(Table 1) Soil physical parameters of sediments obtained in the Lüchow-Dannenberg district, Lower Saxony

The mobility of the radionuclides of the elements Sr, I, Cs and Ce were investigated for three typical sands of Northern Germany under simulated natural, undersaturated flow conditions. The laboratory experiments include the determination of the flow parameters of the seepwater movement as well as the transport velocities of the radionuclides in the sands. For the three selected sands, the following mobility sequence/order has been established for the radionuclides: I < Sr < Cs < Ce

Soil physical and microbiological attributes cultivated with the common bean under two management systems

Agricultural management systems can alter the physical and biological soil quality, interfering with crop development. The objective of this study was to evaluate the physical and microbiological attributes of a Red Latosol, and its relationship to the biometric parameters of the common bean (Phaseolus vulgaris), irrigated and grown under two management systems (conventional tillage and direct seeding), in Campinas in the state of Sao Paulo, Brazil. The experimental design was of randomised blocks, with a split-plot arrangement for the management system and soil depth, analysed during the 2006/7 and 2007/8 harvest seasons, with 4 replications. The soil physical and microbiological attributes were evaluated at depths of 0.00-0.05, 0.05-0.10, 0.10-0.20 and 0.20-0.40 m. The following were determined for the crop: density, number of pods per plant, number of beans per pod, thousand seed weight, total weight of the shoots and harvest index. Direct seeding resulted in a lower soil physical quality at a depth of 0.00-0.05 m compared to conventional tillage, while the opposite occurred at a depth of 0.05-0.10 m. The direct seeding showed higher soil biological quality, mainly indicated by the microbial biomass nitrogen, basal respiration and metabolic quotient. The biometric parameters in the bean were higher under the direct seeding compared to conventional tillage.

Ground penetrating radar early-time technique for soil electromagnetic parameters estimation

In recent years, thanks to the technological advances, electromagnetic methods for non-invasive shallow subsurface characterization have been increasingly used in many areas of environmental and geoscience applications. Among all the geophysical electromagnetic methods, the Ground Penetrating Radar (GPR) has received unprecedented attention over the last few decades due to its capability to obtain, spatially and temporally, high-resolution electromagnetic parameter information thanks to its versatility, its handling, its non-invasive nature, its high resolving power, and its fast implementation. The main focus of this thesis is to perform a dielectric site characterization in an efficient and accurate way studying in-depth a physical phenomenon behind a recent developed GPR approach, the so-called early-time technique, which infers the electrical properties of the soil in the proximity of the antennas. In particular, the early-time approach is based on the amplitude analysis of the early-time portion of the GPR waveform using a fixed-offset ground-coupled antenna configuration where the separation between the transmitting and receiving antenna is on the order of the dominant pulse-wavelength. Amplitude information can be extracted from the early-time signal through complex trace analysis, computing the instantaneous-amplitude attributes over a selected time-duration of the early-time signal. Basically, if the acquired GPR signals are considered to represent the real part of a complex trace, and the imaginary part is the quadrature component obtained by applying a Hilbert transform to the GPR trace, the amplitude envelope is the absolute value of the resulting complex trace (also known as the instantaneous-amplitude). Analysing laboratory information, numerical simulations and natural field conditions, and summarising the overall results embodied in this thesis, it is possible to suggest the early-time GPR technique as an effective method to estimate physical properties of the soil in a fast and non-invasive way.

