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[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[Bulk Density Prediction for Histosols and Soil Horizons with High Organic Matter Content]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832017000100409&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[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[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.