decrease in the cohesive intercept, and practically maintaining the soil friction angle. Confined compression tests with inundation indicated that the soil presented itself as potentially collapsible. The results obtained from the conducted pile load tests, revealing a substantial decline in carrying capacity ranging from 29 to 43% attributed to saturation of unsaturated soils, emphasize the paramount significance of this scientific article in comprehending the potential hazards associated with diminished bearing capacity and the subsequent emergence of structural pathologies or, in extreme cases, structural collapse. [ABSTRACT FROM AUTHOR]

Copyright of Revista Brasileira de Engenharia Agricola e Ambiental - Agriambi is the property of Revista Brasileira de Engenharia Agricola e Ambiental and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Several studies have reported increased copper (Cu) and zinc (Zn) levels in agricultural soils worldwide, mainly due to organic waste and successive leaf fungicide applications in crops. However, the critical transfer thresholds in soils, which can indicate the real risk of environmental contamination and toxicity to plants, remain poorly understood. This study aimed to define the maximum Cu and Zn adsorption capacity (MAC) and threshold (T-Cu and T-Zn) in different soils in Southern Brazil, which present different clay and organic matter (OM) levels. Bw (Oxisol) and A horizon (Inceptisol) samples were used to obtain soils with clay and OM contents ranging from 4 to 70% and from 0.5 to 9.5%, respectively. Cu and Zn adsorption curves were plotted for MAC determination purposes. Based on Cu and Zn MAC values, different concentrations of these elements were applied to the soils for subsequent quantification of available Cu and Zn levels (Mehlich-1 and water). T-Cu in soils with different clay contents ranged from 81 to 595 mg Cu kg−1, whereas T-Zn, from 195 to 378 mg Zn kg−1. T-Cu in soils with different OM levels ranged from 97 to 667 mg Cu kg−1, whereas T-Zn, from 226 to 495 mg Zn kg−1. T-Cu can be calculated through the equation: T-Cu = 75 × (%CL0.34) × (%OM0.39), whereas T-Zn: T-Zn = 2.7 × (CL) + 126 (by taking into consideration the clay content) and T-Zn = − 9.3 × (%OM)2 + 92.4 × (%OM) + 66 (by taking into consideration OM content). T-Cu and T-Zn can be used by researchers, inspection bodies, technical assistance institutions, and farmers as safe indicators to monitor the potential for environmental contamination. [ABSTRACT FROM AUTHOR]

Soils from the superficial layers of the Guabirotuba formation (in Brazil) are problematic due to their expansive and low-bearing capacity. Stabilizing these soils with a calcium-based binder is a technique that must be explored. Therefore, this study aims to determine the mechanical behavior of stabilized sedimentary silts with cement and binder in various conditions. Four types of fine soils were used in deformed conditions. These soils were mixed with cement and compacted to measure their mechanical behavior. The specimens were tested in unconfined compressive and split tensile tests prepared with respect to several molding conditions: the moisture content, the curing period, durability cycles, the dry unit weight, the cement content, the cement type, and the soil type. This study was also carried out to develop a simplified approach to estimating the unconfined compressive strength (qu or UCS) and split tensile strength (qt or STS) of soil-cement or soil-cement–binder mixes. The results further demonstrate the influence of the porosity/volumetric cement index (η/Civ) on the qu- and qt-adjusted two new parameters—bo = 0.174 (dependent on cement) and k = 2.565 (dependent on the type of soil)—proposed herein for all mixtures studied. Using the proposed new parameters, a unique equation was developed to estimate the strength of the compacted blends as a function of the porosity and binder content, with an acceptance of 93% and an error close to 6%. [ABSTRACT FROM AUTHOR]

Maize (Zea mays L.) is a major cereal crop worldwide and demands N fertilizers, which can be replaced partially by plant growth‐promoting bacteria. In Brazil, inoculants carrying Azospirillum brasilense strains Ab‐V5 and Ab‐V6 have exponentially grown, but a quantitative study on the replacement of N fertilizer by inoculants is still missing. Under greenhouse conditions, we investigated the effects of A. brasilense cells and metabolites applied via seeds or leaf‐sprayed at the V3 growth stage on roots and confirmed strong benefits in traits that improve the uptake of water and nutrients. In the field, 30 trials were performed at 13 sites in Brazil over 10 yr, comparing noninoculated and inoculated maize receiving 0, 50, 75, and 100% (90 kg ha–1 of N) of N fertilizer (urea) applied as side‐dress 35 d after emergence. Overall, inoculation significantly increased grain yield by 3.1%. Increases were confirmed in lower and higher yield levels, subtropical and tropical conditions, and clayey and sandy soils, with low and higher soil organic carbon levels. Yield increases due to inoculation were statistically significant at all levels of N fertilizer, except for at 50%. Inoculation with the supply of 75% of N increased yield by 4.6% compared with the noninoculated counterpart and, noteworthy, did not differ statistically from the non‐inoculated control receiving 100% of N. These results confirmed the feasibility of replacing 25% of N‐fertilizer applied as side‐dress by seed inoculation with A. brasilense, besides the possibility of avoiding the emission of 4.95 million Mg of CO2‐e per year. Core Ideas: Maize requires N fertilizers; is it feasible to replace them partially by inoculation with A. brasilense?Results of 30 field trials in Brazil indicate the possibility of replacing 25% of N fertilizer by inoculation.Benefits observed in different yield levels, subtropical/tropical conditions, clayey/sandy soils, and low/higher soil organic C.The replacement could save US$15 ha−1 and avoid the emission of 236 kg of CO 2‐e ha−1. [ABSTRACT FROM AUTHOR]

Improvements in nitrogen use efficiency (NUE) in corn production systems are necessary, to decrease the economic and environmental losses caused by loss of ammonia volatilization (NH3-N). The objective was to study different nitrogen (N) fertilizer technologies through characterization of N sources, NH3-N volatilization losses, and their effects on the nutrient concentration and yield of corn grown in clayey and sandy soils in south Brazil. The treatments consisted of a control without N application as a topdressing, three conventional N sources (urea, ammonium sulfate, and ammonium nitrate + calcium sulfate), and three enhanced-efficiency fertilizers [urea treated with NBPT + Duromide, urea formaldehyde, and polymer-coated urea (PCU) + urea treated with NBPT and nitrification inhibitor (NI)]. The losses by NH3-N volatilization were up to 46% of the N applied with urea. However, NI addition to urea increased the N losses by NH3-N volatilization by 8.8 and 23.3%, in relation to urea alone for clayey and sandy soils, respectively. Clayey soil was 38.4% more responsive than sandy soil to N fertilization. Ammonium sulfate and ammonium nitrate + calcium sulfate showed the best results, because it increased the corn yield in clayey soil and contributed to reductions in NH3-N emissions of 84 and 80% in relation to urea, respectively. [ABSTRACT FROM AUTHOR]

Forage grasses cultivation in production system with soybean and maize is an alternative to improve tropical weathered soils quality in Brazil. The aim of the study was to evaluate the effects in the production systems involving cultivation of Urochloa brizantha cv. Piatã, in monoculture or in succession with soybean and maize crops, on organic matter and structuring of soil in Brazilian savanna. The experiment was implemented in the 2010/2011 season. The treatments consisted of nine production systems and a native forest (savanna) as a reference area. In March 2017, soil sampling was carried out for C and N analysis, physical and chemical fractionation of SOM and aggregate stability. Production systems influenced total organic carbon (TOC) and aggregate stability, mainly in the surface layers, leading to changes in SOM quality. TOC was 31% lower in monoculture soybean production system, when compared to native savanna area, in the 0.00–0.20 m layer. The agricultural production systems influence organic matter quality and soil aggregates stability. For the Brazilian savanna conditions, grain cultivation systems under no-tillage that integrate Urochloa brizantha cv. Piatã contribute to the soil quality improvement. Soybean monoculture generally provides worse soil quality indices compared to other agricultural production systems. [ABSTRACT FROM AUTHOR]

