Scielo RSS <![CDATA[Revista Brasileira de Ciência do Solo]]> http://www.scielo.br/rss.php?pid=0100-068320200001&lang=en vol. 44 num. lang. en <![CDATA[SciELO Logo]]> http://www.scielo.br/img/en/fbpelogp.gif http://www.scielo.br <![CDATA[Mapping soil properties in a poorly-accessible area]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100300&lng=en&nrm=iso&tlng=en ABSTRACT Soil maps are important to evaluate soil functions and support decision-making process, particularly for soil properties such as pH, carbon content (C), and cation exchange capacity (CEC), but the spatial resolution and soil depth should meet the needs of users. On another hand, the efficiency of statistical models to create soil maps, with an acceptable level of accuracy, often require a large number of samples with an appropriate distribution across the area of interest. However, accessibility for sampling can be a trouble in remote areas, such as the Itatiaia National Park (INP). The hypothesis of this work is that it is possible to obtain a viable result in soil mapping of areas with limited access by using DSM tools. The general objective of this paper was to create 2- and 3-D maps of the soil properties pH, carbon content, and CEC, with the correspondent spatial uncertainty, in the INP plateau. The sampling strategy was designed using conditioned Latin Hypercube Sample (cLHS), and different methods were tested to produce the soil properties maps. For calibration of the models: linear (MLR, multiple linear regression) and nonlinear (GAM, Generalised Additive Models). The results showed differences in predictive performance for all statistical methods and covariate selection approaches. The GAM, with covariates selection based on soil formation factors, was the best method for the limited number of soil samples. The greatest uncertainty was associated with areas with the lowest accessibility and, consequently, with low sampling density and/or noises in covariates. Even though the 2- and 3-D maps of soil properties, each associated with explicit uncertainty, can contribute to the INP decision makers/managers by providing information not available before. <![CDATA[Non-allophanic Andosols of Trindade Island, south Atlantic: a new soil order in Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100301&lng=en&nrm=iso&tlng=en ABSTRACT The pedological studies carried out so far in Trindade Island (TI) have obtained patchy evidences of allophane, without detailed mineralogical and micromorphological studies to confirm the occurrence of Andosols in TI. Therefore, in this study, the mineralogical, micromorphological, physical and chemical characterization of four soil profiles from Vulcão do Paredão (P1) and Morro Vermelho formations (P2, P3, and P4) were carried on the latest volcanic events in Brazil from Trindade Island (TI) with the aim of to evaluate the presence of Andosols in this oceanic island. Profiles P1 and P2 are developed on pyroclastic bombs, and show, respectively, A-Bi- C and decapitated A-C horizons, whereas P3 and P4 are developed on lapillitic and bomb pyroclasts, show A-C horizons. The soil profiles have a reddish and brownish clayey matrix, are highly friable and show a plastic consistency. Their microstructures are granular, single grain and intergrain microaggregate, in which aggregates display an undifferentiated b-fabric. The mineralogical constituents of the bulk fraction are biotite, hematite, magnetite, ilmenite, pyroxene, olivine, halloysite, goethite, anatase, and rutile. The clay fraction is marked by the presence of halloysite, ferrihydrite, and little amounts of allophane. All soils presented andic properties and can be classified as non-allophanic Andosols. In addition, micromorphological features closely resemble those reported in Andosols from other volcanic islands from elsewhere. The predominance of halloysite in the clay fraction formed by alteration of sideromelane, suggests that allophane would be an intermediate phase of this rapid transformation favored by the wet climate conditions of the highest parts of TI. <![CDATA[Potato cultivation and livestock effects on microorganism functional groups in soils from the neotropical high Andean <em>Páramo</em>]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100400&lng=en&nrm=iso&tlng=en ABSTRACT Páramo ecosystems are of great importance because they are considered hotspots within the Tropical Andes. They are also very important for their role as producers and regulators of water processes in the Neotropic. However, the human occupation of the Colombian Páramos has generated conflict between environmental benefits and productive land uses, specifically the potato cultivation and livestock. To assess possible changes associated with potato cultivation (Solanum tuberosum L.) and livestock on the microbial communities of Páramo soils, the objective of this research was to evaluate the possible effects of potato cultivation and livestock farming on the soil microorganisms associated with different functional groups (nitrogen fixers, phosphate solubilizers and cellulolytic) in the Páramo of Nevados National Natural Park (Nevados NNP), Colombia. Samples were collected from soils under potato cultivation, livestock, and Páramo conservation areas over two climatic seasons (rainy and dry) in three farms at different elevations (3769, 3590, and 3432 m a.s.l.). The microorganisms were isolated using selective culture media for each functional group and identified using molecular markers; microbial diversity was analyzed using multivariate statistical tools. Changes were dependent on land use, elevation, and climate and were statistically significant in the rainy season on all three farms and one of the farms during the dry season. Similarly, the results indicated that climate has a greater impact on the evaluated microbial communities than land use does; the changes were significantly different between the soil under potato cultivation and in conserved Páramo sites at most of the evaluated locations and between soil subjected to livestock farming and Páramo in certain locations. However, the differences between potato cultivation and livestock farming were smaller. This study showed for the first time that the microbial structure (abundance and composition) of microorganism functional groups was different as a result of potato cultivation and livestock farming on Páramo soils, although these changes were dependent on farm elevation and climate. <![CDATA[Structural quality and load-bearing capacity of an Ultisol (Argissolo Vermelho amarelo) in mechanized coffee areas with different deployment times]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100401&lng=en&nrm=iso&tlng=en ABSTRACT The mechanized management systems used in Brazilian coffee plantations generate heavy machine traffic and lead to the application of loads on the soil that affect the soil structure and lead to widespread compaction. This study aimed to evaluate the influence of mechanized operations on coffee plantations with different deployment times on the soil structural quality of an Ultisol, based on its soil physical properties and soil load-bearing capacity. The experiment was carried out in Muzambinho, São Paulo State, Southeast Brazil, in coffee plantations (Coffee arabica L.) with 3, 16, and 32 years of service. In each area, corresponding to the coffee plantation’s establishment period, soil samples were collected in the planting row (R), under the coffee canopy (UCC), and inter-row center (IRC) at the layers of 0.00-0.10, 0.10-0.20, and 0.20-0.40 m to evaluate soil penetration resistance, bulk density, porosity, wet aggregate stability, and preconsolidation pressure, to model soil