Technical Note: Field-Scale Surface Soil Moisture Patterns and Their Relationship to Topographic Indices

Understanding variability patterns in soil moisture is critical for determining an optimal sampling scheme both in space and in time, as well as for determining optimal management zones for agricultural applications that involve moisture status. In this study, distributed near-surface gravimetric soil moisture samples were collected across a 3.3 ha field in central Illinois for ten dates in the summer of 2002, along with dense elevation data. Temporal stability and consistency of the moisture patterns were analyzed in order to determine a suitable grid size for mapping and management, as well as to investigate relationships between moisture patterns and topographic and soil property influences. Variogram analysis of surface moisture data revealed that the geospatial characteristics of the soil moisture patterns are similar from one date to another, which may allow for a single, rather than temporally variable, variogram to describe the spatial structure. For this field, a maximum cell size of 10 m was found to be appropriate for soil moisture studies on most of the sampling occasions. This could indicate an appropriate scale for precision farming operations or for intensive ground sampling. While some areas had consistent behavior with respect to field mean moisture content, no conclusive relationships between the overall patterns in the moisture data and the topographic and soil indices were identified. There were, however, some small but significant correlations between these two sets of data, particularly plan and tangential curvature, and also slopes. In areas of convergent flow, moisture content exhibited a slight tendency to be wetter than average. There also seemed to be a small influence of scale on the relationship between moisture patterns and topographic curvatures

Modeling Soil Erosion with Emphasis on Steep Slopes and the Rilling Process

A soil erosion model, known as KYERMO, was developed for use in soil erosion research. The model was written in Microsoft FORTRAN, which is a subset of the ANSI FORTRAN 77 standard, allowing the model to be run on an IBM-PC as well as a mainframe computer. The model structure consisted of many interrelated subroutines which facilitated model development, testing, and future expansion. A sensitivity analysis of the detachment component was performed, examining the number of rills, the number of space and time steps, and the detachment parameters. This analysis indicated that the model performed as expected for the detachment limiting case. Field plots for the collection of justification data were designed and constructed on steep slopes (28 and 30.5 percent). Their surfaces were shaped to provide controlled rill patterns. Rainfall was applied through use of an irrigation nozzle rainfall simulator. The field simulations included initial full plot (22.1 m) runs on unrilled surfaces with two and six rill watersheds, full plot runs on established surfaces, and half plot runs on established surfaces. Eight field simulations were conducted. Measured or sampled quantities included runoff rate, delivered sediment concentration, delivered sediment size distribution, rainfall intensity, soil moisture content, plot surface shape, and rill cross-sections. Each of the field erosion events was simulated using KYERMO. Hydrologic parameters were fitted to provide the proper runoff characteristics to allow justification of the erosion component of the model. The detachment parameters were initially set using parameters and relationships from the literature. Prediction was comparable to that reported by other researchers. The detachment parameters were then fitted individually to gain insights about their effects. The resultant values were then considered in light of plot characteristics. These analyses indicated that a more complete knowledge of the rill bed particle size distribution could be used to increase accuracy and that soil structure changes due to tillage should be considered. The detachment rate was found to be the limiting factor rather than the sediment transport rate