Azocyclotin and cyhexatin are pesticides commonly used in mite control. However, these organotin compounds (OTC) are highly harmful to the aquatic ecosystem and supposedly mobile in the soil. In addition to not existing defined rules of use, few studies have been carried out on organotins' behavior and environmental control. Liquid chromatography has been pointed out for the OTC quantitation because of gas chromatography's thermal stability and derivatization limitations. Hence, a new high-performance liquid chromatography method with photodiode array detection was developed for quality assurance and quality control and environmental performance assessment purposes. Hysteresis index (HI) and mobilization factor were determined from sorption/desorption in sandy and clayey soils to assess mobility and environmental risk. Mobilization was observed for the two compounds by applying the dual-mode Freundlich–Langmuir model to the isotherms. Azocyclotin showed greater mobility, 23% and 19%, and HI of − 0.15 and 7.8 × 10 - 4 for clayey and sandy soil samples, respectively. Although cyhexatin was practically immobile for both soil samples, it can be mobilized as an azocyclotin metabolite, increasing the environmental impact and risk for agricultural uses. [ABSTRACT FROM AUTHOR]

There are growing evidence that nitrogen (N) recommendation based on the expected yield concept developed by Stanford in 1973 lacks in agronomic principles, despite it widespread use worldwide. In Brazil, the main sugarcane producer worldwide, for example, a fixed N factor of 1 kg N per Mg−1 of stalk is used. However, literature demonstrates that sugarcane responsiveness to N is much higher in sandy soils rather than in clayey soils, whereas the recommended N is usually higher in clayey soils because of its improved yield potential. We investigated 146 response curves of sugarcane (Saccharum spp.) to N to define a better approach for determining N rates instead of using exclusively the expected yield concept. First, we found no correlation between the economically optimal N rate (Nopt, kg ha−1) and the yield (Mg ha−1) obtained in Nopt. Second, we calculate the N requirement (Nreq, kg N Mg−1 stalk) as the quotient between Nopt and the yield, for each response curve. There was a negative correlation between yield at control plot and Nreq, demonstrating that higher N rates are required to maximize yield in sandy (low yield) sites. The Nreq was 1.3, 0.9, 0.7 and 0.6 kg N Mg−1 stalk for expected yields < 69, 69–84, 84–102, and > 102 Mg ha−1, respectively, differing from the standard 1 kg N Mg−1 stalk currently used. The method proposed here is based indirectly on the N-supplying power of the soil and should be tested for other crops to deliver an improved N recommendation system. [ABSTRACT FROM AUTHOR]

Defining the ideal soybean stand is essential for obtaining maximum grain yield. As a hypothesis of the work, it was questioned whether it is possible to vary seeding population of soybean based on the physical–chemical attributes of soil related to grain yield. The objectives of this work were (i) to identify soil attributes that help obtain the maximum grain yield grown in the Cerrado region of Brazil; and (ii) to generate a model to define the seeding rate according to these attributes. The experiment was carried out in the 2017/2018 and 2018/2019 crop seasons. In the first year, plots with different rate-seeding were sown on site one and site two. In the second crop season, site three was sown at a variable rate based on the results found in 2017/2018. The pH, calcium, magnesium, phosphorus, potassium, organic matter and clay contents, cation exchange capacity, base saturation and apparent electrical conductivity of the soil were evaluated. The results were subjected to Pearson's correlation network, followed by path analysis and decision tree. The variable-rate seeding suggested by the decision tree was applied on site 3 and the similarity between the soil attributes contained in the decision tree and the grain yield was verified using the relative deviation coefficient technique. The apparent electrical conductivity of the soil and the clay contents are the soil attributes that should be used to determine the soybean seeding rate. Areas with the highest values of electrical conductivity and clay contents should receive the higher soybean rate seeding in the Cerrado region. [ABSTRACT FROM AUTHOR]

Purpose: Potato (Solanum tuberosum L.) is important to the world population's food security. However, potato production is implicated in several environmental problems, particularly soil loss due to crop harvest (SLCH). Moreover, a knowledge bias about this process exists given that most related studies are from Europe. Most studies compare SLCH differences among tuber and root characteristics of distinct crops but not the tuber morphologies, e.g., spherical and elongated ones, within the same crop. Aims: This study aimed to (a) estimate the SLCH in potatoes with contrasting morphologies in a very clayey soil; (b) test whether the potato morphology allied to soil moisture affects the sediment exportation. Methods: A total of 205 potatoes from four plots were collected for morphological and sediment exportation assessments. Several morphological characteristics were measured: weight (g), volume (cm3), axis dimension (mm), concavities (the number and volume), sediment adherence (g), and soil moisture (g kg−1). Results: The spherical potatoes exported 1.28 kg sediment per ton−1 of harvested potato, whereas the elongated ones exported 20% more sediment (1.54 kg). The harvested field with a high soil moisture content (≈ 26%) exported three times more sediment than the field with the lowest moisture content (≈ 16%). Conclusions: The SLCH measured in the study area was lower (0.062 Mg ha−1 harvest−1) than most values reported in the literature. In addition, the potato morphological characteristics affected soil adherence at distinct soil moisture contents. The harvesting technique can be critical to reduce the SLCH. [ABSTRACT FROM AUTHOR]

Unstable soil aggregates can easily be dispersed when mechanical energy is applied, denominated as readily dispersible clay (RDC) which is usually measured by turbidimetry. Faster methods that require minimum preparation at reduced costs are needed, such as the spectroscopy technique. Nevertheless, the technique has not yet been tested on soils. Electromagnetic radiation has strong interaction with soil physical elements (sand, silt, and clay) and with selective elements of the clay fraction, such as mineralogy. Thus, this study assessed the potential of 400–16,680 nm range (visible – Vis; near-infrared – NIR; short-wave infrared – SWIR; and medium infrared – MIR) spectroscopy to estimate RDC in some tropical soils. We also evaluated the wavelengths and regions that contribute to this prediction. We collected 68 samples from the underlying horizon of three different soils from three important states in Brazil The soil analyses were performed (physical and chemical) in the laboratory. RDC quantification was compared with the Vis-NIR-SWIR and MIR wavelengths models. The random forest (RF) algorithm was used to generate the prediction in the soil database. For RDC, the Vis-NIR-SWIR and MIR configuration presented a better relationship (coefficient of correlation (r) = 0.659 and root of the mean square error (RMSE) = 0.469%), although the results were similar when the regions were evaluated separately (Vis-NIR-SWIR – 350 to 2500 nm and MIR 2500 to 16,680 nm). RDC determination is more related to bands from 1980 to 2040, 6840 to 7360, and 7750 to 9820 nm. Spectroscopy showed its importance in RDC quantification, as it is fast and does not require soil preparations. The results show that spectral wavelengths are appropriate to assist on the estimative of RDC in the studied soils and may provide a basis for future research. [ABSTRACT FROM AUTHOR]

