Mechanical weeding effects on soil structure under organic vegetables

Mechanical weeding of vegetables involves the repeated use of cultivators and tractors. This repeated tillage and compaction changes soil structure. We studied these changes in fields of organic beans and carrots. Structure was described using visual assessment and by measuring soil strength. Under beans, the soil strength below the growing root zone was highly variable and in some areas was strong enough to restrict root growth. The carrots were grown in beds containing zones of crop and bare, weeded soil. The structure of the weeded soil in the top 10 cm layer eventually became disrupted and compacted enough to deter root growth. In addition the topsoil and subsoil in the wheel-tracks between the beds became very compact with little distinguish-able structure. This compaction extended to the sub-soil and persisted into the next cropping season

Virus occurrence and transport in a school septic system and unconfined aquifer

A study was conducted to analyze viral indicators of fecal contamination using a high school population as a community source. The study also examined the occurrence, distribution and transport rate of viruses in a productive sand and gravel aquifer. Concentrated septic tank effluent samples were tested for virucidal activity. Results indicated that recovery values for enteroviruses in the ground water ranged between 5 and 30%

Ansätze zur Bewertung von Bodengüte und Ertragspotentialen

Gegenwärtig wird an einer Weltbodenklassifikation gearbeitet.Deren Informationsgehalt zur Bodenfunktionalität wird unzureichend sein. Wir gehen von der Hypothese aus, dass ein einheitliches einfaches Verfahren zur Bewertung der landwirtschaftlichen Bodenqualität im transnationalen oder globalen Rahmen nützlich wäre. Verfügbare Ansätze wurden nach verschiedenen Kriterien wie Praktikabilität im Felde, skalenübergreifende Anwendbarkeit und Korrelation mit Erträgen vergleichend analysiert. Testergebnisse des Müncheberger Soil Quality Rating(M-SQR)in verschiedenen Agrarregionen bestätigen das Potential dieses Ansatzes für die Funktionsbewertung der Böden im globalen Maßstab

Greenhouse gas emissions from soil under organic management

ABSTRACT Land emissions of N 2 O, CO 2 and NH 3 have been subject to little study under organic systems, yet form important aspects of sustainability of such systems. We describe innovative methods developed at SAC to assess trace gas emission using both automatic closed chamber systems (intensive, short term monitoring) and manually-operated closed chamber systems (occasional, long term monitoring). Long-term data were collected from organic ley-arable rotation trials in North-east of Scotland. Short term data were collected to show the effect of timing and depth of ploughing-out of the ley phase on gas emissions. Ploughing gave a shortterm stimulation of CO 2 and, more markedly, of N 2 O emission. Emissions of N 2 O from organic grass-clover leys were considerably lower than from conventional grass. However, some N 2 O emissions from organic arable are higher than from conventional systems, particularly in the first year after ploughing out ley. Ammonia emissions after spreading manure on grass were significant in the summer, though only short-lived

Airborne electromagnetic imaging of discontinuous permafrost

The evolution of permafrost in cold regions is inextricably connected to hydrogeologic processes, climate, and ecosystems. Permafrost thawing has been linked to changes in wetland and lake areas, alteration of the groundwater contribution to stream flow, carbon release, and increased fire frequency. But detailed knowledge about the dynamic state of permafrost in relation to surface and groundwater systems remains an enigma. Here, we present the results of a pioneering ~1,800 line-kilometer airborne electromagnetic survey that shows sediments deposited over the past ~4 million years and the configuration of permafrost to depths of ~100 meters in the Yukon Flats area near Fort Yukon, Alaska. The Yukon Flats is near the boundary between continuous permafrost to the north and discontinuous permafrost to the south, making it an important location for examining permafrost dynamics. Our results not only provide a detailed snapshot of the present-day configuration of permafrost, but they also expose previously unseen details about potential surface – groundwater connections and the thermal legacy of surface water features that has been recorded in the permafrost over the past 1,000 years. This work will be a critical baseline for future permafrost studies aimed at exploring the connections between hydrogeologic, climatic, and ecological processes, and has significant implications for the stewardship of Arctic environments

Dispersion, solvent and metal effects in the binding of gold cations to alkynyl ligands: implications for Au(i) catalysis.

