Scielo RSS <![CDATA[Revista Brasileira de Ciência do Solo]]> http://www.scielo.br/rss.php?pid=0100-068320170001&lang=pt vol. 41 num. lang. pt <![CDATA[SciELO Logo]]> http://www.scielo.br/img/en/fbpelogp.gif http://www.scielo.br <![CDATA[Magnetic Susceptibility of Soil to Differentiate Soil Environments in Southern Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100301&lng=pt&nrm=iso&tlng=pt ABSTRACT The interest in new techniques to support digital soil mapping (DSM) is increasing. Numerous studies pointed out that the measure of magnetic susceptibility (MS) can be extremely useful in the identification of properties related with factors and processes of soil formation, applied to soil mapping. This study addressed the effectiveness of magnetic soil susceptibility to identify and facilitate the distinction of different pedogenic environments of a representative hillslope in the highland Planalto Médio in the state of Rio Grande do Sul (RS), Brazil. In a 350-ha area in the municipality of Santo Augusto, RS, a representative transect was selected, trenches opened for soil characterization and 29 grid points marked at regular distances of 50 m, where soil samples were collected (layers 0.00-0.05, 0.05-0.15, 0.15-0.30, and 0.30-0.60 m) to analyze soil properties. Data from the transect samples were subjected to descriptive statistics. Limits of the pedogenetic environments along the slope were identified by the Split Moving Window (SMW) Boundary Analysis. The combined use of soil magnetic susceptibility and the SMW technique was effective in identifying different pedogenetic environments in the study area. <![CDATA[Cemented Horizons and Hardpans in the Coastal Tablelands of Northeastern Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100302&lng=pt&nrm=iso&tlng=pt ABSTRACT Horizons with varying degrees of cementation are a common feature of the soils from the coastal tablelands of Northeastern Brazil. In most cases, these horizons are represented by the following subsurface horizons: fragipan, duripan, ortstein, and placic. The aims of this study were to analyze differences regarding the development and the degree of expression of cementation in soils from the coastal tablelands of Northeastern Brazil: Planossolo Háplico (p-SX), Espodossolo Humilúvico (p-EK), Espodossolo Ferrihumilúvico (p-ESK), and Argissolo Acinzentado (p-PAC) pedons. The pedons studied displayed features related to drainage impediments. The cemented horizons from p-SX and p-EK had the same designation (Btgm), displaying a duric character that coincided with gleization features and are under podzolized horizons. In the p-ESK, the podzolization process is of such magnitude that it leads to the cementation of its own spodic horizons, which were both of the ortstein type (Bhsx and Bsm). In the p-PAC cementation is observed in two placic horizons and in the Btx/Bt horizon, as well as in the upper parts of the Bt/Btx horizon. Analysis of the micrographies from the cemented horizons showed predominance of a low porosity matrix. Such porosity is relatively greater in the horizons of “x” subscript than in the horizons with duric character. The Fe segregation lines were notable in the cemented horizons from p-EK and p-PAC, which corroborates the presence of placic horizons in such pedons. The preponderance of kaolinite in the clay fraction was widely verified in all the cemented horizons analyzed. Water immersion tests were the criteria adopted to define the duric character of the Btgm horizons from p-SX and p-EK, and in the Bsm horizon from the p-ESK. These tests were also used to confirm field morphology. In most cases, the maximum values of Fe, Al, and Si, determined by different extractions, occurred in positions overlaying the cemented horizons, whether they were spodic or not. The extracts of the aqueous solution displayed a noticeable accumulation of Si in the cemented horizons, except in the p-PAC. The presence of argillans in all cemented horizons allows them to be defined as illuvial, with the exception of the placic horizons, regardless of the presence of podzolization processes. The cemented horizons were preponderantly apedal, with a matrix of little porosity. The Fe, Al, and Si contents extracted by acid ammonium oxalate were effective at highlighting the influence of compounds with a low degree of crystallinity in the morphology of cemented horizons. <![CDATA[Pedodiagenetic Characterization of Cretaceous Paleosols in Southwest Minas Gerais, Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100303&lng=pt&nrm=iso&tlng=pt ABSTRACT The influence of post-burial geological processes on preserving pedogenic properties has great importance in identifying ancient paleosols both in the field and in a laboratory. However there are not many publications that focus on characterizing paleosol diagenesis. As temperature and pressure progressively increase, evidence of pedogenesis is modified and destroyed, hindering paleoenvironment characterization and interpretation. This paper discusses diagenetic evidence and its relation to strictly pedogenic features, like structure, cements, nodules, and neoformation of clay minerals using the carbonate paleosols of the Marília Formation in the upper unit of the Bauru Basin as a case study. Despite the long geotectonic and thermal history of the Marília Fomation, paleosols bring us pedogenic evidence that can undergo micromorphological analyses, such as cementation, clay illuviation, bioturbation, and ped structures. The results of analyses in 25 paleopedogenic horizons indicate that the paleotopographic features were responsible for distribution of the diagenetic processes and preservation of the paleosol properties. The maturity of those paleosols controls lithification. In mature paleosols that developed in more stable portions of the landscape, characteristics such as carbonate cementation and development of pedogenic structures are the main factors that inhibit diagenesis. However diagenetic processes that influence poorly-developed paleosols are controlled by depositional characteristics and by changes in the water table, enabling more advanced diagenetic processes, compared to mature paleosols. <![CDATA[Micromorphology of Paleosols of the Marília Formation and their Significance in the Paleoenvironmental Evolution of the Bauru Basin, Upper Cretaceous, Southeastern Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100304&lng=pt&nrm=iso&tlng=pt ABSTRACT Deduction of associated paleoenvironments and paleoclimate, definition of the chronosequence of paleosols, and paleogeographic reconstruction have become possible through the application of micromorphology in paleopedology. Micromorphology has also been useful in recognition of weathering processes and definition of minerals formed in succession. In this respect, the objective of this study was to identify the development of pedogenic processes and discuss their significance in the paleoclimate evolution of the Marília Formation (Maastrichtian) of Bauru Basin. Three sections of the Marília Formation (A1, A2, and A3) were described, comprising nine profiles. Micromorphologic al analysis was carried out according to the specialized literature. In the Marília Formation, the paleosols developed in sandstones have argillic (Btkm, Bt) and carbonate (Bk) horizons with different degrees of cementation, forming mainly calcretes. The evolution of pedogenic processes, in light of micromorphological analysis, evidenced three moments or stages for the genesis of paleosols with Bkm, Btk, and Bt horizons, respectively. In the Maastrichtian in the Bauru Basin, the paleosols with Bkm are older and more arid environments, and those with Bt were formed in wetter weather, but not enough to lead to the genesis of enaulic-related distributions, typical of current Oxisols. <![CDATA[Chemical-Mineralogical Characterization of Magnetic Materials from Magnetic Soils of the Southern Espinhaço Mountain Chain and of the Upper Jequitinhonha Valley, State of Minas Gerais, Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100305&lng=pt&nrm=iso&tlng=pt ABSTRACT In the Southern Espinhaço Mountain Chain and in the Upper Jequitinhonha Valley, magnetic soils, in different pedogenetic stages, are found to be forming over intrusions of basic lithology. The essential chemical and mineralogical properties of samples from magnetic soil profiles from those two physiographic environments in the state of Minas Gerais, Brazil, are reported. Three of the pedons (Rhodic Kandiustox – RKox, Rhodic Haplustox – RHox, and Typic Argiustoll - TAoll) were identified as being indeed developed over basic rocks; the fourth pedon (Typic Haplustox - THox) is currently forming on an acidic rock. Particle size and routine chemical analyses were performed on samples from all horizons of the four selected soil profiles. For a deeper insight into the dominant mineralogy of each diagnostic soil horizon, the elemental contents, expressed in terms of the corresponding metal cation oxides, namely Fe2O3, Al2O3, and MnO2, were obtained from digesting the whole soil samples with sulfuric acid. A similar chemical analytical procedure was performed for the residual solid extracts obtained from attacking the whole soil materials with mixtures of (i) dithionite - citrate - bicarbonate and (ii) oxalate - oxalic acid. The soil samples were also analyzed by Mössbauer spectroscopy at room temperature (~298 °K) in an attempt to better identify the main magnetic iron oxides. Maghemite (δFe2O3) was found in all samples and magnetite (Fe3O4) was identified only for the sample from the Typic Argiustoll. The pedogenetic loss of silica and consequent accumulation of iron and aluminum oxides along the profile are found to be somehow correlated to the weathering sequence in the soils forming on basic rocks: TAoll &lt; RKox &lt; RHox. <![CDATA[Methods for Quantifying Shrinkage in <em>Latossolos</em> (Ferralsols) and <em>Nitossolos</em> (Nitisols) in Southern Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100308&lng=pt&nrm=iso&tlng=pt ABSTRACT Brown Nitossolos (Nitisols) and Latossolos (Ferralsols), according to the Brazilian System of Soil Classification (SiBCS), have a “caráter retrátil” as their distinctive property. Because this is a new topic, it is necessary to propose methods for evaluation. The objectives of this study were to evaluate methodologies for quantifying the shrinkage of soil using the Syringe Method and the Metallic Mercury Method, and to propose a new one, the “Ring with Sand Method”. Soil samples from eight pedons were used, with six Nitossolos and Latossolos with shrinkage, a Latossolo without shrinkage, and a Vertissolo (Vertissol) with admittedly high shrinkage and expansion. The methods were effective in identifying the greater degree of shrinkage of the Vertissolo . However, the Ring with Sand Method was the only one to indicate significant differences between the Vertissolo and the Latossolo without shrinkage, and this method differentiated the shrinkable soils as to the intensity of the characteristic. The proposed method was effective and can serve as a standard to quantify shrinkage. <![CDATA[Bulk Density Prediction for Histosols and Soil Horizons with High Organic Matter Content]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100309&lng=pt&nrm=iso&tlng=pt ABSTRACT Bulk density (Bd) can easily be predicted from other data using pedotransfer functions (PTF). The present study developed two PTFs (PTF1 and PTF2) for Bd