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 (R2) 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) (BEN-C) and by Manrique and Jones (1991) (M&J-B) presented the best results. The separation of data into two layers according to depth (0-10 cm and 10-30 cm) demonstrated better performance in the 10-30 cm layer. The REC curve allowed for a simple and visual evaluation of the PTFs.

A 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 m³ ha-1). O controle foi feito por meio de tratamentos com água (200 m³ 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 Ca2+, Mg2+ 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 orgânicos podem ter ocorrido. Concluiu-se que o uso de mistura de pó de rocha e vinhaça é uma alternativa promissora para a adubação de solos e para o reaproveitamento de resíduos da indústria sucroalcooleira e de mineradoras.

Can 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 m³ ha-1) to the soils. The control was made by treatments with water (200 m³ 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 Ca2+, Mg2+, 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.

Este trabalho objetivou avaliar o efeito do fungo Aspergillus niger, linhagem CCT4355, na liberação de nutrientes contidos em pós de dois tipos de rocha (fonolito e diabásio), por meio de ensaios de solubilização in vitro. O delineamento experimental foi o inteiramente casualizado, em esquema fatorial 5x4, com três repetições. Foram avaliados cinco tratamentos (pó de fonolito + meio; pó de fonolito + fungo + meio, pó de diabásio + meio, pó de diabásio + fungo + meio e fungo + meio) e quatro épocas de amostragens (0, 10, 20 e 30 dias). Adicionou-se pó de rocha (0,4% m/v) a Erlenmeyers de 125 mL, com 50 mL de meio de cultura líquido adaptado para A. niger. Os frascos foram incubados a 30 °C, por 30 dias, e foram feitas análises de pH em água, acidez titulável e teores de potássio, cálcio, magnésio, zinco, ferro e manganês solúveis. O A. niger foi capaz de produzir ácidos orgânicos que solubilizaram íons. Este resultado indica o potencial de A. niger para alterar minerais contidos em pós de rocha, com capacidade de interagir de diferentes formas com os nutrientes. Houve aumento significativo da quantidade de K solúvel, no tratamento com pó de fonolito, em presença do fungo. Conclui-se que a linhagem CCT4355 de A. niger pode solubilizar minerais contidos nesses pós de rochas.

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.