Effect of grassland management on soil carbon sequestration in Rondonia and Mato Grosso states, Brazil

Grassland management affects soil organic carbon (SOC) content and a variety of management options have been proposed to sequester carbon. However, studies conducted in Brazilian pastures have shown divergent responses for the SOC depending on management practices. Our objective was to evaluate the effects of management on SOC stocks in grasslands of the Brazilian states of Rondonia and Mato Grosso, and to derive region-specific factors for soil C stock change associated with different management conditions. Compared to SOC stocks in native vegetation, degraded grassland management decreased SOC by a factor of 0.91 +/- 0.14, nominal grassland management reduced SOC stock for Oxisols by a relatively small factor of 0.99 +/- 0.08, whereas, SOC storage increased by a factor of 1.24 +/- 0.07 with nominal management for other soil types. Improved grassland management on Oxisols increased SOC storage by 1.19 +/- 0.07, relative to native stocks, but there were insufficient data to evaluate the impact of improved grassland management for other soil types. Using these results, we also evaluated the potential for grassland management to sequester or emit C to the atmosphere, and found that degraded grassland management decreased stocks by about 0.27-0.28 Mg C ha(-1) yr(-1); nominal management on Oxisols decreased C at a rate of 0.03 Mg C ha(-1) yr(-1), while nominal management on others soil types and improved management on Oxisols increased stocks by 0.72 Mg C ha(-1) yr(-1) and 0.61 Mg C ha(-1) yr(-1), respectively. Therefore, when well managed or improved, grasslands in Rondonia and Mato Grosso states have the potential to sequester C. (c) 2008 Elsevier B.V. All rights reserved.

Functional specialization of Eucalyptus fine roots: contrasting potential uptake rates for nitrogen, potassium and calcium tracers at varying soil depths

1. Little is known about the role of deep roots in the nutrition of forest trees and their ability to provide a safety-net service taking up nutrients leached from the topsoil. 2. To address this issue, we studied the potential uptake of N, K and Ca by Eucalyptus grandis trees (6 years of age - 25 m mean height), in Brazil, as a function of soil depth, texture and water content. We injected NO(3)(-)- (15)N, Rb(+) (analogue of K(+)) and Sr(2+) (analogue of Ca(2+)) tracers simultaneously in a solution through plastic tubes at 10, 50, 150 and 300 cm in depth in a sandy and a clayey Ferralsol soil. A complete randomized design was set up with three replicates of paired trees per injection depth and soil type. Recently expanded leaves were sampled at various times after tracer injection in the summer, and the experiment was repeated in the winter. Soil water contents were continuously monitored at the different depths in the two soils. 3. Determination of foliar Rb and Sr concentrations and (15)N atom % made it possible to estimate the relative uptake potential (RUP) of tracer injections from the four soil depths and the specific RUP (SRUP), defined as RUP, per unit of fine root length density in the corresponding soil layer. 4. The highest tracer uptake rates were found in the topsoil, but contrasting RUP distributions were observed for the three tracers. Whilst the RUP was higher for NO(3)(-)- (15)N than for Rb(+) and Sr(2+) in the upper 50 cm of soil, the highest SRUP values for Sr(2+) and Rb(+) were found at a depth of 300 cm in the sandy soil, as well as in the clayey soil when gravitational solutions reached that depth. 5. Our results suggest that the fine roots of E. grandis trees exhibit contrasting potential uptake rates with depth depending on the nutrient. This functional specialization of roots might contribute to the high growth rates of E. grandis trees, efficiently providing the large amounts of nutrients required throughout the development of these fast-growing plantations.

Total carbon measurement in whole tropical soil sample

Soils are an important component in the biogeochemical cycle of carbon, storing about four times more carbon than biomass plants and nearly three times more than the atmosphere. Moreover, the carbon content is directly related on the capacity of water retention, fertility. among other properties. Thus, soil carbon quantification in field conditions is an important challenge related to carbon cycle and global climatic changes. Nowadays. Laser Induced Breakdown Spectroscopy (LIBS) can be used for qualitative elemental analyses without previous treatment of samples and the results are obtained quickly. New optical technologies made possible the portable LIBS systems and now, the great expectation is the development of methods that make possible quantitative measurements with LIBS. The goal of this work is to calibrate a portable LIBS system to carry out quantitative measures of carbon in whole tropical soil sample. For this, six samples from the Brazilian Cerrado region (Argisoil) were used. Tropical soils have large amounts of iron in their compositions, so the carbon line at 247.86 nm presents strong interference of this element (iron lines at 247.86 and 247.95). For this reason, in this work the carbon line at 193.03 nm was used. Using methods of statistical analysis as a simple linear regression, multivariate linear regression and cross-validation were possible to obtain correlation coefficients higher than 0.91. These results show the great potential of using portable LIBS systems for quantitative carbon measurements in tropical soils. (C) 2008 Elsevier B.V. All rights reserved.

