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Background: Deforestation threatens the integrity of the Amazon biome and the ecosystem services it provides. Most of this deforested land is converted to pastures for cattle raising. Early studies revealed that forest-to-pasture conversion alters the flux of methane gas (CH4) in Amazonian soils, driving a switch from acting as a sink to a source of atmospheric CH4. We sought to better understand this phenomenon by investigating the soil microbial metagenomes, focusing on the taxonomic and functional structure of methane-cycling communities. Results: Metagenomic data were combined with in situ measurements of CH4 fluxes, and measurements of soil edaphic factors. We found a significantly higher abundance of methanogens and reduced methanotrophs in pasture soils. As inferred by co-occurrence networks, these microorganisms seem to be less interconnected within the soil microbiota in pasture soils. Metabolic traits were also different between land uses, with increased hydrogenotrophic and methylotrophic pathways of methanogenesis in pasture soils. Similarly, methanotrophs harboring the soluble form of methane monooxygenase enzyme (sMMO) were depleted in pasture soils. Redundancy analysis and multimodel inference revealed that the shift in methane-cycling communities in pasture soils was associated with higher soil compaction, pH, organic matter, and micronutrients. Conclusions: These results provide new knowledge about the effect of forest-to-pasture conversion on the community traits of methane-cycling microorganisms in the Amazon region, resulting in increased abundance and functional potential of methanogens in pastures, and thus increasing the emission of CH4 in deforested soils. Keywords: land-use change, methanogens, methanotrophs, soil properties, multimodel inference

The impact of soil compaction on soybean root growth and grain yield can be alleviated by the presence of biopores and root channels in the soil profile. We hypothesize that cover crops (ruzigrass and oats) are better than grain crops (wheat and maize) to reduce the soil physical limitation to soybean root growth. We aimed to identify which precrops have higher potential to reduce the mechanical and water stresses resulting from soil compaction and soil desegregation, and to enhance soybean (Glycine max L) root growth and yield in an Oxisol (Rhodic Eutrudox), with clayey soil texture. Soybean was grown after four precrops (ruzigrass, oats, wheat, or maize), under four soil compaction levels [soil chiselling (MTC), no-tillage (NT), NT additionally compacted with four passes of a tractor (NTCT), and NT additionally compacted with eight passes of a grain harvester (NTCH)]. Soil physical attributes (bulk density, macroporosity, water-filled pore space and soil penentration resistance) in the soil profile (0−50 cm) and soybean components (grain yield, cumulative root length density and root dry mass) were investigated. Soil physical attributes were improved over time due to the combined effects of natural wetting-drying cycles and biopores created by the roots of precrops. Ruzigrass increased soybean root biomass and length density, mainly at deeper soil layers of compacted treatments (NTCT and NTCH). The rate of increase of soybean root length density in the soil profile was higher after ruzigrass cultivation in comparison with maize and oats. Soil compaction effects on grain yield were partially (NTCH) or totally (NTCT) alleviated after two years and ruzigrass intensified the mitigation process. Ruzigrass also resulted in higher soybean yields in comparison with maize, whereas NTCH and MTC reduced yields in approximately 400 kg ha−1 (∼13 %) compared to NT and NTCT. Soil strengthening was more evident after ruzigrass and oats cultivation than maize or wheat cropping. Soil compaction in clayey Oxisols can be alleviated over time as a result of root channels provided by precrops combined with natural wetting-drying cycles. Among the evaluated precrops, ruzigrass is of particular interest, as it provides the most suitable soil physical environment for soybean root growth and grain yield. In contrast, chiselling was demonstrated to be a non-viable strategy to mitigate soil physical constraints for root growth and grain yields. © 2020 Elsevier B.V.

Intensive cattle grazing and machine traffic may negatively affect soil structure, hydrologic processes and plant development in integrated crop-livestock systems. The pasture management is the critical factor controlling the efficiency of crop-livestock systems, because soil compaction by animal trampling can reduce the soil quality and system productivity. We aimed to study the effects of pasture management and animal trampling on soil physical attributes and water infiltration in a long-term no-tillage and integrated crop-livestock system in Subtropical Brazil. The long-term experiment of an integrated soybean-beef cattle grazing system was conducted in southern Brazil in a randomized block design with five treatment and three blocks. Pasture (Italian ryegrass and black oat) was grazed in the autumn/winter, with sward heights of 10, 20, 30, 40 cm and an ungrazed treatment, while soybean was grown in the spring/summer season. Soil physical attributes (bulk density, soil porosity and water retention curve) and water infiltration were evaluated after 14 years of started the integrated system. The soil physical properties at 0–5 cm depth were strongly affected by cattle grazing, especially in the pastures with sward heights of 10 cm and 20 cm. Consequently, there was a reduction in the water infiltration rate of 81% after grazing, and 47% after soybean harvest, and in pasture with a sward height of 10 cm, when compared with the ungrazed area. Pasture at 10 and 20 cm sward height decreased the water content at matric potentials between −1 and −10 kPa and increased water content between -10 and -1500 kPa, decreasing soil aeration and water availability. Higher soil available water content was found at the moderate grazing intensities of 30 cm and 40 cm pasture sward height. For the sustainability of the integrated soybean-cattle system the results suggest that well-managed grazing systems (30 cm of pasture sward height) should have beneficial soil physical conditions and water infiltration to promote sustainability and limit soil degradation.

Soil compaction is a result of soil compression, and this effect depends on the pressure applied and the soil structure. Nevertheless, studies regarding the effects of long-term tillage systems on strengthening of particle bonds are scarce. Thus, we aimed to study the soil bond strengthening due to the age-hardening phenomenon using the soil load support capacity model of an Oxisol managed under different tillage systems in Southern Brazil. Soil samples were collected from three soil layers (0.0–0.10 m; 0.10–0.20 m and 0.20–0.30 m) and five soil tillage systems of conventional tillage; minimum tillage with chiselling performed every year or every three years; and no-tillage for 11 or 24 years. Age-hardening was investigated using the soil load support capacity model. Soil cores were equilibrated at four matric potentials (−6, −33, −100 and −500 kPa) and submitted to uniaxial compression tests to obtain preconsolidation pressure. The soil load support capacity models were affected by the tillage systems. The long-term no-tillage presented the highest soil load support capacity for the same bulk density and water content in all layers, demonstrating greater resistance to additional compaction. Higher preconsolidation pressure values in long-term no-tillage at the same soil bulk density and water content were attributed to the age-hardening phenomena, which increased the number and strength of bonds among soil particles, leading to higher soil cohesion. Longer time under no-tillage improves the soil structure and soil load support capacity. Thus, soil mobilization strongly affected the soil structure by breaking particle bonds leading to the greater compaction.

Hydrolyzed leather, obtained from industrial leather waste, is an organic nitrogenous fertilizer with a high chromium (Cr) content. Soybean crops can be adversely affected by the presence of residual Cr in soil after application of hydrolyzed leather fertilizer. The aim of this work was to assess the effect of hydrolyzed leather on Cr absorption, root development, and symbiotic nodulation of soybean plants grown on three different soils including two Lixisols and a Gleysol. These soils were previously fertilized with hydrolyzed leather at three different rates (0.0, 0.1, and 0.8 kg m−2). Soybean shoot height, root development, nodulation, and mineral nutrient concentrations in plant tissues were determined after 45 d of crop growth. The application of hydrolyzed leather significantly increased Cr content in soil and Cr uptake by plants. Surprisingly, Cr was stored mainly in the aerial part of the plants. The presence of Cr had an adverse impact on shoot dry matter (41% reduction) and number of nodules (49% reduction) per plant grown on the soil with the lowest cation exchange capacity. However, no other significant effect was observed in nodule weight, diameter, or any other measured parameters.