load-bearing capacity. The deployment time of the coffee crop was a decisive factor in reducing the deterioration of the soil structure in the row, which was confirmed by better structural quality in the plantations with 16 and 32 years of establishment. Irrespective of crop deployment time, the effects of intensive machinery traffic on the coffee crop in the middle between the rows and in the area under the canopy are similar, resulting in high soil compaction, reflected in soil penetration resistance, soil bulk density, macroporosity, and load-bearing capacity. The longer the deployment time of the coffee cultivation areas (32 and 16 years), the higher the stability of the soil aggregates, and the larger the mean aggregate size. <![CDATA[Using root water uptake estimated by a hydrological model to evaluate the least limiting water range]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100402&lng=en&nrm=iso&tlng=en ABSTRACT The least limiting water range (LLWR) has been extensively determined, but evaluating if LLWR can indeed indicate soil physical stress on plant growth is still a controversial issue. In this study, we used the Hydrus-1D hydrological model to simulate root water uptake (RWU) to analyze if RWU and LLWR are correlated under stress conditions. The LLWR was determined in a sandy-loam Ultisol and a clayey Oxisol. In both soils, RWU extracted by plants (leaf area index set as 3) from a rooted layer of 0.4 m was simulated over 20 days under a potential evapotranspiration rate of 6 mm day-1. For each soil, RWU was simulated over the same range of soil compaction in which LLWR was determined. The cumulative RWU over the 20 days varied between 23 to 58 mm in the Ultisol and 20 to 48 mm in the Oxisol, indicating that plants were able to take up only a small part of the cumulative potential transpiration (93 mm) and experienced severe water stress in some soil conditions. However, RWU under water stress was poorly correlated with both bulk density and LLWR. The correlation between RWU and LLWR was 0.5 (p&lt;0.01) for the Ultisol and 0.22 (p&lt;0.19) for the Oxisol, suggesting that LLRW has little (for Ultisol) or almost no (for Oxisol) ability to indicate soil quality related to plant water availability. Our simulations suggest that RWU in the water availability range (between field capacity and wilting point) may be little affected or even improved by light soil compaction. Studies to elucidate this phenomenon would contribute to the understanding of the compaction effect on RWU and the weak correlation between RWU and LLWR. <![CDATA[Termite participation in the soil-forming processes of 'murundus' structures in the semi-arid region of Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100403&lng=en&nrm=iso&tlng=en ABSTRACT Regularly spaced earth mounds called “murundus” are scattered in several landscapes in the semi-arid region of Brazil. Although recent evidence indicates that termites are involved in the building of murundus, the contribution of these insects to soil-forming processes in those structures remains poorly understood. In this study, we tested a set of hypotheses to examine whether there are consistent evidence for suggesting the participation of termites in the formation of murundus soils. Morphological and physicochemical features of murundus were compared with adjacent soil profiles in the inter-mounds surface and one epigeic nest built by one species of Syntermes Holmgren. The murundus soils had a more clayey texture, higher contents of nutrients (C, N, P, K, Ca, and Mg) and organic matter compared with adjacent soils. We identified a set of recent and ancient traces inside the murundus that reveals the intense building activity of termite colonies (e.g., galleries, tunnels, and royal chambers), confirming that these structures are not only occupied by these insects but also built-up by them. Taken together, our results provide hard evidence that the long-term activity of mound-building termites was the hierarchically dominant process in producing murundus structures in the semi-arid region of Brazil. Based on available empirical data, we propose an explanatory model on how that construction process may have taken place. <![CDATA[Glyphosate dynamics prediction in a soil under conventional and no-tillage systems during the crop cycle]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100404&lng=en&nrm=iso&tlng=en ABSTRACT Simulation models are efficient tools to predict the fate of different solutes in agricultural soils. This work aimed to compare measured and predicted glyphosate and AMPA (aminomethyl phosphonic acid; its main metabolite) contents in a soil under no-tillage (NT), and conventional tillage (CT); and to compare the predictions considering constant and time-variable hydraulic properties. Additionally, we evaluated the ability of the model to predict glyphosate and AMPA accumulation during the crop cycle. Hydrus 1-D code was used to predict the glyphosate and AMPA dynamics, considering constant and time-variable hydraulic properties during the studied crop cycle. In general, the prediction of glyphosate and AMPA distribution along the soil profile using HYDRUS 1-D was satisfactory; however, an overestimation of both compounds was observed in the first 0.20 m of the soil probably because of the preferential flow. Additionally, the accumulation process of glyphosate and AMPA in the soil during the crop cycle was underestimated by HYDRUS 1-D, as compared with the observed field data. Simulated data show that higher values of K0 increase the risk of glyphosate and AMPA vertical transport. The inclusion of temporal variation of hydraulic properties in glyphosate and AMPA simulation did not improve the simulation performance, showing that the model is more sensitive to the parameters related to the solutes. From the obtained results, HYDRUS 1-D code allowed to predict glyphosate and AMPA dynamics reasonably well in agricultural soils of the Argentinean Pampas region and is a potential model to give support in the analysis of the environmental risk of leaching and soil contamination. <![CDATA[Diversity and abundance of soil macrofauna in three land use systems in eastern Amazonia]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100405&lng=en&nrm=iso&tlng=en ABSTRACT Given the influence of edaphic macrofauna in the physical, chemical, and biological processes that sustain the organic matter cycle in the soil of tropical ecosystems, this study aimed to evaluate the effect of the sequence: Secondary Forest – Pasture – Eucalyptus monoculture on the macrofauna structure in Southeast of Pará State, Brazil. In each land use system, two 350 m transect were taken. The data was collected in 8 sampling sites, which were 50 m apart in each transect at 0.10 and 0.20 m depths. Correlations between the community structure Family Richness (S), Shannon-Wiener diversity index (H’), Pielou equitability (J), and macrofauna density (ind. m-2) were tested with soil pH(H2O), Al3+, Ca2+, Mg2+, K+, P, SOC, N, Fe, Zn, and Mn and the litter dry matter total content of Ca, Mg, K, P, TOC., N, Fe, Zn. The land use has affected the macrofauna community parameters S, H’, and J (p&lt;0.05). The macrofauna density did not differ between land use systems Pasture and Secondary Forest (p&gt;0.05). The evaluated indexes were highly correlated with the disturbance level, increasing gradually from the Pasture, where the lowest levels were found, to the Secondary Forest with the best indexes in this study, with 29 families exclusive to this land use system. Correlations between the community structure and soil and litter chemical parameters were not detected. <![CDATA[Abundance and diversity of beetles (Insecta: Coleoptera) in land use and management systems]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100406&lng=en&nrm=iso&tlng=en ABSTRACT Soil beetles’ communities are responsible for many ecosystem services, and are very sensitive to environmental changes. Thus, this study aimed to evaluate the abundance and diversity of the soil coleoptera fauna under uses and management and also to identify relationships of the beetle community with soil’s physical and chemical properties. The experiment had six experimental plots set up an Oxisol (Latossolo): corn (CO), soybean (SO), 7-year-old eucalyptus (EI), 4-year-old eucalyptus (EII), preserved Cerrado (PC), and disturbed Cerrado (DC). Soil beetles were sampled at 128 points for each experimental plot, where the soil physical and chemical properties were analyzed. The Coleoptera fauna organisms were identified at the family, subfamily, and gender level, and then, the number of individuals per day, richness, Shannon diversity indexes, and Pielou evenness were determined. The data were analyzed using multivariate techniques (hierarchical grouping and factor analysis). On total, 750 specimens of beetles were collected, distributed into 9 families, 14 subfamilies, and 27 genera. The most abundant family was Scarabaeidae (11 genera) with the highest occurrence in the PC (143 specimens) and DC (81 specimens). Cultivation with SO presented the greatest number of trap day individuals (ind trap-1 day-1 = 0.548); however, the highest diversity was found in the PC. (20 taxonomic groups) and CO (16 taxonomic groups). Shannon diversity was higher for the CO (H’ = 3.107), followed by the PC (H’ = 2.699), and the lowest value was found for the SO (H’ = 1.530). The similarity dendrogram grouped the plots into two extracts, demonstrating how the intensity of land use influences the abundance and diversity of beetle fauna. The factor analysis grouped the Coleoptera and the physical and chemical soil properties in two factors: elements related to the state of aggregation and porous system’s elements. The Coleoptera community was influenced by the intensity of land use and the portion with anthropized natural vegetation showed the highest richness, demonstrating that the Coleoptera fauna responds to environmental changes. Edaphic beetles in the different use and management systems were primarily related to soil physical properties, which explain the state of aggregation (pH, altitude, Ca2+, BD, clay, macroporosity, silt, K+, and microporosity) and the porous soil system (sand and total porosity). <![CDATA[Comparison of field measurement methods of nitrous oxide soil emissions: from the chamber to the vial]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100407&lng=en&nrm=iso&tlng=en ABSTRACT Nitrous oxide (N2O) is a greenhouse gas that contributes substantially to global climate change. The N2O soil emissions have a large uncertainty because of its low atmospheric concentration levels and enormous spatial and temporal variability, which hinders its correct field measurement. For this reason, there are many papers focused on improving the N2O measurements in the field, which focus on different parts of the measurement process. However, no studies have focused on determining the appropriate method, in terms of simplicity and precision, for the sample extraction from inside of the chambers and its transfer to the storage vials, although this step is key in the sampling process. This study aimed to assess and compare the accuracies of three simple and economical methods in transfer soil emitted N2O from inside of the chambers to the vials. For this, a highly accepted method (vacuum by manual pump) and two simpler alternative methods (gas exchange by displacement and vacuum by syringe) were compared. Thirty static chambers were assessed with the quantified N2O emission values varied from 0 to 450 µg m-2 h-1 of N-N2O. Out of the three assessed methods, the vacuum method through the use of a manual vacuum pump was the best to quantifying N2O soil emissions (capturing 57 % of the highest emission values), followed by the gas exchange method by displacement (30 %), and finally by the vacuum method by syringe extraction (13%). <![CDATA[Soil compaction effect on black oat yield in Santa Catarina, Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100408&lng=en&nrm=iso&tlng=en ABSTRACT Cultivated soils, when submitted to agricultural practices, tend to compact due to the pressure exerted by agricultural machines and implements, a process that compromises soil quality and system sustainability. Specific properties of each soil, such as particle size and organic matter content, interfere with the process and degree of compaction and, consequently, plant growth. This study aimed to analyze the effect of different degrees of compaction (DC) on soil physical properties and black oat (Avena strigosa Schreb) growth. For this purpose, four soils were collected: Latossolo Vermelho distrófico retrático (Ferralsol LVCN), Cambissolo Húmico alumínico típico (Cambisol CHLG), Nitossolo Bruno distrófico típico (Nitisol NBPA), and Nitossolo Bruno distrófico húmico (Nitisol NBSJ). They were submitted to five degrees of compaction (bulk densities corresponding to 80, 85, 90, 95, and 100 % DC), defined by their relation to the maximum density obtained by the Normal Proctor Test. For each DC, porosity, soil water retention curve, penetration resistance, hydraulic conductivity, and aeration capacity were determined. In a greenhouse, the oats were cultivated in the four soils with five different degrees of compaction. The experiment was carried out in a completely randomized design, factorial scheme, and five replications. Crop measurements included the growth rate, shoot dry matter, and forage quality analysis. Soil compaction changed the physical properties of soils. In all tested soils, macroporosity and total porosity decreased, more intensely at LVCN. It had macroporosity below the critical level (0.10 m3 m-3) from DC 85. Hydraulic conductivity also decreased in all soils, which is evidence of significant environmental degradation from DC 90 onwards. Microporosity increased in the four soils due to compaction effect, and it is one of the reasons why permanent wilting point has increased. It resulted in a problem at NBSJ, mainly because it reduced the available water volume at DC 90, 95, and 100. Penetration resistance has also increased from DC 80 to 100 at all soils, exceeding the limit of 2 MPa in DC 80 for NBSJ, DC 85 for NBPA and LVCN, and DC 95 for CHLG, representing a risk to root development. Regarding black oat crop, there was a reduction in shoot dry matter only in Cambisol and in the higher DC, fiber content keeps within a satisfactory amount, without affecting forage quality in all soils and DC, thus showing that black oat is tolerant to compaction. <![CDATA[Sand fraction is not suitable for forensic investigations in subtropical soils]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100409&lng=en&nrm=iso&tlng=en ABSTRACT Most of the forensic comparison of soils has focused on the clay and silt fractions at the expense of the coarser particles. This study aimed to test the potential of elemental and physical analyses in the sand fraction from subtropical soils to discriminate samples collected in areas under different parent material (claystone and marble) and in areas with the same parent material at a simulated crime scene. Scanning electron microscopy coupled to an energy dispersive X-ray spectrometer (SEM-EDS) analysis was used on the finer sized sand particles (0.05-0.25 mm). X-ray diffraction (XRD) and particle size distribution (PSD) analyses were performed on the whole sand