Copyright of Revista Ambiente e Água is the property of Revista Ambiente e Agua and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Mining operations produce large quantities of tailings that must be handled and stored safely in a technical framework that reconciles economic restrictions and environmental sustainability. Unfortunately, the history of tailings deposits is marked by episodes of catastrophic failures, which is confirmed by the recent tailings dam collapses that occurred in Canada (Mount Polley), Australia (Cadia) and Brazil (Samarco and Brumadinio). Due to this alarming empirical evidence left by the mining industry worldwide, there is international concern and a demand to build these deposits safely from every point of view. In this scenario, the main geotechnical parameter that requires significant attention is the undrained residual shear strength, which is crucial to ensure the physical stability of a tailings dam. The critical state soil mechanic (CSSM) and/or the steady state of deformation provide the conceptual framework for evaluating this strength mobilized by particulate materials. However, despite the fact that these concepts are long established, some important aspects of soil behavior have not been clearly incorporated, which can seriously affect the estimation of the residual undrained shear strength. In this paper the effects of strain rate and reorientation of platy particles in fine-grained soils, the existence of a quasi-steady state (condition of minimum undrained strength) in sandy soils and the limitations of the state parameter are analyzed and discussed. In this context, the main goals are to minimize misjudgments in the estimation of the undrained strength and to introduce an alternative tool, the flow index, I f , to evaluate the susceptibility of the occurrence of flow failure in tailings dams. • The history of tailings deposits is marked by episodes of failures, many of them associated with the occurrence of static liquefaction. • The critical state soil mechanic (steady state of deformation) provides the framework to evaluate static liquefaction. • It is shown that the critical state is more suitable for clayey soils, while the steady state is more useful in sandy soils. • The state parameters do not consider the static shear stress, which in contractive states is responsible for triggering a flow failure. • An alternative state parameter based on the quasi-steady state and the static shear stress is proposed to identify flow failures. [ABSTRACT FROM AUTHOR]

Knowing which restoration approach provides the best returns on investment for accumulating carbon is essential to foster restoration planning, financing, and implementation. Here, we explored the cost‐effectiveness and drivers of aboveground and soil carbon accumulation in restored forests across an agricultural landscape of Brazil's Atlantic Forest. The recovery of aboveground and soil carbon stocks, as well as the implementation and land opportunity costs, was assessed across chronosequences (10–60 years) of second‐growth forests and mixed‐species tree plantings and old growth, reference forest remnants. Plantations accumulated approximately 50% more aboveground carbon than second‐growth forests throughout the chronosequence. When controlling for soil clay content, soil carbon stocks were higher in reference than in restored forests, but they were comparable between plantations and second‐growth forests. After 60 years of stand development, recovery of total carbon stocks in both restoration approaches reached only half of the average stocks of reference forests. Total cost‐effectiveness for carbon accumulation, including both implementation and land opportunity costs, was on average 60% higher for second‐growth forests than for plantations (15.1 and 9.4 kgC US$−1, respectively). Although tree plantations initially showed higher rates of carbon storage than second‐growth forests, their higher implementation and land opportunity costs make them less cost‐effective for carbon farming. Our results further suggest that, at current pricing levels, carbon markets alone have a limited potential to up‐scale restoration efforts in Brazil's Atlantic Forest. [ABSTRACT FROM AUTHOR]

The study aimed to investigate the effect of controlled-release fertilizer N14-P14-K14 (CRF) on the morphological traits and chlorophyll indices of black pepper plantlets (cv. Bragantina). One experimentation was carried out in a greenhouse between March and July 2018 in the Rio de Janeiro state/Brazil. Were tested four doses' equivalents to 0.0, 2.5, 5.0, and 10.0 kilogram of CRF per cubic meter of the substrate, which was obtained by mixing clayey soil and crushed coconut fiber, on 1:3 volume proportion. The experimental design was completely randomized, with 17 replicates to assess the morphological characteristics and nine replicates to assess the chlorophyll contents. At 120 days after transplanting were assessed main stem height (H), the number of leaves (NL), leaf area index (LAI), total dry matter (TDM), shoot dry matter (SDM), and root dry matter (RDM). Chlorophyll a, b, a+b contents and a/b ratio were assessed too. The application of CRF fertilizer increased the NL and SDM values until 9.6 kg m-3 dose. The values of H, TDM, LAI, and RDM increase until 9.3, 8.4, 8.2, and 6.4 kg m-3 doses, respectively. The chlorophyll a and b contents increased until 7.7 kg m-3 dose. It's recommended to apply 8.4 kg of CRF 14N-14P-14K per cubic meter of the substrate to produce black pepper plantlets with adequate commercial pattern and chlorophyll levels. [ABSTRACT FROM AUTHOR]

The objective was to study the habitat complexity of mite populations on Caryocar brasiliense trees under natural and cultivated field conditions. The study was performed in the municipality of Montes Claros, in the state of Minas Gerais, Brazil, over 3 years. Three types of areas were studied: 1) Cerrado, 2) pasture, and 3) a university Campus. Several chlorotic spots were detected on leaves with larger populations of Tetranychus sp. and Eutetranychus sp. (Tetranychidae). The greatest numbers of Agistemus sp. (Stigmaeidae) on leaves and Histiostoma sp. (Histiostomidae) and Proctolaelaps sp. (Ascidae) on fruits were observed in the pasture, and that of Histiostoma sp. on leaves in the pasture and on the university Campus. In general, the herbivorous mites (e.g., Tetranychus sp.) found on C. brasiliense plants were correlated with more clayey soils with a higher cationic exchange capacity; larger populations of mites (e.g., Agistemus sp. and Histiostoma sp.) were found on the C. brasiliense trees with the largest crown sizes; and associations between predator mites (e.g., Agistemus sp.) and phytophagous mites (e.g., Tetranychus sp.1) were observed. Greater habitat diversity and more complex plant architectures favored the mite populations. The positive effect of loamier soil on herbivorous mites indicates that these species are adapted to Cerrado conditions. Some recorded species of herbivorous mites can be pests in commercial plantations of C. brasiliense. [ABSTRACT FROM AUTHOR]

The Mehlich-1 extractor is the most used in Brazil, however it extracts low phosphorus (P) levels in soils with high clay levels and iron-bound (Fe) and aluminum (Al) fractions. Thus, we aimed to evaluate the P availability and fertility classes in Yellow Latosol (YL) and Gleysol Haplicum (GH) soils using Mehlich-1, Mehlich-3 and anion exchange resin extractors, as well as to estimate the critical P levels in the soil and in plants for establishing Urochloa humidicola cv. Common. All extractors were efficient in evaluating the availability of P in the soil, however the anion exchange resin showed a high correlation with the P accumulation in the shoot, which can be considered the most efficient method in P extraction. However, we recommend the Mehlich-3 extractor due to its high efficiency in extracting the P linked to the Fe and Al fractions, in addition to being a multi-element extractor. The critical level of P in the soil for establishing U. humidicola by Mehlich-3 in YL is 10.32 mg dm-3, while it is 7.46 mg dm-3 in GH. The critical P level in plants grown in YL is 1.20 mg dm-3, and it is 1.54 mg dm-3 in GH. The estimated phosphate doses can be recommended for cultivating U. humidicola and can serve as a reference for future research on correlating and calibrating P doses. [ABSTRACT FROM AUTHOR]