prediction in Brazilian organic soils and horizons and compared their performance with nine previously published equations. Samples of 280 organic soil horizons used to develop PTFs and containing at least 80 g kg-1 total carbon content (TOC) were obtained from different regions of Brazil. The multiple linear stepwise regression technique was applied to validate all the equations using an independent data set. Data were transformed using Box-Cox to meet the assumptions of the regression models. For validation of PTF1 and PTF2, the coefficient of determination (R2) was 0.47 and 0.37, mean error -0.04 and 0.10, and root mean square error 0.22 and 0.26, respectively. The best performance was obtained for the PTF1, PTF2, Hollis, and Honeysett equations. The PTF1 equation is recommended when clay content data are available, but considering that they are scarce for organic soils, the PTF2, Hollis, and Honeysett equations are the most suitable because they use TOC as a predictor variable. Considering the particular characteristics of organic soils and the environmental context in which they are formed, the equations developed showed good accuracy in predicting Bd compared with already existing equations. <![CDATA[Root Proteomic Analysis of Grapevine Rootstocks Inoculated with Rhizophagus irregularis and Fusarium oxysporum f. sp. herbemontis]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100401&lng=pt&nrm=iso&tlng=pt ABSTRACT Grapevine decline and death caused by the pathogenic fungus Fusarium oxysporum f. sp. herbemontis is among the main phytosanitary problem for viticulture in southern Brazil. The eradication of infected plants is presently the most common procedure for disease control in vineyards. Inoculation with arbuscular mycorrhizal fungi is an option to reduce or neutralize the negative impacts of soil pathogenic microorganisms, but the mechanisms of plant response involved in this process are not yet completely elucidated. In order to better understand these mechanisms, an experiment was carried out to identify proteins related to plant defence induced by the mycorrhizal fungus after infection with the pathogenic fungus. We used the grapevine rootstocks SO4 and R110 (susceptible and resistant to the pathogenic fungus, respectively) inoculated or not inoculated with the mycorrhizal fungus Rhizophagus irregularis, and inoculated or not inoculated with Fusarium oxysporum f. sp. herbemontis. Growth of the rootstocks’ shoot and root and presence of pathogenic symptoms were evaluated. The protein profiles of roots were characterized by two-dimensional electrophoresis and proteins were identified using mass spectrometry. The grapevine rootstocks inoculated with R. irregularis had higher biomass production and lower level of pathogenic symptoms. The R110 rootstock differentially accumulated 73 proteins, while SO4 accumulated 59 proteins. Nine plant-defence proteins were expressed by SO4 rootstock, and six were expressed by R110 rootstock plants. The results confirm the effect of mycorrhizal fungi in plant growth promotion and their potential for biological control against soil pathogenic fungus. Protein expression is dependent on rootstock characteristics and on the combination of plant material with the fungi. <![CDATA[Soil Quality after Six Years of Paper Mill Industrial Wastewater Application]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100402&lng=pt&nrm=iso&tlng=pt ABSTRACT The application of wastewater to irrigate soils may be an attractive option for paper mills, especially when the effluents can also provide nutrients to plants. Since there could be negative environmental effects, such activity must be preceded by a thorough evaluation of the consequences. The changes in soil quality of a Neossolo Flúvico Distrófico (Typic Udifluvent) were evaluated over a period of six years of irrigation with treated effluent from a wood pulp company. Although effluent application for six years did not affect soil resistance to penetration and soil hydraulic conductivity, it promoted a decrease in the mean size of aggregates and an increase in clay dispersion. Effluent application increased soil pH but did not change exchangeable Ca and Mg contents and organic carbon. After a full rotation of eucalyptus cultivation common in Brazil (six years), no negative effects in tree growth were found due to effluent irrigation. However, effluent addition caused higher values of Na adsorption ratio and intermediate electrical conductivity in the soil, which indicates a possible negative effect on soil quality if the application continues over a longer period. Therefore, a monitoring program should be carried out during subsequent crop rotations, and alternatives must be studied to obtain better effluent quality, such as adding Ca and Mg to the wastewater and using gypsum in the soil. <![CDATA[Symbiotic effectiveness of <em>Bradyrhizobium ingae</em> in promoting growth of <em>Inga edulis</em> Mart. seedlings]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100403&lng=pt&nrm=iso&tlng=pt ABSTRACT Inga edulis Mart. is a leguminous tree adapted to acidic and low-fertility soils that establishes symbioses with nitrogen (N)-fixing bacteria. The identification of effective bacteria in biological N fixation may bolster the use of I. edulis in degraded or modified areas and agroforestry systems. Therefore, the aims of this study were evaluation of the symbiotic effectiveness of eight strains of the Bradyrhizobium genus native to Roraima in Inga edulis plants, and in vitro evaluation of the ability of the eight strains of Bradyrhizobium to develop plant growth-promoting characteristics. Determination of symbiotic effectiveness was carried out via three experiments: the first in a greenhouse in pots with a sterile substrate; the second in a greenhouse in pots containing non-sterile soil; and the third in a nursery in bags with a non-sterile substrate. Twelve treatments were evaluated: inoculation with eight strains of Bradyrhizobium ingae (ERR 490, ERR 492, ERR 493, ERR 494T, ERR 496, ERR 497, ERR 498, and ERR 569); inoculation with two strains indicated for Inga marginata, BR 6609 and BR 6610 (positive controls); no inoculation but with mineral N; and neither inoculation nor mineral N. All of the experiments were conducted in a completely randomized design with four replicates. The first experiment was conducted for 60 days, and the other experiments were conducted for 100 days. For all of the experiments, the number of nodules, nodule dry matter, root dry matter, shoot dry matter, number of leaflets, plant height, stem diameter, total N in the shoots, root/shoot dry matter ratio, Dickson’s quality index, relative effectiveness, and the Pearson correlation between the variables under study were evaluated. The strains were also evaluated by their ability to solubilize calcium and aluminum phosphates and to produce indolic compounds. The results showed that B. ingae strains were effective in biological N fixation, especially the ERR 493, ERR 498, and ERR 569 strains. These strains increased the production of shoot dry matter and total N and exhibited relative effectiveness higher than 100 % in all of the experiments. The B. ingae strains were also able to solubilize calcium and aluminum phosphates, despite their synthesis of indolic compounds. Thus, the strains of B. ingae can be used for inoculation in the production of I. edulis seedlings. <![CDATA[Genetic Variability and Symbiotic Efficiency of <em>Erythrina velutina</em> Willd. Root Nodule Bacteria from the Semi-Arid Region in Northeastern Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100404&lng=pt&nrm=iso&tlng=pt ABSTRACT Legume-rhizobia symbiosis is a cross-kingdom association that results in large amounts of nitrogen incorporated in food webs. For the Brazilian semi-arid region, data on genetic variability and symbiotic efficiency of Papilionoidae rhizobial communities are very scarce. The aim of this study was to evaluate the genetic variability and the symbiotic efficiency of eight rhizobial isolates obtained from “mulungu” (Erythrina velutina Willd.) nodules. For 16S rRNA gene sequencing, the genomic DNA was extracted using a commercial kit, amplified with universal primers, and subjected to sequencing reactions. For the isolate ESA 71, PCR amplifications for nodC and nodA genes were attempted. Rhizobial efficiency was assessed by two greenhouse experiments. The first assay was carried out under gnotobiotic conditions, with sterile sand as a substrate; the second experiment was conducted in a non-sterile soil. For both experiments, the inoculation treatments consisted of a single inoculation of each isolate, in addition to a treatment with Bradyrhizobium elkanii BR 5609 as a reference strain. Furthermore, two non-inoculated control treatments, supplied and not supplied with mineral N, were also evaluated. Bacterial identification indicated that both α and β-rhizobia could be found in “mulungu” root nodules. Three isolates where classified within the Rhizobium genus, four bacteria belonged to Bradyrhizobium and one isolate clustered with Burkholderia. Positive amplification of an intragenic fragment of the nodA gene using a primer set to β-rhizobia could be found for ESA 71 (Burkholderia). All bacterial isolates were effective in colonizing “mulungu” roots. In the first experiment, all inoculated treatments and N fertilization increased the N concentration in “mulungu” shoot tissues. For total N in the shoots, the isolates ESA 70, ESA 72, and ESA 75 stood out. In the non-sterile substrate experiment, the isolates ESA 70, ESA 71, ESA 72, and ESA 75, together with the reference strains, induced increases in the shoot N concentration and total accumulation compared to the absolute control. The results indicate that “mulungu” is able to establish associations with efficient α and β-rhizobia in Brazilian semi-arid soils. <![CDATA[New Native Rhizobia Strains for Inoculation of Common Bean in the Brazilian Savanna]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100405&lng=pt&nrm=iso&tlng=pt ABSTRACT Maximization of biological nitrogen fixation in the common bean (Phaseolus vulgaris L.) crop depends on the genetic characteristics related to the plant, the symbiotic efficiency of rhizobia, and environmental factors. The objective of this study was to evaluate the performance of rhizobia selected beforehand from Cerrado (Brazilian tropical savanna) soils in Mato Grosso do Sul. The experiments were conducted in 2007 in the municipalities of Aquidauana, Anaurilândia, Campo Grande, and Dourados, all located in the state of Mato Grosso do Sul. All procedures established followed the current recommendations of the Brazilian Ministry of Agriculture (Ministério de Agricultura, Pecuária e Abastecimento – MAPA), in accordance with the “official protocol for assessing the feasibility and agronomic efficiency of strains, and inoculant technologies linked to the process of biological nitrogen fixation in legumes”. The program for selection of rhizobia for inoculation in bean plants resulted in identification of different strains with high symbiotic efficiency, competitiveness, and genetic stability, based on the Embrapa Agropecuária Oeste collection of multifunctional microorganism cultures. In previous studies, 630 isolates of Rhizobium were evaluated. They were obtained from nodules of leucaena (380) or dry beans (250) from 87 locations, including 34 municipalities in Mato Grosso do Sul. Three of them