Funções de pedotransferência relacionadas à variabilidade espacial da retenção de água em solos de várzea

The estimation of non available soil variables through the knowledge of other related measured variables can be achieved through pedotransfer functions (PTF) mainly saving time and reducing cost. Great differences among soils, however, can yield non desirable results when applying this method. This study discusses the application of developed PTFs by several authors using a variety of soils of different characteristics, to evaluate soil water contents of two Brazilian lowland soils. Comparisons are made between PTF evaluated data and field measured data, using statistical and geostatistical tools, like mean error, root mean square error, semivariogram, cross-validation, and regression coefficient. The eight tested PTFs to evaluate gravimetric soil water contents (Ug) at the tensions of 33 kPa and 1,500 kPa presented a tendency to overestimate Ug 33 kPa and underestimate Ug1,500 kPa. The PTFs were ranked according to their performance and also with respect to their potential in describing the structure of the spatial variability of the set of measured values. Although none of the PTFs have changed the distribution pattern of the data, all resulted in mean and variance statistically different from those observed for all measured values. The PTFs that presented the best predictive values of Ug33 kPa and Ug1,500 kPa were not the same that had the best performance to reproduce the structure of spatial variability of these variables.A estimativa de variáveis do solo não disponíveis, por meio do conhecimento de outras variáveis medidas, pode ser obtida com o uso de funções de pedotransferência (FPT) com economia de tempo e custos. Entretanto, havendo grande diferença entre os solos, o uso desse método pode conduzir a resultados indesejáveis. Neste estudo é discutida a aplicação de FPTs desenvolvidas por alguns autores usando solos de diferentes características, para avaliar a retenção de água em dois solos de várzea brasileiros. As comparações foram feitas entre os dados medidos e estimados pelas FPTs, usando ferramentas estatísticas e da geoestatística, como erro médio, raiz quadrada do erro médio, semivariogramas, validação cruzada e coeficiente de regressão. As oito FPTs testadas para avaliar o conteúdo gravimétrico de água no solo (Ug) sob as tensões de 33 e 1.500 kPa apresentaram tendência em superestimar Ug 33 kPa e em subestimar Ug 1.500 kPa. As FPTs foram classificadas de acordo com seu desempenho e também em relação ao seu potencial em descrever a estrutura de variabilidade espacial do conjunto de dados medidos. Embora nenhuma das FPTs tenha alterado o padrão de distribuição dos dados, todas resultaram em média e variância estatisticamente diferentes daquelas verificadas para o conjunto dos valores medidos. As FPTs com melhor capacidade preditiva dos valores de Ug33 kPa e Ug1.500 kPa não foram as mesmas que tiveram o melhor desempenho para reproduzir a estrutura de variabilidade espacial dessas variáveis.ICTP (Trieste-Italy)Ghent University (Ghent-Belgium)CNPqCoordenacao de Aperfeicoamento de Pessoal de Nivel Superior (CAPES)EMBRAPA - Clima Temperad

Comparação da cinética de adsorção de azul de metileno utilizando cinza de casca de arroz ativada com diferentes agentes químicos