fraction. These methods did not provide clear discrimination of the sand of the soils sampled in the subtropical environment. This can be explained by the large homogenization observed in the sand fraction related to its chemical (EDS), physical (particle size distribution), morphological (SEM), and mineralogical (XRD). Under tropical and subtropical conditions, the chemical weathering processes dissolve most of the primary minerals, such as the feldspars, biotite, and Fe-bearing particles, and concentrates quartz in the sand fraction. In these environments, we recommend the prioritization of the finer soil fractions for forensic studies, both inorganic and organic. <![CDATA[Greenhouse gas emissions during rice crop year affected by management of rice straw and ryegrass]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100410&lng=en&nrm=iso&tlng=en ABSTRACT One of the challenges in rice areas is the sustainable post-harvest system, which involves using rice straw management and cover crop species. In this context, this study aimed to evaluate the emission of methane (CH4) and nitrous oxide (N2O) with the use of different post-harvest management of rice straw as well as with the combined use of ryegrass. A field experiment was conducted during the 2016 off-season and 2016/17 rice crop season with different post-harvest rice straw management: maintaining rice straw on the soil surface (No-tillage); incorporating straw into dry soil with a disc (Disc); incorporating straw into flooded soil with a roller crimper (Roller Crimper); maintaining rice straw on the soil surface with subsequent rolling of the soil with a roller (Roller). In each straw management, treatments with and without ryegrass were established. The results demonstrate that incorporating rice straw in flooded soil with a roller crimper increases CH4 emissions in the off-season, and used in combination with ryegrass, proved to be the most significant contributor to partial global warming potential. Most annual N2O emissions occur in the off-season for all management treatments, especially for the no-tillage treatment, which showed increased emissions when combined with the use of ryegrass. However, as global warming potential is influenced mainly by emissions of CH4, the no-tillage system showed the best mitigation potential on greenhouse gas emissions. <![CDATA[Pedotransfer functions: the role of soil chemical properties units conversion for soil classification]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100427&lng=en&nrm=iso&tlng=en ABSTRACT Chemical soil analysis data can be expressed by weight (i.e., gravimetric basis) or volume (i.e., volumetric basis) of the fine earth (sieved ≥2 mm), resulting in different units, cmolc kg-1 and cmolc dm-3, respectively. The research problem is that the difference between methods to express the same soil properties hinders the comparison of results and database or dataset standardization. This paper aims to develop pedotransfer functions (PTF) to obtain the density of fine earth, which will then be used for conversion data expressed in volumetric to gravimetric basis, or vice versa, that will be applied to compare results and to standardize databases with different units. Soils samples, including profiles of the main soil orders in Brazil such as Latossolos (Ferralsols or Oxisols) and Argissolos (Acrisols or Ultisols), from the states of Rondônia, Roraima, and Mato Grosso do Sul (132 horizons) were selected and weighed (in triplicate) to obtain the fine earth mass contained in a volume of 10 cm3. The mass values were used to calculate the fine earth density. Spearman’s correlation analysis was used between the density and nine soil properties (coarse sand, fine sand, total sand, silt, clay, clay dispersed in water, clay dispersion, particle density, and organic carbon). The total sand, clay, and organic carbon showed the best correlations, therefore they were selected to construct the pedotransfer functions. Nonlinear regression techniques were used to obtain the models (PTFs) to predict density, which was used for unit conversion. As a result, the residual standard error (RSE) statistics of the models were: 0.0920, 0.1231, and 0.1633 g cm-3, respectively for PTF1 (using total sand as a predictor), PTF2 (using clay), and PTF3 (using organic carbon). Independent data was used to evaluate the accuracy of the models by residue analysis and the RSE. For the validation, the lowest RSE obtained was from the PTF1, so the best performance. Thus, to convert values of the chemical properties from a volumetric to gravimetric basis, the value must be divided by the predicted density. While, the conversion from gravimetric to volumetric basis requires that the value be multiplied by the predicted density. The PTFs using the properties total sand, clay, and organic carbon as predictor variables, allowed conversion of analytical data of soil samples expressed in the volumetric basis to gravimetric and vice versa, which can be used for dataset or database standardization. <![CDATA[Incorporation in soil and addition of enzyme inhibitor as a way to increase the efficiency of pig slurry and mineral fertilizer]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100500&lng=en&nrm=iso&tlng=en ABSTRACT The incorporation of nitrogen (N) fertilizers in the soil and the use of enzyme inhibitors (EI) can improve the efficiency of N fertilization by reducing losses by ammonia volatilization and nitrate leaching. This study aimed to evaluate the efficiency of EI addition and fertilizer incorporation on both grain and dry mass yields of corn as well as on some soil chemical properties, with focus on N availability. A field experiment was carried out for three years in randomized blocks with four replications. The treatments consisted of a 2 × 5 factorial, including two forms of fertilizers application: superficial (SUP) and incorporated (INC), allocated in the plots; and five fertilizations: mineral fertilizer (NPK); NPK + EI; pig slurry (PS); PS+EI; and control (TEST), allocated in the subplots. The soil mineral N content was determined at 30, 60, and 90 days after fertilizer application (DAA) and these times were considered as sub-subplots. All fertilizers increased the dry corn matter and grain yields and the soil availability of N, P, and K, mainly in the upper layer (0.00-0.05 m). However, only the PS promoted higher productivity when incorporated into the soil relative to the soil superficial application. The incorporation of fertilizers increases soil available P but has little effect on soil mineral N. The EI addition to the fertilizers promotes higher soil mineral N contents in the soil until 30 and 60 DAA respectively when superficially applied and soil incorporated, although this does not increase the corn productivity. <![CDATA[Interrill erodibility of different sandy soils increases along a catena in the Caiuá Sandstone Formation]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100501&lng=en&nrm=iso&tlng=en ABSTRACT Soil erosion in tropical areas is a major problem for sustainability in agriculture and soil stability. In the Northwest of Paraná, cassava crop is produced using a conventional tillage system along a catena consisting of different soil classes: Ferralsols (near the summit), Lixisols (mid-slope), and Arenosols (foot-slope). Therefore, differential soil erosion rate and soil degradation are expected along the catena. Here, we test the erodibility of the three sandy soil classes in a representative catena of the Caiuá Sandstone Formation. Disturbed soil samples were collected from a depth of 0.20 m. The soil erodibility test was performed in the laboratory through a multi-drop rainfall simulator. A