stood out from the others: CPAO 12.5 L2, CPAO 17.5 L2, and CPAO 56.4 L2. Inoculation of these strains in bean plants demonstrated economic viability and high potential for obtaining a more effective inoculant suitable for trading purposes. <![CDATA[Dependency and Response of <em>Apuleia leiocarpa</em> to Inoculation with Different Species of Arbuscular Mycorrhizal Fungi]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100406&lng=pt&nrm=iso&tlng=pt ABSTRACT Inoculation with arbuscular mycorrhizal fungi (AMF) is a strategy to improve the efficiency of forest plantations, reducing costs and increasing the survival of plant species. The objective of this study was to assess the response and mycorrhizal dependency of seedlings of the forest species Apuleia leiocarpa (Vogel) J.F. Macbr to inoculation with AMF. The experiment was conducted in a completely randomized design using a 5 × 5 factorial arrangement with six replications. The treatments consisted of combinations of five P rates (0, 24, 71, 213, and 650 mg kg-1) with five types of inoculations with AMF (inoculation with the fungi Rhizophagus clarus, Gigaspora margarita, Dentiscutata heterogama, inoculation with an AMF mix of these three species, and a treatment without inoculation). The A. leiocarpa showed the highest biomass accumulations in inoculation with D. hetorogama combined with the P rates of 213 and 650 mg kg-1, and in the AMF mix combined with the P rates of 71, 213, and 650 kg-1. Biomass accumulation showed a linear, positive response to inoculation with D. heterogama combined with the different P rates, and a positive square root fit to inoculation with the AMF mix. The plants inoculated with G. margarita had no significant biomass accumulation. The plant species had a positive response to inoculation with R. clarus combined with the lowest P rates; however, it had a negative response to combination with the highest P rate (650 mg kg-1). The relative benefit of inoculation with these fungi was more than 100 % in most treatments, showing the high mycorrhizal dependency of A. leiocarpa and the nutritional benefit of AMF inoculation for this species. However, this response is dependent on the fungus species that colonize the plant roots. The best combination between fungus and P rate was inoculation with the AMF mix combined with the P rate of 71 mg kg-1. <![CDATA[Dung Beetles Associated with Agroecosystems of Southern Brazil: Relationship with Soil Properties]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100407&lng=pt&nrm=iso&tlng=pt ABSTRACT Knowing the biodiversity of dung beetles in agricultural and livestock environments is the basis for understanding the contribution that these organisms make in nutrient cycling and ecosystem functions. The aim of the present study was to investigate the structure of copronecrophagous dung beetle communities inhabiting the main agroecosystems in southern Brazil and correlate the presence of these organisms with soil properties. From December 2012 to April 2013, samples of dung beetles were taken in the municipality of Tubarão, Santa Catarina, Brazil (28° 28’ S; 48° 56’ W) in corn, bean, and sugarcane crops, and in cattle pastures. Beetles were captured in 16 sampling sites, four from each agroecosystem, following a standardized methodology: 10 baited pitfall traps (feces and rotting meat) at a spacing of 50 m with exposure for 48 h. The beetles were identified, weighed, and measured. Soil analyses were performed in order to correlate data on organic matter, texture, macro and micronutrients, and pH with data on the abundance of beetle species using canonical correspondence analysis. A total of 110 individuals belonging to 10 species of dung beetles was found. Twenty-four individuals from seven species (with total biomass of 2.4 g) were found in the corn crop; five individuals from three species (1.8 g) were found in the bean crop; 81 individuals from nine species (30.3 g) were found in cattle pasture areas; and lastly, there were no dung beetles recorded in the sugarcane crop. In areas of cattle grazing, the tunnelers Dichotomius nisus and Trichillum externepunctatum correlated positively with organic matter content, whereas the roller species Canthon chalybaeus correlated positively with soil texture, preferring sandier soils. In corn crop areas, D. nisus was again correlated with organic matter content. Paracoprid dung beetle species were correlated with organic matter content in the soil, and species belonging to the roller functional group were associated with soil texture in the corn crop, preferring sandy soils. Information regarding the relationship of dung beetles with physical-chemical soil properties may be an important strategy for increasing fertility and management of soil conservation in agroecosystems. <![CDATA[Physical Properties and Crop Management for Corn in an Albaqualf]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100408&lng=pt&nrm=iso&tlng=pt ABSTRACT Rice monoculture in lowlands can cause problems for management practices in crop fields, for example, in weed control. For this reason, corn in rotation with irrigated rice in lowlands may be advantageous, despite problems with soil compaction and water excess. The objective of this study was to evaluate soil physical properties and corn performance in soil management systems in an Albaqualf soil (lowlands). Two experiments were conducted in the field, in the 2013/14 and 2014/15 crop seasons. The experimental design was randomized blocks with two factors. There were three levels for the first factor, consisting of soil management practices: soil chiseling 45 days before sowing to a depth of 0.3 m; conventional tillage with two diskings to a depth of 0.1 m and subsequent leveling of the soil; and no-till. The second factor was composed of two levels: sowing on raised seedbeds, and without raised seedbeds. The soil parameters of bulk density, total porosity, macroporosity, microporosity, volumetric moisture, and soil resistance to mechanical penetration (RP) were evaluated. The corn parameters were plant height, shoot dry matter, leaf area, height of the first ear of corn, grains per ear, and grain yield. Soil chiseling resulted in lower RP and higher macroporosity in the 0.1-0.2 and 0.2-0.3 m layers. In raised seedbeds, the 0.00-0.05, 0.05-0.10, and 0.10-0.20 m layers were lower in RP and bulk density. Moreover, higher soil macroporosity was observed in relation to the treatment without raised seedbeds. In general, the highest grain yields were found in the treatments with lower RP and higher macroporosity in the root system region. Increased porosity accelerated water drainage in the soil, reducing the time that soil airspace was filled with water, which is a limiting factor for root development. In Albaqualf soils, planting corn in chiseled soil provides higher corn yields compared to conventional tillage, and planting corn on raised seedbeds provides higher corn yields compared to the lack of raised seedbeds. <![CDATA[Kinetics of Thermal Transformation of Synthetic Al-Maghemites into Al-Hematites]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100410&lng=pt&nrm=iso&tlng=pt ABSTRACT Maghemite (γ-Fe2O3) and hematite (α-Fe2O3) are important iron oxides in Brazilian soils derived from basalt. Maghemite can transform into hematite when exposed to high temperatures. However, isomorphic substitution (e.g., Al3+) may largely influence this process. We analyzed the kinetics of thermal transformation of Al-maghemites into Al-hematites and some of its mineralogical aspects. Synthetic substituted maghemites with different degrees of Al-substitution (0.0, 1.0, 2.0, 2.9, 3.8, 5.6, 6.7, 10.0, 12.0, and 17.1 mol% Al) were subjected to a temperature of 500±10 °C for 0, 5, 10, 16, 64, 128, 192, 360, 720, 2160, 3600, 5040, and 6480 min. After thermal treatment, samples were characterized by X ray diffraction (XRD), differential thermal analysis (DTA), specific surface area (SSA) measurement, and total chemical analysis. XRD patterns were analyzed by Rietveld refinement, and maghemite and hematite contents were calculated using Rietveld refinement and the method proposed by Sidhu. Isomorphic substitution of Fe by Al increased the critical temperature of transformation and the time necessary for maghemite to hematite transformation. Rietveld refinement data showed a better fit than the data adjusted by the Sidhu method. Increasing isomorphic substitution also decreased lattice parameters and mean crystallite dimension (MCD) values in maghemite; but only c-dimension and MCD decreased with increasing Al-substitution in hematite. For maghemite, the SSA increased with isomorphic substitution, rising up to 5.9 mol% Al; for hematite, SSA increased linearly. SSA decreased with heating time, regardless of isomorphic substitution. <![CDATA[Sampling Design of Soil Physical Properties in a Conilon Coffee Field]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100411&lng=pt&nrm=iso&tlng=pt ABSTRACT Establishing the number of samples required to determine values of soil physical properties ultimately results in optimization of labor and allows better representation of such attributes. The objective of this study was to analyze the spatial variability of soil physical properties in a Conilon coffee field and propose a soil sampling method better attuned to conditions of the management system. The experiment was performed in a Conilon coffee field in Espírito Santo state, Brazil, under a 3.0 × 2.0 × 1.0 m (4,000 plants ha-1) double spacing design. An irregular grid, with dimensions of 107 × 95.7 m and 65 sampling points, was set up. Soil samples were collected from the 0.00-0.20 m depth from each sampling point. Data were analyzed under descriptive statistical and geostatistical methods. Using statistical parameters, the adequate number of samples for analyzing the attributes under study was established, which ranged from 1 to 11 sampling points. With the exception of particle density, all soil physical properties showed a spatial dependence structure best fitted to the spherical model. Establishment of the number of samples and spatial variability for the physical properties of soils may be useful in developing sampling strategies that minimize costs for farmers within a tolerable and predictable level of error. <![CDATA[Aggregate Stability in Soil with Humic and Histic Horizons in a Toposequence under Araucaria Forest]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100412&lng=pt&nrm=iso&tlng=pt ABSTRACT Aggregate stability is one of the most important factors in soil conservation and maintenance of soil environmental functions. The objective of this study was to investigate the aggregate stability mechanisms related to chemical composition of organic matter in soil profiles with humic and histic horizons in a toposequence under Araucaria moist forest in southern Brazil. The soils sampled were classified as Humic Hapludox (highest position), Fluvaquentic Humaquepts (lowest slope position), and Typic Haplosaprists (floodplain). The C and N contents were determined in bulk soil samples. The chemical composition of soil organic matter was evaluated by infrared spectroscopy. Aggregate stability was determined by applying increasing levels of ultrasound energy. Carbon content increased from the top of the slope to the alluvial plain. Higher ultrasonic energy values for clay dispersion were observed in the C-rich soils in the lower landscape positions, indicating that organic