Integrated farming systems are sustainable strategies to intensify land productivity by combining annual crop, livestock and/or forestry activities in different spatio-temporal arrangements. Therefore, they may help tackle global food and energy insecurity and climate change in the coming decades. We investigated the effects of integrated crop-livestock (ICL) and integrated crop-livestock-forestry (ICLF) systems on quantity, quality, and origin of soil organic matter (SOM) in southeastern Brazil. A native forest and an extensive low-grazing intensity pasture system were used as references. In integrated systems, corn (Zea mays) was alternated with two consecutive years of piata grass (Urochloa bryzantha) for cattle grazing. In ICLF, eucalyptus trees (Eucalyptus urograndis) were planted in simple rows of 15 × 2 m. Soil sampling was performed three times; in 2014, after two years of grazing; in 2015, after crop cultivation; and in 2016, after a successive grazing year, to evaluate chemical and physical composition changes of organic matter (C, N, δ13C, δ15N, and organic matter fractions) with time. Our findings showed that from 2010 to 2016, all systems (extensive grazing, ICL and ICLF) promoted increments on soil C and N stocks. However, land intensification converting extensive low-grazing intensity pasture to ICL was the most promising strategy, increasing soil C stocks at the rate of 0.28 Mg C ha−1 yr−1 from 2010 to 2016. Annual crop cultivation (corn intercropped with piata grass) promoted high organic matter inputs on the soil, increasing the amount of soil labile organic matter fractions, which presented higher δ13C and lower δ15N values over time. SOM in the integrated farming systems was originated mainly from C4 plants. Therefore, optimizing development of piata grass and corn increases organic residue inputs and then, soil C and N stocks. In addition, the crop period increased soil fertility parameters, which favors plant growth, thus providing high labile C inputs to the soil. In contrast, land intensification by adding the forestry component into the system (i.e., conversion from ICL to ICLF) reduced soil C (-0.22 Mg C ha−1 yr−1) and N (-0.03 Mg N ha−1 yr−1) stocks from 2010 to 2016, likely due to the reduction of C and N inputs to the soil caused by limited growth of annual crop and grass species under tree shades. In conclusion, land use intensification through ICL system contributes towards a more efficient and low-C agriculture, whereas the studied ICLF system did not bring further benefits to increase the quantity and/or quality of SOM.

Considering the increasing pet owner’s concern about the food their pets are consuming, in this study we investigated the origin of the main ingredients in wet and dry foods produced in Brazil using stable isotope ratios of carbon and nitrogen. We concluded that chicken and pork seem to be the dominant ingredients in most of the samples, with larger proportions in wet cat food. Even in pet foods showing ‘beef’ as the main ingredient on the label, we found a low proportion of bovine products in both wet and dry cat foods. Comparing the contribution of plant-derived products (C3 and C4 plants) and animal-derived products (chicken–pork, bovine and fish), approximately 21 % of cat foods had more than 30 % of ingredients with plant origin in their composition. The high amount of plant-derived products in cat foods found here raises the question whether this should be mentioned on package labels.

Root elongation is generally limited by a combination of mechanical impedance and water stress in most arable soils. However, dynamic changes of soil penetration resistance with soil water content are rarely included in models for predicting root growth. Better modelling frameworks are needed to understand root growth interactions between plant genotype, soil management, and climate. Aim of paper is to describe a new model of root elongation in relation to soil physical characteristics like penetration resistance, matric potential, and hypoxia. A new diagrammatic framework is proposed to illustrate the interaction between root elongation, soil management, and climatic conditions. The new model was written in Matlab®, using the root architecture model RootBox and a model that solves the 1D Richards equations for water flux in soil. Inputs: root architectural parameters for Soybean; soil hydraulic properties; root water uptake function in relation to matric flux potential; root elongation rate as a function of soil physical characteristics. Simulation scenarios: (a) compact soil layer at 16 to 20 cm; (b) test against a field experiment in Brazil during contrasting drought and normal rainfall seasons. (a) Soil compaction substantially slowed root growth into and below the compact layer. (b) Simulated root length density was very similar to field measurements, which was influenced greatly by drought. The main factor slowing root elongation in the simulations was evaluated using a stress reduction function. The proposed framework offers a way to explore the interaction between soil physical properties, weather and root growth. It may be applied to most root elongation models, and offers the potential to evaluate likely factors limiting root growth in different soils and tillage regimes.

Soil physical limitations that affect directly crop root elongation are the water, heat and mechanical stresses. In the literature, there are few studies that present a clear relationship of root elongation rate and soil physical stresses that could be used into a root growth models. The aim of this study was to carry out a systematic review, compiling and analyzing the impacts of the physical limitations of the soil (water stress, heat stress and soil strength) on the root elongation rate of soybean. The PRISMA method was used to select scientific papers published in the Scopus and Web of Science databases. The terms "root elongation", "soybean", "Glycine max", "water stress", "mechanical impedance", "heat stress", "hypoxia", "soil penetration resistance", "matric potential" and "temperature" were used as selection criteria. These procedures resulted only in ten papers, which were published until June 2021. The results indicate that the soybean root elongation was increased due to the increase in soil temperature, until 30 °C. Soil penetration resistance reduce exponentially the root elongation, and 4 MPa was sufficient to slow root elongation to approximately 7% of its unimpeded rate. The root elongation decay exponentially due to the reduction of the water potential. Even though soil compaction, heat stress, and water potential are relevant factors that affect directly the soybean root elongation, very few studies have published comparisons of the root responses to soil physical condition for soybean.

Integrated farming systems are promising strategies towards land-use efficiency and sustainable agriculture. The integrated crop-livestock-forestry (ICLF) system stablish complex interactions were synergies or competition depend on the arrangements throughout time and space. Fine root (≤2 mm) growth dynamics of crops, pasture and trees remains unclear when these species are integrated. We aimed to assess root growth dynamics after Eucalyptus urograndis introduction into an integrated crop-livestock (ICL) system. Previous ICL area was used as a reference. We assessed ICLF 1.9, 4.3 and 7.5 m distances from tree rows, starting the study when trees had three years of age. Eucalyptus rows were spaced 15 m apart and integrated to annual crops and pasture. We evaluated the root growth under two different successional periods: (i) corn cultivation interspaced with palisade grass (Urochloa brizantha); and (ii) a pasture, when palisade grass was grazed. We tracked fine root length using the minirhizotron technique, capturing 3200 images scanning up to 70 cm soil depth. Data of photosynthetically active radiation (PAR) transmission, soil bulk density, rainfall and air temperature were used as complementary information to support the discussion. Our results showed that Eucalyptus trees impaired root growth of annual crops cultivated in the interrow position, regardless of distance from the row. From 31 to 80 days after corn germination, root length production in ICLF was reduced by 120–179 cm m−2.d−1 along the tree interrow space. For the pasture period, total produced root length density reduced 6% at 1.9 m but increased 25% at 4.3 and 7.5 m, when compared to ICL. Shade of Eucalyptus trees at ICLF 1.9 m position, with PAR transmission mainly below 60%, sharply impaired root growth. Eucalyptus roots represented 12% from total root length produced in ICLF system, and 38% of these roots had positive ectomycorrhizal status. In conclusion, under Eucalyptus trees higher than 20 m, pasture of palisade grass is more adaptable than corn when considering the root growth dynamics of our studied ICLF arrangement. Based on our findings, corn intercropped with palisade grass should not be introduced in future management of the ICLF system, unless part of the trees is chopped to reduce light competition. However, implemented pasture of palisade grass showed belowground synergies with Eucalyptus, increasing root growth in intermediary interrow positions and emerging new fungal symbiosis, which could be playing important functions in soil, as soil carbon storage and nutrient cycling.