Effect of conservation tillage on soil physical properties, in-situ rainwater harvesting, and erosion control in arid and semi-arid regions

La escasez del agua en las regiones áridas y semiáridas se debe a la escasez de precipitaciones y la distribución desigual en toda la temporada, lo que hace de la agricultura de secano una empresa precaria. Un enfoque para mejorar y estabilizar el agua disponible para la producción de cultivos en estas regiones es el uso de tecnologías de captación de agua de lluvia in situ y su conservación. La adopción de los sistemas de conservación de la humedad del suelo in situ, tales como la labranza de conservación, es una de las estrategias para mejorar la gestión de la agricultura en zonas áridas y semiáridas. El objetivo general de esta tesis ha sido desarrollar una metodología de aplicación de labranza de depósito e investigar los efectos a corto plazo sobre las propiedades físicas del suelo de las diferentes prácticas de cultivo que incluyen labranza de depósito: (reservoir tillage, RT), la laboreo mínimo: (minimum tillage, MT), la no laboreo: (zero tillage, ZT) y laboreo convencional: (conventional tillage, CT) Así como, la retención de agua del suelo y el control de la erosión del suelo en las zonas áridas y semiáridas. Como una primera aproximación, se ha realizado una revisión profunda del estado de la técnica, después de la cual, se encontró que la labranza de depósito es un sistema eficaz de cosecha del agua de lluvia y conservación del suelo, pero que no ha sido evaluada científicamente tanto como otros sistemas de labranza. Los trabajos experimentales cubrieron tres condiciones diferentes: experimentos en laboratorio, experimentos de campo en una región árida, y experimentos de campo en una región semiárida. Para investigar y cuantificar el almacenamiento de agua a temperatura ambiente y la forma en que podría adaptarse para mejorar la infiltración del agua de lluvia recolectada y reducir la erosión del suelo, se ha desarrollado un simulador de lluvia a escala de laboratorio. Las características de las lluvias, entre ellas la intensidad de las precipitaciones, la uniformidad espacial y tamaño de la gota de lluvia, confirmaron que las condiciones naturales de precipitación son simuladas con suficiente precisión. El simulador fue controlado automáticamente mediante una válvula de solenoide y tres boquillas de presión que se usaron para rociar agua correspondiente a diferentes intensidades de lluvia. Con el fin de evaluar el método de RT bajo diferentes pendientes de superficie, se utilizaron diferentes dispositivos de pala de suelo para sacar un volumen idéntico para hacer depresiones. Estas depresiones se compararon con una superficie de suelo control sin depresión, y los resultados mostraron que la RT fue capaz de reducir la erosión del suelo y la escorrentía superficial y aumentar significativamente la infiltración. Luego, basándonos en estos resultados, y después de identificar la forma adecuada de las depresiones, se ha diseñado una herramienta combinada (sistema integrado de labranza de depósito (RT)) compuesto por un arado de una sola línea de chisel, una sola línea de grada en diente de pico, sembradora modificada, y rodillo de púas. El equipo fue construido y se utiliza para comparación con MT y CT en un ambiente árido en Egipto. El estudio se realizó para evaluar el impacto de diferentes prácticas de labranza y sus parámetros de funcionamiento a diferentes profundidades de labranza y con distintas velocidades de avance sobre las propiedades físicas del suelo, así como, la pérdida de suelo, régimen de humedad, la eficiencia de recolección de agua, y la productividad de trigo de invierno. Los resultados indicaron que la RT aumentó drásticamente la infiltración, produciendo una tasa que era 47.51% más alta que MT y 64.56% mayor que la CT. Además, los resultados mostraron que los valores más bajos de la escorrentía y pérdidas de suelos 4.91 mm y 0.65 t ha-1, respectivamente, se registraron en la RT, mientras que los valores más altos, 11.36 mm y 1.66 t ha-1, respectivamente, se produjeron en el marco del CT. Además, otros dos experimentos de campo se llevaron a cabo en ambiente semiárido en Madrid con la cebada y el maíz como los principales cultivos. También ha sido estudiado el potencial de la tecnología inalámbrica de sensores para monitorizar el potencial de agua del suelo. Para el experimento en el que se cultivaba la cebada en secano, se realizaron dos prácticas de labranza (RT y MT). Los resultados mostraron que el potencial del agua del suelo aumentó de forma constante y fue consistentemente mayor en MT. Además, con independencia de todo el período de observación, RT redujo el potencial hídrico del suelo en un 43.6, 5.7 y 82.3% respectivamente en comparación con el MT a profundidades de suelo (10, 20 y 30 cm, respectivamente). También se observaron diferencias claras en los componentes del rendimiento de los cultivos y de rendimiento entre los dos sistemas de labranza, el rendimiento de grano (hasta 14%) y la producción de biomasa (hasta 8.8%) se incrementaron en RT. En el experimento donde se cultivó el maíz en regadío, se realizaron cuatro prácticas de labranza (RT, MT, ZT y CT). Los resultados revelaron que ZT y RT tenían el potencial de agua y temperatura del suelo más bajas. En comparación con el tratamiento con CT, ZT y RT disminuyó el potencial hídrico del suelo en un 72 y 23%, respectivamente, a la profundidad del suelo de 40 cm, y provocó la disminución de la temperatura del suelo en 1.1 y un 0.8 0C respectivamente, en la profundidad del suelo de 5 cm y, por otro lado, el ZT tenía la densidad aparente del suelo y resistencia a la penetración más altas, la cual retrasó el crecimiento del maíz y disminuyó el rendimiento de grano que fue del 15.4% menor que el tratamiento con CT. RT aumenta el rendimiento de grano de maíz cerca de 12.8% en comparación con la ZT. Por otra parte, no hubo diferencias significativas