Copyright of Revista Caatinga is the property of Revista Caatinga and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to clarify the effect of mixed planting in the dynamics of phosporus (P), we assessed the fractions of this element in mixed plantings of Eucalyptus urophylla × E. grandis (Urograndis) and Acacia mangium in a tropical soil clay, analysing changes in the fractions of P and examining the correlation of these changes with the fractions of soil organic matter. Pure stands of Urograndis (E) and A. mangium (A) (0A:100E and 100A:0E) and mixed stands of the two species (50A:50E and 37A:66E) were established. The fractionation of P, the granulometric fractionation of organic matter and the labile carbon (POXC) were determined at soil depths of 0–5 and 5–10 cm. Regarding the availability of P, organic parts contributed 34.6% to 38.1% relative to the total P, with the highest percentages being observed for the moderately labile fraction. Highest levels of labile organic P were observed in the mixed plantations. About soil carbon (C), the highest levels of the more labile C fractions were recorded in plantations in which Acacia was present. Mixed plantations were found to show a greater balance between labile P and C fractions. The C fractions warrant particular attention in future studies, notably those related to the emission of greenhouse gases. [ABSTRACT FROM AUTHOR]

Applying the upcoming technologies in agriculture has been a major economic, environmental and social challenge for scientists and farmers. In order to overcome such challenge, this study evaluated the advantages and limitations of using geostatistics and machine learning for soil mapping in agricultural practices and soil surveys. The study occurred in Tocantins State, Brazil, and consisted into seven areas with a total extension of 17.24 km², 222 meters regular gridded resulting in one-point sampling per 0.0493 km² of five randomly sampled cores within a 1 m circle radius. It was collected 332 georeferenced soil samples at 0-20 cm depth using an auger and then, soil laboratory analyses performed. Afterward, liming rate maps were originated from the predicted soil attributes clay, cation exchange capacity and base saturation comparing four methods: ordinary kriging, random forest, cubist, support vector machine and the best model results of each soil attribute. Evaluating the methods, the Pearson's index presented strong results for soil attributes predicted by random forest and ordinary kriging. Machine learning methods can be successfully applied for soil mapping in agricultural practices and soil surveys using less soil samples rather than geostatistical framework. [ABSTRACT FROM AUTHOR]

Brazil is the largest charcoal producers in the world, with the main centers of charcoal consumption located in the states of Minas Gerais, Mato Grosso do Sul, Espírito Santo, Maranhão, and Pará. Planting of Eucalyptus in the northern and northeastern states of Brazil is relatively new and is limited the lack of genetic materials adapted to the region’s high temperatures and severe, prolonged periods of drought. The objective of this study was to assess the genetic parameters and variability and determine the genotype x environment interaction for drought tolerance in Eucalyptus clonal tests established in two environments in the municipality of Grajaú, Maranhão State, Brazil. The tests were planted in January 2011 in clayey and sandy soils in a randomized complete block design with 130 clones, one plant per plot, and 20 replicates. The studied clones showed high genetic variability for drought tolerance, with coefficients of relative variance (CVr) consistently greater than 0.8 for DBH and volume. This indicates high levels of genetic control and less influence of environmental factors on the phenotype, which allows for selection and obtaining gains through breeding. Heritability estimates were high for growth traits, with average clone heritabilities (ĥ2m ) greater than 0.85, as well as acuracies (ȓaa) above 0.9 for DBH and volume in clone selection. There was a simple interaction between genotype x environment for the clones under the two different soil conditions. [ABSTRACT FROM AUTHOR]

All processes in agro-industries consume water and generate large volumes of nutrient-rich effluents. To recycle effluents from a sugar–alcohol industry in the Northeastern Brazil (Coruripe, Alagoas), the effect of a daily application of a microbial formulation (containing five indigenous bacteria and two fungi), at the entrance of the two first facultative ponds (D, E) of its treatment plant formed by seven ponds (A–G), was evaluated in the sugarcane harvests of 2014/2015 and 2015/2016. Fortnightly, the values of 11 physicochemical parameters were checked and statistically compared (one and two-way ANOVA) in untreated (sedimentation pond A) and post-treated effluent (last facultative pond G), during both harvests. The treated effluent presented statistically significant improvements (p > 0.05), even between harvests, with averages of removal of organic matter of ca. 79.21% and 90.62%, and increases of the dissolved oxygen (DO) of ca. 72% and 74%, as well as the average increase of pH was ca. 42% and 50%. This better quality residue generally satisfied the class III level of the Brazilian Resolution 357/2005 (National Council for the Environment (CONAMA)), for water reuse in sugarcane irrigation on the yellow clay latosol soil, since it still is a light source of organic matter, nitrites and phosphorus, reducing the need of fertilizers for maintaining the productivity with low risk of salinization. According to Pearson's bivariate correlation coefficient, while the DO and pH have positive correlation, they both have general inverse relation with the other physicochemical parameters evaluated and vice versa. [ABSTRACT FROM AUTHOR]

Clayey soils have been used as liners at the base of waste deposits due to their geotechnical characteristics and capacity to adsorb metallic cations. However, a number of soils may not possess all required properties to ensure contaminant retention and therefore require additives. This study investigated whether the addition of commercial peat to a tropical residual soil (from the Ribeira Valley, Brazil) could improve its lead (Pb) and cadmium (Cd) adsorption capacity for its use as a liner in mining waste disposal. Pure soil and 10 and 20% soil-peat mixtures were compared. The application of peat increased the organic matter (OM) content (from 9 g kg−1 in soil to 58 g kg−1 in the 20% soil-peat mixture) and the cationic exchange capacity (CEC) (from 41.4 mmolc dm−3 in soil to 143.1 mmolc dm−3 in the 20% soil-peat mixture). Batch equilibrium test results revealed that the maximum Pb adsorption capacity of 623.6 μg g−1 also increased (to 1089.1 and 1270.0 μg g−1 in the 10 and 20% soil-peat mixtures, respectively). The soil Cd adsorption capacity of 261.2 μg g−1 increased to 304.0 and 631.3 μg g−1, respectively, with increasing peat proportions. The results suggest that peat can improve soil liner performance in waste deposits. Soil-peat mixtures are alternatives for minimizing potentially toxic metal contamination with available and low-cost materials. [ABSTRACT FROM AUTHOR]

Wood density, an important parameter for evaluating forest biomass productivity and wood product quality control, is influenced by a complex combination of variables of forest plantations, including environmental conditions and the management practices adopted. In this paper, we demonstrate that three site variables (annual rainfall, temperature, and soil texture) and 10 plantation variables (e.g., age and genetic material) are associated with basic wood density (evaluated in two situations: with and without bark) in 936 trees of different species of Eucalyptus L'Hér across five distinct edaphoclimatic regions in Brazil. A canonical correlation analysis was used to identify the most contributory variables affecting wood density. The variables globally associated with high basic wood densities were, in order of importance, the genetic material and area per tree (both under direct control of plantation managers), as well as mean annual temperature and soil texture of the site. These results confirmed the advantage of using clonal material (instead of seedling origin material) planted in larger spacings in sites with higher mean annual temperatures and clayey soils to obtain higher basic wood densities. Conversely, low basic wood densities were associated with high-productivity sites, higher rainfall, and plantations with a higher basal area per stem in second rotation. [ABSTRACT FROM AUTHOR]