rainfall intensity of 55 mm h-1 with an energy of 453 Jm2 h-1 was applied for the rainsplash tests (splash pan), whereas a rainfall intensity of 65 mm h-1 with an energy of 534 Jm2 h-1 was applied for the soil erodibility tests (using a small flume). The three soils showed differences in soil particles detached by raindrop on very fine sand class &lt;0.15 mm as follows: Ferralsols 10 %, Arenosol 12 %, and Lixisol 15 %. The maximum soil erodibility increased gradually according to the soil position on the catena: Ferralsols (1.81 × 106 kg s m-4), Lixisols (2.83 × 106 kg s m-4), and Arenosols (3.41 × 106 kg s m-4). Finally, the position of the soil along the catena and total sand were the best in explaining soil interrill erodibility. Therefore, farmers and stakeholders should be cautious about applying a homogeneous tillage system from the summit to the foot-slope along a catena with different sandy soils. <![CDATA[Nitrogen doses and nutritional diagnosis of virus-free garlic]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100502&lng=en&nrm=iso&tlng=en ABSTRACT The recommendations of nitrogen (N) fertilization in garlic are still based on different varieties of the current types that are infected with phytopathogenic virus. There are several methods for recommendation of nitrogen (N) fertilization in garlic, but there are no enough methods for N diagnosis in garlic obtained by meristem culture. The objective of this work was to evaluate methods for diagnosing the nutritional status of virus-free garlic subjected to N doses through the use of a specific NO3- meter in soil solution and foliar sap, portable chlorophyll meter, N content in the leaf, and its relationship with yield and quality of the bulbs. The experiments were conducted with the use of virus-free seed bulbs from the meristem culture from three sites in the 2015 growing season and two locations in the 2016 growing season in South Brazil. The treatments consisted of the application of five nitrogen doses (0, 100, 200, 300, and 400 kg ha-1) distributed in three applications during the crop cycle: 1/3 in planting, 1/3 between 30 and 40 days after planting, and 1/3 after visual bulb differentiation. The highest commercial yield was associated with doses between 269 and 307 kg ha-1 of N and the content of 26 g kg-1 of N, in the diagnostic leaf. The relative chlorophyll content was the only diagnostic technology that showed a significant correlation with commercial yield in all experimental conditions. The evaluation of the N status in the virus-free garlic crop by a portable chlorophyll meter can be a quick strategy for recommending N fertilization and ensuring high yields. <![CDATA[Assessment of soil erosion in olive orchards (<em>Olea europaea L</em>.) under cover crops management systems in the tropical region of Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100503&lng=en&nrm=iso&tlng=en ABSTRACT In the tropics, water erosion is one of the most important factors leading to the degradation and deterioration of agricultural land. Olive orchards have a low canopy coverage, especially during the first years after planting, due to the low density of olive trees. Given the fast expansion of olive orchards in Brazil, this study aimed to evaluate the effect of cover vegetation on soil and water losses under natural rainfall. In addition, it was assessed the crop performance and the vegetation cover index in different management systems in olive orchards. The study was carried out in soil erosion plots, where water and sediment were sampled and measured over two crops season, under the following treatments: in the first season, bare soil with olive cultivation (OBS); olive trees intercropped with spontaneous vegetation (OSV); olive trees intercropped with jack beans (OJB); olive trees intercropped with millet (OM) and, as a control, only bare soil (BS). In the second season, the OM treatment was replaced by olive trees intercropped with sunn hemp (OSH). On bare soils, soil loss was the highest reaching 303.9 Mg ha-1 yr-1 and where the surface runoff amounted to 484.8 mm yr-1. However, in the absence of competition for resources with other crops, olive trees performed best under this system. The olive orchards planted in shallow and sloping soils without cover crops showed unsustainable soil loss, crusting, and sealing in the superficial soil layer, which can progress quickly for soil degradation in the future. The efficiency in the reduction of loss in relation to bare soil was 4.11 and 12.93 % for the soil loss and 12.15 and 25.17 % for water loss, respectively, for olive with spontaneous vegetation and olive with jack beans. Cover crops combined with olive trees, and reconciled with the crop performance aspects of cultivation in tropical regions, is of great relevance for improving sustainability, especially regarding the reduction of soil and water losses due to water erosion. <![CDATA[Interpretation of soil phosphorus availability by Mehlich-3 in soils with contrasting phosphorus buffering capacity]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100504&lng=en&nrm=iso&tlng=en ABSTRACT Increasingly rational use of phosphate fertilizers by agriculture is important, especially in Brazil, due to its importance for global food security and its high dependence on phosphate fertilizers for crop production. Thus, correlation and calibration researches with soil available phosphorus (P) extractants to improve the recommendation and the use of P are extremely important. Our objectives were (i) to determine soil P recovery rates and critical levels by the extractants Mehlich-1 (M1), Mehlich-3 (M3), and Ion Exchange Resin (RTI); (ii) to adjust predictive models of P recovery rates and critical levels for each extractant, as a function of soil properties related to the soil P buffer capacity, and (iii) to adjust the an interpretation table of soil P availability by M3 taking into account soil P buffer capacity indices. A pot experiment under greenhouse condition was conducted, in which the treatments were generated by the combination of a factorial 12 × 6, being 12 soil samples collected at a layer of 0.00-0.20 m, and six doses of P. The experimental units were constituted by plastic pots with capacity for 2.0 dm3 of soil, in which four hybrid corn plants (Zea mays L.) were cultivated for 45 d. The experimental design was a randomized complete block with four replicates. After cultivation, soil samples were collected from each experimental unit, and the determination of soil available P was performed by the extractants. The remaining P and the clay content were the soil properties that best correlated with the P recovery rates and P critical levels in the soil by the M1 and M3. The IER did not show sensitivity to soil P buffer capacity. The M3 had a discontinuous loss of extraction capacity with increasing soil P buffer capacity. Therefore, it is recommended the use of M3 as P extractant in soils with different characteristics, but a measure of soil P buffer capacity such as remaining P or clay content have to be used. <![CDATA[Banana crop nutrition: insights into different nutrient sources and soil fertilizer application strategies]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100505&lng=en&nrm=iso&tlng=en ABSTRACT Considerable attention has been given to the development of new nutritional management strategies that can contribute to banana production be overestimated. The present study was motivated by the possibility that fertilizer application in front of the daughter plant might be more effective than application to the total banana production area. This study aimed to determine the most suitable site for soil collection to evaluate the