Activated carbon is widely used in several industrial sectors and has a high production cost. To reduce costs, different materials have been studied, for example, rice husks (RH). RH is an abundant, low-cost residue of the agricultural sector and can be used to generate energy due to its high calorific value. However, burning husk generates waste, the ashes. Thus, the objective of this work was to optimize the synthesis of activated carbon using pre-carbonized RH with different chemical agents as activators (KOH, NaOH, NaCl, H₂SO₄, and Na₂CO₃), at different particle sizes. Subsequently, Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), and energy dispersive spectroscopy (EDS) were used to characterize the materials. Of these, KOH was the best activating agent. The adsorption kinetics for the adsorbents was 30 min, reaching equilibrium after 70 min. Of the three fitted kinetic models, pseudo-second-order and Elovich best fit the data. The FT-IR shows that the adsorbents have oxygenated surface groups such as alcohol, ester, ether, and phenol. From the point of zero charge, the predominance of negative charges on the surface of the adsorbents is observed. Therefore, the activated carbon from rice husk ash (RHA) showed potential in the adsorption of the methylene blue dyes.O carvão ativado é amplamente utilizado em diversos setores industriais e apresenta alto custo de produção. De modo a reduzir custos, diferentes materiais vêm sendo estudados, a exemplo da casca de arroz. Esta é um resíduo abundante do setor agrícola, apresenta baixo custo de obtenção e pode ser utilizada na geração de energia graças ao seu alto poder calorífico. Contudo, a queima da casca gera resíduo, as cinzas. Assim, o objetivo do trabalho foi otimizar a síntese de carvão ativado utilizando casca de arroz pré-carbonizada com diferentes agentes químicos como ativantes (KOH, NaOH, NaCl, H₂SO₄ e Na₂CO₃), em diferentes granulometrias; e, posteriormente, espectroscopia de infravermelho por transformada de Fourier (FT-IR), microscopia eletrônica de varredura (MEV) e espectroscopia de raios X dispersiva de energia (EDS) foi aplicado na caracterização dos materiais. Destes, o KOH foi o melhor agente ativador. A cinética de adsorção para os adsorventes foi de 30 min, atingindo equilíbrio em 70 min. Dos três modelos cinéticos ajustados, pseudossegunda ordem e Elovich foram os que melhor se ajustaram aos dados. O FT-IR demonstra que os adsorventes apresentam grupos de superfícies oxigenados como álcool, éter, éster e fenol. Do ponto de carga zero em diante, observa-se a predominância de cargas negativas na superfície dos adsorventes. Sendo assim, o carvão ativado da cinza de casca de arroz mostrou-se promissor na adsorção do corante azul de metileno

Variability of hydromorphic soils: a state space approach.

