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Mar del Plata, Argentina

Taher H.I.,UNMdP | Aparicio V.C.,Instituto Nacional de Tecnologia Agropecuaria | Costa J.L.,Instituto Nacional de Tecnologia Agropecuaria | Puricelli M.,Instituto Nacional de Tecnologia Agropecuaria
Ciencia del Suelo | Year: 2013

The increasing predominance of soybeans in crop rotations, without the proper presence of cereals and under scarce or null fertilizer applications has been causing soil physical and chemical degradation. In addition, conventional tillage followed by intense rainfall events in southeastern Buenos Aires maximizes the risk of soil erosion. The adoption of conservation tillage practices in the region could help solve these problems. The aim of this study was to evaluate the evolution of physical properties and organic matter content during the soybean growing season under no- tillage and vertical tillage, under two N rates, 0 kg N ha-1 and 150 kg N ha-1 applied to the previous crop. The experiment was conducted from November 2009 until August 2010, in a Typical Argiudol soil complex. Soil samples were taken at planting, 60 days after planting (60 dap) (in vegetative stages), 100 dap (in reproductive stages) and 280 dap (after harvest). The following soil properties were determined: organic matter content, change of mean weight diameter and bulk density. Tillage systems and previous N fertilization rates had no effect on soybean yields. No negative correlations were found between organic matter and bulk density. The results of this study are relevant because we were able to follow the physical parameters during the soybean crop cycle in southeastern Buenos Aires, providing information that did not exist before. Results are expected to be confirmed from the soilanalyses of more crop cycles in this long-term experiment. Source


Roldan M.F.,Instituto Nacional de Tecnologia Agropecuaria | Studdert G.A.,UNMdP | Videla C.D.C.,UNMdP | Martino S.S.,UNMdP | Picone L.I.,UNMdP
Ciencia del Suelo | Year: 2014

Tillage systems affect soil aggregation and aggregate stability, both directly and by affecting other factors such as organic matter content (MO). Changes in both variables may be good soil health indicators. The aim of this work was to evaluate aggregate size distribution and stability in two sites representative of the Southeastern Buenos Aires province (Balcarce and Barrow, soils with different texture and MO) and under two tillage systems (no- (SD) and conventional (LC) tillage). Soil samples were taken (0-5 and 5-20 cm) from two long-term experiments started in 1997 with continuous cropping under SD and LC after four-year old grass-based pastures. Besides, in each site soil samples were taken from undisturbed situations. Soil was sieved in water to separate large (>2000 μm) and small (2000-250 μm) macroaggregates (MA), microaggregates (mA, 250-50 μm) and the fraction <50 μm, after 2 re-wetting methods: 1) capillary (MC) and 2) by immersion (MV). Mean weight diameter change (CDMP) between re-wetting methods was determined as a measure of aggregate stability. There was a greater proportion of MA (large+small) under SD respect to LC in both sites and re-wetting methods. The amount of MA tended to change less between re-wetting methods under SD, especially in the top layer, and in Barrow, whereas the amount of mA increased more under LC and with a like trend in Balcarce. Similar trends were observed when changes were expressed relative to the undisturbed situations. No significant differences (P>0.05) were observed in CDMP between tillage systems nor sites. For both soils under study, SD increased aggregate stability in the surface layer possibly due to the greater MO content. Likewise, the greater clay content in Barrow could be the cause of the greater stability of the different aggregate fractions. © 2014, Asociacion Argentina de la Ciencia del Suelo. All rights reserved. Source


Paolinelli L.D.,UNMdP | Perez T.,R and D Tenaris Siderca | Simison S.N.,UNMdP
Materials Chemistry and Physics | Year: 2011

A study has been conducted to analyze the influence of 1% Cr additions, microstructure, and pre-corrosion on the performance of CO2 corrosion inhibitors for C-Mn steels. Two carbon steels with two different microstructures were tested in a deoxygenated 5 wt.% NaCl solution, saturated with CO2 at 40 °C, pH 6. An imidazoline-based inhibitor was added after different pre-corrosion periods. Its performance was studied by means of d.c. electrochemical measurements, SEM and EDS. The results demonstrated a detrimental effect of 1% Cr and pre-corrosion on the inhibitor efficiency. It was also proven that the impact of pre-corrosion depends on microstructure and chemical composition. © 2010 Elsevier B.V. All rights reserved. Source


Peressutti J.,UNMdP | Sampayo O.A.,UNMdP
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2012

We investigate the possibility of setting model independent limits for a nonstandard anomalous magnetic moment aτNP of the tau lepton, in future γγ colliders based on Compton backscattering. For a hypothetical collider we find that, at various levels of confidence, the limits for aτNP could be improved, compared to previous studies based on LEP1, LEP2 and SLD data. We show the results for a realistic range of the center of mass energy of the e +e - collider. As a more direct application, we also present the results of the simulation for the photon collider at the TESLA project. © 2012 American Physical Society. Source


Bosch Mayol M.,UNMdP | Costa J.L.,Instituto Nacional de Tecnologia Agropecuaria | Cabria F.N.,UNMdP | Aparicio V.C.,Instituto Nacional de Tecnologia Agropecuaria
Ciencia del Suelo | Year: 2012

Precision agriculture utilizes modern tools in order to obtain and analyze georreferenced data. Direct measuring sensors of soil apparent electrical conductivity (ECa) are part of these modern tools and are widely used to quantify ECa spatial variability. This variable is correlated with other soil properties (water holding capacity, organic matter content, salinity, drainage, topography, tillage managing and soil texture). Plants are negatively affected by elevated salts amount and elevated exchangeable sodium content, which causes physical and chemical damage of soils, affecting crop's grown and production. In order to determinate sodium spatial content and distribution, three fields about 80 Has average were selected. All fields are under central pivot irrigation system and are located in the southeast of Buenos Aires province, Argentina. In these fields ECa was measured and georreferenced whit a direct measure sensor. Obtained data was used to create ECa maps in every field using spatial interpolation methods (Kriging). All fields were divided into four different zones, based on its ECa value, where soil samples were taken. Soil samples were laboratory processed in order to determinate gravimetric humidity (θg), electrical conductivity of soil saturation paste extract (ECe) and soluble cations (Na+, Ca+2 and Mg+2), and sodium adsorption ratio (SAR) was calculated. Experimental data was statistically analyzed using SAS PROC MIXED procedure. We observed CEa spatial variability, and associations between ECa and SAR. Significantly relationships between ECa, ECe and soil sodium content were found. Sodium content was statistically differenced between different ECa zones in every field. The ECa direct measuring sensors are accurately tools to estimate soil sodium spatial content. Source

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