Soil water retention data are fundamental in soil modeling studies. Temperate pedotransfer functions (PTFs) have been commonly used to estimate water retention of Brazilian soils, mainly because of the lack of soil data for Brazil. However, these PTFs may not be suitable for tropical or subtropical conditions such as those found in Brazil. The objective of this study was to establish a dedicated Hydrophysical Database for Brazilian Soils (HYBRAS) suitable for PTF development. Data present in HYBRAS comprise 445 soil profiles with 1075 samples and are representative of a wide range of Brazilian soils. The data are organized in a relational structure of tables that cover general site descriptions, land cover, and hydrophysical and chemical measurement methods. Raw data (e.g., water retention points covering the 0-15,000-cm suction range) and derived data are included in the tables. Another objective of this study was to use the database to compare the accuracy of water retention estimates based on PTFs developed for Brazilian and temperate regions. In general, the Brazilian PTFs performed better than the temperate models, especially for weathered (Ferralsols, Acrisols, and Nitisols) finetextured (clay, sandy clay, clay loam, silty clay loam, and silty clay) soils. Silt content was not a successful criterion for distinguishing performance of Brazilian and temperate PTFs for Brazilian weathered soils. The water retention of weathered soils was shown to differ from that of temperate soils due to differences in pore structure resulting from their clay content and mineralogical nature, thus confirming results reported in the literature.Abbreviations: HYBRAS, Hydrophysical Database for Brazilian Soils; HYPRES, Hydraulic Properties of European Soil; ME, mean error; pF, log 10 suction; PTF, pedotransfer function; UNSODA, Unsaturated Soil Hydraulic Database; VG, van Genuchten.Soil water retention data are fundamental in soil modeling studies. Their direct measurement is costly and demands intense field work, which makes it infeasible for large areas. As a result, pedotransfer functions (PTFs) (Bouma, 1989) are being developed and used increasingly to estimate water retention data from routinely available soil measures.Brazil plays an important role in the development of tropical water retention PTFs (Botula et al., 2014). Barros and de Jong van Lier (2014) extensively reviewed water retention PTFs for Brazilian soils. These PTFs are commonly developed to estimate the available water content on the basis of field capacity and permanent wilting point, with their use often restricted to certain types of soils or geographic regions (Barros and de Jong van Lier, 2014). To our knowledge and according to Barros and de Jong van Lier (2014), the studies by Tomasella and Hodnett (1998), Tomasella et al. (2000Tomasella et al. ( , 2003, da Silva (2002), de Mello et al. (2005), Fidalski and Tormena (2007), da Silva et al. (2008), Fiorin (2008, Barros et al. (2013) and Medrado and Lima (2014) are the main publications on PTF developme...

SUMMARYCan vinasse accelerate the change of minerals in rock dust to obtain fertilizers, using residues from alcohol agro-industries and mining? Answering this question was the main objective of this study. Therefore, an experiment was set up in the laboratory in a completely randomized design using Polyvinyl Chloride (PVC) columns, in which the 0-50 cm layers of a clayey soil (eutroferric Red Oxisol) and sandy soil (Typic Quartzipsamment) were reproduced. We applied three different rates of basalt powder (0.0; 2.0, and 4.0 t ha -1 ) and one rate of vinasse (200 m 3 ha -1 ) to the soils. The control was made by treatments with water (200 m 3 ha -1 ) with the same rates of rock powder. Samples were first collected on the surface of each column (1, 15, 30, 45, 60, and 90 days after the application of vinasse and rock powder), and, at the end of the experiment, at the various depths and in leached water, to determine pH and the concentration of soluble Ca 2+ , Mg 2+ , and K + . There was a significant effect of the solvent and the soil on the surface layer, with higher concentrations found in the treatments with vinasse and in clayey soil, confirming the potential of vinasse to alter minerals in basalt powder. The resulting levels from the beginning to the end of the experiment suggest that sorption phenomena with neoformed mineral phases or organic acids may have occurred. It may be concluded that the use of rock powder and vinasse mixtures is a promising alternative for soil fertilization and recycling of waste from the sugarcane and mining industries.Index terms: basalt powder, pH, cation availability, reuse of waste.( RESUMO: EFEITO DE PÓ DE ROCHA E VINHAÇA EM DOIS TIPOS DE SOLOSA vinhaça pode acelerar a alteração de minerais em pó de rocha para obtenção de fertilizantes, com aproveitamento de resíduos de agroindústrias de álcool e de mineradoras? Responder a esta pergunta foi o principal objetivo deste estudo. Assim, foi montado em laboratório um experimento no delineamento inteiramente casualizado em colunas de PVC, onde se reproduziram as camadas de 0-50 cm de um solo argiloso (Latossolo Vermelho muito argiloso) e de um solo arenoso (Neossolo Quartzarênico). Aos solos, foram adicionadas três doses de pó de basalto (0; 2,0; e 4,0 t ha -1 ) e uma dose de vinhaça (200 m 3 ha -1 ). O controle foi feito por meio de tratamentos com água (200 m 3 ha -1 ) e com as mesmas doses de pó de rocha. Foram coletadas amostras na superfície de cada coluna (1, 15, 30, 45, 60 e 90 dias após a aplicação da vinhaça e do pó de rocha) e, ao final do experimento, em profundidade e no lixiviado, para determinar o pH e os teores solúveis de Ca 2+ , Mg 2+ e K + . Houve efeito significativo do solvente e do solo, na camada superficial, com maiores teores nos tratamentos com vinhaça e no solo argiloso, confirmando o potencial da vinhaça para alterar minerais contidos no pó de basalto. No balanço de teores no início e no fim do experimento, os resultados sugeriram que fenômenos de sorção com fases minerais neoformadas ou com ácidos orgân...