Copyright of Engenharia na Agricultura is the property of Engenharia na Agricultura and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Straw removal for bioelectricity, cellulosic ethanol, or other bio-products has become a common practice in Brazilian sugarcane areas, but long-term effects on soil organic carbon (SOC) and yield are unknown. Our objective was to quantify tillage intensity and removal levels on SOC stocks and sugarcane yield on contrasting edaphoclimatic conditions in Brazil. Conventional tillage-CT and reduced tillage-RT coupled with three straw removal levels (none—NR; moderate—MR; total—TR) were combined to create six treatment combinations: CTNR, CTMR, CTTR, RTNR, RTMR, and RTTR, respectively. Sugarcane yield was measured annually and soil samples to a depth of 40 cm were collected and analyzed before and after 5 years of treatments. Neither tillage practices nor straw removal significantly affected sugarcane yield on sandy loam soil, but CTMR, CTTR, and RTTR showed substantial yield reductions on clayey soil. SOC stocks for RTNR increased by as much as 1.64 Mg ha−1 year−1 on clayey soil, while CTMR and CTTR favored depletion of SOC stocks on both soils. Overall, each Mg of straw returned to the soil increased SOC stock by 95 kg ha−1 for clayey soil under both tillage practices and 55 kg ha−1 for sandy loam under the CT system. Furthermore, straw removal decreased microbial biomass C and b-glucosidase activity. These findings suggest that the adoption of RT attenuates the adverse impacts of straw removal on SOC stocks while ensuring sugarcane yields for a more sustainable bioenergy production in Brazil. [ABSTRACT FROM AUTHOR]

Sugarcane (Saccharum officinarum) residue (straw) has been identified as a promising feedstock for bioenergy production, but excessive straw removal may impair soil macrofauna and related ecosystem services. To quantify straw removal effects on abundance, richness, and diversity of soil macrofauna, four experiments were conducted in São Paulo state, Brazil, under different edaphoclimatic conditions. A secondary goal was to evaluate seasonal changes on soil macrofauna and identify linkages between those changes and soil chemical and physical attributes. Four straw removal treatments (NR, no removal, LR, low removal, HR, high removal, and TR, total removal) were evaluated. Macrofauna and other soil attributes were sampled within the 0- to 0.30-m depth increment. Soil macrofauna were impaired by TR with the magnitude of response being related to both edaphoclimatic conditions and management practices. Numerous interactions among seasons, straw removal rates, and soil macrofauna were found, especially for total abundance and diversity of organisms. Partial straw removal (HR and LR) may be a strategy to protect soil health and increase bioenergy production with minimal effects on soil macrofauna, although long-term experiments are needed to confirm our hypothesis. The NR treatment generally had better soil quality as indicated by greater soil moisture, macropore number, soil organic carbon (SOC) content, and soil fertility, which led to a higher abundance of most macrofauna organisms. Total removal resulted in greater soil compaction and decreased macrofauna abundance, especially in clay soils. Our findings confirm that an integrated approach using soil indicators as guidelines should be adopted to better predict sustainable straw management practices for sugarcane in Brazil. [ABSTRACT FROM AUTHOR]

The adoption of green cane harvesting system without burning has triggered the increase of pest infestations in sugarcane fields. This makes straw removal a promising alternative for pest control in sugarcane fields. However, further research is needed to understand the impacts of straw removal on pest infestation under field conditions. The objective of this study was to evaluate the incidence of root spittlebug (Mahanarva fimbriolata) and sphenophorus (Sphenophorus levis) under different rates of straw removal and contrasting edaphoclimatic conditions in the São Paulo state, southeastern Brazil. Eight field experiments were conducted throughout the sugarcane cropping cycle (two crop seasons) and were arranged in a randomized block design with four replicates. The experimental design included four straw removal rates: total removal, low removal, high removal, and no removal. The incidence of pests was evaluated during September and March (spring/summer seasons in the Southern Hemisphere) for root spittlebug and April to August (autumn/winter) for sphenophorus populations. Straw removal reduced root spittlebug infestation and this effect was more evident in clayey soils. The incidence of root spittlebug was three times higher in clayey soils compared to sandy soils. Straw removal did not influence sphenophorus population but reduced damages in sugarcane plants especially in clayey soils. The damage caused by sphenophorus was three times higher in clayey than in sandy soils. This study emphasizes that straw removal by itself is not a feasible strategy to control the root spittlebug and sphenophorus infestations in sugarcane cultivated areas of Brazil, thus an integrated management strategy should be a high priority. [ABSTRACT FROM AUTHOR]

Industrial use of sugarcane straw for bioenergy production represents a promising opportunity for the Brazilian sugarcane sector. Nonetheless, intensified straw removal may aggravate the effects of mechanized harvesting and increase the risks of soil compaction, declining sugarcane yield. An experiment was designed, and four field studies were conducted to evaluate the cumulative effects of straw removal on soil physical attributes (bulk density, BD; soil resistance to penetration, SRP; macroporosity, MaP; microporosity, MiP, and mean weight diameter of soil aggregates, MWD) and their relationship with crop yield under clayey and sandy soils in the São Paulo state, Brazil. In each field study, four straw removal rates (no removal, NR; low removal, LR, removal of 5 Mg ha−1; high removal, HR, removal of 10 Mg ha−1; and total removal, TR, removal of 15 Mg ha−1) were arranged in a randomized block design with four replicates. The 4-year intensive management of straw removal (HR and TR) resulted in an increased soil compaction (BD and SRP values) and reduced the MWD in both sandy and clayey soils. Our findings also showed that these effects are more significant in sandy soils, where soil carbon content was substantially reduced in HR and TR treatments. Sites with higher BD and SRP induced by straw removal were strongly associated with lower sugarcane yields, especially in sandy soils. Conversely, our findings indicate that LR was not detrimental to soil physical quality and sugarcane yield. Nevertheless, considering the multifunctionality of straw in sustaining multiple ecosystem services in different soil types, straw management should be defined taking into consideration site-specific conditions. We advocate that recommendations for straw removal should also be combined with other conservationist soil management practices in order to minimize soil compaction and its negative implications on sugarcane yield and other ecosystem services. [ABSTRACT FROM AUTHOR]

Question: How do biotic forest conditions, in terms of plant functional traits and tree basal area, and soil variables influence old‐growth forest dynamics? Location: A subtropical old‐growth forest in Southern Brazil. Methods: Forest inventories were conducted in 1999 and 2017, in 24 permanent plots of 500 m2. All trees with a circumference at breast height of ≥ 30 cm were measured, identified to the species level, and tagged. We fitted linear models to evaluate the effect of the biotic variables of initial forest communities (tree basal area, trait community‐weighted mean [CWM] and both species and functional diversity metrics) and of soil variables on forest dynamics. These models included biomass dynamics (annual rate of biomass increment and mortality) and demographic rates (recruitment and mortality rates). Furthermore, linear models were used to evaluate the effect of tree survival, recruitment and mortality and biomass increment on the net biomass change. Results: We observed a positive effect of species diversity and a negative effect of CWM leaf phosphorus content on the biomass increment. Biomass loss was positively related to basal area and negatively related to the CWM of leaf nitrogen content. Overall, net biomass change was negatively influenced by biomass loss due to mortality. Recruitment rates were negatively affected by soil potassium content and were positively affected by soil pH and functional evenness of the community. Mortality rates were positively predicted by soil clay content and negatively predicted by species diversity. Conclusions: Community functional traits, basal area and soil variables predicted growth, mortality and recruitment dynamics of this subtropical old‐growth forest. This work provides important information about the biomass and demographic dynamics of subtropical forests, showing that initial community characteristics influence the gain and loss of biomass and individuals over a period of almost two decades. [ABSTRACT FROM AUTHOR]