Modeling Erosion on Long Steep Slopes with Emphasis on the Rilling Process

A model of soil erosion, known as KYERMO, is presented which emphasizes those processes which are important on steep slopes. Particular emphasis is placed on modeling rill development and geometry since this is the least understood process in erosion mechanics. The model requires an input rill pattern. Rainfall inputs to the model require the use of breakpoint rainfall and kinetic energy. Surface storage is calculated based on random roughness data of Linden (1979). Infiltration is modeled by use of the two layer Green-Ampt-Mein-Larson model as proposed by Moore and Eigel (1981). Runoff is related to rainfall excess and surface storage by the exponential, relationship of Thelin and Keifer (1960). Erosion is modeled separately as rill and interrill erosion. Interrill erosion is modeled by evaluating raindrop splash and interrill transport capacity. Raindrop splash is predicted by using the Bubenzer and Jones (1971) equation which requires kinetic energy, rainfall intensity, and percent clay. In terr ill transport capacity is modeled by either the Yalin (1963) or Yang (1973) equation depending on user preference. The rate of delivery of soil to a rill is a minimum of either the transport rate or splash rate. Rill detachment capacity is calculated using the shear excess equation of Foster (1982). Transport capacity is calculated from either the Yalin (1963) or Yang ( 1973) depending on user preference. The distribution of detachment around the rill boundary is calculated as a function of the shear distribution. Shear is distributed by using a modification of the area method of Lundgren and Jonsson (1964). Rill wall sloughing is calculated by using the procedure of Wu et al. (1982) which uses a critical wall angle. Flow routing in rills is calculated by using the kinematic routing procedures of Brakensiek (1966). Data is presented showing that predictions made with model components are reasonable. A limited sensitivity analysis with the model shows that predictions follow the trends that one would expect

RESIDUE MANAGEMENT TO CONTROL SOIL EROSION BY WATER

The Erosion Process Erosion of topsoil begins when water detaches individual soil particles from clod and other soil aggregates. A single raindrop may seem insignificant, yet collectively, raindrops strike the ground with surprising force. During an intense storm, rainfall can loosen and detach up to 100 tons of soil per acre and can be especially erosive when residue mulch or vegetation are not present to absorb their impact. Two problems often occur during rainstorms. The rate of rainfall can exceed the rate at which water can enter the soil and raindrop impact forces can partially seal the soil surface. In the first in distance, the excess water either collects on or runs off the soil surface and in the second, less water can infiltrate into the soil, causing more runoff. This runoff will travel downhill, carrying soil particles with it. Runoff from steeper areas flows at greater velocities and may transport considerable amounts of soil. Further, longer slopes have greater flows because water is concentrated from a larger area. As runoff flow across unprotected soil surfaces, additional soil particles are dislodged, thus creating even more soil erosion. Residue Reduces Erosion Crop residue helps protect the soil surface from raindrop impact. It. also reduces surface crusting, sealing and rainfall-induced soil compaction, all of which increase water runoff by reducing infiltration. In addition, runoff is reduced because pieces of residue form a complex series of small dams and obstructions that slow the runoff. Years of research show that no-till planting systems, which leave the greatest amount of residue cover, can reduce soil erosion by 90 to 95 percent of that occurring from cleanly tilled systems. As little as a 30 percent residue cover can reduce erosion by 65 percent as shown in the illustration. Prior land use, crop canopy and surface roughness also influence erosion from different tillage and planting systems, but residue cover is the single most important factor

NuGrid: Toward High Precision Double-Degenerate Merger Simulations with SPH in 3D

We present preliminary results from recent high-resolution double-degenerate merger simulations with the Smooth Particle Hydrodynamics (SPH) technique. We put particular emphasis on verification and validation in our effort and show the importance of details in the initial condition setup for the final outcome of the simulation. We also stress the dynamical importance of including shocks in the simulations. These results represent a first step toward a suite of simulations that will shed light on the question whether double-degenerate mergers are a viable path toward type 1a supernovae. In future simulations, we will make use of the capabilities of the NuGrid collaboration in post-processing SPH particle trajectories with a complete nuclear network to follow the detailed nuclear reactions during the dynamic merger phase.Comment: To appear in the Conference Proceedings for the "10th Symposium on Nuclei in the Cosmos (NIC X)", July 27 - August 1 2008, Mackinack Island, Michigan, US

The Bern Birth Cohort (BeBiCo) to study the development of the infant intestinal microbiota in a high-resource setting in Switzerland: rationale, design, and methods.

