Sorption and leaching of s-metolachlor in surface horizons of Romania

Sorption is the major process that determines the fate and behavior of most herbicides in soil. Understanding herbicide sorption within soil profile is the first step to predict groundwater contamination. Laboratory studies were conducted to determine the influence of surface soil properties on s-metolachlor sorption. Sorption isotherms were determined from soil plough layer (0-25 cm) using the batch equilibrium method and six concentration (0, 1, 5, 10, 20 and 50 mg L-1). Sorption affinity of herbicide was approximated by the Freundlich equation. The environmental behavior of smetolachlor was studied at the Didactical and Experimental Research Station Ezareni belonging to ’’Ion Ionescu de la Brad’’ University of Agriculture and Veterinary Medicine Iasi, Romania. A randomized complete block design with three replications was used in the experiment. S-metolachlor EC (96% v/v) was applied as a pre-emergence at dosages of 1500, 2100 and 2700 mL ha-1 1 day before sowing the soybean seeds in the field. The soil was collected at different layers and the residues of s-metolachlor were analyzed by GC-MS. Maximum concentration of s–metolachlor was recovered from 0-15 cm depth in all three doses. Results indicated high mobility of s-metolachlor under field conditions that may be significant in terms of ground water contamination

Investigations on the influence of fertilization system and erosion on wheat yield and on some soil agrochemical characteristics

By diminishing soil fertility, the erosion process determined the differentiation of mean wheat yield according to slope and erosion, from 3905 (100%) to 3078 kg/ha (78.8%). The mean annual losses of yield registered in wheat in the last 10 years, caused by erosion, were of 827 kg/ha (21.2%). The humus and nutrient content from soil was maintained at a supply level proper to the requirements of plant nutrition, only under 3 or 4 year rotation, and in case of annual use of rates of at least 100 kg N + 100 kg P2O5 or mean rates of mineral elements with 60 t/ha manure. The use of mineral fertilizers with manure resulted in increasing mobile phosphorus content from soil until 94 ppm, achieving a good and very good supply in mobile phosphorus and increasing humus content from soil to 4.18%. On weakly and highly eroded soils, the application of moderate rates of mineral fertilizers with 3 t/ha pea stalks determined the improvement in soil ureasic and phosphatasic potential, ensuring a better plant supply with assimilate phosphorus. The use of manure or residues, which are easily degradable with mean rates of mineral elements, resulted in achieving soil nutrient supply and biological characteristics very close to those obtained by using high rates of mineral fertilizers. On slope lands, poor in organic matter and mineral elements, establishing the best fertilizer rates, which ensure crop consumption and maintain good soil supply in mineral elements, is more difficult, especially in crops requiring high amounts of mineral elements, as wheat and maize

Optical Polarization and Spectral Variability in the M87 Jet

During the last decade, M87's jet has been the site of an extraordinary variability event, with one knot (HST-1) increasing by over a factor 100 in brightness. Variability was also seen on timescales of months in the nuclear flux. Here we discuss the optical-UV polarization and spectral variability of these components, which show vastly different behavior. HST-1 shows a highly significant correlation between flux and polarization, with P increasing from $\sim 20$ at minimum to >40% at maximum, while the orientation of its electric vector stayed constant. HST-1's optical-UV spectrum is very hard ($\alpha_{UV-O}\sim0.5$, $F_\nu\propto\nu^{-\alpha}$), and displays "hard lags" during epochs 2004.9-2005.5, including the peak of the flare, with soft lags at later epochs. We interpret the behavior of HST-1 as enhanced particle acceleration in a shock, with cooling from both particle aging and the relaxation of the compression. We set 2$\sigma$ upper limits of $0.5 \delta$ parsecs and 1.02$c$ on the size and advance speed of the flaring region. The slight deviation of the electric vector orientation from the jet PA, makes it likely that on smaller scales the flaring region has either a double or twisted structure. By contrast, the nucleus displays much more rapid variability, with a highly variable electric vector orientation and 'looping' in the $(I,P)$ plane. The nucleus has a much steeper spectrum ($\alpha_{UV-O} \sim 1.5$) but does not show UV-optical spectral variability. Its behavior can be interpreted as either a helical distortion to a steady jet or a shock propagating through a helical jet.Comment: 14 pages, 7 figures, ApJ, in pres

The influence of conservation tillage systems on productivity elements in the maize crop on the Moldavian Plain

The experiment was carried out between 2005 – 2008 at Ezareni – The Experimental Farm of the Agricultural University of Iasi, in the East side of Romania (47o 07’ N latitude, 27o 30’E longitude), on a cambic chernozem (SRTS2003), or haplic chernozems (WRB-SR, 1998), with a clay-loamy texture, 6.8 pH, 2.7% humus content and a medium level of fertilization. The experimental area has an annual average temperature of 9.4o C and precipitation of 587 mm. The experiment was a “split plot” design with three replicates. Plots covered an area of 60 m2 with a rotation of soybean - winter wheat - maize. The maize mean yield values showed significant differences in plots plowed at 20 cm and very significant results in the disc harrow treatment when compared to the control treatment. These findings confirm that increasing tillage depth result in higher yields. In disc harrow plots, the mean yield over three years was 4532 kg/ha while the conventional tillage variant (plowed at 20 cm) yield recorded 5528 kg/ha. The highest yield of 6482 kg/ha was recorded in the control treatment (plowed at 30 cm). The conservation variants, chisel and paraplow, resulted in intermediate yields between disc harrow and the control treatment, the differences being statistically nonsignificant