Crop residues may buffer part of compressive stress applied over the soil surface. Thus, indiscriminate crop residue removal would magnify soil compaction in highly mechanized cultivation systems, such as sugarcane in Brazil. Nevertheless, the effect of different amounts of sugarcane crop residue (straw) on soil compaction mitigation still needs to be tested. We conducted a laboratory study to quantify the effects of sugarcane straw rates on soil compaction indicators in response to external applied stress. The experiment involved remolded soil cores with four initial bulk densities: 1.25, 1.35, 1.45 and 1.55 Mg m−3, and five amounts of straw were left on soil surface, equivalent to 0, 5, 10, 15 and 20 Mg ha−1. The soil cores were subjected to uniaxial compression test and seven successive vertical static loads (25, 50, 100, 200, 400, 800 and 1600 kPa) were applied over the soil surface using a pneumatic consolidometer. Soil displacement was measured after each applied load. Based on these values, apparent precompression stress (σp), apparent compression index (CI) and final bulk density were calculated as indications of soil deformation. Because, soil inherent properties should not change, we call the changes due to straw layer addition "apparent" in this study. Our results revealed that large amounts (>10 Mg ha−1) of straw increased subtly apparent soil load bearing capacity (i.e., increased up to 15 kPa in apparent σp; 7%). The bulk density change rate (soil deformation) decreased due to presence of straw under low stress ( 400 kPa) levels in loose soil. On the other hand, compaction was slightly reduced in compacted soil, with corresponding reduction on apparent CI values. Nevertheless, despite this buffer effect provided straw, we noticed that increases in surface straw amount are likely insufficient to reduce the risk of compaction (little gain in apparent load-bearing capacity), but a reduction of about 5% on the soil deformation (as apparent σp is overcome) could occurs in compacted soils. We advocate that benefits of leaving sugarcane straw covering the soil go beyond the direct “damper” effect, because straw is source of carbon, which is fundamental for enhancing soil structure stability and biological activity, and thus, reducing soil compaction risks or even alleviating soil compaction restrictions to plant growth. Finally, we encourage future studies to test the straw effects under machinery traffic in field conditions, which could involve the additional effect of shear stress over the tyre-straw-soil interface.

The ability of soil to recover from disturbances is important for the proper functioning of agroecosystems. The objective of this study was to investigate the effect of the physical resilience in subtropical soils, due to organic matter content, texture, and mineralogy. For this purpose, both undisturbed soil core and disturbed soil samples were taken from two depths from three soils under no-tillage in long-term field experiments: two Oxisols and one Ultisol. Soil core samples were subjected to wetting–drying cycles and the soil physical attributes (bulk density, total porosity, macro- and microporosity, and air permeability) were determined before and after soil compaction or wet-dry cycles. Organic matter and clay contents were greater in the Oxisols, with iron oxides, reducing the stress level. Soil bulk density, total porosity, macro- and microporosity, and air permeability returned values like their originals after compaction and three wetting–drying cycles. Macroporosity was the individual attribute most strongly affected by compaction and it recovered to the greatest extent. The Oxisols were more resilient than the Ultisol due to their higher organic matter, clay contents and the presence of iron oxides.

Soil strength is not only affected by water content and bulk density, but also by the age-hardening phenomena, which plays a key role in increasing the soil strength as a function of time. It has been demonstrated that soil penetration resistance in no-tillage is higher when compared with other tillage systems at the same bulk density and water content. The objectives of this study was to investigate the effects of the age-hardening phenomena on soil penetration resistance in a long-term soil management system, running since 1988 in a very clayey Oxisol, in southern Brazil. Soil samples were collected from three soil layers (0.0–0.10 m; 0.10–0.20 m and 0.20–0.30 m) and five soil tillage systems: conventional tillage; minimum tillage with chiselling performed every year or every three years; and no-tillage for 11 or 24 years. Age-hardening was investigated using soil penetration resistance analysis and modelling. We used the area under the soil resistance to penetration curve to compare the age-hardening phenomena under the different tillage systems. For the same bulk density and water content, the soil resistance to penetration increased with time under no-tillage or without soil chiselling. For the same bulk density, no differences were found for macroporosity and microporosity among the tillage systems. Higher soil penetration resistance values in long-term no-tillage at the same soil bulk density and water content were attributed to the age-hardening phenomena, which increased the number and strength of bonds among soil particles, leading to higher soil cohesion. It is necessary to establish critical limits of soil penetration resistance as a function of the soil tillage system, and the time without soil chiselling or under no-tillage system.

Understanding the pathways of soil phosphorus (P) transformations and determining the factors related to P nutritional status of soils when land use changes is critical for a better management, especially in Amazon region. We investigated different P fractions and their transformations in different land uses (primary forest and pasture) and soil textures (clayey and sandy) in Amazonian Oxisols using path analysis. Besides P fractionation, phosphatase activity and its correlation with soil carbon (C):organic P (Po) ratio was evaluated to correlate it with soil P nutritional status. After 15 years from forest slashing and burning, total P in pasture reaches to the forest levels in Amazonian soils, regardless of soil texture. Path analysis showed that land use conversion from forest to pasture decreased the diversity of the contribution of P pools to buffer P extracted by anion exchange resin. However, Po accounted for one-fourth of total P in our sites, it plays an important role as source of plant available P and contributed more in pasture compared to forest. Our results from P fractionation and C:Po ratio revealed that Amazonian pastures and forests are not P deficient. We also showed that with increasing C:Po ratio, plant-available P content became more dependent on P mineralization. Soil acid phosphatase activity can be used as an indicator for evaluating soil P nutritional status; however, its range changes according to the land use.

Sustainability of crop production systems depends on the preservation of soil physical quality over time. This study aimed to determine long-term effects of soil tillage and cropping systems on physical attributes and hydraulic properties of an Oxisol in Southern Brazil, emphasising management practices to preserve or improve the soil structure quality under no-tillage system. The experiment was conducted in randomized block design, using a 5 × 2 factorial arrangement (tillage × cropping systems), with four replications. The five tillage systems consisted of conventional tillage (CT); minimum tillage, chiselled soil every year (MTC1); minimum tillage, chiselled soil every three years (MTC3); continuous no-tillage for 11 years (NT11); and continuous no-tillage for 24 years (NT24). The two cropping systems consisted of annual crop sequence with wheat in the winter and soybean in the summer, designated as crop succession (CS); and a 4-year crop rotation (CR) with white lupine-maize—black oat-soybean—wheat-soybean—wheat-soybean in winter–summer, respectively. Undisturbed soil cores were collected from 0–0.10; 0.10–0.20 and 0.20–0.30 m of soil depth, to determine the soil bulk density (BD), total porosity, macroporosity, microporosity, pore size distribution and classes, soil water retention curve, infiltration rate and field-saturated hydraulic conductivity. There was no interaction between tillage and cropping systems, and no effects of cropping systems on soil physical and hydraulic properties. Regardless the cropping system, chiselling effects on soil physical properties persisted for less than 22 months, and were restricted to below 0.20 m soil depth. The CT resulted in soil pulverization at 0–0.10 m depth, leading to lower BD and higher macroporosity compared to the other soil tillage systems. At layers below 0.10 m, CT increased the BD and reduced the macroporosity to critical levels for crop growth. Continuous use of no-tillage improved soil physical quality mainly at deeper layers, and provided higher plant available water retention in the soil at matric potentials ranging from −10 to −200 kPa in relation to CT and MTC1. The adoption of NT improves soil physical quality and plant available water over time, and periodic soil chiselling aiming to disrupt compacted layers should be avoided because of its effects on reducing soil compaction level are short-lived.