entre (RT, MT y CT) sobre el rendimiento del maíz. En resumen, según los resultados de estos experimentos, se puede decir que mediante el uso de la labranza de depósito, consistente en realizar depresiones después de la siembra, las superficies internas de estas depresiones se consolidan de tal manera que el agua se mantiene para filtrarse en el suelo y por lo tanto dan tiempo para aportar humedad a la zona de enraizamiento de las plantas durante un período prolongado de tiempo. La labranza del depósito podría ser utilizada como un método alternativo en regiones áridas y semiáridas dado que retiene la humedad in situ, a través de estructuras que reducen la escorrentía y por lo tanto puede resultar en la mejora de rendimiento de los cultivos. ABSTRACT Water shortage in arid and semi-arid regions stems from low rainfall and uneven distribution throughout the season, which makes rainfed agriculture a precarious enterprise. One approach to enhance and stabilize the water available for crop production in these regions is to use in-situ rainwater harvesting and conservation technologies. Adoption of in-situ soil moisture conservation systems, such as conservation tillage, is one of the strategies for upgrading agriculture management in arid and semi-arid environments. The general aim of this thesis is to develop a methodology to apply reservoir tillage to investigate the short-term effects of different tillage practices including reservoir tillage (RT), minimum tillage (MT), zero tillage (ZT), and conventional tillage (CT) on soil physical properties, as well as, soil water retention, and soil erosion control in arid and semi-arid areas. As a first approach, a review of the state of the art has been done. We found that reservoir tillage is an effective system of harvesting rainwater and conserving soil, but it has not been scientifically evaluated like other tillage systems. Experimental works covered three different conditions: laboratory experiments, field experiments in an arid region, and field experiments in a semi-arid region. To investigate and quantify water storage from RT and how it could be adapted to improve infiltration of harvested rainwater and reduce soil erosion, a laboratory-scale rainfall simulator was developed. Rainfall characteristics, including rainfall intensity, spatial uniformity and raindrop size, confirm that natural rainfall conditions are simulated with sufficient accuracy. The simulator was auto-controlled by a solenoid valve and three pressure nozzles were used to spray water corresponding to different rainfall intensities. In order to assess the RT method under different surface slopes, different soil scooping devices with identical volume were used to create depressions. The performance of the soil with these depressions was compared to a control soil surface (with no depression). Results show that RT was able to reduce soil erosion and surface runoff and significantly increase infiltration. Then, based on these results and after selecting the proper shape of depressions, a combination implement integrated reservoir tillage system (integrated RT) comprised of a single-row chisel plow, single-row spike tooth harrow, modified seeder, and spiked roller was developed and used to compared to MT and CT in an arid environment in Egypt. The field experiments were conducted to evaluate the impact of different tillage practices and their operating parameters at different tillage depths and different forward speeds on the soil physical properties, as well as on runoff, soil losses, moisture regime, water harvesting efficiency, and winter wheat productivity. Results indicated that the integrated RT drastically increased infiltration, producing a rate that was 47.51% higher than MT and 64.56% higher than CT. In addition, results showed that the lowest values of runoff and soil losses, 4.91 mm and 0.65 t ha-1 respectively, were recorded under the integrated RT, while the highest values, 11.36 mm and 1.66 t ha -1 respectively, occurred under the CT. In addition, two field experiments were carried out in semi-arid environment in Madrid with barley and maize as the main crops. For the rainfed barley experiment, two tillage practices (RT, and MT) were performed. Results showed that soil water potential increased quite steadily and were consistently greater in MT and, irrespective of the entire observation period, RT decreased soil water potential by 43.6, 5.7, and 82.3% compared to MT at soil depths (10, 20, and 30 cm, respectively). In addition, clear differences in crop yield and yield components were observed between the two tillage systems, grain yield (up to 14%) and biomass yield (up to 8.8%) were increased by RT. For the irrigated maize experiment, four tillage practices (RT, MT, ZT, and CT) were performed. Results showed that ZT and RT had the lowest soil water potential and soil temperature. Compared to CT treatment, ZT and RT decreased soil water potential by 72 and 23% respectively, at soil depth of 40 cm, and decreased soil temperature by 1.1 and 0.8 0C respectively, at soil depth of 5 cm. Also, ZT had the highest soil bulk density and penetration resistance, which delayed the maize growth and decreased the grain yield that was 15.4% lower than CT treatment. RT increased maize grain yield about 12.8% compared to ZT. On the other hand, no significant differences among (RT, MT, and CT) on maize yield were found. In summary, according to the results from these experiments using reservoir tillage to make depressions after seeding, these depression’s internal surfaces are consolidated in such a way that the water is held to percolate into the soil and thus allowing time to offer moisture to the plant rooting zone over an extended period of time. Reservoir tillage could be used as an alternative method in arid and semi-arid regions and it retains moisture in-situ, through structures that reduce runoff and thus can result in improved crop yields.