• Agroforestry complexity and soil texture influence ecosystem service provision. • P and Ca cycling through litter and stable soil carbon stocks are synergistic. • Sandy soils are most suited for complex agroforestry. • Agroforestry Complexity Index encompassing diversity, density and management. Agroforestry systems are often promoted as solutions to address land degradation and climate change. However, agroforestry is an umbrella term for a large variety of systems and it is not clear how their degree of complexity influences their provision of soil-based ecosystem services, such as soil organic carbon (SOC) storage and nutrient cycling. Furthermore, a knowledge gap remains whether agroforestry systems perform equally well on all soil types. The objectives of this study were 1) to assess the links between agroforestry complexity, nutrient cycling and SOC fractions, and 2) to assess how soil texture influences these relationships in Brazilian agroforestry systems. We sampled 59 agroforestry plots across 30 sites in Sao Paulo state, Brazil, and 8 monocrop sites (6 pastures and 2 crop monocultures). The 38 sites represented a soil textural gradient, ranging from very sandy to very clayey (clay content range 25 – 620 g kg−1). An Agroforestry Complexity Index (ACI) was defined based on tree species richness, stem density and pruning management. Nutrient (N, P, K, Ca, Mg) and C contents were determined in litter and soil (0–30 cm depth) samples, and mineral-associated organic C (MAOC) and particulate organic C (POC) in soil samples were assessed as well. ACI was positively associated with C, N, P, Ca and Mg stocks in litter, and these litter nutrients were in turn positively associated with the corresponding soil nutrient stocks. Associations between soil nutrients and MAOC were stronger on sandy soils than on clayey soils, particularly for P, Ca and Cation Exchange Capacity (CEC). For POC, robust relationships with nutrients were only found on sandy soils. Structural Equation Models indicated causal relationships between agroforestry complexity, P and Ca cycling, and MAOC and POC stocks in topsoils. Our results indicate that nutrients effectively cycle from in situ mulch into plant-available soil pools and highlight the synergies between nutrient cycling and stable C stocks that can be achieved in complex agroforestry systems. These synergies seem to be particularly strong on sandy soils (<15 % clay). [ABSTRACT FROM AUTHOR]

Soil tillage is an agricultural practice that directly affects the global carbon cycle. Our study sought to assess the implications of adopting sunn hemp cover crops with different tillage practices on CO2 emissions for two soil types (clayey and sandy soil) cultivated with sugarcane in Brazil. The experimental design was a split‐plot with randomized blocks, with the main plots being with cover crop or fallow and sub‐plots being under conventional or minimum tillage. Our results indicate that during the first 50 days after soil tillage, the variation in soil CO2 emissions was stimulated by cover crop and soil tillage, while after that, it became dominated by the root respiration of sugarcane plants. We also found that over the first 97 days after the tillage, the clayey soil showed differences between minimum tillage with cover crop and fallow. Conversely, for sandy soil over the first 50 days following, there were differences between the tillage systems under cover cropping. Emissions from sugarcane rows were found to be greater than those from inter‐row positions. We concluded that soils under different textural classes had distinct patterns in terms of soil CO2 emissions. The correct quantification of CO2 emissions during the sugarcane renovation period should prioritize having a short assessment period (~50 days after soil tillage) as well as including measurements at row and inter‐row positions. [ABSTRACT FROM AUTHOR]

Leak noise correlators are commonly used to detect and locate leaks in buried water pipes. They use the cross-correlation function between leak noise signals measured using hydrophones or accelerometers placed on the pipe either side of the leak. The efficacy of a correlator is dependent upon knowledge of the speed at which the leak noise propagates along the pipe as well as how much it attenuates with distance. The leak noise is carried in a predominantly fluid-borne wave in the pipe, which is heavily influenced by the pipe and soil properties. Although the pipe properties can be determined relatively easily, estimation of the soil properties surrounding the pipe is more problematic. It is desirable to have an accurate estimate of the soil properties, so that current models can be developed and used to improve understanding of leak noise propagation and hence leak detection capabilities. In this paper a novel approach to determining the bulk and shear moduli of the soil from measurements of the predominantly fluid-borne wave in a buried plastic pipe, is described. The measured data are compared with corresponding data predicted from a model, and the soil properties are determined using an optimization algorithm. The method is applied to two different sites, one in the UK, where the soil properties surrounding the pipe are representative of sandy soil, and one in Brazil, where the surrounding soil has properties that are representative of clay soil. It is found that the bulk and shear modulus can be estimated in the pipe buried in sandy soil, but in the clay soil it is only possible to estimate the shear modulus. • A new approach to determine the bulk and shear moduli of the soil is described. • The approach is based on measurements of the predominantly fluid-borne wave (s=1) in a buried plastic pipe. • Two experimental test sites with different geometry and properties are used to demonstrate the efficacy of the method. • In sandy and clay soil, the soil shear modulus can affect the speed of s=1 wave in the pipe. • The attenuation of s=1 wave is affected by the soil bulk modulus in sandy soil, and shear modulus in clay soil. [ABSTRACT FROM AUTHOR]

One of the most damaging species in sunflower crops in Brazil is the hairy beggartick (Bidens pilosa L). The large number of seeds, the various vegetative cycles during the year, the staggered germination and the scarcity of selective and effective herbicides to control this weed in sunflower are some of attributes that hinder the control of hairy beggartick populations. Two experiments were carried out to evaluate the control of hairy beggarticks, as well as sunflower tolerance to herbicides. The treatments were as follows: S-metolachlor (1,200 and 2,400 g ai ha-1), flumioxazin (60 and 120 g ai ha-1), and sulfentrazone (150 and 300 g ai ha-1) and two controls (weedy and weed-free check). The selectivity of the herbicides was higher at low doses. Flumioxazin and sulfentrazone caused injury to sunflowers at the highest doses and mainly in sandy soils. Although S-metolachlor did not cause visual symptoms of injury, the higher dose reduced sunflower yield. The herbicides sulfentrazone and flumioxazin provided satisfactory control of hairy beggartick plants in both types of soils. S-metolachlor presented medium control of hairy beggarticks in clay soil; however, its efficiency was slightly higher when applied in sandy soil. The most efficient herbicide for controlling hairy beggartick plants was flumioxazin, followed by sulfentrazone. [ABSTRACT FROM AUTHOR]