The use of biochar, which is the solid product of biomass pyrolysis, in agricultural soils, has been shown as a strategic solution for building soil carbon stocks and mitigating greenhouse gas emissions. However, biochar amendment might also benefit other key soil processes and services, such as those that are related to water retention, particularly in sandy soils. Here, we conducted an experiment to investigate the potential of biochar to enhance pore size distribution and water retention properties in a tropical sandy soil. Three biochar rates were incorporated (equivalent to 6.25, 12.5, and 25 Mg ha&minus, 1) into plastic pots containing a sandy Oxisol sampled from a sugarcane field in Brazil. Undisturbed samples of the mixture were collected at two evaluation times (50 and 150 days) and used to determine water retention curves and other soil physical properties. The results showed that biochar amendment decreased soil bulk density and increased water retention capacity, micropore volume, and available water content. Higher soil water retention in amended soil is associated with the inherent characteristics of biochar (e.g., internal porosity) and potential improvements in soil structure. Microporosity and water retention were enhanced with intermediate biochar rate (12.5 Mg ha&minus, 1), instead of the highest rate (25 Mg ha&minus, 1) tested. Further studies are needed to validate these results under field conditions.

The objective of this work was to determine whether compaction by tractor traffic in areas managed under controlled traffic can be limiting to corn crop, under different tillage systems, in a Typic Paleudult of medium texture. Two experiments were carried out, one in the field over two crop seasons and another in a greenhouse. The treatments consisted of minimum tillage with chiselling; no-tillage subjected to one, three, or six passes of a tractor weighing 3.8 Mg; and an area without traffic. Evaluations were performed for soil physico-hydraulic parameters (soil bulk density, penetration resistance, and water retention curve), root and shoot growth, and grain yield. The agricultural traffic increased bulk density, soil penetration resistance, and water content at field capacity. The highest values for soil penetration resistance (1,600 kPa) and bulk density (1.67 g cm-3) in the trafficked soil were not limiting to corn development and increased grain yield for both crop seasons. Tractor traffic of up to six passes is beneficial to corn cultivation, and it increases water availability and corn grain yield. Resumo: O objetivo deste trabalho foi determinar se a compactação imposta pelo tráfego de trator, em áreas com tráfego controlado, pode ser limitante à cultura do milho em sistemas de preparo de um Argissolo Vermelho de textura média. Dois experimentos foram conduzidos, um no campo, em duas safras, e outro em casa de vegetação. Os tratamentos constituíram-se do uso de um sistema de preparo reduzido; um sistema plantio direto submetido a uma, três e seis passadas de trator de 3,8 Mg; e de uma área sem tráfego. Avaliaram-se os parâmetros físico-hídricos do solo (densidade do solo, resistência à penetração e curva de retenção de água), o crescimento radicular e da parte aérea, além da produtividade de grãos de milho. O tráfego agrícola incrementou os valores de densidade do solo e de resistência do solo à penetração, bem como o conteúdo de água do solo à capacidade de campo. Os máximos valores de resistência do solo à penetração (1.600 kPa) e densidade do solo (1,67 g cm-3), nas parcelas trafegadas, não foram limitantes ao desenvolvimento do milho e incrementaram a produtividade de grãos em ambas as safras. O tráfego de até seis passadas com trator sobre a mesma área é benéfico à cultura de milho, e incrementa a disponibilidade de água e a produtividade de grãos de milho.

The soybean plant has long been known to have a high phenotypic plasticity, altering shoot morphological traits in response to variations on plant density. However, plant density effects on soybean root growth and distribution in the soil profile are not elucidated. This paper aimed at evaluating the effects of three plant densities on soybean root growth at different soil layers and horizontal positions relative to the crop planting row. The study comprised two field experiments carried out during 2014/2015 growing season in Londrina, PR, Southern Brazil, one with the soybean cultivar BRS 359 RR, and other with the cultivar BMX Potencia RR. Both experiments were laid out in a randomized complete block design and split-split-plot arrangement, with three replications. In the main plots, three soybean seeding rates (150; 300; and 450 thousand seeds ha -1 ) were distributed; in the subplots, five soil layers (0-10; 10-20; 20-30; 30-40 and 40-50 cm depth); and, in the sub-subplots, three horizontal sampling positions (row; interrow on the left; and interrow on the right). Higher soybean plant densities led to thinner roots, with greater growth towards the crop interrows and deeper soil layers, but the cultivars can affect this behavior.

Treated and reused industrial residues and urban waste are depicted as potential alternative sources for agricultural use. In this context, the objective of this study was to determine the chemical element concentrations in organic residues from the Medium-High Uruguay Region of the Rio Grande do Sul, using energy dispersive x-ray fluorescence spectrometry (EDXRF). The organic compounds analyzed were meat agroindustry sludge, organic composites from agribusiness meat, and organic compounds from urban waste (particle sizes: >4.75 mm, 2.00 mm, and

A utilização de composto de lixo urbano como fonte de nutrientes para a agricultura vem sendo investigada; entretanto, as alterações físicas do solo ainda são pouco conhecidas. Objetivouse avaliar a influência do uso de composto de lixo urbano e da adubação mineral na estabilidade de agregados e nos teores de carbono orgânico e nitrogênio total de um Latossolo Vermelho, em sistema plantio direto na região noroeste do Rio Grande do Sul. Utilizou-se o delineamento de blocos ao acaso, em esquema fatorial 6 × 2 (adubação e épocas), com quatro repetições. O fator épocas de avaliação constituiu-se dos anos agrícolas de 2009/10 (girassol) e 2010/11 (milho). O fator adubação foi composto por cinco doses de composto de lixo urbano (0, 25, 50, 75 e 100 m3 ha-1), além de um tratamento adicional com fertilização mineral. Na camada de 0,0-0,10 m, foram determinados a estabilidade de agregados (diâmetro médio geométrico e ponderado), os teores de carbono orgânico (CO) e o nitrogênio total (NT). A utilização de doses crescentes de composto de lixo urbano favoreceu melhorias na agregação do solo, em relação à fertilização mineral. A utilização de até 75 m3 ha-1 de composto de lixo urbano, após dois anos de aplicações em cultivos agrícolas com milho e girassol em um Latossolo Vermelho, sob sistema plantio direto, promoveu melhorias na agregação do solo, quando comparada à fertilização mineral. O teor de CO e o de NT, após o segundo cultivo, apresentaram incrementos lineares, em relação às doses de composto de lixo urbano. The use of urban waste compost as nutrient source in agriculture has been a subject of investigation in Brazil and elsewhere, although the effects on soil physical and chemical properties and processes are still poorly known. The aim of this study was to evaluate the effect of application of urban waste compost and mineral fertilizer on soil aggregate stability and organic carbon and total nitrogen content of a Rhodic Hapludox under no-tillage in the northwestern region of Rio Grande do Sul, Brazil, in the 2009/2010 and 2010/2011 growing seasons. The experiment was arranged in a 2 × 6 (seasons and fertilization) factorial in a randomized complete block design with four replications. The factor time consisted of two growing seasons (sunflower in 2009/10 and maize in 2010/11) and the factor fertilization of five rates of urban waste compost (0, 25, 50, 75 and 100 m3 ha-1), and mineral fertilizer. Soil samples were collected from the 0.0-0.10 m layer to determine aggregate stability (mean weight and geometric diameter), soil organic carbon (SOC) and total nitrogen (TN). Rates of up to 75 m3 ha-1 of urban waste compost, after two years of application to no-tillage maize and sunflower, improved aggregation compared to mineral fertilization in a Rhodic Hapludox. After the second crop, the SOC and TN contents increased linearly with the levels of urban waste compost.

