Arranjo espacial de plantas em duas cultivares de trigo

A densidade de plantas e o espaçamento entre fileiras podem afetar a produtividade e a qualidade de grãos de trigo. O objetivo deste trabalho foi avaliar o efeito de arranjos espaciais de plantas de trigo sobre a produtividade de grãos e peso hectolitro, em duas cultivares. Foi realizado um experimento na safra 2010 no município de Barracão, RS, em delineamento experimental de blocos completos casualizados, com quatro repetições e esquema fatorial 2 x 2 x 2. Foram avaliadas as cultivares “Fundacep Campo Real” e “Quartzo”, em duas densidades de plantas (200 e 330 plantas m-2) e em dois espaçamentos entre fileiras 17/17 e 17/34 cm (fileiras pareadas). Nenhum fator experimental afetou a produtividade e o peso hectolitro do trigo, demonstrando a alta plasticidade fenotípica dessa cultura.Palavras-chave: Triticum aestivum. Densidade de plantas. Espaçamento entre fileiras. Produtividade de grãos

Physical modelling of a surface-wave survey over a laterally varying granular medium with property contrasts and velocity gradients

International audienceLaboratory experiments using laser-based ultrasonic techniques can be used to simulate seismic surveys on highly controlled small-scale physical models of the subsurface. Most of the time, such models consist in assemblies of homogeneous and consolidated materials. To enable the physical modelling of unconsolidated, heterogeneous and porous media, the use of granular materials is suggested here. We describe a simple technique to build a two-layer physical model characterized by lateral variations, strong property contrasts and velocity gradients. We use this model to address the efficiency of an innovative surface-wave processing technique developed to retrieve 2-D structures from a limited number of receivers. A step by step inversion procedure of the extracted dispersion curves yields accurate results so that the 2-D structure of the physical model is satisfactorily reconstructed. The velocity gradients within each layer are accurately retrieved as well, confirming current theoretical and experimental studies regarding guided surface acoustic modes in unconsolidated granular media

Small-Scale Seismic Monitoring of Varying Water Levels in Granular Media

International audienceCore Ideas - We tested the sensitivity of seismic measurements to water saturation variations. - We used ultrasonic techniques to reproduce a small-scale seismic acquisition setup. - Measurements were performed on glass bead layers with varying water levels. - Results of 3D numerical modelling were used to validate data at the dry state. - Data difference trends between the dry and wet models match with the water level.Physical properties of soils in the vadose zone, and especially their water content, are characterized by strong spatial and temporal variations mostly driven by weather and anthropogenic activities. To understand this variability and help water resource management, seismic methods have been recently suggested as a complement to electrical and electromagnetic techniques. The simultaneous in situ estimation of pressure (P) and shear (S) wave velocities (VP and VS, respectively) and their ratio (VP/VS) offers novel perspectives for the monitoring of space and time variations of vadose zone mechanical properties. However, the seismic response in partially saturated and unconsolidated soils remains complex and deserves to be studied both theoretically and experimentally. In this study, we tested the sensitivity of seismic measurements (i.e., P-wave travel times and surface-wave phase velocities) to water saturation variations using controlled physical models at the laboratory scale. Ultrasonic techniques were used to reproduce a small-scale seismic acquisition setup at the surface of glass bead layers with varying water levels. Travel times and phase velocity measurements obtained at the dry state were validated with both theoretical models and numerical simulations and serve as reference datasets. The increasing water level clearly affected the recorded wave field in both its phase and amplitude. In these cases, the collected data cannot yet be inverted in the absence of a comprehensive theoretical model for such partially saturated granular media. The differences in travel time and phase velocity observed between the dry and wet models show patterns that interestingly match the observed water level and depth of the capillary fringe, thus offering attractive perspectives for studying soil water content variations