Effect of integrated reservoir tillage for in-situ rainwater harvesting and other tillage practices on soil physical properties

There is a need for in-situ soil moisture conservation in arid and semi-arid regions due to insufficient rainfall for agriculture. For this purpose, a combination implement [integrated reservoir tillage system (RT)] comprised of a single-row chisel plow, single-row spike tooth harrow, modified seeder, and spiked roller was developed and compared to the popular tillage practices, viz., minimum tillage (MT) and conventional tillage (CT) in an arid Mediterranean environment in Egypt. The different tillage practices were conducted at tillage depths of 15, 20, and 25 cm and forward speeds of 0.69, 1, 1.25, and 1.53 m s-1. Some soil physical properties, runoff, soil loss, water harvesting efficiency and yield of wheat were evaluated. The different tillage practices caused significant differences in soil physical properties as the RT increased soil infiltration, producing a rate of 48% and 65% higher than that obtained in MT and CT, respectively. The lowest values of runoff and soil loss were recorded under RT as 4.91 mm and 0.65 t ha-1, whereas the highest values were recorded under CT as 11.36 mm and 1.66 t ha-1, respectively. In conclusion, the RT enhanced the infiltration rate, increased water harvesting efficiency, reduced runoff and achieved the highest yield of wheat. The best tillage operating parameters appeared to be at a tillage depth of 20 cm and speed between 1.00 and 1.25 m s-1.