The expansion of sugarcane (Saccharum spp.) over extensive pasture areas has been one of the primary land-use change (LUC) scenarios in central-southern Brazil. However, LUC could negatively affect soil fauna along with the multiple functions and services associated with these organisms. Numerous groups of macroinvertebrates inhabiting the soil surface (i.e., epigeic) or the soil profile (i.e., edaphic) are fundamental for litter fragmentation, soil structuring and stabilization, water infiltration, biogeochemical cycling. In this study, both the edaphic and epigeic macrofauna communities were surveyed simultaneously to assess responses induced by the expansion of sugarcane cultivation over extensive pastures and to investigate whether the magnitude of such responses to LUC differs according to the community niche (i.e., soil profile versus surface). We hypothesized that LUC to a semi-perennial crop such as sugarcane would increase the density and diversity of the edaphic macrofauna, while the epigeic community would be negatively affected by LUC due to drastic changes in surface litter. The studied areas were two sites varying in soil texture (i.e., clay versus sandy soils) each including the following land uses: i) native vegetation, ii) extensive pasture, iii) newly planted sugarcane crop (sugarcane); and iv) established sugarcane (sugarcane ratoon). To evaluate edaphic macrofauna the TSBF methodology was adopted, while pitfall traps were installed at the same sampling points to collected epigeic macrofauna. The evaluated community attributes were density, Shannon diversity index, evenness index, richness of soil macrofauna taxa, as well as the chemical and physical attributes of the soil. Linear mixed effects analysis showed that LUC affected the relative abundance of edaphic (Land use p = 0.1191 r2 marginal = 0.28, r2 conditional = 0.33) and epigeic (Land use p = 0.0176; r2 marginal = 0.22, r2 conditional = 0.32) macroinvertebrates. Both groups showed the greatest density of organisms under native vegetation. Coleoptera and earthworms were associated with pasture areas, especially in clayey soil. Response ratios of LUC effects on macrofauna showed stronger responses of the epigeic compared to edaphic macrofauna, indicating a greater sensitivity of surface-dwelling organisms and their functions to disturbances such as those caused by LUC. In general, the density and diversity of macrofauna exhibited a positive correlation with soil organic matter, microbial carbon and nitrogen, macroporosity, and total porosity, and a negative correlation with soil density (p < 0.05). Also, the conversion of pasture to sugarcane cultivation (planting) causes significant macrofauna losses, particularly, in the clay soil. The cultivation of ratoon sugarcane led to a reduction of the density, taxonomic richness, diversity, and evenness of macrofauna. Given the importance of epigeic macroinvertebrates for litter fragmentation and decomposition, these results may indicate a rapid loss of key soil functions related to decomposition and carbon and nutrient cycling following LUC. [Display omitted] [ABSTRACT FROM AUTHOR]

Mechanisms generating and maintaining biodiversity at regional scales may be evaluated by quantifying β-diversity along environmental gradients. Differences in assemblages result in biotic complementarities and redundancies among sites, which may be quantified through multi-dimensional approaches incorporating taxonomic β-diversity (TBD), functional β-diversity (FBD) and phylogenetic β-diversity (PBD). Here we test the hypothesis that snake TBD, FBD and PBD are influenced by environmental gradients, independently of geographic distance. The gradients tested are expected to affect snake assemblages indirectly, such as clay content in the soil determining primary production and height above the nearest drainage determining prey availability, or directly, such as percentage of tree cover determining availability of resting and nesting sites, and climate (temperature and precipitation) causing physiological filtering. We sampled snakes in 21 sampling plots, each covering five km², distributed over 880 kmin the central-southern Amazon Basin. We used dissimilarities between sampling sites to quantify TBD, FBD and PBD, which were response variables in multiple-linear-regression and redundancy analysis models. We show that patterns of snake community composition based on TBD, FBD and PBD are associated with environmental heterogeneity in the Amazon. Despite positive correlations between all β-diversity measures, TBD responded to different environmental gradients compared to FBD and PBD. Our findings suggest that multi-dimensional approaches are more informative for ecological studies and conservation actions compared to a single diversity measure. [ABSTRACT FROM AUTHOR]

Liquid manure applied on the soil surface may alter its hydraulic conductivity by surface sealing. In this study, we evaluated the chemical and physical mechanisms of the surface sealing process acting in sandy clay loam and clayey soils after liquid manure application (LDM). Factors affecting surface sealing, such as LDM dosage, total solids content of LDM, straw cover, and time after LDM application, were also studied. The saturated hydraulic conductivity (K sat ) was determined before and 24 h and 7 days after LDM application, and the sealing index was calculated. The liquid dairy manure application on the soil surface promoted surface sealing in both soils; around 93% of sealing surface was due to physical mechanisms and around 7% chemical mechanisms. The application of LDM with 9.4% total solids (TS) promoted a greater sealing index (greater surface sealing) compared to LDM with 0% TS, mainly within 24 h of LDM application. Greater surface sealing was also observed with a higher LDM dose (60 m 3  ha −1 ). Soil cover with 5 Mg ha −1 of straw resulted in a lower sealing index (lower surface sealing) than soil with 0 Mg ha −1 of straw. Sealing index was greatest at 24 h after LDM application for all treatments (solids content, LDM dose and soil cover) in both soils (clayey and sandy clay loam). The clayey soil was more susceptible to surface sealing after LDM application than the sandy clay loam. In practical terms, application of LDM with a high total solids content to bare soil when followed by rainfall 24 h after LDM application, enhanced susceptibility to surface sealing and, consequently, greater detrimental effect on surface water quality. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the sorption-desorption and leaching of aminocyclopyrachlor from three Brazilian soils. The sorption-desorption of 14C-aminocyclopyrachlor was evaluated using the batch method and leaching was assessed in glass columns. The Freundlich model showed an adequate fit for the sorption-desorption of aminocyclopyrachlor. The Freundlich sorption coefficient [Kf (sorption)] ranged from 0.37 to 1.34 mmol (1-1/n) L1/n kg-1 and showed a significant positive correlation with the clay content of the soil, while the Kf (desorption) ranged from 3.62 to 5.36 mmol (1-1/n) L1/n kg¡1. The Kf (desorption) values were higher than their respective Kf (sorption), indicating that aminocyclopyrachlor sorption is reversible, and the fate of this herbicide in the environment can be affected by leaching. Aminocyclopyrachlor was detected at all depths (0-30 cm) in all the studied soils, where leaching was influenced by soil texture. The total herbicide leaching from the sandy clay and clay soils was <0.06%, whereas, ~3% leached from the loamy sand soil. The results suggest that aminocyclopyrachlor has a high potential of leaching, based on its low sorption and high desorption capacities. Therefore, this herbicide can easily contaminate underground water resources. [ABSTRACT FROM AUTHOR]

Urea is the most consumed nitrogen (N) fertilizer but is susceptible to high N losses that can result in lower crop yields compared to other N sources. The aim of this study was to evaluate the effects of the continuous usage of urea and calcium ammonium nitrate (CAN) at different N rates on cotton yield, fiber quality, nitrogen agronomic efficiency (NAE), and soil N stock. Two field trials were conducted across four seasons in two regions of Brazil with contrasting soil textures, with clayey and sandy loam soil. The experiment design consisted of two N sources (urea and CAN), four N rates (48, 96, 144, and 192 kg of N per hectare [kg ha−1]), a control plot (no N), and an additional treatment (different N split). Cotton was sown in the rainy summer season using the cultivars TMG 47 B2RF and DP 1536 B2RF, where rows were spaced 0.90 and 0.76 m apart, with densities of 100,000 and 90,000 plants ha−1, in the clayey and sandy loam soils, respectively. Climate conditions were favorable (>800 mm rainfall and 26ºC) during growing, and cotton yield ranged from 2514 to 5437 kg ha−1. Nitrogen application increased cotton yield for both N sources in clayey soil, but not in sandy loam, probably due to N mineralization and a low C/N ratio. In the clayey soil, the N addition at 192 kg ha−1 increased cotton yield by up to 50 % (3500 to 5300 kg ha−1 in the 2019 season) and increased the accumulated yield (4 years) from 12,000 to 16,000 kg ha−1 compared with control. Over the four seasons, CAN application resulted in a higher yield per unit of N compared with urea, resulting in means for NAE of 10.3 and 8.3 kg kg−1, respectively. The N addition improved the micronaire index from the base range, 4.3–4.8 micrograms per inch (control), to premium values of 3.8–4.3 and had no effect on other cotton quality properties or soil N stock. The management of N plays a major role in cotton production and quality, which depend on site-specific conditions. In the long term, yield responsiveness to N was intensified, which suggests that further differences may occur between urea and CAN. • Cotton yield increased by up to 50 % when applying 192 kg ha−1 of N in clayey soil. • The N addition had no effect on cotton yield in sandy loam soil due to soil N status. • Calcium ammonium nitrate resulted in a higher cotton yield per N applied than urea. • Split N application twice or three times resulted in comparable cotton yield and quality. • The N addition improved the micronaire index but had no effect on other quality traits. [ABSTRACT FROM AUTHOR]