Soil land leveling is a technique used in low land areas and has the objective to improve agricultural use to facilitate the management of water both for irrigation and drainage operations, for the establishment of agricultural practices and crop harvest. However, it causes changes in the physical environment where the plant grows, and many studies have sought to identify the effect of this practice in the structure of soil spatial variability and in the relationship between the hydric-physical and chemical soil attributes. Thus, the objective of this study was to identify and characterize the structure of spatial variability of soil hydric-physical and chemical attributes of a low land soil, before and after land leveling, and to study the relationship between these soil attributes through an autoregressive state space model. In an experimental area of 0.81 ha belongs to Embrapa Clima Temperado situated in Capão do Leão county, state of Rio Grande do Sul, Brazil, was established a regular grid of 100 points spaced 10 m apart in both directions. At each point, soil disturbed and undisturbed samples were collected at the depth of 0-0.20 m to determine, before and after land leveling, the following soil attributes: clay, silt and sand contents, soil macroporosity, soil microporosity and soil total porosity, soil bulk density and soil water content at field capacity and permanent wilting point, soil organic carbon and cation exchange capacity. All data sets were organized into a spreadsheet in the form of a spatial transect consisting of 100 points and they were ordered following the gradient slope area resulting from the soil land leveling. Autocorrelograms and crosscorrelograms were built to evaluate the structure of spatial correlation of all soil attributes having served as a subsidy for the selection of variables in each autoregressive state-space model. The results show that the soil land leveling changed the structure of soil spatial dependence of all variables and between them as well. The soil cation exchange capacity and soil microporosity variables were the variables that made up the largest number of state space models, before and after soil land leveling. The contribution of the each variable at position i-1 to estimate its value at position increased to the sand content, silt content, soil bulk density, soil microporosity, soil macroporosity, soil water content at permanent wilting point, soil organic carbon and cation exchange capacity variables and decreased to soil water content at field capacity variable after land leveling. Soil land leveling improved the state space model performance for soil organic carbon content, sand content, soil bulk density, soil total porosity and soil water content at field capacity and permanent wilting point variables. The worst state space model performances, after soil land leveling, were found taking silt content, soil microporosity and cation exchange capacity variables as response variables. The best state space model performance, before land leveling, was obtained taking the soil total porosity as response variable.A sistematização do solo é uma técnica utilizada em regiões planas, com características de várzea, e tem por objetivo aperfeiçoar o uso agrícola facilitando o manejo da água tanto de irrigação como de drenagem, as operações de implantação da lavoura, de tratos culturais e de colheita. No entanto, a sistematização do solo provoca alterações no ambiente físico onde a planta se desenvolve, sendo que muitos estudos têm buscado identificar o efeito dessa prática na estrutura de variabilidade espacial e no relacionamento entre os atributos físico-hídricos e químicos do solo. Dessa forma, o objetivo deste trabalho foi identificar e caracterizar a estrutura de variabilidade espacial dos atributos físico-hídricos e químicos de um solo de várzea, antes e depois da sistematização, assim como estudar o relacionamento entre esses atributos por meio de um modelo autoregressivo de espaço de estados. Em uma área experimental de 0,81 ha pertencente a Embrapa Clima Temperado, Capão do Leão-RS, foi estabelecida uma malha regular de 100 pontos, espaçados de 10 m entre si em ambas as direções. Em cada ponto foram coletadas amostras de solo deformadas e com estrutura preservada na profundidade de 0-0,20 m para a determinação, antes e depois da sistematização, dos teores de argila, silte e areia, macroporosidade, microporosidade e porosidade total, densidade do solo, conteúdo de água retido na capacidade de campo e ponto de murcha permanente, carbono orgânico e capacidade de troca de cátions. Os dados foram organizados em uma planilha de cálculo na forma de uma transeção espacial composta de 100 pontos e foram ordenados seguindo o gradiente de declividade da área resultante do processo de sistematização do solo. Para avaliar a estrutura de correlação espacial foram construídos autocorrelogramas e crosscorrelogramas que serviram de subsídio para a seleção de variáveis em cada um dos modelos autoregressivos de espaço de estados. Os resultados mostram que a sistematização do solo alterou a estrutura de dependência espacial tanto da variável como entre as variáveis deste estudo. A capacidade de troca de cátions e a microporosidade do solo foram as variáveis que compuseram o maior número de modelos de espaço de estados, antes e depois da sistematização. A contribuição da variável na posição i-1 na estimativa na posição i, por meio do modelo autoregressivo de espaço de estados, aumentou com a sistematização para as variáveis teor de areia, teor de silte, densidade do solo, microporosidade, macroporosidade, conteúdo de água no solo retido no ponto de murcha permanente, carbono orgânico e da capacidade de troca de cátions; e diminuiu para a variável conteúdo de água no solo retido na capacidade de campo.A sistematização do solo melhorou a estimativa, por meio dos modelos de espaço de estados, das variáveis carbono orgânico, teor de areia, densidade do solo, macroporosidade e do conteúdo de água no solo retido na capacidade de campo e no ponto de murcha permanente, sendo o modelo da variável porosidade total, antes da sistematização, que apresentou o melhor desempenho. Já os piores desempenhos dos modelos, depois da sistematização do solo, foram encontrados quando utilizadas as variáveis teor de silte, microporosidade e capacidade de troca de cátions como resposta

State-space Approach To Evaluate Effects Of Land Levelling On The Spatial Relationships Of Soil Properties Of A Lowland Area