Soil physical quality can be easily and quickly evaluated by using simple equipment to identify levels of soil compaction. Hence, it is necessary to know the variables responsible for changes in the soil penetration resistance (SPR). The aim of this review is to identify the main factors related to the various equipment used for assessing SPR as a soil physical quality indicator in agriculture. This literature review describes the different types of equipment used and its relationship with SPR. A wide range of procedures, devices, and equipments are available. Much of variability in SPR results is related to the equipment model, cone angle and diameter, and penetration rate. Usually, restrictions to root growth are correlated with SPR values above 2-3 MPa. However, comparisons of SPR values obtained under different soil moisture regimes in the same soil type have provided conflicting results of difficult interpretation. In order to minimize these problems, there is a need for standardization of measurement procedures and interpretation, and/or correction of SPR values according to a soil water content of reference. A qualidade física dos solos pode ser fácil e rapidamente avaliada com o uso de equipamento simples para a identificação do nível de compactação do solo. Para isso, é necessário o conhecimento das variáveis responsáveis por alterações da resistência do solo à penetração (RP). O objetivo desta revisão é identificar os principais fatores relacionados com os equipamentos utilizados para a avaliação da RP como indicador da qualidade física do solo na agricultura. Essa revisão bibliográfica descreve os tipos de equipamentos utilizados e sua relação com a RP. Existe disponível uma grande variabilidade de equipamentos, dispositivos e procedimentos. Grande parte da variabilidade dos resultados de valores de RP está relacionada com os modelos de equipamentos, diâmetro e ângulo de cone e taxa de penetração. Usualmente, as restrições ao crescimento radicular, estão correlacionadas com valores de RP acima de 2 a 3 MPa. Porém, comparações entre valores de RP obtidos sob diferentes conteúdos de água no solo, em áreas com mesmo tipo de solo, proporcionaram resultados conflitantes e de difícil interpretação. Para reduzir esses problemas, recomenda-se uma normatização no procedimento de medida e interpretação e/ou correção dos valores de RP para um conteúdo de água do solo de referência.

Soil penetration resistance is an important indicator of soil physical quality and the critical limit of 2 MPa has been widely used to characterize the soil physical quality, in both no-tillage and conventional systems. The aim of this study was to quantify the influence of different tillage and cropping systems on the soil penetration resistance in a Rhodic Eutrudox. The experiment was carried out in a 5 × 2 factorial, completely randomized block design (tillage systems vs cropping systems), with four replications. The tillage systems consisted of: conventional tillage disk harrow; minimum tillage with annual chiseling; minimum tillage with chiseling every three years; no-tillage for 11 consecutive years; and no-tillage for 24 consecutive years. The factor cropping systems was represented by: crop rotation and crop succession. The soil penetration resistance (SPR) was determined in 20 soil samples per treatment and layer (0.0-0.10; 0.10-0.20 and 0.20-0.30 m) for each soil matric potential: -6, -10, -33, -100, -500 kPa. The SPR was determined at a volumetric soil water content equivalent to the fraction of plant-available water of 0.7. There were no differences of soil penetration resistance between the two cropping systems. Differences in soil penetration resistance among tillage systems were related to the matric potential at which the samples were equilibrated. The critical SPR limit of 2 MPa normally used for conventional tillage should be maintained. However, this value of 2 MPa is inappropriate for the physical quality characterization of Rhodic Eutrudox under no-tillage and/or minimum tillage with chiseling. Regardless of the cropping systems, the critical SPR limit should be raised to 3 MPa for minimum tillage with chiseling and to 3.5 MPa for no-tillage. RESUMO: A resistência do solo à penetração é um importante indicador da qualidade física do solo, e o limite crítico de 2 MPa vem sendo utilizado para caracterizar a qualidade física do solo, tanto em sistema plantio direto como em cultivos convencionais. Objetivou-se com este trabalho verificar a influência de diferentes sistemas de manejo do solo e modelos de produção sobre a SPR em um Latossolo Vermelho distroférrico. O experimento foi conduzido em um delineamento de blocos ao acaso, em esquema fatorial 5 × 2 (manejos do solo × modelos de produção), com quatro repetições. Os manejos do solo foram: sistema preparo convencional; sistema preparo mínimo escarificado a cada ano; sistema preparo mínimo escarificado a cada três anos; sistema plantio direto contínuo por 11 anos; e sistema plantio direto contínuo por 24 anos. O fator modelo de produção foi composto por: rotação e sucessão de culturas. A resistência do solo à penetração foi determinada em 20 amostras indeformadas de solo por tratamento e por camada (0,0-0,10; 0,10-0,20 e 0,20-0,30 m), as quais foram equilibradas nos potenciais matriciais de -6, -10, -33, -100 e -500 kPa. Foi determinada a resistência do solo à penetração no conteúdo de água volumétrico equivalente à fração de água disponível às plantas de 0,7. Não houve diferenças de resistência do solo à penetração entre os modelos de produção. A detecção de diferenças de resistência do solo à penetração entre os sistemas de manejo do solo foi dependente do potencial matricial de água no solo, em que as amostras foram equilibradas. O limite crítico de resistência do solo à penetração usualmente utilizado de 2 MPa deve ser mantido para o sistema preparo convencional. Todavia, esse valor foi inadequado para a caracterização da qualidade física do Latossolo Vermelho distroférrico, sob sistema plantio direto e, ou, no sistema de preparo mínimo. Independentemente do modelo de produção, os limites crítico de resistência do solo à penetração devem ser ampliados para 3 MPa, no sistema preparo mínimo com escarificação, e para 3,5 MPa, no sistema plantio direto.

A dinâmica da água no solo é um dos principais fatores que determinam o potencial produtivo das culturas agrícolas e uma ferramenta importante para a modelagem do fluxo de água no solo é o modelo agrohidrológico Soil Water Atmosphere Plant (SWAP). Nesse sentido, objetivou-se utilizar esse modelo na modelagem da dinâmica da água em um Latossolo Vermelho Distroférrico com sistemas de preparo do solo de longo prazo. O fluxo de água no solo foi simulado diariamente na camada de 0,0-0,50 m em três sistemas de preparo do solo (plantio direto, preparo reduzido com escarificação anual e preparo convencional). Foram utilizados dados agrometeorológicos do período de 01/2001 a 11/2013 para o fluxo de água no solo. A fração da água disponível foi influenciada pelo sistema de preparo do solo. O preparo convencional incrementou os períodos com baixa disponibilidade hídrica às culturas. Ao longo do tempo, houve adequada disponibilidade hídrica tanto no plantio direto quanto no preparo reduzido. No plantio direto ocorreram as menores taxas de escoamento superficial, favorecendo aumentos no armazenamento de água e drenagem profunda. O preparo convencional favoreceu o aumento das taxas de escoamento superficial e a redução da percolação profunda de água no solo, reduzindo a fração da água disponível e incrementando os dias com que o conteúdo de água do solo ficou abaixo da fração crítica de água disponível de 0,5. O modelo SWAP foi eficiente para simular o fluxo de água em sistemas de preparo neste Latossolo Vermelho. Sistemas conservacionistas de longo prazo preservam a estrutura do solo para a melhoria do fluxo de água.