compounds play an important role in the structural stabilization of these profiles. Both aliphatic and carbohydrate-like structures were pertinent to aggregate stability. In the Oxisol, organo-mineral interaction between carbohydrates and the clay mineral surface was the most important mechanism affecting aggregation. In soils with a higher C content (Humaquepts and Haplosaprists), stabilization is predominantly conferred by the aliphatic groups, which is probably due to the structural protection offered by these hydrophobic organic groups. <![CDATA[Pedogenic Iron Oxides in Iron-Rich Oxisols Developed from Mafic Rocks]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100413&lng=pt&nrm=iso&tlng=pt ABSTRACT Despite the considerable amount of information on the mineralogical characteristics of pedogenic Fe oxides in Brazilian soils, there are few studies on Fe-rich soils developed from mafic rocks with taxonomic identities at lower categorical levels. This study evaluated the mineralogical characteristics of pedogenic Fe oxides in B horizons (Bw) of Fe-rich Oxisols developed from several mafic rocks in the state of Minas Gerais, Brazil. The Bw horizons were sampled at a 0.8-1.0 m depth in 13 Ferric and Perferric Rhodic Oxisols along with a Mesoferric Typic Oxisol originating from basalt, gabbro, tuffite, amphibolite and itabirite in Minas Gerais. The selected soils have taxonomic identities up to the fourth categorical level of the Brazilian System of Soil Classification. In the laboratory, the following analyses were made: a) powder X ray diffraction (XRD) of the clay fraction before and after selective concentration of Fe oxides by silicate alkaline dissolution (5 mol L-1 NaOH); b) selective chemical dissolution of the clay fraction by citrate-bicarbonate-dithionite (CBD), acid ammonium oxalate (AAO), and sulfuric acid (H2SO4 1.8 mol L-1); c) quantitative estimation of minerals in the clay fraction through allocation of phases from the XRD patterns, magnetic susceptibility of the clay fraction, and quantification of elements after sulfuric acid digestion (H2SO4 1:1) of the air-dried fine earth and treatment of the clay fraction with CBD; and d) estimation of the mean crystal size (MCS), specific surface area (SSA), and isomorphic Al-substitution (IS) of hematite, goethite, and maghemite from the XRD patterns obtained from concentrates of Fe oxides. The results showed that estimation of Fe content of maghemite by selective dissolution with 1.8 mol L-1 H2SO4 may not be accurate enough to realistically reflect the maghemite contents in the soil sample. The Al content extracted may also be influenced by other minerals that are sources of this element. Hematite crystals were predominantly placoid in shape in all Rhodic Oxisols and had smaller SSA compared to goethite, which showed both isodimensional and asymmetric habit. Higher crystallinity of maghemite and the IS values generally lower than those of hematite and goethite suggest that in well-drained soils derived from mafic rocks, the IS phenomenon in maghemites seems to result from pedogenetic advancement after its formation from magnetite oxidation. <![CDATA[Interaction between Thermotolerant Coliforms and Rhizobacteria in Soil Fertilized with Treated Domestic Wastewater]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100414&lng=pt&nrm=iso&tlng=pt ABSTRACT Studies on the survival of pathogenic microorganisms in the soil after use of wastewater for fertilization of agricultural crops report the effects of moisture, pH, organic matter, and soil temperature on microorganisms. There are few studies that assess the survival of these microorganisms in the rhizosphere of plants fertilized with wastewater. Thus, the aim of this study was to quantify the number of fecal coliforms and rhizobacteria (fluorescent Pseudomonas spp., Bacillus spp,) in the rhizosphere of winter and summer crops fertilized with wastewater. In the experiment, we used 20 plots, and each plot occupied an area of 200 m2. The treatments used in the winter crop consisted of uncultivated plots and single crops of wheat, triticale, black bean, and intercropped black bean/wheat. In the summer season, we used uncultivated plots and single crops of corn, sunflower, bean, and intercropped bean/corn. The experiment was conducted in a randomized block design with five treatments and four replications. Soil samples from the rhizosphere for microbiological analyses were collected at the flowering stage of the crops at a depth of 0.00-0.20 m. Plants stimulated fluorescent Pseudomonas spp. and Bacillus spp. in the rhizosphere, with average scores of 7.9 and 6.9 log CFU g-1 of dry soil, respectively, whereas in bare soil, these scores were 6.7 and 5.8 log CFU g-1 of dry soil for these rhizobacteria groups. However, this stimulating effect was not seen for fecal coliforms, which had an average score of 31.7 × 103 MPN g-1 of dry soil in the uncultivated area and 20.0 × 103 MPN g-1 of dry soil in crop areas. Overall, the numbers of rhizobacteria colonies in the rhizosphere soil under intercropping were higher than those observed in the rhizosphere soils of single winter and summer crops. Therefore, the presence of plants enhances the development of rhizobacteria and changes the balance among the species of microorganisms in the soil microbial community fertilized with wastewater. <![CDATA[Biological Soil Properties in Integrated Crop-Livestock-Forest Systems]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100415&lng=pt&nrm=iso&tlng=pt ABSTRACT Currently, agricultural productivity and sustainable development are the desired bases for the creation of production systems. Farming for greater production and the efficient use of soil resources are at the core of modern systems. However, the way in which agricultural management and practices can change soil quality has become increasingly important. The aim of this study was to detect changes in soil biological properties caused by implementation of the integrated crop-livestock-forest system (iCLF) and to identify the properties suitable for detecting changes in soil biological quality. Soil samples were collected from the 0.00-0.10 m layer in Nova Canaã do Norte, MT, Brazil, and Cachoeira Dourada, GO, Brazil, in areas of the iCLF with 1 (iCLF1) or 3 (iCLF3) eucalyptus rows and in areas of recovered and degraded pasture. In Cachoeira Dourada, in the iCLF1, samples were taken in the tree row and at 2.5, 5.0, and 10.0 m from this row. In Nova Canaã in the iCLF3, samples were taken in the center row and at 3.0, 6.0, 9.0, and 12.0 m from this row. In Cachoeira Dourada, samples were taken in the center row and at 1.5, 3.0, 4.5, 6.0, and 9.0 m from this row. All samples had five replicates. In Nova Canaã, the iCLF1 caused less disturbance in the microbial population than the degraded pasture, which was evidenced by the lower metabolic quotient and basal respiration. The sampling position in relation to the tree row had little effect on comparison of the iCLF with the degraded pasture in regard to soil biological properties. Carbon and N of the microbial biomass and the microbial quotient were the best properties for differentiating the iCLF from the degraded pasture. ICLFs have not yet led to improvements in soil biological quality in relation to the degraded pasture. <![CDATA[Reforestation of a Degraded Area with <em>Eucalyptus</em> and <em>Sesbania</em>: Microbial Activity and Chemical Soil Properties]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100416&lng=pt&nrm=iso&tlng=pt ABSTRACT Mining activities generally affect soil quality, degrading it and creating the need for consistent environmental recovery efforts. This study evaluates the influence of monospecific and mixed stands of Sesbania virgata (S) and Eucalyptus camaldulensis (E) on the chemical properties and microbial activity of the soil in a degraded area by clay extraction in the northern part of the state of Rio de Janeiro, Brazil. Four treatments (100S:100 % Sesbania , 100E: 00 % Eucalyptus , 50S:50E: 50 % Sesbania + 50 % Eucalyptus , and DASV: a degraded area with spontaneous vegetation) were established according to a randomized complete block design with three replicates. Samples were collected in the 0.00-0.10 m layer in the rainy season (March) and the dry season (September). The properties evaluated were pH in water; contents of P, K + , Ca 2+ , Mg 2+ , Al 3+ , H+Al, N, and C; C/N ratio; total microbial activity (soil respiration - CO 2 emission); and total enzymatic activity (fluorescein diacetate hydrolysis). The reforestation of degraded areas by clay mining with the species S. virgata and E. camaldulensis either in monospecific or mixed stands increased the nutrient contents, C levels, and total microbial activity in the soil. It was possible to separate the planting systems (100S, 100E, 50S:50E) and the DASV using principal component analysis. In both seasons, soil C contents, chemical properties, and biological variables improved in the planted areas, in contrast with the DASV. The revegetation of degraded areas by mining improved the chemical and biological properties of the soil, leading to higher soil quality in revegetated areas compared to degraded areas with natural vegetation. <![CDATA[Organic Matter Stocks and the Interactions of Humic Substances with Metals in Araucaria Moist Forest Soil with Humic and Histic Horizons]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100417&lng=pt&nrm=iso&tlng=pt ABSTRACT Soils with humic and histic horizons in tropical and subtropical ecosystems play an important role in determining the atmospheric C stock and its stabilization, climate regulation, water holding capacity, and environmental filtering, due to the different functions of soil organic matter (SOM). However, the processes and mechanisms that regulate SOM dynamics in these soils are not clear. The objectives of this study were: i) determine the C and N stocks and ii) investigate the SOM chemical fractions and their interactions with Fe and Al ions in soils with humic and histic horizons of a toposequence under Araucaria moist forest in southern Brazil. The soils sampled were classified as Humic Hapludox (top - not hydromorphic), Fluvaquentic Humaquepts (lower third - hydromorphic), and Typic Haplosaprists (floodplain - hydromorphic). The C and N contents were determined in bulk soil samples and SOM chemical fractions; in these fractions, Fe and Al co-extracted contents were also determined. The chemical composition of humin and humic acid fractions was investigated by FTIR spectroscopy. The C content in the toposequence increased from the top to the lowest position. The differences observed in SOM content and SOM chemical composition were defined by the differences in soil water regime. The amount of C stored in the subsurface horizons is about 70 % of total organic C. The carbohydrate-like structures in the humin fraction were protected from solubilization through interaction with iron oxides, which may represent an important mechanism for labile organic compound preservation in these soils. The soluble humic substances showed the highest Fe and Al contents, and their compartments have different affinities for Fe and Al. <![CDATA[Biological Nitrogen Fixation by Legumes and N Uptake by Coffee Plants]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100501&lng=pt&nrm=iso&tlng=pt ABSTRACT Green manures are an alternative for substituting or supplementing mineral nitrogen fertilizers. The aim