Phosphorus (P) retention capacity of soils directly affects the management of phosphate fertilization, and has economic and environmental importance. Brazil has expressive agricultural production and high edaphoclimatic variability; still, the detailed spatial distribution of P retention capacity is not known. Thus, machine learning models were created to estimate the P retention capacity of soils at superficial horizons using the variables: clay content, sand content, soil organic matter, pH, base saturation. The four best models were combined to create an ensemble (a combination of models), which was applied in a dataset (5524 samples) that comprises a sample data from the entire Brazilian territory. The ensemble was used to build a map of P retention capacity. Most of the country presented soils with medium P retention (40–60%), and large areas with very high retention capacity were found in the south of Brazil, a subtropical region mostly associated with clayey soils. High P retention was observed for Histosols, probably related to humic-Al(Fe) complexes. Nitisol, Ferralsol, Gleysol and Cambisol classes presented high P retention, especially for clayey soils with qualifiers related to bases/weathering (Dystric) and organic matter (Umbric and Humic). The correlation between Fe oxide minerals and P retention varied with soil color and drainage conditions mainly associated to redoximorphic reactions; the same was not observed for Al oxide minerals. This pioneer study revealed the distribution of P retention capacity across different soil classes in Brazil, which can help to define land use suitability and soil P management strategies that ensure profitable agricultural exploration. [Display omitted] • In 34% of the country, soils had P retention capacity framed as Low and 22% as High. • The Histosol class presenting soils with elevated P retention capacity (>60%). • For mineral soils, the highlighted classes were Nitisol, Ferralsol, Gleysol and Cambisol. • Soil color and drainage conditions had little effect on soil P retention capacity. [ABSTRACT FROM AUTHOR]

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Intensive soil disturbance by conventional tillage and heavy machinery traffic for planting, cultivation, and harvesting operations are the main causes of soil compaction and degradation of soil physical quality in sugarcane fields. However, the adoption of conservation soil tillage practices, such as no-till and reduced tillage associated with traffic control have been proposed as a key strategy to preserve soil physical quality, enhancing water availability and air fluxes. Nevertheless, the effects of reduced tillage associated with traffic control in sugarcane fields are still not well documented. A study was carried out to quantify soil water availability and air flux indicators in two soils with contrasting textures (named Sandy Loam and Clayey soil) under conventional and reduced tillage practices associated with and without controlled machinery traffic in central-southern Brazil. Soil physical parameters such as bulk density, total porosity, air-filled porosity, air permeability, pore continuity index, and the least limiting water range (LLWR) were measured. In both soils, there was no difference between conventional and reduced tillage in bulk density, air permeability, and LLWR. However, reduced tillage with non-traffic decreased bulk density and increased macroporosity, air-filled porosity, air permeability, pore continuity, and LLWR in Sandy Loam soil. In Clayey soil, the bulk density and LLWR did not change between tillage practices, but air permeability and pore continuity index were larger under reduced tillage with non-traffic. These results highlighted that soil disturbance by conventional tillage does not improve the water availability and air permeability during the crop cycle. However, the traffic control is essential to support the adoption of reduced tillage in sugarcane fields, preserving soil water availability and air fluxes for the subsequent ratoons. Reduced tillage and traffic control are two of the most important pillars for reducing soil compaction and promoting sustainability of sugarcane production in Brazil. • Reduced tillage system did not negatively impact the least limiting water range (LLWR) compared to conventional tillage. • Reduced and conventional tillage system sustain similar air-filled porosity and air permeability. • Reduced tillage associated with traffic control increase LLWR in Sandy loam soils. • Traffic control is essential to support the adoption of reduced tillage in sugarcane fields. [ABSTRACT FROM AUTHOR]

• β-carotene content was stable in sweet potato under different site conditions. • Dry matter and sugar content do not explain sweet potato eating preference. • Clay soil can affect β-carotene concentration. • Altitude does not impact sugar and β-carotene concentration. Blind starvation caused by micronutrient deficiency is a major issue in many countries. The use of crops with higher micronutrient content, also known as biofortification, is one of different strategies to overcome this issue. Brazil has been using this approach within the last years but in order to expand this program it is necessary to characterize and develop new cultivars that meet consumer's demands. Three orange fleshed sweet potato genotypes were evaluated in eight different site locations with different soil, management and altitude conditions. Total soluble sugars, carotenoids, dry matter and sensory evaluation were performed. β-carotene was the predominant carotenoid in the three sweet potato genotypes. This provitamin A compound was consistently higher than 70 μg g−1 in all genotypes, independent of site locations. CIP BRS Nuti cultivar presented significant higher dry matter and sucrose content in comparison with Beauregard and Clone 11. These last genotypes presented higher fructose and glucose content than CIP BRS Nuti. Acceptance evaluation demonstrated that despite having different organoleptic characteristics, CIP BRS Nuti and Beauregard were preferred by tasters. This finding is relevant since CIP BRS Nuti is a new commercial sweetpotato cultivar that will be part of the portfolio of biofortified cultivars in Brazil. [ABSTRACT FROM AUTHOR]

Effective agricultural planning requires basic soil information. In recent decades visible near-infrared diffuse reflectance spectroscopy (vis- NIR) has been shown to be a viable alternative for rapidly analysing soil properties. We studied 7172 samples of seven different soil types collected from several regions of Brazil and varying in organic matter ( OM) (0.2-10.3%) and clay content (0.2-99.0%). The aim was to explore the possibility of enhancing the performance of vis- NIR data in predicting organic matter and clay content in this library by dividing it into smaller sub-libraries on the basis of their vis- NIR spectra. We used partial least square regression ( PLSR) models on the sub-libraries and compared the results with PLSR and two non-linear calibration techniques, boosted regression trees ( BT) and support vector machines ( SVM) applied to the whole library. The whole library calibrations for clay performed well ( ME (modelling efficiency) > 0.82; RMSE (root mean squared error) < 10.9%), reflecting the influence of the direct spectral responses of this property in the vis- NIR range. Calibrations for OM were reasonably good, especially in view of the very small variation in this property ( ME > 0.60; RMSE < 0.55%). The best results were, however, found when dividing the large library into smaller subsets by using variation in the mean-normalized or first derivative spectra. This divided the global data set into clusters that were more uniform in mineralogy, regardless of geographical origin, and improved predictive performance. The best clustering method improved the RMSE in the validation to 8.6% clay and 0.47% OM, which corresponds to a 21% and 15% reduction, respectively, as compared with whole library PLSR. For the whole library, SVM performed almost equally well, reducing RMSE to 8.9% clay and 0.48% OM. [ABSTRACT FROM AUTHOR]