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Land levelling is an agricultural practice to correct soil surface irregularities turning the area more efficient for management of agronomic inputs. The technique has been adopted mainly in lowland areas used for flood irrigation of rice. As a result sub-surface soil layers may be exposed with possible impact on crop production by changing soil properties. This study aimed to evaluate the effects of land levelling on the spatial relationships of soil properties. Relations among them were quantified using a state-space approach in different scenarios constructed from data sets in a 1 ha lowland area sampled as a grid. The grid consisted of 100 sampling points (10 m x 10 m), with samples collected from the 0-0.20 m soil layer, before and after levelling, totalizing 200 samples. Soil water contents at field capacity (theta(FC)) and permanent wilting point (theta(PWP)) were taken as response variables due to their importance on rice water management. Sand, silt and clay contents, soil microporosity (Micro) and bulk density (BD), cation exchange capacity (CEC), organic carbon content (Corg), and the depth of the top of the B horizon in relation to soil surface (DTB) were used as co-variables through an evaluation of their spatial auto- and cross-correlation behaviors with theta(FC) and theta(PWP). Eight data-array scenarios were tested. Results showed that levelling induced negative effects on soil quality since this procedure decreased theta(FC) and theta(PWP), Corg, and CEC as well as increased BD. Using the state-space approach, we concluded that its performance in estimating theta(FC) and theta(PWP) was affected by the scenarios after levelling, the best performance being for the vertical scenarios. DTB and CEC contributed to the estimation of both soil water contents for all scenarios after levelling. The main problem associated to the levelling is the cutting of shallow soils which decreases their capacity to store water and to exchange cations in the effective arable depth which will be explored by the crop root system. As DTB is directly related to the spatial distribution of taxonomic soil profile properties, the state-space approach, which considers sampling location coordinates, may be a potential on-site-specific tool aiming at the recuperation of degraded soils through amendments since it opens the possibility for farmers to manage a crop field based on local environmental properties, with their spatial association and localized variation being a function of the distance between their measurements. (C) 2014 Elsevier B.V. All rights reserved.145135147Abdus Salam International Centre for Theoretical Physics (ICTP), Trieste, ItalyConselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES

State-space approach to evaluate effects of land levelling on the spatial relationships of soil properties of a lowland area

Land levelling is an agricultural practice to correct soil surface irregularities turning the area more efficient for management of agronomic inputs. The technique has been adopted mainly in lowland areas used for flood irrigation of rice. As a result sub-surface soil layers may be exposed with possible impact on crop production by changing soil properties. This study aimed to evaluate the effects of land levelling on the spatial relationships of soil properties. Relations among them were quantified using a state-space approach in different scenarios constructed from data sets in a 1 ha lowland area sampled as a grid. The grid consisted of 100 sampling points (10 m × 10 m), with samples collected from the 0–0.20 m soil layer, before and after levelling, totalizing 200 samples. Soil water contents at field capacity (θFC) and permanent wilting point (θPWP) were taken as response variables due to their importance on rice water management. Sand, silt and clay contents, soil microporosity (Micro) and bulk density (BD), cation exchange capacity (CEC), organic carbon content (Corg), and the depth of the top of the B horizon in relation to soil surface (DTB) were used as co-variables through an evaluation of their spatial auto- and cross-correlation behaviors with θFC and θPWP. Eight data-array scenarios were tested. Results showed that levelling induced negative effects on soil quality since this procedure decreased θFC and θPWP, Corg, and CEC as well as increased BD. Using the state-space approach, we concluded that its performance in estimating θFC and θPWP was affected by the scenarios after levelling, the best performance being for the vertical scenarios. DTB and CEC contributed to the estimation of both soil water contents for all scenarios after levelling. The main problem associated to the levelling is the cutting of shallow soils which decreases their capacity to store water and to exchange cations in the effective arable depth which will be explored by the crop root system. As DTB is directly related to the spatial distribution of taxonomic soil profile properties, the state-space approach, which considers sampling location coordinates, may be a potential on-site-specific tool aiming at the recuperation of degraded soils through amendments since it opens the possibility for farmers to manage a crop field based on local environmental properties, with their spatial association and localized variation being a function of the distance between their measurements145135147CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO - CNPQCOORDENAÇÃO DE APERFEIÇOAMENTO DE PESSOAL DE NÍVEL SUPERIOR - CAPESSem informaçãoSem informaçã