of this study was to quantify biological N fixation (BNF) and the N contribution derived from BNF (N-BNF) to N levels in leaves of coffee intercropped with legumes grown on four family farms located in the mountainous region of the Atlantic Forest Biome in the state of Minas Gerais, Brazil. The following green manures were evaluated: pinto peanuts (Arachis pintoi), calopo (Calopogonium mucunoides), crotalaria (Crotalaria spectabilis), Brazilian stylo (Stylosanthes guianensis), pigeon pea (Cajanus cajan), lablab beans (Dolichos lablab), and velvet beans (Stizolobium deeringianum), and spontaneous plants. The experimental design was randomized blocks with a 4 × 8 factorial arrangement (four agricultural properties and eight green manures), and four replications. One hundred grams of fresh matter of each green manure plant were dried in an oven to obtain the dry matter. We then performed chemical and biochemical characterizations and determined the levels of 15N and 14N, which were used to quantify BNF through the 15N (δ15N) natural abundance technique. The legumes C. mucunoides, S. guianensis, C. cajan, and D. lablab had the highest rates of BNF, at 46.1, 45.9, 44.4, and 42.9 %, respectively. C. cajan was the legume that contributed the largest amount of N (44.42 kg ha-1) via BNF.C. cajan, C. spectabilis, and C. mucunoides transferred 55.8, 48.8, and 48.1 %, respectively, of the N from biological fixation to the coffee plants. The use of legumes intercropped with coffee plants is important in supplying N, as well as in transferring N derived from BNF to nutrition of the coffee plants. <![CDATA[Release of Phosphorus Forms from Cover Crop Residues in Agroecological No-Till Onion Production]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100502&lng=pt&nrm=iso&tlng=pt ABSTRACT Cover crops grown alone or in association can take up different amounts of phosphorus (P) from the soil and accumulate it in different P-forms in plant tissue. Cover crop residues with a higher content of readily decomposed forms may release P more quickly for the next onion crop. The aim of this study was to evaluate the release of P forms from residues of single and mixed cover crops in agroecological no-till onion (Allium cepa L.) production. The experiment was conducted in Ituporanga, Santa Catarina (SC), Brazil, in an Inceptisol, with the following treatments: weeds, black oat (Avena sativa L.), rye (Secale cereale L.), oilseed radish (Raphanus sativus L.), oilseed radish + black oat, and oilseed radish + rye. Cover crops were sown in April 2013. In July 2013, plant shoots were cut close to the soil surface and part of the material was placed in litterbags. The bags were placed on the soil surface and residues were collected at 0, 15, and 45 days after deposition (DAD). Residues were dried and ground and P in the plant tissue was determined through chemical fractionation. The release of P contained in the tissue of cover crops depends not only on total P content in the tissue, but also on the accumulation of P forms and the quality of the residue in decomposition. The highest accumulation of P in cover crops occurred in the soluble inorganic P fraction, which is the fraction of fastest release in plants. Black oat had the highest initial release rate of soluble inorganic P, which became equal to the release rate of other cover crop residues at 45 DAD. Weeds released only half the amount of soluble inorganic P in the same period, despite accumulating a considerable amount of P in their biomass. The mixtures of oilseed radish + rye and oilseed radish + black oat showed higher release of P associated with RNA at 45 DAD in comparison to the single treatments. <![CDATA[Soil Quality Evaluation Using the Soil Management Assessment Framework (SMAF) in Brazilian Oxisols with Contrasting Texture]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100503&lng=pt&nrm=iso&tlng=pt ABSTRACT The Soil Management Assessment Framework (SMAF) was developed in the U.S.A. and has been used as a tool for assessing and quantifying changes in soil quality/health (SQ) induced by land uses and agricultural practices in that region and elsewhere throughout the world. An initial study using SMAF in Brazil was recently published, but additional research for a variety of soils and management systems is still needed. Our objective was to use data from five studies in southern Brazil to evaluate the potential of SMAF for assessing diverse land-use and management practices on SQ. The studies examined were: (i) horizontal and vertical distribution of soil properties in a long-term orange orchard; (ii) impacts of long-term land-use change from native vegetation to agricultural crops on soil properties; (iii) effects of short-term tillage on soil properties in a cassava production area; (iv) changes in soil properties due to mineral fertilizer and pig slurry application coupled with soil tillage practices; and (v) row and inter-row sowing effects on soil properties in a long-term no-tillage area. The soils were classified as Oxisols, with clay content ranging from 180 to 800 g kg-1. Six SQ indicators [pH(H2O), P, K, bulk density, organic C, and microbial biomass] were individually scored using SMAF curves and integrated into an overall Soil Quality Index (SQI) focusing on chemical, physical, and biological sectors. The SMAF was sensitive for detecting SQ changes induced by different land uses and management practices within this wide textural range of Brazilian Oxisols. The SMAF scoring curve algorithms properly transformed the indicator values expressed in different units into unitless scores ranging from 0-1, thus enabling the individual indicators to be combined into an overall index for evaluating land-use and management effects on soil functions. Soil sector scores (i.e., chemical, physical, and biological) identify the principal soil limitations and can therefore be used to establish priorities for specific management actions. The SMAF can be used as a tool for assessing SQ in Brazilian soils, thus helping farmers, land managers, and politicians make better decisions regarding sustainable land-use and management practices. <![CDATA[Classical Methods and Calculation Algorithms for Determining Lime Requirements]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100504&lng=pt&nrm=iso&tlng=pt ABSTRACT The methods developed for determination of lime requirements (LR) are based on widely accepted principles. However, the formulas used for calculation have evolved little over recent decades, and in some cases there are indications of their inadequacy. The aim of this study was to compare the lime requirements calculated by three classic formulas and three algorithms, defining those most appropriate for supplying Ca and Mg to coffee plants and the smaller possibility of causing overliming. The database used contained 600 soil samples, which were collected in coffee plantings. The LR was estimated by the methods of base saturation, neutralization of Al3+, and elevation of Ca2+ and Mg2+ contents (two formulas) and by the three calculation algorithms. Averages of the lime requirements were compared, determining the frequency distribution of the 600 lime requirements (LR) estimated through each calculation method. In soils with low cation exchange capacity at pH 7, the base saturation method may fail to adequately supply the plants with Ca and Mg in many situations, while the method of Al3+ neutralization and elevation of Ca2+ and Mg2+ contents can result in the calculation of application rates that will increase the pH above the suitable range. Among the methods studied for calculating lime requirements, the algorithm that predicts reaching a defined base saturation, with adequate Ca and Mg supply and the maximum application rate limited to the H+Al value, proved to be the most efficient calculation method, and it can be recommended for use in numerous crops conditions. <![CDATA[Water Erosion in Different Slope Lengths on Bare Soil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100505&lng=pt&nrm=iso&tlng=pt ABSTRACT Water erosion degrades the soil and contaminates the environment, and one influential factor on erosion is slope length. The aim of this study was to quantify losses of soil (SL) and water (WL) in a Humic Cambisol in a field experiment under natural rainfall conditions from July 4, 2014 to June 18, 2015 in individual events of 41 erosive rains in the Southern Plateau of Santa Catarina and to estimate soil losses through the USLE and RUSLE models. The treatments consisted of slope lengths of 11, 22, 33, and 44 m, with an average degree of slope of 8 %, on bare and uncropped soil that had been cultivated with corn prior to the study. At the end of the corn cycle, the stalk residue was removed from the surface, leaving the roots of the crop in the soil. Soil loss by water erosion is related linearly and positively to the increase in slope length in the span between 11 and 44 m. Soil losses were related to water losses and the Erosivity Index (EI30), while water losses were related to rain depth. Soil losses estimated by the USLE and RUSLE model showed lower values than the values observed experimentally in the field, especially the values estimated by the USLE. The values of factor L calculated for slope length of 11, 22, 33, and 44 m for the two versions (USLE and RUSLE) of the soil loss prediction model showed satisfactory results in relation to the values of soil losses observed. <![CDATA[Nutrient and Organic Carbon Losses, Enrichment Rate, and Cost of Water Erosion]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100506&lng=pt&nrm=iso&tlng=pt ABSTRACT Soil erosion from water causes loss of nutrients and organic carbon, enriches the environment outside the erosion site, and results in costs. The no-tillage system generates increased nutrient and C content in the topsoil and, although it controls erosion, it can produce a more enriched runoff than in the conventional tillage system. This study was conducted in a Humic Cambisol in natural rainfall from 1997 to 2012 to quantify the contents and total losses of nutrients and organic C in soil runoff, and to calculate the enrichment rates and the cost of these losses. The treatments evaluated were: a) soil with a crop, consisting of conventional tillage with one plowing + two harrowings (CT), minimum tillage with one chisel plowing + one harrowing (MT), and no tillage (NT); and b) bare soil: one plowing + two harrowings (BS). In CT, MT, and NT, black oat, soybean, vetch, corn, turnip, and black beans were cultivated. Over the 15 years, 15.5 Mg ha-1 of limestone, 525 kg ha-1 of N (urea), 1,302 kg ha-1 of P2O5 (triple superphosphate), and 1,075 kg ha-1 of K2O (potassium chloride) were used in the soil. The P, K, Ca, Mg, and organic C contents in the soil were determined and also the P, K, Ca, and Mg sediments in the runoff water. From these contents, the total losses, the enrichment rates (ER), and financial losses were calculated. The NT increased the P, K, and organic C contents in the topsoil. The nutrients and organic C content in the runoff from NT was greater than from CT, showing that NT was not a fully conservationist practice for soil. The linear model y = a + bx fit the data within the level of significance (p≤0.01) when the values of P, K, and organic C in the sediments from erosion were related to those values in the soil surface layer. The nutrient and organic C contents were higher in the sediments from erosion than in