chemical properties when fertilizer is applied in front of the daughter plant; to evaluate the efficacy of organic-mineral fertilizer in terms of soil nutrient availability, and to evaluate the effect on banana production. The experiment was conducted in three consolidated areas of banana plantation in Santa Catarina State. The effects of the combination of two main factors were evaluated: three fertilizer sources (mineral, mineral + organic compost or organic-mineral) and two application management (total area or in front of the plants), together with time (three years) and location (three municipalities). Each treatment was evaluated using a grid containing 20 banana plants (spaced at 2.5 × 2.5 m), with three replications of two plants in the central part. The experiment was arranged in a completely randomized design with three replicates. The use of a mineral source reduced the pH over the years, regardless of the application technique. Application of fertilizers in front of the daughter plant increased available P and K in the soil, compared to the application of fertilizers to the total area “uniformly distributed between banana planting lines and between plants”. In addition, the increase in soil P content was higher using organic-mineral sources. The nutrient contents in the banana leaves did not differ according to the fertilization source. The application of fertilizers in front of the daughter plant optimized banana fertilization and increased fruit production. Under these fertilization conditions, soil for chemical analyses should be collected at around 0.70 m from the site of fertilizer application. <![CDATA[Nitrous oxide emissions from a tropical Oxisol under monocultures and an integrated system in the Southern Amazon – Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100506&lng=en&nrm=iso&tlng=en ABSTRACT Although agriculture and livestock systems represent important sources of N2O from the soil, they may also aid in emissions mitigation, mainly when integrated systems are taken into account, such as crop-livestock-forest, for food production. This work assessed the soil N2O emissions from a tropical Oxisol under row-crop, livestock, forest monocultures, and an integrated crop-livestock-forest system in the Southern Amazon - Brazil. Soil N2O emissions were measured using static chambers from November 2014 to October 2016 in four soil use systems [row-crop, livestock, forest, and integrated crop-livestock-forest (CLF)], and in a reference area under native forest fragment. For the whole period, the average of soil N2O fluxes was 16.9, 12.2, and 15.4 µg N2O-N m-2 h-1, to row-crop, livestock, and CLF systems, respectively, all with a similar average among them. The lowest fluxes were observed in the forest system and native forest fragment, with average fluxes of 4.0 and 6.3 µg N2O-N m-2 h-1, respectively, both lower than the agricultural systems. The largest soil N2O fluxes were observed throughout the rainy seasons in the row-crop, livestock, and CLF, mostly after N-fertilizer application to the soil surface or in the planted row. As a consequence, the cumulative emissions were greater in row-crop, livestock, and CLF systems, which in the averages of two cycles emitted respectively 1.40, 1.15, and 1.27 kg N2O-N ha-1 yr-1, all different of the forest system and native forest fragment (0.33 and 0.52 kg N2O-N ha-1 yr-1, respectively). Nitrogen fertilization and soil moisture influenced soil N2O emissions of all systems assessed in the Southern Amazon. The N2O emissions took place after both factors were met, corroborating the hole-in-the-pipe model. Even with more soil use intensification, once in the same area there were three cultures in succession during a year and perennial trees, CLF did not lead to greater N2O emissions from the soil than row-crop and livestock. Thus, CLF represents a good option for N2O mitigation for the edaphic and climatic conditions of the Southern Amazon. <![CDATA[Controlled-release nitrogen fertilizers: characterization, ammonia volatilization, and effects on second-season corn]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100507&lng=en&nrm=iso&tlng=en ABSTRACT The development of new fertilizer technologies to reduce nitrogen (N) losses from an agricultural system and to increase nitrogen use efficiency (NUE) is a global research objective. Controlled-release nitrogen fertilizers have shown great potential for reducing N losses and synchronizing N release according to crop demand, thereby improving the NUE. The objective of this study was to characterize controlled-release nitrogen fertilizers and compare them with conventional nitrogen sources in terms of N release, N loss via NH3 volatilization, and fertilizer effects on second-season corn. The field experiment was performed on an Ultisol in a randomized block design. The treatments consisted of two conventional nitrogen sources (urea and ammonium sulfate) and three brands of polymer-coated urea (PCU; Agrocote®, FortBlen®, and Kimcoat®). The variables N release and N loss by NH3 volatilization were subjected to nonlinear regression analysis using a logistic model and the Korsmeyer-Peppas model, respectively. Leaf N content and dry matter yield were subjected to the Tukey test, and the morphologies of the PCUs were observed by scanning electron microscopy (SEM). Electron micrographs revealed differences in the number of layers and the thickness of the coatings of the studied PCUs. FortBlen®, containing granules with single- or double-layer coatings with thicknesses ranging from 34.53 to 50.34 µm, promoted more gradual N release and reduced N-NH3 losses by 36.4 % compared with those observed with uncoated urea. Kimcoat® released approximately 98 % of the applied N within 24 hours, resulting in N-NH3 volatilization, and the responses in second-season corn were similar to those with uncoated urea. Although no benefits were observed in second-season corn for PCUs over uncoated nitrogen sources, some PCUs promoted more gradual N release and reduced N-NH3 volatilization, providing a promising alternative for environments prone to N loss. <![CDATA[Nutrient uptake and removal by sweet potato fertilized with green manure and nitrogen on sandy soil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100508&lng=en&nrm=iso&tlng=en ABSTRACT Sweet potato crops take up large amounts of nutrients, especially nitrogen. In low-fertility soils, the addition of nitrogen (N) increases the sweet potato yield. Green manure may be an alternative method for improving soil quality and supplying nutrients to this crop. This study aimed to evaluate the plant’s nutritional status and the amount of nutrients taken up and removed by sweet potato plants subjected to green manure and mineral N fertilization. The experiment was carried out in the field for two growing seasons using a randomized block design in a split-plot scheme with four replications. The plots consisted of a control treatment (spontaneous weeds) and the previous cultivation of Crotalaria spectabilis and Mucuna aterrima. The subplots consisted of four N rates (0, 50, 100, and 200 kg ha-1) that were applied to the sweet potato. The species M. aterrima is more suitable for use as green manure in the sweet potato than C. spectabilis. Nitrogen application rates promoted a greater increase in the biomass of the storage root, nutrient uptake, and removal in the sweet potatoes unfertilized with green manure. In the sweet potato fertilized with M. aterrima, mineral N supply in excess (above 50 kg ha-1) increases the nutrient uptake and removal without a significant increase in the biomass of the storage root. In the sweet potatoes unfertilized with green manure, high rates of