Estimation of soil load-bearing capacity from mathematical models that relate preconsolidation pressure (σp) to mechanical resistance to penetration (PR) and gravimetric soil water content (U) is important for defining strategies to prevent compaction of agricultural soils. Our objective was therefore to model the σp and compression index (CI) according to the PR (with an impact penetrometer in the field and a static penetrometer inserted at a constant rate in the laboratory) and U in a Rhodic Eutrudox. The experiment consisted of six treatments: no-tillage system (NT); NT with chiseling; and NT with additional compaction by combine traffic (passing 4, 8, 10, and 20 times). Soil bulk density, total porosity, PR (in field and laboratory measurements), U, σp, and CI values were determined in the 5.5-10.5 cm and 13.5-18.5 cm layers. Preconsolidation pressure (σp) and CI were modeled according to PR in different U. The σp increased and the CI decreased linearly with increases in the PR values. The correlations between σp and PR and PR and CI are influenced by U. From these correlations, the soil load-bearing capacity and compaction susceptibility can be estimated by PR readings evaluated in different U. A estimativa da capacidade de suporte de carga do solo a partir de modelos matemáticos que relacionam a pressão de preconsolidação (σp), a resistência mecânica do solo à penetração (RP) e o conteúdo gravimétrico de água do solo (U) é importante na definição de estratégias para prevenção da compactação de solos agrícolas. Portanto, objetivou-se modelar a σp e o índice de compressão (IC) em função da RP (em campo com penetrômetro de impacto e em laboratório com penetrômetro digital de bancada) e do U em um Latossolo Vermelho. O experimento foi composto por seis tratamentos: sistema plantio direto (SPD); SPD com escarificação; e SPD com compactação adicional pelo tráfego de uma colhedora por 4, 8, 10 e 20 passadas. Os valores de densidade do solo, porosidade total, RP (no campo e no laboratório), U, σp e IC foram determinados nas camadas de 5,5-10,5 cm e 13,5-18,5 cm. A modelagem da σp e do IC foi realizada em função da RP em diferentes U. A σp aumentou e o IC diminui linearmente com incremento nos valores de RP. As relações entre σp e RP e IC e RP são influenciadas pelo U. A partir dessas relações, é possível estimar a capacidade de suporte de carga e a suscetibilidade do solo à compactação por meio das leituras de RP, avaliadas em diferentes U.

O reforço e estabilização de solos por plantas são facilmente observados na natureza. Entretanto, o uso de plantas (e suas raízes) em obras de Engenharia Natural requer conhecimentos e medições de seus efeitos na estabilidade do solo. O objetivo desta revisão foi abordar e discutir conceitualmente a influência das raízes sobre a melhoria da resistência mecânica do solo e na estabilidade de taludes. O efeito das raízes e sua arquitetura sobre as propriedades físicas dos solos foram brevemente discutidos. A estabilização de taludes, seja pela redução da erodibilidade ou ancoramento do solo em profundidade, está diretamente associada à arquitetura e à densidade de comprimento radicular das espécies e do tipo de planta utilizada (gramínea, arbusto ou árvore). As informações compiladas mostram-se úteis aos trabalhos que envolvem o uso de plantas em dimensionamentos geotécnicos, seja para a contenção de processos erosivos ou para a estabilização superficial de massas de solo. O reforço mecânico do solo devido à presença de raízes tem papel de grande importância na estabilidade de taludes, no entanto, técnicas de avaliação da interação solo-raízes ainda devem ser aprimoradas para condições de campo.

No-tillage system have been a mainly conservationist system specially in tropical and subtropical climate conditions. The aim of this work was to evaluate yield components and morphological soybean and wheat in Rhodic Eutrudox under tillage and cropping systems in Subtropical climate. This study was carried with five tillage and two cropping systems, on completely randomized block design, with four replications. Tillage systems consisted of conventional tillage with disk harrow; minimum tillage with annual chiselling; minimum tillage with chiselling every three years; no-tillage for 11 years; and no-tillage for 24 years. The factor cropping systems was represented by crop rotation and crop succession. In the soybean crop were evaluated yield, mass of 1000 grains, plant height, and first pod insertion of soybean, chlorophyll content and the vegetation index normalized difference. Furthermore, for the wheat cropping was evaluated the grain yield and hectolitre weight. Soybean and wheat grain yield was not changed due to cropping systems. Soybeans yield in no-tillage with 24 years was higher than in conventional tillage; and soybean and wheat yield was not affected by times under no-till adoption. Soil chiselling not favoured increased in productivity of soybean and wheat. Soil chiselling is an unnecessary practice due to absence of productive and morphological improvement for soybean and wheat cropping.

A utilização de fontes não renováveis, para a produção de adubos minerais, causa grandes impactos ao meio ambiente. A redução desses impactos é favorecida pela crescente busca por novas fontes nutricionais orgânicas, para as culturas. Este trabalho objetivou avaliar a utilização de resíduo de indústria de carnes (RIC) como fonte alternativa de nutrientes para as culturas do girassol e milho. Foram utilizadas cinco doses de RIC (0 m³ ha-1, 25 m³ ha-1, 50 m³ ha-1, 75 m³ ha-1 e 100 m³ ha-1) e um tratamento com adubação mineral. O RIC proporcionou aumento na produtividade de grãos das culturas de girassol e milho. Na cultura do milho, a máxima produtividade foi obtida com a dose de 87 m³ ha-1 de RIC, equivalendo a 92% da produtividade obtida com a adubação mineral. Na cultura do girassol, doses iguais ou superiores a 20 m³ ha-1 de RIC proporcionaram produtividades iguais ou superiores às obtidas com adubação mineral. O RIC apresentou potencial agrícola para uso como fertilizante orgânico, podendo substituir, parcial ou totalmente, a adubação química. The use of non-renewable sources for the production of mineral fertilizers causes major impacts to the environment. The reduction of these impacts favors the increasing search for new organic nutrient sources for crops. This study aimed to evaluate the use of residue from meat industry (RMI) as an alternative source of nutrients for sunflower and maize crops. Five doses of RMI (0 m³ ha-1, 25 m³ ha-1, 50 m³ ha-1, 75 m³ ha-1 and 100 m³ ha-1) and one treatment with mineral fertilization were tested. The RMI provided an increase in grain yield for the sunflower and maize crops. In the maize crop, the highest yield was obtained with the dose of 87 m³ ha-1 of RMI, equivalent to 92% of the yield obtained with mineral fertilization. In the sunflower crop, doses equal to or higher than 20 m³ ha-1 of RMI provided equal or higher yields than those obtained with mineral fertilization. The RMI presented agricultural potential for use as an organic fertilizer and can partially or totally replace chemical fertilization.