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The objective of this study was to evaluate the effect of the fungus Aspergillus niger strain CCT4355 in the release of nutrients contained in two types of rock powder (diabase and phonolite) by means of in vitro solubilization trials. The experimental design was completely randomized in a 5 x 4 factorial design with three replications. It was evaluated five treatments (phonolite dust + culture medium; phonolite dust + fungus + culture medium; diabase powder + culture medium; diabase powder + fungus + culture medium and fungus + culture medium) and four sampling dates (0, 10, 20 and 30 days). Rock dust (0.4% w/v) was added to 125 mL Erlenmeyer flasks containing 50 mL of liquid culture medium adapted to A. niger. The flasks were incubated at 30°C for 30 days, and analysis of pH (in water), titratable acidity, and concentrations of soluble potassium, calcium, magnesium, zinc, iron and manganese were made. The fungus A. niger was able to produce organic acids that solubilized ions. This result indicates its potential to alter minerals contained in rock dust, with the ability to interact in different ways with the nutrients. A significant increase in the amount of K was found in the treatment with phonolite dust in the presence of the fungus. The strain CCT4355 of A. niger can solubilize minerals contained in these rocks dust.

Access to soil hydrological data is vital for hydrology projects and for supporting decision-making in issues related to the availability of food and water and the forecasting of phenomena related to geomechanics. Brazil is a country of continental dimensions and has accumulated a significant body of soil information, holding a prominent position in tropical soil science. Nevertheless, a database with hydrophysical information on Brazilian soils has not been compiled so far, whereas much information is registered and analyzed. In this study we discuss the potential for the development of a Brazilian hydrophysical database and pedotransfer functions (PTFs). We present on metadata the measurement methods of soil hydrophysical

Patterns in the errors of three pedotransfer functions (PTFs) for estimating water retention at −10 and −1500 kPa were investigated using a data set of Brazilian soils. Of the three PTFs, one was developed using soils from temperate regions, one using soils from different tropical areas, and one was specifically based on Brazilian soils. We used classification tree models to obtain rules that represent patterns in PTF errors, reflecting differences between measured and predicted water content values. These errors were classified as acceptable or unacceptable according to a defined threshold. The tree models had an accuracy of about 70% and could be used to identify the main attributes that control PTF performance. For the temperate PTF, the main error controls were silt content at −10 kPa and clay content at −1500 kPa. Overall, acceptable errors at one pressure head occurred under the same conditions as the unacceptable errors at the other pressure head. The tree rules reflected the differences between the data sets used to generate the PTFs and the data set used to evaluate the PTFs. Geographical closeness appeared to be insufficient to ensure good performance of a PTF. Rather, the statistical distribution of the input attributes used to develop PTFs plays a more important role in error classification. Classification trees allow us to better understand the factors that control PTF performance and how these factors interact.

ABSTRACT:The aim of this study was to evaluate the performance of pedotransfer functions (PTFs) available in the literature to estimate soil bulk density (ρb) in different regions of Brazil, using different metrics. The predictive capacity of 25 PTFs was evaluated using the mean absolute error (MAE), mean error (ME), root mean squared error (RMSE), coefficient of determination (R 2 ) and the regression error characteristic (REC) curve. The models performed differently when comparing observed and estimated ρb values. In general, the PTFs showed a performance close to the mean value of the bulk density data, considered as the simplest possible estimation of an attribute and used as a parameter to compare the performance of existing models (null model).The models developed by Benites et al. (2007)

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