Suzana Romeiro Araújo

Cadmium availability and accumulation by lettuce and rice

Among the toxic elements, Cd has received considerable attention in view of its association with a number of human health problems. The objectives of this study were to evaluate the Cd availability and accumulation in soil, transfer rate and toxicity in lettuce and rice plants grown in a Cd-contaminated Typic Hapludox. Two simultaneous greenhouse experiments with lettuce and rice test plants were conducted in a randomized complete block design with four replications. The treatments consisted of four Cd rates (CdCl2), 0.0; 1.3; 3.0 and 6.0 mg kg-1, based on the guidelines recommended by the Environmental Agency of the State of Sao Paulo, Brazil (Cetesb). Higher Cd rates increased extractable Cd (using Mehlich-3, Mehlich-1 and DTPA chemical extractants) and decreased lettuce and rice dry matter yields. However, no visual toxicity symptoms were observed in plants. Mehlich-1, Mehlich-3 and DTPA extractants were effective in predicting soil Cd availability as well as the Cd concentration and accumulation in plant parts. Cadmium concentration in rice remained below the threshold for human consumption established by Brazilian legislation. On the other hand, lettuce Cd concentration in edible parts exceeded the acceptable limit.

Variation of routine soil analysis when compared with hyperspectral narrow band sensing method.

The objectives of this research were to: (i) develop hyperspectral narrow-band models to determine soil variables such as organic matter content (OM), sum of cations (SC = Ca + Mg + K), aluminum saturation (m%), cations saturation (V%), cations exchangeable capacity (CEC), silt, sand and clay content using visible-near infrared (Vis-NIR) diffuse reflectance spectra; (ii) compare the variations of the chemical and the spectroradiometric soil analysis (Vis-NIR). The study area is located in Sao Paulo State, Brazil. The soils were sampled over an area of 473 ha divided into grids (100 × 100 m) with a total of 948 soil samples georeferenced. The laboratory RS data were obtained using an IRIS (Infrared Intelligent Spectroradiometer) sensor (400–2,500 nm) with a 2-nm spectral resolution between 450 and 1,000 nm and 4-nm between 1,000 and 2,500 nm. Satellite reflectance values were sampled from corrected Landsat Thematic Mapper (TM) images. Each pixel in the image was evaluated as its vegetation index, color compositions and soil line concepts regarding certain locations of the field in the image. Chemical and physical analysis (organic matter content, sand, silt, clay, sum of cations, cations saturation, aluminum saturation and cations exchange capacity) were performed in the laboratory. Statistical analysis and multiple regression equations for soil attribute predictions using radiometric data were developed. Laboratory data used 22 bands and 13 “Reflectance Inflexion Differences, RID” from different wavelength intervals of the optical spectrum. However, for TM-Landsat six bands were used in analysis (1, 2, 3, 4, 5, and 7).Estimations of some tropical soil attributes were possible using laboratory spectral analysis. Laboratory spectral reflectance (SR) presented high correlations with traditional laboratory analyses for the soil attributes such as clay (R2 = 0.84, RMSE = 3.75) and sand (R2 = 0.85, RMSE = 3.74). The most sensitive narrow-bands in modeling (using 474 observations) these attributes were B8 (1,350–1,417 nm), B10 (1,417–1,449 nm), B11 (1,449–1,793 nm), B15 (1,927–2,102 nm), B16 (2,101–2,139 nm), and B17 (2,139–2,206 nm); B7 (975–1,350 nm), B10, B11, B16, B19 (2,206–2,258 nm) and B21 (2,258–2,389 nm) for clay and sand, respectively. The bands selected to model sand and clay, by orbital data, were 3, 5 and 7 of TM-Landsat-5 and 2, 5 and 7 sand and clay, respectively. The use of soil analysis methodology by ground remote sensing constitutes an alternative to traditional routine laboratory analysis.

Analysing the effects of applying agricultural lime to soils by VNIR spectral sensing: a quantitative and quick method

The potential of visible and near-infrared (VNIR) diffuse reflectance spectra to predict the chemical properties of Ferralsols and Arenosols cultivated with maize during four crop cycles were evaluated. The study was carried out in a greenhouse and aimed to (i) evaluate soil chemistry variation induced by plants and the application of lime with different degrees of reactivity using conventional methods and proximal soil-sensing techniques, (ii) identify the wavelength ranges related to soil chemistry changes, and (iii) construct models that predict soil chemistry attributes using soil VNIR spectra. Treatments used were three lime rates applied to raise the base saturation to 40%, 60% and 80% and one control. Partial least squares regression with cross-validation was used to establish relationships between the VNIR spectra and the reference data from chemical analyses. The predicted results were evaluated based on the values of coefficient of determination (R2), the ratio of the standard deviation of the validation set to the root mean square error of cross-validation (RPD), and the root mean square of prediction. The predicted results were excellent (R2 > 0.90 and RPD > 3) for potassium and for the lime requirement calculation. Good predictions (0.81 < R2 < 0.90 and 2.5 < RPD < 3) were also obtained for pH and sum of bases. The resulting models for exchangeable calcium, cation exchangeable capacity, and base saturation had moderate predictive power (0.66 < R2 < 0.80 and 2.0 < RPD < 2.5). Our findings suggest that VNIR reflectance spectroscopy could be used as a rapid, inexpensive, and non-destructive technique to predict some soil chemistry properties for these soil types. As this methodology evolves, it may eventually permit real-time analyses of soil variability and real-time management responses via sensors installed on tractors.