N (greater than 120 kg ha-1) must be applied to obtain the utmost biomass of the storage root, nutrient uptake and removal. <![CDATA[Establishment of critical nutrient levels in soil and plant for eucalyptus]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100509&lng=en&nrm=iso&tlng=en ABSTRACT The adoption of more productive and nutrient-demanding genotypes, in addition soils with low availability of nutrients of soils under forest plantations, lead high fertilizer demand and justify research that seeks to rationalize the use of these inputs. Therefore, we aimed with this research to determine classes of interpretation of soil fertility using boundary line (BL) and estimate macronutrient sufficiency ranges for eucalyptus. Fertility classes and sufficiency ranges were obtained using a database of areas cultivated with eucalyptus in the Central-East region of Minas Gerais, Brazil, totaling 689 plots, containing information on yield, leaf contents, and soil chemical properties. Scatter plots were drawn relating the mean annual increment (MAI) in trunk volume (relative) with soil organic matter (OM), phosphorus (P), potassium (K+), calcium (Ca2+), and magnesium (Mg2+) of the 0.00-0.20 m layer. Those graphs and equations were used to estimate soil fertility classes. Leaf contents of N, P, K, Ca, and Mg were plotted with soil contents of OM, P, K+, Ca2+, and Mg2+. Using the Quadrant Diagram of the plant-soil Relationship (QDpsR) method, horizontal and vertical lines were drawn separating the cloud of points in four quadrants. With the points at the quadrants III and I, regression equations were fitted. To obtain foliar sufficiency ranges, soil values of critical and optimal levels of OM, P, K+, Ca2+, and Mg2+, obtained by BL, were substituted in the equations generated by the QDpsR method. The appropriate soil content ranges determined by BL for productivity of 47.7 m3 ha-1 yr-1 were: 24.75-38.28 g kg-1 of OM, 8.5-14.6 mg dm-3 of P, 100.0-150.35 mg dm-3 of K+, 0.77-1.47 cmolc dm-3 of Ca2+, and 0.25-0.43 cmolc dm-3 of Mg2+. Leaf content ranges determined by QDpsR are: 19.4-21.3 g kg-1 of N, 1.0-1.2 g kg-1 of P, 8.5-10.6 g kg-1 of K, 4.8-6.1 g kg-1 of Ca, and 1.9-2.4 g kg-1 of Mg. The critical levels of nutrients in the soil, obtained by the BL method, and the leaf sufficiency ranges, obtained using the QDpsR method, are similar to those existing in the literature. This indicates that this methodology is reliable in establishing standards and that the critical levels obtained can be used to improve the recommendation of fertilizers for eucalyptus. <![CDATA[Soil loss as a desertification risk indicator: mapping and simulation in the Salitre River Sub-Basin, Northeast Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100510&lng=en&nrm=iso&tlng=en ABSTRACT Discussions on desertification frequently highlight soil erosion as a striking feature of this phenomenon. In particular, the high spatial density of gullies represents a strong indication of the formation of desertification hotspots. In this study, through field activities and Monte Carlo simulations, we estimated the volume of soil loss by linear erosion on the slopes of the middle course of the Salitre river in the North of Bahia State. This estimative contributes to the recognition of a desertification process in the studied local. The lengths of the gullies and rills, visible through high-spatial-resolution satellite images, were vectorized. The width and depth of the Linear Erosion Features (LEFs) were measured through field study and recorded via geoprocessing. Statistical treatment was applied to the data to indicate the probability of occurrence of the width and depth classes. Subsequently, the Monte Carlo simulation was used to indicate the volume of soil removed from the slopes by the linear erosion process. Several ramified systems of LEFs are identified and mapped. Monte Carlo simulation fits the measured data well. Estimates indicate that linear erosion event eroded approximately 450,000 m3 of soil in an area of 2,000 hectares, which indicates extreme land degradation. <![CDATA[Residual and immediate effect after 16 applications of organic sources on yield and nitrogen use efficiency in black oat and corn]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100511&lng=en&nrm=iso&tlng=en ABSTRACT Soils with a long-term history of animal manure application exhibit higher residual effects of nitrogen (N) in soil and can affect the efficiency with which N will be used. This study aimed to evaluate how the immediate and residual effect of 16 applications of animal manure reflects on yields of black oat and corn rotation system, as well as N use efficiency. The study was carried out in no-tillage from 2004 to 2016 in Brazil. The treatments were pig slurry (PS), dairy slurry (DS), pig deep-litter (PL), mineral fertilizer (MF), and control (C). Prior to the sowing of black oat, in which 16 animal manure applications had already been made, an area of the soil was delimited where the treatments were not applied. This area was referred to as unfertilized (U) soil. Applications were carried out in the remaining area and were referred to as fertilized (F) soil. The highest dry matter yield and N accumulation in black oat and corn were found in F soils treated with DS and PL, respectively. In corn, the highest grain yield and N accumulation in grains were found with DS and PS. In U soil, the 16 applications (of DS especially) resulted in yields and N accumulation greater than the control and MF, but lower than those in F. The highest N use efficiency was found with DS. The history of animal manure applications was not enough to rule out additional applications in the following years. <![CDATA[New methods for estimating lime requirement to attain desirable pH values in Brazilian soils]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100512&lng=en&nrm=iso&tlng=en ABSTRACT In Brazil, empirical models are traditionally used to determine lime requirement (LR), but their reliability is doubtful in most cases, since they can lead to under- or overestimation of LR for different soil types. In this study, the most critical characteristics influencing LR were selected to develop reliable models for predicting LR that raise soil pH to optimum values for crop production in Brazil. Soil samples (n = 22) with varying proportions of clay (5-88 %) and organic matter (OM) levels (3.78-79.35 g kg-1) were used to develop the models. Organic matter and potential acidity (HAl) combined with ΔpH [target pH(H2O) - initial pH(H2O)] were the best predictor variables for estimating LR. Four models were developed (OMpH5.8, OMpH6.0, HAlpH5.8, and HAlpH6.0) for estimating LR to attain target pH values of 5.8 or 6.0 with reasonably high prediction performance (0.758≤ R2 ≤0.886). An algorithm was further developed for selecting the LR to be recommended among those estimated by the models. The proposed algorithm enables to select the minimum LR that ensure the adequate supply of Ca and Mg to plants and does not exceed the levels of soil HAl, thus preventing excessive pH increase. The new predictive models were less sensitive to predict LR high enough to meet Ca2+ and Mg2+ requirements of plants in soils containing levels of HAl lower than 5 cmolc dm-3 and OM lower than 40 g kg-1. However, they ensured an adequate supply of Ca2+ and Mg2+ to plants and avoided the overestimation of LR for most soils used in this research. Validation via an independent dataset (n = 100 samples) confirmed the good predictive performance of the models across a wide range of soil types. In summary, the proposed models can be used as good alternatives to traditional methods for predicting LR for a great variety