Soil nitrous oxide emissions in long-term cover crops-based rotations under subtropical climate

It has been shown that cover crops can enhance soil nitrous oxide (N(2)O) emissions, but the magnitude of increase depends on the quantity and quality of the crop residues. Therefore, this study aimed to evaluate the effect of long-term (19 and 21 years) no-till maize crop rotations including grass [black oat (Avena strigosa Schreb)] and legume cover crops [vetch (Vigna sativa L), cowpea (Vigna unguiculata L. Walp), pigeon pea (Cajanus cajan L. Millsp.) and lablab (Dolichos lablab)] on annual soil N(2)O emissions in a subtropical Acrisol in Southern Brazil. Greater soil N(2)O emissions were observed in the first 45 days after the cover crop residue management in all crop rotations, varying from -20.2 +/- 1.9 to 163.9 +/- 24.3 mu g N m(-2) h(-1). Legume-based crop rotations had the largest cumulative emissions in this period, which were directly related to the quantity of N (r(2) = 0.60, p = 0.13)and inversely related to the lignin:N ratio(r(2) = 0.89,p = 0.01) of the cover crop residues. After this period, the mean fluxes were smaller and were closely related to the total soil N stocks (r(2) = 0.96, p = 0.002). The annual soil N(2)O emission represented 0.39-0.75% of the total N added by the legume cover crops. Management-control led soil variables such as mineral N (NO(3)(-) and NH(4)(+)) and dissolved organic C influenced more the N(2)O fluxes than environmental-related variables as water-filled pore space and air and soil temperature. Consequently, the synchronization between N mineralization and N uptake by plants seems to be the main challenge to reduce N(2)O emissions while maintaining the environmental and agronomic services provided by legume cover crops in agricultural systems. (C) 2009 Elsevier B.V. All rights reserved.

Contribuition of nitrogen from biological nitrogen fixation, nitrogen fertilizer and soil nitrogen on the growth of the common bean and cowpea

Biological nitrogen fixation (BNF) constitutes a valuable source of this nutrient for the common bean Phaseolus vulgaris L and cowpea Vigna unguiculata (L.) Walp., being its avaibility affected by mineral N in the soil solution. The objectives of this work were to evaluate the effects of nitrogen rate, as urea, on symbiotic fixation of N(2) in common bean and cowpea plants, using the isotopic technique, and quantifying the relative contributions of N sources symbiotic N(2) fixation, soil native nitrogen and urea N on the growth of the common bean and cowpea. Non nodulating soybean plants were used as standard. The research was carried out in greenhouse, using pots with 5 kg of soil from a Typic Haplustox (Dystrophic Red Yellow Latosol). The experimental design was completely randomized blocks, with 30 treatments and three replications, arranged in 5x3x2 factorial outline. The treatments consisted of five N rates: 2, 15, 30, 45 and 60 mg N kg(-1) soil; three sampling times: 23, 40 and 76 days after sowing (DAS) and two crops: common bean and cowpea. The BNF decreased with increase N rates, varying from 81.5% to 55.6% for cowpea, and from 71.9% to 55.1% for common bean. The symbiotic N(2) fixation in cowpea can substitute totally the nitrogen fertilization. The nitrogen absorption from soil is not affected by nitrogen fertilizer rate. The N recovery from fertilizer at 76 DAS was of 60.7% by common bean, and 57.1% by cowpea. The symbiotic association in common bean needs the application of a starting dose (40 kg N ha(-1)) for economically acceptable yields.