BACKGROUND Microbiota composition is fundamental to human health with the intestinal microbiota undergoing critical changes within the first two years of life. The developing intestinal microbiota is shaped by maternal seeding, breast milk and its complex constituents, other nutrients, and the environment. Understanding microbiota-dependent pathologies requires a profound understanding of the early development of the healthy infant microbiota. METHODS Two hundred and fifty healthy pregnant women (≥20 weeks of gestation) from the greater Bern area will be enrolled at Bern University hospital's maternity department. Participants will be followed as mother-baby pairs at delivery, week(s) 1, 2, 6, 10, 14, 24, 36, 48, 96, and at years 5 and 10 after birth. Clinical parameters describing infant growth and development, morbidity, and allergic conditions as well as socio-economic, nutritional, and epidemiological data will be documented. Neuro-developmental outcomes and behavior will be assessed by child behavior checklists at and beyond 2 years of age. Maternal stool, milk, skin and vaginal swabs, infant stool, and skin swabs will be collected at enrolment and at follow-up visits. For the primary outcome, the trajectory of the infant intestinal microbiota will be characterized by 16S and metagenomic sequencing regarding composition, metabolic potential, and stability during the first 2 years of life. Secondary outcomes will assess the cellular and chemical composition of maternal milk, the impact of nutrition and environment on microbiota development, the maternal microbiome transfer at vaginal or caesarean birth and thereafter on the infant, and correlate parameters of microbiota and maternal milk on infant growth, development, health, and mental well-being. DISCUSSION The Bern birth cohort study will provide a detailed description and normal ranges of the trajectory of microbiota maturation in a high-resource setting. These data will be compared to data from low-resource settings such as from the Zimbabwe-College of Health-Sciences-Birth-Cohort study. Prospective bio-sampling and data collection will allow studying the association of the microbiota with common childhood conditions concerning allergies, obesity, neuro-developmental outcomes , and behaviour. Trial registration The trial has been registered at www. CLINICALTRIALS gov , Identifier: NCT04447742

Portraying the nature of corruption: Using an explorative case-study design

What is the nature of corruption in Western democracies? To answer this research question, the authors study 10 Dutch corruption cases in depth, looking at confidential criminal files. The cases allow them to sketch a general profile of a corruption case. The authors offer nine propositions to portray the nature of corruption. They conclude that corruption usually takes place within enduring relationships, that the process of becoming corrupt can be characterized as a slippery slope, and that important motives for corruption, aside from material gain, include friendship or love, status, and the desire to impress others. The explorative multiple case study methodology helps to expand our understanding of the way in which officials become corrupt. © 2008 The American Society for Public Administration

Endogenous VEGF Is Required for Visual Function: Evidence for a Survival Role on Müller Cells and Photoreceptors

Vascular endothelial growth factor (VEGF) is well known for its role in normal and pathologic neovascularization. However, a growing body of evidence indicates that VEGF also acts on non-vascular cells, both developmentally as well as in the adult. In light of the widespread use of systemic and intraocular anti-VEGF therapies for the treatment of angiogenesis associated with tumor growth and wet macular degeneration, systematic investigation of the role of VEGF in the adult retina is critical.Using immunohistochemistry and Lac-Z reporter mouse lines, we report that VEGF is produced by various cells in the adult mouse retina and that VEGFR2, the primary signaling receptor, is also widely expressed, with strong expression by Müller cells and photoreceptors. Systemic neutralization of VEGF was accomplished in mice by adenoviral expression of sFlt1. After 14 days of VEGF neutralization, there was no effect on the inner and outer retina vasculature, but a significant increase in apoptosis of cells in the inner and outer nuclear layers. By four weeks, the increase in neural cell death was associated with reduced thickness of the inner and outer nuclear layers and a decline in retinal function as measured by electroretinograms. siRNA-based suppression of VEGF expression in a Müller cell line in vitro supports the existence of an autocrine role for VEGF in Müller cell survival. Similarly, the addition of exogenous VEGF to freshly isolated photoreceptor cells and outer-nuclear-layer explants demonstrated VEGF to be highly neuroprotective.These results indicate an important role for endogenous VEGF in the maintenance and function of adult retina neuronal cells and indicate that anti-VEGF therapies should be administered with caution