Soil contaminated with chromium by tannery sludge and identified by vis-NIR-mid spectroscopy techniques

Soil contamination is an ever-growing concern and demands efficient methods for diagnosis of areas under suspected contamination. Spectroscopy reflectance vis-NIR has been shown to be a reliable and environmentally friendly method for the rapid detection and monitoring of soil properties. Despite the use of vis-NIR it is necessary to test the effectiveness of other wavelengths (mid-IR 4000–400 cm−1). We aim with this study to (1) evaluate the contamination of Cr applied by tannery sludge and CrCl3·6H2O in tropical soils through sequential extraction procedures and spectroscopy techniques; (2) identify parameters of soil spectral variation (vis-NIR-mid) associated with Cr and explore their viability in the evaluation of contaminated soils; and (3) investigate the feasibility of using soil spectral data and chemometrics methods to predict Cr in soils. Results indicate that metal adsorption to soil constituents caused expressive changes in soil spectral curves, showing differentiation between highly contaminated soils and those that are relatively contaminant-free. Cr content can be predicted by spectroscopy reflectance in vis-NIR-mid data. The mid-IR models of Cr outperformed vis-NIR. Organic matter played a more important role in determining soil spectral signatures than the mineralogical characteristics of soils, especially in those with high organic carbon content.

Aplicação de calcário com diferentes graus de reatividade: alterações químicas no solo cultivado com milho

With acidity correction, important nutrients for the corn development become more available to the plants, increasing yield. The objective of this study was to evaluate chemical changes in two soils and corn dry matter yield as affected by lime application with different degrees of reaction. The experiment was carried out in a greenhouse on a Oxisol and a Quartzpsament. Three rates of three commercial limes were applied, one with mean reactivity A (RE = 85.7 %; PRNT = 88.3 %), another with low reactivity B (RE = 83.7 %; PRNT = 76.2 %) and C (RE = 99.1 %; PRNT = 105.3 %) with high reactivity, in four successive corn cycles. A randomized complete block design was used with four replications. The treatments consisted of three lime rates, calculated to increase base saturation to 40, 60 and 80 %, plus a control treatment. In parallel, another experiment was performed to verify the residual lime effect over time by incubation. Liming increased the values of pH, Ca2+ and Mg2+ and reduced Al3+. The best corn development was observed on the Oxisol. In this soil, the limes A and B were more efficient to increase the pH throughout the cycles, whereas product C had the lowest efficiency in Al3+ reduction in the last cycles due its higher reactivity degree. Limes A and C performed similarly in both soils. The shoot dry matter yield declined in the course of the successive corn cycles. In the incubation experiment, the exchangeable calcium content was higher than the residual.

Assessment of soil physical attributes at sowing row and inter-row under no-till system

In no-till systems, two different soil conditions are created during the sowing operation: row and inter-row positions. The objectives of this study were to evaluate, using static and dynamic soil attributes, the influence of no-till sowing operation on creating better physical environment for soybean crop growth. A field transect with clay content ranging from 150 to 400 g kg-1 was selected in Ponta Grossa, Parana State, Brazil, from a Typic Hapludox that has been cultivated under no-till system for 16 years. After soybean harvest, 68 undisturbed soil samples were collected at both sowing row and inter-row positions. The following soil properties were evaluated: saturated hydraulic conductivity, air permeability, bulk density, total porosity, soil moisture at field capacity, texture, and total organic carbon. Multiple regressions among dynamic and static soil properties were fitted, and differences between sowing row and inter-rows were tested by paired t test. Saturated hydraulic conductivity and air permeability were positively correlated with macroporosity (r = 0.75 and 0.74, respectively; p<0.001). Total porosity, bulk density, air permeability, and macroporosity were position-dependent. In general, soil physical quality was higher at row position due to lower bulk density and higher total porosity, hydraulic conductivity, air permeability and macroporosity.

Espectroscopia VIS-NIR-SWIR na avaliação de solos ao longo de uma topossequência em Piracicaba (SP)

Objetivou-se neste trabalho caracterizar diferentes solos por espectrorradiometria de reflectância ao longo de uma topossequencia na regiao de Piracicaba, SP. Amostras de solo foram coletadas e analisadas em campo, em laboratorio de analises quimicas e por sensores Vis-NIR (400-2500 nm). Alteracoes nos solos da topossequencia foram identificaveis nas informacoes espectrais. Constituintes dos solos, tais como, materia orgânica, mineralogia, formas de oxidos de ferro e granulometria foram determinantes nas variacoes das feicoes de absorcao e intensidades de reflectância. Cada perfil mostrou caracteristicas espectrais diferenciadoras entre horizontes, relacionadas a intensidade, feicoes de absorcao e morfologia da curva. A avaliacao morfologica nao pode ser avaliada pelo sensor, sendo uma de suas limitacoes. Existe relacao entre grau de intemperismo (indices ki, relacao silte/argila e mineralogia) e dados espectrais. Isso foi observado nos solos originados de basalto, onde houve aumento do ferro extraido pelo ditionito (cristalino e amorfo) na sequencia Nitossolo Vermelho Latossolico (NVL) em direcao ao Cambissolo (C) e, aumento do ferro amorfo nesta mesma sequencia. Na avaliacao da topossequencia completa observou-se a sequencia de absorcao centrada em 500 e 850 nm decrescente do Nitossolo Vermelho Latossolico em direcao ao Chernossolo, ou seja, na sequencia de decrescimo dos teores de ferro cristalino (hematita e goethita) e aumento de ferro amorfo, corroborado pelo aumento dos valores do indice ki. Houve relacao entre os dados espectrais, o indice ki e a posicao do solo na paisagem. Esses resultados mostram que a espectrorradiometria e uma ferramenta promissora para auxiliar o levantamento de solos. Entretanto, ha necessidade do suporte a implantacao de bibliotecas de dados espectrais de solos com acesso irrestrito aos usuarios.