A utilização de resíduos urbanos compostados como fonte de nutrientes na agricultura é uma alternativa econômica de descarte deste material. Todavia, devido à diversidade dos materiais que compõem estes resíduos, há a necessidade de estudos constantes sobre os efeitos de sua utilização nas propriedades químicas do solo e na produtividade das culturas. Objetivou-se avaliar o potencial fertilizante de um composto de lixo urbano (CLU) nas culturas de girassol e milho e seu efeito nas propriedades químicas de um Latossolo Vermelho. Realizou-se experimento de campo com tratamentos compostos por doses de 0 Mg ha-1, 10 Mg ha-1, 20 Mg ha-1, 30 Mg ha-1 e 40 Mg ha-1 de CLU e adubação mineral conforme a recomendação de cada cultura. Os resultados indicaram aumento no pH do solo de 6 para 6,5, com a adição do CLU. A acidez potencial do solo diminuiu linearmente de 3,0 cmol c dm-3 para 2,4 cmol c dm-3, contribuindo para o acréscimo no índice SMP, o que refletiu no aumento da capacidade de troca de cátions do solo. A saturação por bases aumentou de 77% para 85%, devido, principalmente, ao acréscimo nos teores de cálcio e magnésio. O CLU proporcionou produtividade de grãos de girassol semelhante à da adubação mineral, nas doses de 10 Mg ha-1, 20 Mg ha-1 e 30 Mg ha-1, sendo que, na dose de 40 Mg ha-1, foi significativamente superior. A produtividade de grãos de milho em doses iguais ou superiores a 20 Mg ha-1 de CLU não diferiu da adubação mineral. O CLU apresentou potencial fertilizante, podendo substituir a adubação mineral nas culturas de girassol e milho. The use of composted urban waste as a source of nutrients in agriculture is an economic alternative for discarding this material. However, due to the diversity of materials that compose this waste, long term studies on its effects on soil chemical attributes and crop yield are necessary. This study aimed at evaluating the potential of urban waste compost (UWC) as a fertilizer for sunflower and maize crops, as well as its effects on the chemical attributes of an Oxisol. A field experiment, with UWC doses of 0 Mg ha-1, 10 Mg ha-1, 20 Mg ha-1, 30 Mg ha-1 and 40 Mg ha-1 and mineral fertilization according to the recommendation for each crop, was carried out. The results showed an increase in soil pH from 6 to 6.5, with the UWC application. The soil potential acidity decreased linearly from 3.0 cmol c dm-3 to 2.4 cmol c dm-3, contributing to the SMP index increase, what reflected on the increase of the soil cation exchange capacity. The bases saturation increased from 77% to 85%, mainly due to the increase in calcium and magnesium levels. The use of UWC resulted in sunflower grain yield similar to that for mineral fertilization, at 10 Mg ha-1, 20 Mg ha-1 and 30 Mg ha-1, being significantly higher at 40 Mg ha-1. The maize grain yield at or above 20 Mg ha-1 of UWC did not differ from the mineral fertilization. The UWC presented potential to replace the mineral fertilization for sunflower and maize crops.

Soil compaction caused by machinery traffic reduces crop yields. This study aimed to evaluate the effects of intensive traffic, and the soil water content, on the soil penetration resistance (PR) of a Rhodic Eutrudox (Distroferric Red Latosol, Brazilian Classification), managed under no-tillage (NT). The experiment consisted of six treatments: NT with recent chiseling, NT without additional compaction, and NT with additional compaction by 4, 8, 10 and 20 passes of a harvester with a weight of 100 kN (70 kN on the front axle). Undisturbed soil samples were collected at 5.5-10.5 cm and 13.5-18.5 cm depth to quantify the soil bulk density (BD). The PR was assessed in four periods, using an impact penetrometer, inserted in the soil to a depth of 46 cm. The effect of traffic intensities on the PR was small when this variable was assessed with the soil in the plastic consistency. Differences in PR among treatments increased as the soil water content decreased. The increase in the values of PR and BD was higher in the first passes, but the increase in the number of traffics resulted in deeper soil compaction. The machinery traffic effects on PR are better characterized in the friable soil consistency. A compactação do solo causada pelo tráfego de máquinas reduz a produtividade das culturas. O objetivo deste trabalho foi avaliar os efeitos do tráfego intensivo e do conteúdo de água do solo na resistência à penetração (PR) de um Latossolo Vermelho distroférrico, muito argiloso, manejado em sistema plantio direto (NT). O experimento foi composto por seis tratamentos: NT escarificado; NT sem compactação adicional; e NT com compactação adicional pelo tráfego de uma colhedora com massa de 100 kN (70 kN no eixo dianteiro) por 4; 8; 10 e 20 passadas. A densidade do solo (BD) foi determinada utilizando amostras indeformadas, coletadas nas camadas de 5,5-10,5 cm e 13,5-18,5 cm. A RP foi determinada em quatro épocas, utilizando um penetrômetro de impacto, inserido no solo até a profundidade de 46 cm. O efeito das intensidades de tráfego no NT sobre a PR foi pequeno quando esta variável foi avaliada com o solo na consistência plástica. As diferenças na PR entre os tratamentos aumentaram à medida que o conteúdo de água no momento da avaliação diminuiu. O aumento nos valores de PR e BD foi maior nas primeiras passadas, mas o incremento do número de tráfegos aumentou a profundidade de compactação do solo. O aumento da PR proporcionado pelo tráfego de máquinas é mais bem caracterizado quando determinado com o solo na consistência friável.

The use of swine residue (SR) as a source of nutrients in growing crops such as maize, may be an option for disposal of organic waste produced in large quantities in pig farms, allowing total or partial substitution of mineral fertilizer in agricultural crops. The objective of this study was to enable the use of SR as an alternative source of nutrients to the mineral fertilization in maize under conditions of a Rhodic Hapludox. The treatments consisted of the use of mineral fertilizer recommended for maize; no fertilization (control), and doses of SR (25, 50, 75, 100 m³ ha-1). The variables: length and ear diameter, number of grains per spike, thousand grain weight and yield. The highest grain yields were obtained with chemical fertilizers and doses of 50, 75 and 100 m³ ha-1 of SR. The mineral fertilization in maize can be replaced by doses of SR from 50 m³ ha-1, with no loss in productivity of maize in a Rhodic Hapludox with very clayey texture.

The value of soil water infiltration is very important in several areas, such as agriculture, water resources, engineering projects. The methods to determinate the water infiltration in general is difficult and produce often unreliable results. The work aimed to evaluate the soil water infiltration rate in a Rhodic Hapludox under three management systems. The results were compared using two methods to determine the water infiltration rate. In the three management systems, the water infiltration rate in the soil was determined using the double ring infiltrometer. Using this method the results showed higher values when compared to the Cornell infiltrometer. For both methods, the native forest presented the highest soil water infiltration rate, followed by the no tillage area and perennial pasture grown. Through the double ring infiltrometer the infiltration rates obtained were 1428.2 mm h-1 (Forest), 46 mm h-1 (no tillage) and 22.6 mm h-1 (perennial pasture). Considering the Cornell infiltration method, the same areas showed infiltration rates of 300, 33.2 and 12.7 mm h-1, respectively. In the native forest the runoff process was not verified, while ingress with no tillage and perennial pasture. In these areas the runoff is started, respectively, at 3.25 and 1.33 minutes after the beginning of the tests.