the soil where the erosion originated, generating values of ER&gt;1 for P, K, and organic C. The value of the total losses of nutrients in the form of triple superphosphate fertilizer, potassium chloride, and urea and limestone by water erosion was higher in CT than in NT. For triple superphosphate, the cost of erosion losses was 29 % higher in NT than in CT, while in urea and limestone, the effectiveness of NT in reducing costs was 65 and 50 %, respectively. <![CDATA[Characteristics of Soils in Highland Wetlands as a Subsidy to Identifying and Setting their Limits]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100507&lng=pt&nrm=iso&tlng=pt ABSTRACT Palustrine areas and wetlands in particular are fragile ecosystems, with high biodiversity and high ecological productivity, and they provide benefits to society. The aim of this study was to describe and classify the main soils occurring in the wetlands of the Southern Plateau of Santa Catarina, and propose criteria for identification of hydromorphic environments as an aid in demarcation of their boundaries. Soils of four wetlands, in the municipalities of Bom Jardim da Serra, Bom Retiro, Lages, and Painel were described, collected, and taxonomically classified. A transection was demarcated in each one in which soils were analyzed in sites with different degrees of hydromorphism, corresponding to the inner, transition, and outer areas. In hydromorphic areas, the content of organic matter in the soil is higher than in non-hydromorphic areas, which influences the color and classification of the soils. In these soils, Aquents, Aquepts, and Histosols predominate, and Udepts predominate in the outer area. The drainage class and the higher chroma in the subsurface horizons of the Udepts indicate that they are outside the boundaries of the wetlands. The dark color in the surface horizons, along with the greyish colors, associated or not with the presence of mottling in the subsurface horizons, were the most obvious characteristics of a hydromorphic condition, indicating that the soil is located in the transitional and inner areas of the wetlands. <![CDATA[Soil Organic Matter Quality in Jatropha spp. Plantations in Different Edaphoclimatic Conditions]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100508&lng=pt&nrm=iso&tlng=pt ABSTRACT The substitution of native vegetation by agricultural ecosystems can change the quantity and quality of soil organic matter (SOM), and the intensity of these changes depends on the soil type, climate, and land use. The objective of this study was to evaluate the quality of organic matter in chronosequences of Jatropha cultivation in contrasting soil and climatic conditions. Soil samples were evaluated at depths of 0.00-0.10, 0.20-0.30, and 0.80-1.00 m in chronosequences located in Planaltina, Distrito Federal (Cerrado-Pasture-Jatropha), Dourados, Mato Grosso do Sul (Atlantic Forest-Corn-Jatropha), and Araripina, Pernambuco (Caatinga-Jatropha). To assess SOM quality, we determined C contents in the SOM fractions, C stocks, the carbon management index (CMI), the SOM humification index (HLIF), and the C and N concentrations in the microbial biomass. The conversion of native vegetation to agropastoral systems changed the composition of SOM in the biomes evaluated, especially in the surface layers. The CMI and the C and N contents in the microbial biomass were the most responsive to land use changes in all the biomes studied. The pasture improved SOM quality by increasing the CMI (116) and the C content by 8, 21, and 6 % in the organic, mineral, and organomineral fractions, respectively, while maintaining the SOM humification index and the C and N contents in the microbial biomass in the 0-0.10 m layer. The lowest values of C in the SOM fractions, the CMI (52), and C microbial biomass (136 mg kg-1) were observed for annual crops. Jatropha cultivation increased C contents in the SOM fractions, C stocks, the CMI, and C and N in the microbial biomass with an increase in cultivation time, which demonstrates the potential of this long-term system for improving SOM quality. <![CDATA[Nutrient Release, Plant Nutrition, and Potassium Leaching from Polymer-Coated Fertilizer]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100509&lng=pt&nrm=iso&tlng=pt ABSTRACT The increase in food consumption and limitations in food production areas requires improved fertilizer efficiency. Slow- or controlled-release fertilizers are an alternative for synchronizing nutrient availability with the plant demands, reducing losses to the environment. The aim of this study was to evaluate the efficacy of polymer-coated KCl compared with conventional KCl. The products were incubated in soil under controlled conditions to evaluate the time required for nutrient release. A greenhouse experiment was performed with corn plants in pots with loamy sand- or clay-textured soil types to evaluate plant nutrition and losses due to leaching. The K application rates were 0, 18, 36, and 54 mg dm-3. The pots were irrigated, and the percolated liquid was collected. The plants were harvested 30 days after sowing to quantify dry matter (DM) and its K content. In the incubation study, the K release from the coated fertilizer was found to be 42 % over 154 days. The data were fit to a linear function from which a period of 315 days was estimated as required for the release of 75 % of the nutrient. Meanwhile, conventional KCl releases 85 % of the K nutrient in the first 48h. In the cultivation of plants in pots, the coating reduced K losses due to leaching in the loamy sand soil; however, only the application rate of 54 mg dm-3 promoted DM production equivalent to conventional KCl. It is possible that the need for K in the early stages of corn development was not met by a coated KCl. <![CDATA[The Use of DRIS for Nutritional Diagnosis in Oil Palm in the State of Pará]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100510&lng=pt&nrm=iso&tlng=pt ABSTRACT The oil palm crop has expanded significantly in the state of Pará, which has not been followed in a proportional manner by studies aiming at increasing yield through plant nutrition. The objective of this study was to evaluate general and specific norms of the Diagnosis and Recommendation Integrated System (DRIS) for genetic materials of oil palm (African and interspecific hybrid) at two ages (young and adult plants) and evaluate possible deficiencies in fertilization and soil correction practices. The DRIS norms were composed of means, standard deviations, and coefficients of variation of bivariate, specific, and general relationships among nutrients of 144 leaf samples. The DRIS norms specific for genetic material did not differ from the general norms; however, a large number of differences were found between specific bivariate relationships for age groups, among themselves, and in relation to the general norms. The regression analysis between the nutritional balance index and yield were better explained when age groups were discriminated. In the young plants, the number of cases of stands with deficiencies followed the order Ca &gt; Fe &gt; B &gt; S &gt; Mn &gt; K &gt; Mg = Cu &gt; Zn &gt; N &gt; P; and for adults, this order was Ca &gt; Mn &gt; Zn &gt; Fe &gt; S = B &gt; N = Cu &gt; K &gt; Mg &gt; P. The DRIS norms can be utilized in diagnostics regardless of genetic material; however, they must be specified for the age of the plant. Most of the stands showed deficiency in Ca and micronutrients, coinciding with the least used nutrients in oil palm crops in the state of Pará, as well as emphasizing the need for soil liming. <![CDATA[Relationships between Agriculture, Riparian Vegetation, and Surface Water Quality in Watersheds]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100511&lng=pt&nrm=iso&tlng=pt ABSTRACT Agricultural land use and degradation of natural vegetation in riparian zones can impair water quality. This study was conducted in seven agricultural watersheds in Ibirubá, RS, Brazil, with the following objectives: identify relationships between concentrations of soluble phosphorus (Psol) and nitrate (NO−3) in surface water and agricultural use of soil and current vegetation in riparian zones, and assess the risk of eutrophication. Water samples from the main watercourses in each watershed were collected monthly from 10/2013 to 6/2014. Current land use was established by field surveys in the watersheds. The riparian zones of the watercourses were evaluated in terms of the condition of permanent preservation area (PPA) and access of the animals to the watercourses. The concentration of Psol and NO−3 were correlated with land use indicators obtained from geoprocessing tools. Agricultural use of PPA increases the risk of surface water degradation, which increases through application of manure on crops and free access of livestock to PPAs and to these watercourses for drinking water. Surface water samples obtained showed water Psol concentrations that generate risk of eutrophication, whereas concentrations of NO−3 were generally below critical levels. <![CDATA[Calcium and Magnesium Released from Residues in an Integrated Crop-Livestock System under Different Grazing Intensities]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100512&lng=pt&nrm=iso&tlng=pt ABSTRACT Under integrated crop-livestock production systems (ICLS), plant and animal residues are important nutrient stocks for plant growth. Grazing management, by affecting the numbers of both plants and animals and the quality of residues, will influence nutrient release rates. The objective of this study was to evaluate the impact of grazing intensity on Ca and Mg release from pasture, dung, and soybean residues in a long-term no-till integrated soybean-cattle system. The experiment was established in May 2001 in a Latossolo Vermelho Distroférrico (Rhodic Hapludox). Treatments were a gradient of grazing intensity, determined by managing a black oat + Italian ryegrass pasture at 10, 20, 30, and 40 cm grazing height and no-grazing (NG), followed by soybean cropping. Ca and Mg release rates were determined in two entire cycles (2009/11). Moderate grazing (20 and 30 cm sward height) led to greater Ca and Mg release rates from pasture and dung residues, with low average half-life values (13 and 3 days for Ca and 16 and 6 days for Mg for pasture and dung, respectively). Grazing compared with NG resulted in greater Ca and Mg release from pasture and dung residues. Grazing intensity did not affect Ca and Mg release rates or amounts from soybean residues, but Ca and Mg release rates were greater from soybean leaves than from stems. Although moderate grazing intensities produce higher quality residues and higher calcium and magnesium release rates, a higher total nutrient amount is released by light grazing intensity and no-grazing, determined by higher residue production. Grazing intensity is, then, important for nutrient dynamics in the soil-plant-animal continuum. <![CDATA[Effects of Soil Management Practices on Water Erosion under Natural Rainfall Conditions on a Humic Dystrudept]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100513&lng=pt&nrm=iso&tlng=pt ABSTRACT Water erosion is the main cause of soil degradation and is influenced by rainfall, soil, topography, land use, soil cover and management, and conservation practices. The objective of this study was to quantify water erosion in a Humic Dystrudept in two experiments. In experiment I, treatments consisted of different rates