Assessment of physical and hydrological properties of biological soil crusts using x-ray microtomography and modelling

Biological soil crusts (BSCs) are formed by aggregates of soil particles and communities of microbial organisms and are common in all drylands. The role of BSCs on infiltration remains uncertain due to the lack of data on their role in affecting soil physical properties such as porosity and structure. Quantitative assessment of these properties is primarily hindered by the fragile nature of the crusts. Here we show how the use of a combination of non-destructive imaging X-ray microtomography (XMT) and Lattice Boltzmann method (LBM) enables quantification of key soil physical parameters and the modeling of water flow through BSCs samples from Kalahari Sands, Botswana. We quantify porosity and flow changes as a result of mechanical disturbance of such a fragile cyanobacteria-dominated crust. Results show significant variations in porosity between different types of crusts and how they affect the flow and that disturbance of a cyanobacteria-dominated crust results in the breakdown of larger pore spaces and reduces flow rates through the surface layer. We conclude that the XMT–LBM approach is well suited for study of fragile surface crust samples where physical and hydraulic properties cannot be easily quantified using conventional methods.

Physical parameters affecting sonoluminescence: A self-consistent hydrodynamic study

We studied the dependence of thermodynamic variables in a sonoluminescing ~SL! bubble on various physical factors, which include viscosity, thermal conductivity, surface tension, the equation of state of the gas inside the bubble, as well as the compressibility of the surrounding liquid. The numerical solutions show that the existence of shock waves in the SL parameter regime is very sensitive to these factors. Furthermore, we show that even without shock waves, the reflection of continuous compressional waves at the bubble center can produce the high temperature and picosecond time scale light pulse of the SL bubble, which implies that SL may not necessarily be due to shock waves.

Influence of physical parameters of sound on the sensory gating effects of N40 in rats

Sensory gating is the ability of the brain to modulate its sensitivity to incoming stimuli. The N40 component of the auditory evoked potential, evaluated with the paired click paradigm, was used to probe the gating effect in rats. The physical characteris

Optical and near-infrared coverage of SN 2004et: physical parameters and comparison with other Type IIP supernovae

We present new optical and near-infrared (NIR) photometry and spectroscopy of the Type IIP supernova (SN), SN 2004et. In combination with already published data, this provides one of the most complete studies of optical and NIR data for any Type IIP SN from just after explosion to +500 d. The contribution of the NIR flux to the bolometric light curve is estimated to increase from 15 per cent at explosion to around 50 per cent at the end of the plateau and then declines to 40 per cent at 300 d. SN 2004et is one of the most luminous IIP SNe which has been well studied and characterized, and with a luminosity of log L = 42.3 erg s-1 and a 56Ni mass of 0.06 +/- 0.04 M-circle dot, it is two times brighter than SN 1999em. We provide parametrized bolometric corrections as a function of time since explosion for SN 2004et and three other IIP SNe that have extensive optical and NIR data. These can be used as templates for future events in optical and NIR surveys without full wavelength coverage. We compare the physical parameters of SN 2004et with those of other well-studied IIP SNe and find that the kinetic energies span a range of 1050-1051 erg. We compare the ejected masses calculated from hydrodynamic models with the progenitor masses and limits derived from pre-discovery images. Some of the ejected mass estimates are significantly higher than the progenitor mass estimates, with SN 2004et showing perhaps the most serious mass discrepancy. With the current models, it appears difficult to reconcile 100 d plateau lengths and high expansion velocities with the low ejected masses of 5-6 M-circle dot implied from 7-8 M-circle dot progenitors. The nebular phase is studied using very late-time Hubble Space Telescope photometry, along with optical and NIR spectroscopy. The light curve shows a clear flattening at 600 d in the optical and the NIR, which is likely due to the ejecta impacting on circumstellar material. We further show that the [O i] 6300, 6364 A line strengths in the nebular spectra of four Type IIP SNe imply ejected oxygen masses of 0.5-1.5 M-circle dot.