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Parfitt J.M.B.,Embrapa Brazilian Agricultural Research Corporation | Timm L.C.,Campus Universitario | Reichardt K.,University of Sao Paulo | Pauletto E.A.,Federal University of Pelotas
Revista Brasileira de Ciencia do Solo

The practice of land leveling alters the soil surface to create a uniform slope to improve land conditions for the application of all agricultural practices. The aims of this study were to evaluate the impacts of land leveling through the magnitudes, variances and spatial distributions of selected soil physical properties of a lowland area in the State of Rio Grande do Sul, Brazil; the relationships between the magnitude of cuts and/or fills and soil physical properties after the leveling process; and evaluation of the effect of leveling on the spatial distribution of the top of the B horizon in relation to the soil surface. In the 0-0.20 m layer, a 100-point georeferenced grid covering two taxonomic soil classes was used in assessment of the following soil properties: soil particle density (Pd) and bulk density (Bd); total porosity (Tp), macroporosity (Macro) and microporosity (Micro); available water capacity (AWC); sand, silt, clay, and dispersed clay in water (Disp clay) contents; electrical conductivity (EC); and weighted average diameter of aggregates (WAD). Soil depth to the top of the B horizon was also measured before leveling. The overall effect of leveling on selected soil physical properties was evaluated by paired "t" tests. The effect on the variability of each property was evaluated through the homogeneity of variance test. The thematic maps constructed by kriging or by the inverse of the square of the distances were visually analyzed to evaluate the effect of leveling on the spatial distribution of the properties and of the top of the B horizon in relation to the soil surface. Linear regression models were fitted with the aim of evaluating the relationship between soil properties and the magnitude of cuts and fills. Leveling altered the mean value of several soil properties and the agronomic effect was negative. The mean values of Bd and Disp clay increased and Tp, Macro and Micro, WAD, AWC and EC decreased. Spatial distributions of all soil physical properties changed as a result of leveling and its effect on all soil physical properties occurred in the whole area and not specifically in the cutting or filling areas. In future designs of leveling, we recommend overlaying a cut/fill map on the map of soil depth to the top of the B horizon in order to minimize areas with shallow surface soil after leveling. Source

Scagliusi S.M.,Embrapa Brazilian Agricultural Research Corporation
Australian Journal of Crop Science

The objective of this study was to establish an isolated microspore culture (IMC) protocol in wheat (Triticum aestivum L.) for use in genetic studies and to evaluate its potential for routine use in the Brazilian Wheat Breeding Program at Embrapa Wheat. Important steps of the method were identified and plant physiology of microspore mother plants and ovary co-culture were considered as key factors for effective establishment. Three Brazilian wheat genotypes were tested (Toropi, BRS 194 and F1 wheat cross 020037 × 020062), and two other genotypes were used as controls (Bobwhite and Fielder). Spikes containing uninucleated microspores were subjected to cold pretreatment (4°C) for 21 days in the dark. Number of embryos, green and albino plants were recorded for each genotype. The method was successfully established, and several fertile green plants were produced by using tissue culture and responsive controls. However, the results greatly differed among Brazilian wheat genotypes, suggesting a strong genotype-dependent effect. Microspore induction medium alone did not promote embryogenesis; ovary co-culture was a necessary step for embryo development and green plant formation, for all genotypes. The F1 wheat cross (020037 × 020062) produced a total of 85 green plants (out of 108 spikes), 64% of which were spontaneous diploids. BRS 194 produced many embryos, exhibiting a good androgenic response, but only a few grew into green plants. Toropi behaved as a recalcitrant genotype, and zero plants were produced. To our knowledge, this is the first report on wheat IMC from Brazilian genotypes resulting in androgenic embryogenesis and plant regeneration. Source

Aquino L.S.,Federal University of Pelotas | Timm L.C.,Federal University of Pelotas | Reichardt K.,University of Sao Paulo | Barbosa E.P.,University of Campinas | And 3 more authors.
Soil and Tillage Research

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 1ha lowland area sampled as a grid. The grid consisted of 100 sampling points (10m×10m), with samples collected from the 0-0.20m 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 measurements. © 2014 Elsevier B.V.. Source

Macedo A.N.,University of Sao Paulo | Brondi S.H.G.,Embrapa Brazilian Agricultural Research Corporation | Vieira E.M.,University of Sao Paulo
Food Analytical Methods

Most studies to determine sulfonamide residues in milk samples have used solid-phase extraction as the sample preparation technique. However, the quick, easy, cheap, effective, rugged, and safe (QuEChERS) method, introduced in 2003, has been used in the extraction of various compounds in food matrices. This study aimed to evaluate two sample preparation techniques: solid-phase extraction and QuEChERS, for chromatographic analysis of sulfonamides (sulfathiazole, sulfamethazine, and sulfadimethoxine) in bovine milk. The chromatographic parameters and the QuEChERS extraction procedure were developed by using different experimental designs, obtaining good peak resolution, recovery, precision, accuracy, linearity, selectivity, and limits of detection and quantification. In contrast, using solid-phase extraction, acceptable recoveries and selectivity were not achieved, despite the number of articles published that have applied this sample preparation technique for sulfonamide analysis. As a result of the experiments performed, probably sulfonamides are retained together with other components of the matrix in the sample pretreatment step (prior to its addition in the cartridge containing solid phase), which is an important part of solid-phase extraction with raw whole milk. Therefore, QuEChERS is a better method than solid-phase extraction for the analysis of sulfonamide residues in milk. Validation tests demonstrated that the method is appropriate, within the maximum residue limit (0.1 mg kg-1). Moreover, it was possible to use a lower amount of solvent compared with previously published articles (6 mL against 10 or 15 mL). © 2013 Springer Science+Business Media New York. Source

Porto A.J.V.,University of Sao Paulo | Inamasu R.Y.,Embrapa Brazilian Agricultural Research Corporation
Journal of the Brazilian Society of Mechanical Sciences and Engineering

A current trend in distributed control systems is the application of communication network technologies such as CAN - Controller Area Network. A recent utilization approach of these technologies is the networked control systems (NCS). The fundamental challenges in the development of NCS are the analysis of the network delay effects and the prediction of the timing behavior of the distributed control system. The common parameters that impact the performance of NCS include response time, network utilization and network delays induced by the communication of messages between the devices. In addition, the performance of a NCS is highly dependent on these messages sampling times. A significant emphasis has been put on development and application of methodologies to handle the network delay effect in these systems and improve their performances. This paper presents a detailed timing analysis and a mathematical model to calculate these network delays in CAN-based networks. With the results of this model, the application of a methodology is proposed to minimize the effects of these delays and to achieve the optimization (network operation and utilization) of a CAN-based network. A case study of a CAN-based distributed control system in a mobile robot is described to demonstrate the application of the optimization methodology and the utilization of the CAN mathematical model systemized. © 2010 by ABCM. Source

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