The interest in using sugarcane straw as a feedstock for bioenergy production has been increased considerably. However, indiscriminate straw removal may negatively affect soil functioning. Therefore, this work aimed to quantify and characterize soil solution translocating along the profile, under straw removal rates from the soil surface. Lysimeter systems were built with 1, 20, 50, and 100 cm soil columns, with a sandy clay loam texture, from a commercial sugarcane field in Piracicaba-SP, southeastern Brazil. The experiment was conducted in open area, where the lysimeters were subjected to rainfall and sun radiation. After the soil stabilization within the lysimeters, the treatments were added, consisting of four straw amounts (0, 3, 6, and 12 Mg ha-1), representing straw removal rates of 100 (bare soil), 75, 50, and 0%, respectively. After one year of the first straw addition, the same straw amounts were added again simulating the second harvest. Drained solution was collected and quantified by 17 months and soil moisture was determined over a period of two months using sensors. Dissolved organic carbon (DOC) concentration was measured in automatic analyzer. The soil solution and straw solution, made in water infusion, were characterized in High performance liquid chromatography (HPLC) to verify the presence of toxic compounds. After that, straw and soil solution were used in tests with soybean seed to evaluate the effects in plant germination and initial growth. At the end of the experiment, soil bulk density and soil organic carbon (SOC) analyses were performed. Remaining straw was weight before the new addition, and weight again at the end to determine the decomposition rates. The accumulated volume of solution drained was 30, 11 and 4% lower under 100, 75 and 50% removal rates compared to no removal. Bare soil stored less water, indicating susceptibility to lose water by evaporation. Simulation showed that 100% and 75% removal can induce longer periods of water restriction, which impair sugarcane growth. The DOC production on topsoil was higher in no straw removal; the retention was higher in 1 to 20 cm in no removal and higher in 20 to 50 cm in 50 and 75% removal rates. Bare soil released more DOC below 01 cm indicating a possible C loss. Below 100 cm DOC leachate was quite similar in all treatments, what shows a higher C retention and small C loss even in higher DOC production. Even with differences in DOC retention, increases in C stock below 5 cm were not noticed. We found many phenolic compounds in the straw solution, not found in the soil solution, indicating that in natural conditions straw does not release toxic compounds into soil solution. Plant growth was negatively affected by straw solution, but not by soil solution. Our findings suggest that the medium straw maintenance prevents variations and loss on soil water content. Higher straw amount increases DOC production, which likely alters its composition and subsequent retention in soil. Carbon stock did not increase in the soil subsurface, but probably will in the long-term. The higher straw removal, proportionally, the higher the C losses in the form of CO2 and DOC, consequently the lower soil C retention. More straw on soil surface release more C amounts to the soil, retained or translocated with soil water, may be stored in deeper soil layers. Higher water percolation in the soil profile does not mean higher C losses by leaching in deeper soil. This study has the practical objective of finding an amount of straw to be maintained in the field that ensures the C storage and the better soil functioning, and also supply feedstock for bioenergy production. O interesse no uso da palha de cana-de-açúcar como matéria-prima para a produção de bioenergia vem crescendo consideravelmente. No entanto, a remoção excessiva da palha pode afetar negativamente o funcionamento do solo. Portanto, o objetivo deste trabalho foi quantificar e caracterizar a solução ao longo do perfil sob níveis de remoção de palha da superfície do solo. Para isso, foi construído um sistema de lisímetros com colunas de 1, 20, 50 e 100 cm de solo, de textura franco argilo arenosa, proveniente de área comercial de cana-de-açúcar em Piracicaba-SP, Brasil. O experimento foi conduzido em área aberta, sujeito a precipitação e luz natural. Depois da estabilização do solo dentro dos tubos, foram adicionados os seguintes tratamentos: 0, 3, 6 e 12 Mg ha-1 de massa seca, representando 100 (solo nu), 75, 50 e 0% de intensidade de remoção de palha, respectivamente, sendo adicionados novamente após um ano. A solução percolada foi coletada e quantificada por 17 meses, a umidade do solo foi determinada por dois meses usando sensores. A concentração de carbono orgânico dissolvido (COD) foi mensurada com analisador automático. A solução do solo e solução da palha, feita por infusão em água, foram caracterizadas em HPLC para verificar a presença de compostos tóxicos. Posteriormente, as soluções da palha e solo foram usadas em testes de sementes de soja para avaliar os efeitos na germinação e crescimento inicial. Ao final do experimento, foram realizadas análises de densidade do solo e carbono orgânica do solo (COS). A palha remanescente foi pesada após um ano, anterior a nova adição, e pesada novamente ao final do experimento, para determinar a taxa de decomposição. O volume de solução percolado foi 30, 11 e 4% menor em 100, 75 e 50% do que em 0% de remoção, respectivamente. O solo descoberto armazenou menos água, indicando susceptibilidade à perda de água por evaporação. A simulação mostrou que 100 e 75% de remoção induzem longos períodos de restrição hídrica, que pode prejudicar o crescimento da planta. A produção de COD na camada superficial foi maior no solo sem remoção; a retenção foi maior de 1 a 20 cm em solo sem remoção, e maior em 20 a 50 cm em 50 e 75% de remoção. O solo descoberto liberou mais COD em de 20 cm do que em superfície, indicando perda de C. Abaixo de 100 cm, o COD lixiviado foi similar nos tratamentos, indicando grande retenção de C e pequenas perdas por lixiviação, mesmo em alta produção de COD. Mesmo com diferenças na retenção de COD, não foi identificado aumento no estoque de C abaixo de 5 cm. Foram encontrados compostos fenólicos na solução da palha, não encontrados na solução do solo, indicando que em condições naturais a palha não libera quantidades significativas de compostos tóxicos na solução do solo. O crescimento de plantas foi negativamente afetado pela solução da palha, mas não pela solução do solo. Nossos resultados sugerem que a manutenção de quantidade média de palha previne perdas e variação no conteúdo de água do solo. Maior quantidade de palha aumenta a produção de COD, que provavelmente altera sua composição, alterando a retenção no solo. O estoque de C não aumentou consideravelmente em subsuperfície, mas muito provavelmente aumentará em escala de tempo maior. Quanto maior a remoção de palha, proporcionalmente maior as taxas de C liberadas na forma de CO2 e COD em subsuperfície, consequentemente, menor a retenção de C no solo. Maiores quantidades de palha na superfície liberam mais C para o solo, retido ou translocado com a água, podendo ser estocado em maiores profundidades do solo. Maior percolação de água no solo não significa maiores perdas de C por lixiviação em profundidade.

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A manutenção da palha de cana-de-açúcar sobre a superfície do solo promove diversos benefícios à qualidade do solo, como a redução das altas temperaturas e a manutenção da umidade do solo. Com base nisso, os objetivos deste trabalho consistiram em avaliar o impacto da palha de cana-de-açúcar na dinâmica da umidade e da temperatura do solo em situações edáficas distintas em três regiões do Estado de São Paulo e verificar a influência da temperatura e umidade do solo na decomposição de diferentes quantidades de palha de cana-de-açúcar. O estudo foi conduzido nos municípios de Igaraçu do Tietê, Piracicaba e Dois Córregos (solo muito argiloso, textura média e arenoso, respectivamente) com delineamento experimental de blocos ao acaso. As quantidades de palha utilizadas foram: 0; 2; 3,2; e 7,5 Mg ha-1 (Igaraçu do Tietê) e 0; 3; 6; e 12 Mg ha-1 (Piracicaba e Dois Córregos). Para a determinação da umidade do solo foram realizadas coletas periódicas de amostras indeformadas de solo nas linhas de plantio (0-20, 20-40, 40-60 e 60-80 cm de profundidade) e analisadas através do método da pesagem. A avaliação da temperatura do solo foi feita por sensores termopares inseridos no solo a 0-5 e 5-10 cm de profundidade. Na análise da decomposição da palha utilizaram-se caixas plásticas onde as diferentes quantidades de palha foram mantidas. Cinco coletas de palha (30, 60, 120 e 180 e 360 dias após a implantação do experimento) foram realizadas para quantificar a perda de massa. Os resultados demonstraram que em relação ao solo descoberto, os tratamentos com diferentes quantidades de palha interferiram significativamente (p