Fractionation of Zn, Cd and Pb in a Tropical Soil After Nine-Year Sewage Sludge Applications

A long-term field experiment was carried out in the experiment farm of the Sao Paulo State University, Brazil, to evaluate the phytoavailability of Zn, Cd and Pb in a Typic Eutrorthox soil treated with sewage sludge for nine consecutive years, using the sequential extraction and organic matter fractionation methods. During 2005-2006, maize (Zea mays L.) was used as test plants and the experimental design was in randomized complete blocks with four treatments and five replicates. The treatments consisted of four sewage sludge rates (in a dry basis): 0.0 (control, with mineral fertilization), 45.0, 90.0 and 127.5 t ha(-1), annually for nine years. Before maize sowing, the sewage sludge was manually applied to the soil and incorporated at 10 cm depth. Soil samples (0-20 cm layer) for Zn, Cd and Pb analysis were collected 60 days after sowing. The successive applications of sewage sludge to the soil did not affect heavy metal (Cd and Pb) fractions in the soil, with exception of Zn fractions. The Zn, Cd and Pb distributions in the soil were strongly associated with humin and residual fractions, which are characterized by stable chemical bonds. Zinc, Cd and Pb in the soil showed low phytoavailability after nine-year successive applications of sewage sludge to the soil.

Kernel machines for epilepsy diagnosis via EEG signal classification: A comparative study

Objective: We carry out a systematic assessment on a suite of kernel-based learning machines while coping with the task of epilepsy diagnosis through automatic electroencephalogram (EEG) signal classification. Methods and materials: The kernel machines investigated include the standard support vector machine (SVM), the least squares SVM, the Lagrangian SVM, the smooth SVM, the proximal SVM, and the relevance vector machine. An extensive series of experiments was conducted on publicly available data, whose clinical EEG recordings were obtained from five normal subjects and five epileptic patients. The performance levels delivered by the different kernel machines are contrasted in terms of the criteria of predictive accuracy, sensitivity to the kernel function/parameter value, and sensitivity to the type of features extracted from the signal. For this purpose, 26 values for the kernel parameter (radius) of two well-known kernel functions (namely. Gaussian and exponential radial basis functions) were considered as well as 21 types of features extracted from the EEG signal, including statistical values derived from the discrete wavelet transform, Lyapunov exponents, and combinations thereof. Results: We first quantitatively assess the impact of the choice of the wavelet basis on the quality of the features extracted. Four wavelet basis functions were considered in this study. Then, we provide the average accuracy (i.e., cross-validation error) values delivered by 252 kernel machine configurations; in particular, 40%/35% of the best-calibrated models of the standard and least squares SVMs reached 100% accuracy rate for the two kernel functions considered. Moreover, we show the sensitivity profiles exhibited by a large sample of the configurations whereby one can visually inspect their levels of sensitiveness to the type of feature and to the kernel function/parameter value. Conclusions: Overall, the results evidence that all kernel machines are competitive in terms of accuracy, with the standard and least squares SVMs prevailing more consistently. Moreover, the choice of the kernel function and parameter value as well as the choice of the feature extractor are critical decisions to be taken, albeit the choice of the wavelet family seems not to be so relevant. Also, the statistical values calculated over the Lyapunov exponents were good sources of signal representation, but not as informative as their wavelet counterparts. Finally, a typical sensitivity profile has emerged among all types of machines, involving some regions of stability separated by zones of sharp variation, with some kernel parameter values clearly associated with better accuracy rates (zones of optimality). (C) 2011 Elsevier B.V. All rights reserved.

DOES THE CHRONOTYPE CLASSIFICATION NEED TO BE UPDATED? PRELIMINARY FINDINGS

Traditionally, chronotype classification is based on the Morningness-Eveningness Questionnaire (MEQ). It is implicit in the classification that intermediate individuals get intermediate scores to most of the MEQ questions. However, a small group of individuals has a different pattern of answers. In some questions, they answer as ""morning-types"" and in some others they answer as ""evening-types,"" resulting in an intermediate total score. ""Evening-type"" and ""Morning-type"" answers were set as A(1) and A(4), respectively. Intermediate answers were set as A(2) and A(3). The following algorithm was applied: Bimodality Index = (Sigma A(1) x Sigma A(4))(2) - (Sigma A(2) x Sigma A(3))(2). Neither-types that had positive bimodality scores were classified as bimodal. If our hypothesis is validated by objective data, an update of chronotype classification will be required. (Author correspondence: brunojm@ymail.com)

Sequential production of amylolytic and lipolytic enzymes by bacterium strain isolated from petroleum contaminated soil

Amylases and lipases are highly demanded industrial enzymes in various sectors such as food, pharmaceuticals, textiles, and detergents. Amylases are of ubiquitous occurrence and hold the maximum market share of enzyme sales. Lipases are the most versatile biocatalyst and bring about a range of bioconversion reactions such as hydrolysis, inter-esterification, esterification, alcoholysis, acidolysis, and aminolysis. The objective of this work was to study the feasibility for amylolitic and lipolytic production using a bacterium strain isolated from petroleum contaminated soil in the same submerged fermentation. This was a sequential process based on starch and vegetable oils feedstocks. Run were performed in batchwise using 2% starch supplemented with suitable nutrients and different vegetable oils as a lipase inducers. Fermentation conditions were pH 5.0; 30 degrees C, and stirred speed (200 rpm). Maxima activities for amyloglucosidase and lipase were, respectively, 0.18 and 1,150 U/ml. These results showed a promising methodology to obtain both enzymes using industrial waste resources containing vegetable oils.