of fertilizer applied to the soil surface under no-tillage conditions. In experiment II, treatments consisted of a no-tillage in natural rangeland, burned natural rangeland and natural rangeland. Forage turnip, black beans, common vetch, and corn were used in rotation in the treatments with crops in the no-tillage during study period. The treatments with crops and the burned rangeland and natural rangeland were compared to a bare soil control, without cultivation and without fertilization. Increasing fertilization rates increased organic carbon content, soil resistance to disintegration, and the macropore volume of the soil, due to the increase in the dry mass of the crops, resulting in an important reduction in water erosion. The exponential model of the ŷ = ae-bx type satisfactorily described the reduction in water and soil losses in accordance with the increase in fertilization rate and also described the decrease in soil losses in accordance with the increase in dry mass of the crops. Water erosion occurred in the following increasing intensity: in natural rangeland, in cultivated natural rangeland, and in burned natural rangeland. Water erosion had less effect on water losses than on soil losses, regardless of the soil management practices. <![CDATA[Analysis of Potential for Linear Erosion in the <em>Cerrado</em> Biome Using Morphopedology]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100514&lng=pt&nrm=iso&tlng=pt ABSTRACT The Cerrado is a vegetation complex with a wide variety of phytophysiognomies, and sustainable management is essential for maintaining biodiversity. Morphopedology is a tool that can assist in developing plans for control of soil and land use, especially in evaluating the potential of soil erosion processes. This technique allows landscape units considered “homogeneous” to be distinguished, as a result of interaction between physiographic conditions. The aim of this study was to evaluate potential for erosion in São Miguel do Araguaia, state of Goiás, Brazil, through definition of morphopedological compartments (MPC), on the assumption that soil use has increased erosion. Landscape units were identified through use of geology overlay, hypsometry, slope, geomorphology, soil, and land use. The map information on a 1:100,000 scale was refined, the base of which was available in the Geographic Information System of Goiás. The morphopedological approach enabled identification of five MPC. Predominant soil classes in São Miguel do Araguaia (with matching categories) are Latossolos Vermelho-Amarelo Distróficos (Xanthic Hapludox), Plintossolos Pétricos Concrecionários (Petronodic Haplargids), Plintossolos Háplicos Distróficos (Plinthic Haplaquox), Gleissolos Háplicos Tb Distróficos (Typic Endoaquents), and Neossolos Quartzarênicos Órticos (Typic Quartzipsamments). Generally, every class of soil has some type of limitation that may cause erosion to different degrees. The most dissected areas are associated with lateritic covers, which suggests the importance of these features on topographical formation. The results of analysis of erosion susceptibility and linear erosion potential suggest low risk of erosion, even considering human activities, especially cattle ranching. <![CDATA[Chemical Properties in Macroaggregates of a Humic Dystrudept Cultivated with Onion under No-Till and Conventional Tillage Systems]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100515&lng=pt&nrm=iso&tlng=pt ABSTRACT Nutrients present in soil aggregates are essential for maintaining the productive capacity of agroecosystems and environmental quality. The aim of this study was to evaluate the chemical properties of macroaggregates of a Humic Dystrudept cultivated with onions under a no-till vegetable system (NTVS) compared to the conventional tillage system (CTS) and a forest area in Ituporanga, SC, Brazil. The treatments consisted of the following single and mixed cover crops with onion under the NTVS: spontaneous vegetation, 100 % black oats, 100 % rye, 100 % oilseed radish, intercropped oilseed radish (14 %) + rye (86 %), and intercropped oilseed radish (14 %) + black oat (86 %). Additionally, we evaluated two areas, one with onion grown under the CTS for ±37 years and an area under forest for ±30 years, both adjacent to the experiment. Five years after implementation of the treatments with cover crops, we collected undisturbed soil samples at depths of 0.00-0.05, 0.05-0.10, and 0.10-0.20 m, and we obtained macroaggregates (8.00 mm &gt; Ø ≥ 2.0 mm). We analyzed total organic carbon (TOC), pH in water, Ca2+, Mg2+, Al3+, H+Al, K+, and P in the macroaggregates. The conversion of onion-growing areas from the CTS to the NTVS after five years increases TOC, pH, Ca, Mg, and K in soil macroaggregates at the depth of 0.00-0.05 m. There is increased K content in the macroaggregates of soil under the NTVS at all depths evaluated in this study compared to the CTS. The use of millet in the CTS increases P content at depth (0.05-0.10 and 0.10-0.20 m). Intercropping black oat + oilseed radish increases Ca content at the 0.10-0.20 m depth in comparison to the black oat, rye + oilseed radish, and control treatments, and increases Mg content as well, compared to the other cover crops at the depths of 0.05-0.10 and 0.10-0.20 m. <![CDATA[Nutrient Uptake and Removal by Potato Cultivars as Affected by Phosphate Fertilization of Soils with Different Levels of Phosphorus Availability]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100516&lng=pt&nrm=iso&tlng=pt ABSTRACT Studies in the past decades have focused on how tuber yield of potato grown on different types of soil is affected by phosphate fertilizer rates. However, little is known about the effects of phosphorus availability in the soil and of phosphate fertilization on nutrient uptake and removal by the main potato cultivars currently grown in Brazil. Thus, in this study we investigated the influence of P fertilization rates on dry matter (DM) yield and nutrient uptake and removal in five potato cultivars grown on soils with different levels of P availability. Experiments were conducted on soil with low (14 mg dm-3), medium (36 mg dm-3), and high (70 mg dm-3) P availability, in randomized complete blocks with a 5 × 5 factorial arrangement with four replications. The treatments consisted of five potato cultivars (Agata, Asterix, Atlantic, Markies, and Mondial) and five P rates (0, 125, 250, 500, and 1,000 kg ha-1 P2O5) applied in the planting furrow. In soils with low, medium, and high P availability, P fertilization increased plant growth and tuber DM yield up to rates of 500, 250, and 125 kg ha-1 P2O5, respectively. At a specific initial P availability, all potato cultivars responded to the same P rate for plant growth, tuber yield, and nutrient uptake and removal. At the highest P fertilization rates, leaf analysis showed that the nutritional status of potato plants was not significantly changed and no nutritional deficiency was induced, regardless of the soil P availability levels. However, in the soils with higher P availability, P fertilization decreased plant Mn and Zn and tuber Mn concentrations in a linear manner. The increases in the uptake of N, K, Ca, Mg, S, B, Cu, and Fe and the removal of most nutrients in response to P fertilization were related more to the increase in plant biomass and tuber DM yield than to changes in concentrations of these nutrients in the plant. Application of P at high rates in soil with high P availability caused luxury P uptake, which reduced Mn uptake by 10 % and prevented higher Zn uptake, by reducing plant Zn concentrations, despite the increase in plant biomass. <![CDATA[Mitigation of the Gradient of Chemical Properties in the Rooting Zone of Dystrophic Oxisols by Gypsum and Lime Inputs under a No-Till System]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100517&lng=pt&nrm=iso&tlng=pt ABSTRACT Improvement of soil chemical properties in dystrophic Oxisols managed under long-term no-tillage system (NTS) with surface broadcast lime has been, frequently, restricted to a shallow topsoil layer. As a consequence, a sharply-defined chemical quality gradient is created, with deterioration from the surface towards deeper layers in Oxisols in southern Brazil. The aim of this study was to assess the temporal effects of gypsum, applied alone or in combination with lime, on Ca2+ content and Al3+ saturation in the rooting zone (RZ) (0.00-0.40 m). Four experiments were conducted from 2009 to 2014 in Typic Hapludox soils with distinct chemical qualities in the RZ managed under a long-term NTS (over 20 years) in Rio Grande do Sul (subtropical region). A randomized block experimental design with three replications was used. Experiments I and II were implemented in 2009, with treatments consisting of gypsum rates ranging from 0.0 to 6.5 Mg ha-1. The other two experiments were implemented in 2011. In experiment III, a split-plot design was used, with plots received gypsum rates ranging from 0.0 to 5.0 Mg ha-1, and the subplots received two lime rates (0.0 and 2.0 Mg ha-1). A split-plot design was also used in experiment IV, with plots receiving gypsum rates ranging from 0.0 to 6.0 Mg ha-1, and subplots receiving four lime rates, ranging from 0.0 to 4.8 Mg ha-1. Soil samples were stratified in layers at depth from 0.00 to 0.60 m and taken during the period of the experiment. The use of gypsum increased the Ca2+ and SO42−-S contents, proportional to the rate applied, and lowered Al3+ saturation throughout the soil profile evaluated. However, an increase in base saturation of the subsoil (0.25-0.60 m layer) was only observed at high rates of gypsum (&gt;5.0 Mg ha-1) in the medium-term and through accumulation of a high rainfall volume. A faster and more pronounced effect of subsoil improvement was observed when the chemical quality of the topsoil layer was already high and when gypsum and lime were applied in combination. Greater improvement in subsoil chemical quality induced by gypsum, alone or in combination with lime, was found in a period exceeding 30 months (Experiments III and IV), remaining for up to 54 months (Experiments I and II). The combination of gypsum with lime was an effective strategy to increase vertical movement of bases in the RZ, mitigating the gradient of chemical quality in dystrophic Oxisol, avoiding discontinuity in the NTS. <![CDATA[Organic Carbon and Physical Properties in Sandy Soil after Conversion from Degraded Pasture to Eucalyptus in the Brazilian Cerrado]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100518&lng=pt&nrm=iso&tlng=pt ABSTRACT Soil is currently seen as the most relevant carbon sink and the most effective carbon stabilizer. In contrast, agriculture is the second largest C emitter, after burning of fossil fuels. This organic carbon (OC) introduced into the soil, mainly via organic matter (OM), is essential for several soil properties and plays an extremely important role in sandy soils. The objective of this study was to describe the changes in the amounts and pools of OC and the influence thereof on some physical soil properties in areas converted from pasture to eucalyptus. The following areas were analyzed: a degraded pasture (PAST), two areas of pasture-eucalyptus conversion after 2 and 15 years (EU02 and EU15, respectively) and a preserved Cerrado area (CER) in the east of the state of Mato Grosso do Sul. Soil samples were taken from the 0.00-0.05, 0.05-0.10, and 0.10-0.30 m layers. The OC was measured and