The coordination modes of the [Au(PPh3)](+) cation to metal alkynyl complexes have been investigated. On addition to ruthenium, a vinylidene complex, [Ru(η(5)-C5H5)(PPh3)2([double bond, length as m-dash]C[double bond, length as m-dash]CPh{AuPPh3})](+), is obtained while addition to a gold(iii) compound gives di- and trinuclear gold complexes depending on the conditions employed. In the trinuclear species, a gold(i) cation is sandwiched between two gold(iii) alkynyl complexes, suggesting that coordination of multiple C-C triple bonds to gold is facile

Bodenklassifikation und mittlere Ernteerträge in einigen Agrarlandschaften Eurasiens

Es war zu prüfen, in welchem Maße Bodenklassifikationen Hinweise auf die Ertragsleistung von Getreide und Gras geben. Solche Informationen könnten für die überregional vergleichende Bewertung und standortgerechte agrarische Nutzung von Böden hilfreich sein. Untersucht wurden Catenen und repräsentative Einzelprofile in unterschiedlichen Agrarlandschaften Eurasiens, insbeson-dere in Deutschland, Westsibirien und Nordchina. Die Böden wurden nach der World Reference Base for Soil Resources (WRB 2006) klassifiziert und mittels Müncheberger Soil Quality Rating (M-SQR) funktionell bewertet. Bodendaten wurden nach „FAO Guidelines for soil description, 2006“ im Felde erhoben.Ernte¬erträge und Bewirtschaftungsregime wurden Versuchsberichten entnommen oder im Falle von Praxisflächen gemein¬sam mit dem Bewirtschafter geschätzt. Die Ergebnisse zeigen, dass maßgebliche At-tribute der WRB 2006 wie Referenz-Bodengruppen und Textur- Qualifier be¬reits wesentliche Informationen über die Ertragsleistung von Getreide ge¬ben können. Aufgrund des Fehlens von Informationen über das Thermal- und Feuchteregime der Böden werden im über¬regionalen Maßstab weniger als 50% der Ertragsvariabilität erklärt. Die Bewertungs¬kennziffern des Müncheberger SQR können je nach Landnutzungsintensität und Anpassungsgüte der Indikatoren etwa 50-80 % der Ertragsvariabilität erklären. Es wird geschlussfolgert, dass das M-SQR Potential für die Abschätzung von Ge¬treideerträgen im globalen Maßstab hat. Es könnte eine nützliche Er¬gänzung zur WRB Bodenklassifikation bezüglich der Bodenfunktionalität sein

An EMA analysis of the effect of increasing word length on consonant production in apraxia of speech: A case study

The effect of increasing word length on the articulatory dynamics (i.e. duration, distance, maximum acceleration, maximum deceleration, and maximum velocity) of consonant production in acquired apraxia of speech was investigated using electromagnetic articulography (EMA). Tongue-tip and tongue-back movement of one apraxic patient was recorded using the AG-200 EMA system during word-initial consonant productions in one, two, and three syllable words. Significantly deviant articulatory parameters were recorded for each of the target consonants during one, two, and three syllables words. Word length effects were most evident during the release phase of target consonant productions. The results are discussed with respect to theories of speech motor control as they relate to AOS

Computational Methods for Stability and Control (COMSAC): The Time Has Come

Powerful computational fluid dynamics (CFD) tools have emerged that appear to offer significant benefits as an adjunct to the experimental methods used by the stability and control community to predict aerodynamic parameters. The decreasing costs for and increasing availability of computing hours are making these applications increasingly viable as time goes on and the cost of computing continues to drop. This paper summarizes the efforts of four organizations to utilize high-end computational fluid dynamics (CFD) tools to address the challenges of the stability and control arena. General motivation and the backdrop for these efforts will be summarized as well as examples of current applications