Tillage effects on soil structure and grain yield of maize

To conserve soil fertility and prevent erosion, soil management regimes based on reduced tillage are highly suited to integrated production systems. Tillage effects on soil properties are usually site specific and depend upon the interaction of soil and climatic conditions, with soil and crop management practices. Field experiment were carried out in 2010- 2012 at The Experimental Farm of the Agricultural University of Iasi, in the NE of Romania (47o 07’ N latitude, 27o 30’E longitude), on a cambic chernozem (SRTS-2003, or haplic chernozems WRB-SR, 1998), with a clay-loamy texture, 6.8 pH, 2.7% humus content and a medium level of fertilization. Long-term amount of precipitation at this site is 517.8 mm at an average air temperature of 9.4oC. However, significant deviations from the long term average and temperature have been observed in recent years. The aim of this study is to evaluate the influence of tillage on soil structure and yield in the pedoclimatic conditions of the Moldavian Plain. The experimental soil tillage systems were as follows: V1 – disc harrow , V2 – paraplow, V3 – chisel plow + rotary harrow, V4 – plough at 20 cm and V5 – plough at 30 cm (control variant). One of the main objectives for the soil tillage system was to create an optimal physicochemical state of the soil and to preserve this state over the whole vegetation period. Tillage systems significantly affected the maize yield. In Moldavian plain, in normally climatic conditions, the highest yield was recorded in the control treatment, plough at 30 cm and fertilized (9471 kg ha-1 ), followed by conservation tillage – chisel (9054 kg ha-1 ), but under water stress (2011-2012) we observed that the highest yields was at minimum tillage variants (chisel 3956 kg ha1 , paraplow 3918 kg ha-1 )

Polarimetry and the High-Energy Emission Mechanisms in Quasar Jets. The Case of PKS 1136-135

Since the discovery of kiloparsec-scale X-ray emission from quasar jets, the physical processes responsible for their high-energy emission have been poorly defined. A number of mechanisms are under active debate, including synchrotron radiation, inverse-Comptonized CMB (IC/CMB) emission, and other Comptonization processes. In a number of cases, the optical and X-ray emission of jet regions are inked by a single spectral component, and in those, high- resolution multi-band imaging and polarimetry can be combined to yield a powerful diagnostic of jet emission processes. Here we report on deep imaging photometry of the jet of PKS 1136$-$135 obtained with the {\it Hubble Space Telescope.} We find that several knots are highly polarized in the optical, with fractional polarization $\Pi>30$. When combined with the broadband spectral shape observed in these regions, this is very difficult to explain via IC/CMB models, unless the scattering particles are at the lowest-energy tip of the electron energy distribution, with Lorentz factor $\gamma \sim 1$, and the jet is also very highly beamed ($\delta \geq 20$) and viewed within a few degrees of the line of sight. We discuss both the IC/CMB and synchrotron interpretation of the X-ray emission in the light of this new evidence, presenting new models of the spectral energy distribution and also the matter content of this jet. The high polarizations do not completely rule out the possibility of IC/CMB optical-to-X-ray emission in this jet, but they do strongly disfavor the model. We discuss the implications of this finding, and also the prospects for future work.Comment: 14 pages, 8 figures, ApJ in pres

The effect of some tillage systems on soil pedomorphological indicators in dryness conditions on soybean crop

The main objective of this study consists in the effect of some tillage systems on pedomorphological indicators of cross section made in experimental field Ezareni – Iasi, on the development of advanced agricultural technologies for crop cultivation. In Romania have been conducted many researches on the influence of various tillage systems on physical, chemical and biological indicators and their residual effect, and less insisted on the morphological changes. The study of pedomorphological indicators have been accomplished on cross section (2x0.7m) performed after harvesting maize and the variants were: ploughed at 30 cm depth (V1), paraplow (V2), chisel (V3) and disk harrow (V4). The novelty and originality of the study consists in illustrating the morphological indicators through images performed from cross section and processed with special programs. The morphological description of cross section of cambic chernozem was based on the pedomorphological indicators presented in development methodology of pedological study [16]. Pedomorphological indicators of soil cross section may be additional criteria in choosing a tillage system suited to local climatic features. The cross soil section perpendicular to the direction of tillage in the chisel + superficial rotary tiller plot has a mildly loosened aspect, and locally on the tractor wheel tracks the soil is highly compacted. The repeated disc harrow use determined soil structure degradation by fragmentation of the elements and the reduction of their mean diameter. On tractor wheel tracks the soil structure is massive and the compaction process can be observed to a depth of 20 cm. In the underlying horizon (Ap) the soil maintains mildly to moderately compacted. Locally the soil is crossed by vertical or slightly oblique galleries resulted from soil macrofauna activity. In the subarable horizon formed a dense and compacted soil layer known as plowpan or hardpan