of Brazilian soils. Further, they are versatile and may be easily deployed in soil testing laboratories, since soil pH, OM, and HAl are characteristics determined in routine analysis. <![CDATA[Potential of wind erosion and dust emission in an arid zone of northern Mexico: A simple assessment method]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100513&lng=en&nrm=iso&tlng=en ABSTRACT Wind erosion is the main problem that arid lands in northern Mexico are facing. Quantification of this phenomenon is crucial for planning purposes and to scale its impact. The challenge is to assess the problem under limited availability of climatic information. This study aimed to identify potential areas of dust emissions in an arid zone of Northern Mexico. Wind direction and intensity were characterized through a robust index that involves rainfall and evaporation as well as the climatic factor of the general wind erosion equation. A method for assessing the likelihood of dust emission associated with wind erosion was applied. Data from twelve weather stations within the region of the study was analyzed. The variables considered were wind velocity and direction, temperature, and precipitation. A wind rose of wind direction and intensity was obtained. Results showed that the Thornthwaite’s method for computing the Soil Moisture Index (SMI) is a good approach when computing the climatic factor C of the general function of the potential average annual soil loss. Given the lack of local evaporation data, the precipitation-evaporation ratio P E for each weather station was computed as an intermediate step towards the computation of C. Three of the analyzed climatic stations had intermediate C values (36-71 %) in the scale of wind erosion climatic factor. The wind velocities registered in these climatic stations ranged from 15 to 30 km h -1 . The magnitude-frequency analysis of the P E parameter for the stations showed the differences in rainfall and evaporation regimes. Dust pollution prone areas were identified, showing areas where conservation strategies should be directed. <![CDATA[Critical levels and sufficiency ranges for leaf nutrient diagnosis by two methods in soybean grown in the Northeast of Brazil]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100514&lng=en&nrm=iso&tlng=en ABSTRACT Establishing sufficiency ranges and critical levels of nutrients are important for a correct evaluation of plant nutrition through leaf diagnosis. This study aimed to propose critical levels and sufficiency ranges of macro and micronutrients based on leaf diagnosis of soybean plants. The database used was generated from 86 samples of the third trifoliate leaf without petiole, collected during the flowering stage from soybean plants of the main cultivars used in the states of Piauí and Maranhão, Northeast region of Brazil. The results of macro and micronutrients and grain yield were used to calculate the critical level by the reduced normal distribution and boundary line methods, the latter was also used to generate the sufficiency ranges. Nutrient levels for 90 % maximum grain yield were considered for the critical level by the reduced normal distribution, and nutrient levels at the upper line of a dispersion diagram were considered for the boundary line method, using the relation between grain yield and nutrient concentration to generate sufficiency ranges for 95 and 99 % maximum grain yields. The critical levels generated by the boundary line method presented a larger number of deficient samples than the reduced normal distribution method, except for boron. The sufficiency ranges generated by the boundary line with 95 % of the maximum grain yield could not diagnose nutrient deficiency, except for copper. The critical levels by the reduced normal distribution and boundary line methods for leaf diagnosis of soybean were 40.2 and 42.1 g kg-1, 3.2 and 3.4 g kg-1, 17.6 and 19.5 g kg-1, 8.7 and 10.3 g kg-1, 4.7 and 4.9 g kg-1, 2.1 and 2.4 g kg-1, 44 and 44 mg kg-1, 5 and 12 mg kg-1, 125 and 145 mg kg-1, 33 and 34 mg kg-1, and 48 and 63 mg kg-1 for N, P, K, Ca, Mg, S, B, Cu, Fe, Mn, and Zn, respectively. The critical levels by boundary line showed better distribution for leaf diagnosis for excess, deficiency, and adequate nutrient levels. The sufficiency ranges by the boundary line method for N, P, K, Ca, Mg, S, B, Cu, Fe, Mn, and Zn were 38.6-45.7 g kg-1, 3.1-3.7 g kg-1, 18.3-20.7 g kg-1, 9.4-11.3 g kg-1, 4.4-5.3 g kg-1, 2.1-2.7 g kg-1, 35-53 mg kg-1, 10-14 mg kg-1, 131-159 mg kg-1, 23-46 mg kg-1, and 58-68 mg kg-1, respectively. The reduced normal distribution and boundary line methods allowed the generation of critical levels and sufficiency ranges for leaf diagnosis of soybean. The sufficiency range generated by the boundary line with 95 % maximum grain yield showed no prevalence of diagnosis of nutrient deficiency, except for copper. <![CDATA[How is the learning process of digital soil mapping in a diverse group of land use planners?]]> http://www.scielo.br/scielo.php?script=sci_arttext&pid=S0100-06832020000100600&lng=en&nrm=iso&tlng=en ABSTRACT The use of new technologies, the development of new software, and the advances in the machines ability to process data have brought a new perspective to soil science and especially to pedology, with the advent of digital soil mapping (DSM). To meet the demand for soil surveys in Brazil, it will be necessary to popularize the techniques used in DSM. To identify and map the soil to generate maps of land use capability, we proposed a theoretical and practical course focused on the training in DSM for professionals involved in the management of land resources. The methodology was divided into five modules: I. Introduction to pedology, soil-landscape relationship, soil survey and soil classification (theory); II. Identification of soils in the field and study of the soil-landscape relationship (practice); III. Digital soil mapping and geographic information system (theory) and obtaining environmental covariates (practice); IV. Statistical learners and quality measures of spatial predictions (theory) and spatial pseudo-sampling (practice); V. Database organization, calibration, and validation of predictive models (practice). Results such as the average level of confidence of the participants in the soil classification, as well as the number of pseudo-sampling classified by the participants, chosen statistical apprentice, environmental covariables used, and overall accuracy, were influenced by the participants level of knowledge regarding DSM soils and techniques. The structure, focus, and time of each module should be based on the participants needs. It is suggested that a survey should be carried out to consider the level of knowledge in relation to the topics addressed in DSM before the preparation and execution of the course. The contribution of individual experiences showed the importance of multidisciplinarity in the teaching-learning process because it is a technique that involves soil knowledge, statistics, and mathematics applied to geoinformation science to understand soil variability in the landscape. The practical classes were fundamental, enabling an approximation of the content studied with the participants’ reality and consolidation of the acquired knowledge. In general, the course was well evaluated by the participants regarding the contents covered and practical field training and laboratory geoprocessing, who reported that the practical classes were fundamental for the appropriation of knowledge in DSM. This course could be a model for the PronaSolos, which tend to have heterogeneous groups of participants, being necessary to plan specific protocols to tend the particularity.