Classification of normal swallowing and oropharyngeal dysphagia using wavelet

Oropharyngeal dysphagia is characterized by any alteration in swallowing dynamics which may lead to malnutrition and aspiration pneumonia. Early diagnosis is crucial for the prognosis of patients with dysphagia, and the best method for swallowing dynamics assessment is swallowing videofluoroscopy, an exam performed with X-rays. Because it exposes patients to radiation, videofluoroscopy should not be performed frequently nor should it be prolonged. This study presents a non-invasive method for the pre-diagnosis of dysphagia based on the analysis of the swallowing acoustics, where the discrete wavelet transform plays an important role to increase sensitivity and specificity in the identification of dysphagic patients. (C) 2008 Elsevier Inc. All rights reserved.

A classification methodology for the risk of weed infestation using fuzzy logic

Despite modern weed control practices, weeds continue to be a threat to agricultural production. Considering the variability of weeds, a classification methodology for the risk of infestation in agricultural zones using fuzzy logic is proposed. The inputs for the classification are attributes extracted from estimated maps for weed seed production and weed coverage using kriging and map analysis and from the percentage of surface infested by grass weeds, in order to account for the presence of weed species with a high rate of development and proliferation. The output for the classification predicts the risk of infestation of regions of the field for the next crop. The risk classification methodology described in this paper integrates analysis techniques which may help to reduce costs and improve weed control practices. Results for the risk classification of the infestation in a maize crop field are presented. To illustrate the effectiveness of the proposed system, the risk of infestation over the entire field is checked against the yield loss map estimated by kriging and also with the average yield loss estimated from a hyperbolic model.

Study of the water retention properties of a tropical soil

Some peculiarities of water retention in a tropical lateritic soil of clayey nature are presented and discussed. The typical soil microstructure is shown through thin-layer plates emphasizing soil microaggregation and pore distribution and their repercussion on the soil-water retention curve and on hysteresis. It is shown that the clayey soil has a behavior that to a large extent resembles sandy soil, which is characterized by the relatively high saturated hydraulic conductivity, low air-entry value, and small suction range at which water drainage takes place. The severe weathering processes that originated this soil have produced an altered soil that seems to be homogeneous in terms of physical indices, hydraulic conductivity, and soil-water retention characteristics, up to 4.5 m in depth.

Influence of the microstructure in the collapse of a residual clayey tropical soil

A typical residual clayey soil originating from basalt in southern Brazil has been analyzed in order to assess the influence of wetting-induced deformation and microstructural features on the collapse behavior. Single and double oedometer tests were undertaken on a soil profile to 9 m depth. The results indicated collapsible behaviour at all profile depths. The influence of pre-consolidation stress and pedogenetic factors in the variability of the physical characteristics of the soil and in the magnitude of the collapse was noted. The collapse coefficient has been shown to be related to the both the microaggregate plasma and the varying nature of the pores and their interconnectivity.

Collapse behavior of soil in a Brazilian region affected by a rising water table

Collapsible soils are usually nonsaturated, low density, and metastable-structured soils that are known to exhibit a volume reduction following an episode of moisture increase or suction reduction. This paper describes the collapsible behavior of clayey sand based on controlled soil suction tests carried out on undisturbed samples from the city of Pereira Barreto, in the State of Sao Paulo, Brazil. Foundation settlements due to soil collapse are common in this region and occurred during the filling of the reservoir of the Tres Irmaos Dam, which induced the elevation of the groundwater table in different parts of Pereira Barreto. This paper shows that collapse strains depend on the stress and soil suction acting in the sample and that saturation is not necessary for a collapse to occur. The influence of soil suction, gradual wetting, and the wetting and drying cycle on the collapsible behavior of the soil is also shown and discussed.

Inertia in two simple problems of soil hydrodynamics

In the present paper the dynamic solutions of two non-steady seepage problems are discussed. It is shown that the acceleration term in the equation of motion is important for a correct qualitative description of the flow.