analyzed, the carbon pool (CP) calculated, aggregate stability, bulk density (BD), and macro- and microporosity determined, and total porosity (TP) calculated to analyze the influence of land use on soil properties. The experimental design was completely randomized, and four clusters per area were established, with nine subsampling points, for a total of 36 subsamples per area, organized in 20 × 20 m grids, The soil under natural vegetation (preserved Cerrado) was used as a control. The change from CER to commercial cultivation accelerates the process of OC loss (reductions of 25-35 %) and reductions in soil physical quality. In the PAST area, OC was reduced by 30 % in the 0.00-0.05 m layer. Cumulative OC and CP were highest in the 0.00-0.05 m layer and decreased in the deeper layers in all land use treatments. Organic C in the 0.10-0.30 m layer was not influenced by land use, indicating the possibility of OC persistence in the soil for longer periods. Macroporosity and total porosity may be considered appropriate in CER and EU15, whereas the conditions for plant development in PAST and EU02 were restrictive. Land use systems reduced OC and the CP, indicating anthropogenic disturbance of the soil compared to CER. Fifteen years after planting eucalyptus in the pasture area, signs of recovery of some soil physical properties were observed, e.g., reduced BD and increased TP. <![CDATA[Effect of Harvest Time and Nitrogen Doses on Cassava Root Yield and Quality]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100519&lng=pt&nrm=iso&tlng=pt ABSTRACT Nitrogen is considered the most limiting nutrient for cassava, and N availability can influence the crop cycle, including earlier harvest. The aim of this study was to study the effect of harvest time on the production components of cassava, “Aciolina” cultivar, at different rates of N fertiliser. The experiment was carried out in an area newly incorporated into the productive system in a savannah ecosystem in the northern Amazon. A randomised block experimental design was used in a split plot arrangement with four replications. The N rates (0, 30, 60, 150, and 330 kg ha-1) were allocated to the main plots, and the harvest times (90, 120, 150, 180, 240, 300, and 360 days after emergence of the stalks - DAE) were allocated to the subplots. Plant height, shoot fresh matter yield, number of roots per plant, average root diameter, and root fresh matter yield display an increasing linear response up to 360 DAE in cassava cv. “Aciolina”. For all harvest times, the N rates promote an increase in root fresh matter yield. At 300 and 360 DAE, the root fresh matter and starch yield and the harvest index show a quadratic response as a function of the N level. The greatest efficiency of N topdressing on the production of root fresh matter occurs at 300 DAE, promoting an earlier harvest. At that time, the dose of maximum technical efficiency, 226 kg ha-1 N, results in a yield of 62 Mg ha-1 of root fresh matter, 13 Mg ha-1 of starch, and a harvest index of 81 %. <![CDATA[Modeling Root Growth, Crop Growth and N Uptake of Winter Wheat Based on SWMS_2D: Model and Validation]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100520&lng=pt&nrm=iso&tlng=pt ABSTRACT Simulations for root growth, crop growth, and N uptake in agro-hydrological models are of significant concern to researchers. SWMS_2D is one of the most widely used physical hydrologically related models. This model solves equations that govern soil-water movement by the finite element method, and has a public access source code. Incorporating key agricultural components into the SWMS_2D model is of practical importance, especially for modeling some critical cereal crops such as winter wheat. We added root growth, crop growth, and N uptake modules into SWMS_2D. The root growth model had two sub-models, one for root penetration and the other for root length distribution. The crop growth model used was adapted from EU-ROTATE_N, linked to the N uptake model. Soil-water limitation, nitrogen limitation, and temperature effects were all considered in dry-weight modeling. Field experiments for winter wheat in Bouwing, the Netherlands, in 1983-1984 were selected for validation. Good agreements were achieved between simulations and measurements, including soil water content at different depths, normalized root length distribution, dry weight and nitrogen uptake. This indicated that the proposed new modules used in the SWMS_2D model are robust and reliable. In the future, more rigorous validation should be carried out, ideally under 2D situations, and attention should be paid to improve some modules, including the module simulating soil N mineralization. <![CDATA[Decomposition and Nutrient Release Dynamics of Shoot Phytomass of Cover Crops in the Recôncavo Baiano]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100521&lng=pt&nrm=iso&tlng=pt ABSTRACT Evaluating the decomposition dynamics of vegetative residues from cover crops can provide a better understanding of nutrient release, which is fundamental when choosing a species that is adapted to local conditions. The objective of this study was to evaluate the decomposition rates and nutrient release dynamics of the shoot phytomass of different cover crops that have potential for agricultural use in the Recôncavo Baiano, Brazil. Crop residues of the following species were analyzed: sunn hemp (Crotalaria juncea L.) - CROT; velvet bean (Mucuna aterrima L.) - MUC; lab lab (Dolichos lab lab L.) - LAB; jack bean (Canavalia ensiformis [L.] DC.) - JB; white lupin (Lupinus albus L.) - WLUP; and Guinea grass (Urochloa maxima (Jacq.) R. Webster) - GRAS. The experiment was conducted in a randomized block design with four replications. The decomposition and nutrient release dynamics were evaluated using litter bags, and the remaining dry matter and the nutrient content of litter from each cover crop were quantified. The accumulation of macronutrients in the phytomass was in the following order: N &gt; K &gt; Ca &gt; Mg &gt; P &gt; S. The highest decomposition rates of the phytomass occurred in the species JB, with half-life (t1/2) of 36 days, and GRAS, with t1/2 of 41 days. K was the element with the shortest t1/2, suggesting a rapid transfer rate to the soil. Organic residues from the CROT and WLUP cover crops had lower decomposition rates and are, therefore, recommended for protecting soil in the region. Sunn hemp, unlike WLUP, also had residue of high chemical quality and, thus, it is an excellent nutrient recycler. Jack bean released nutrients into the soil the fastest due to its rapid decomposition rate; therefore, it is not recommended for ground cover. <![CDATA[Soil Compressibility under Irrigated Perennial and Annual Crops in a Semi-Arid Environment]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100522&lng=pt&nrm=iso&tlng=pt ABSTRACT In irrigated soils, a continuous state of high moisture reduces resistance of the soil to applied external forces, favouring compaction. The aim of this study was to evaluate the susceptibility to compaction of developed calcareous soils in irrigated annual and perennial cropping systems of the Apodi Plateau, located in the Brazilian semi-arid region. Four areas of irrigated crops were evaluated: banana after two (B2) and 15 (B15) years cultivation, pasture (P), and a corn and beans succession (MB), as well as the reference areas for soil quality and corresponding natural vegetation (NVB2, NVB15, NVP and NVMB). Samples were collected at layers of 0.00-0.10 and 0.20-0.30 m; and for B2 and B15, samples were collected in the row and inter-row spaces. The following properties were determined: degree of compactness (DC), preconsolidation pressure (σp), compression index (Cc), maximum density (ρmax), critical water content (WCcrit), total organic carbon (TOC) and carbon of light organic matter (Clom). Mean values were compared by the t-test at 5, 10, 15 and 20 % probability. An increase was seen in DC at a layer of 0.20-0.30 m in MB (p&lt;0.15), showing the deleterious effects of preparing the soil by ploughing and chiselling, together with the cumulative traffic of heavy machinery. The TOC had a greater influence on ρmax than the stocks of Clom. Irrigation caused a reduction in Cc, and there was no effect on σp at field capacity. The planting rows showed different behaviour for Cc, ρmax, and WCcrit,, and in general the physical properties displayed better conditions than the inter-row spaces. Values for σp and Cc showed that agricultural soils display greater load-bearing capacity and are less susceptible to compaction in relation to soils under natural vegetation. <![CDATA[Ethnopedology of a Quilombola Community in Minas Gerais: Soils, Landscape, and Land Evaluation]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100601&lng=pt&nrm=iso&tlng=pt ABSTRACT Quilombolas are Afro-brazilian rural peasants who descended from escaped slaves who tried to carve out territories of autonomy (called Quilombos) by collective organization and resistance. Despite many anthropological and ethnopedological studies, little research has been carried out to identify the agricultural practices and the knowledge of people who live in the Quilombos (Quilombolas). Peasant communities who live from land resources have wide empirical knowledge related to local soils and landscapes. In this respect, ethnopedology focuses on their relationship with local practices, needs, and values. We carried out an ethnopedological evaluation of the soils, landscape and land suitability of the Malhada Grande Quilombola Territory, aiming to examine the local criteria involved in land-use decision making, and evaluate the legitimacy of local knowledge. For this purpose, participatory workshops allowed environmental stratification of the Quilombolas into landscape units, recognition of soil types, and evaluation of land-use criteria. This approach was combined with conventional soil sampling, description, and analysis. The Brazilian System of Soil Classification and its approximations to the WRB/FAO system and the SAAT land evaluation system were compared with the local classificatory systems, showing several convergences. The Quilombolas stratified the local environment into eight landscape units (based on soil, topography, and vegetation) and identified eight soil types with distinct morphological, chemical, and physical attributes. The conventional soil survey identified thirteen soil classes, in the same eight landscape units, organized as soil associations. The apparent contradictions between local knowledge and Pedology were relative since the classification systems were established based on different criteria, goals, and sampling references. Most soils are only suitable for pasture, with restricted agricultural use, due to water or oxygen deficiencies. The current land use was only inconsistent with the technical recommendations when socioecological constraints such as the semiarid climate, land availability, and economic conditions for land management led to overuse of the land. Local knowledge demonstrated its legitimacy and allowed a useful and fruitful exchange of information with the academic view of soil-landscape interplays. Although mostly unknown by the scientific community, local knowledge proved capable of achieving social welfare and food security. In addition, a participatory survey proved to be a core factor for more grounded and detailed data collection on how Quilombolas decide land use on a local scale.