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Stanhill G.,Institute of Soil, Water and Environmental Sciences
Journal of Geophysical Research: Atmospheres | Year: 2011

A 120 year series of climate measurements at Armagh Observatory, a rural site in Northern Ireland, was analyzed to yield monthly, seasonal, and annual values of long- and short-wave irradiances which were then related to the measured changes in air temperature. Three quarters of the significant increase and large decadal variations in atmospheric long-wave radiation was associated with the concurrent changes measured in specific humidity; the remaining quarter was associated with increases in the concentrations of carbon dioxide and other anthropogenic radiatively active gases. Significant but smaller long-term decreases in short-wave solar irradiance reduced by half the net, all-wave radiation forcing at the surface. Together the changes in long- and short-wave irradiances at Armagh accounted for more than three quarters of the interannual variations in mean annual temperatures. Climate sensitivity to long-wave forcing at the surface, 0.121°C per W m-2, was 5 times greater than that to short-wave forcing, and two possible explanations for this difference, water vapor feedback and changes in atmospheric circulation, are discussed. Copyright 2011 by the American Geophysical Union. Source


Tanny J.,Institute of Soil, Water and Environmental Sciences
Biosystems Engineering | Year: 2013

The use of porous screens to cover agricultural crops is constantly increasing. Screens are mainly used to reduce high radiation loads and wind speed, to protect the crop from hail storms and to minimise the invasion of insects thus allowing a significant reduction in pesticide application. Since screens impede the exchange rate of radiation, mass, heat and momentum between the crop and the atmosphere they modify the crop microclimate and its water requirements. The increased use of screens by growers has triggered the expansion of research on the effects of various screens and screenhouses on microclimate and crop evapotranspiration, as well as on produce quality and quantity. Although research on screenhouse microclimate can be traced back to the beginning of the 20th century, only during the past few decades has a much better understanding of the screenhouse environment been achieved. This paper reviews past research and recent advances regarding microclimate and evapotranspiration of crops under screens and in screenhouses. It covers the issues of radiation, air velocity, ventilation, turbulence, temperature, humidity, evapotranspiration and water use efficiency. The review shows that although screens reduce the transmission of total radiant energy, the effect on air temperature is complex, and depends on additional factors. Future research should focus on modelling the screenhouse-crop system under realistic conditions, using advanced simulation tools. High quality data sets from field studies will be needed to develop and validate such models. © 2012 IAgrE. Source


Assouline S.,Institute of Soil, Water and Environmental Sciences
Water Resources Research | Year: 2013

Infiltration is a key process in aspects of hydrology, agricultural and civil engineering, irrigation design, and soil and water conservation. It is complex, depending on soil and rainfall properties and initial and boundary conditions within the flow domain. During the last century, a great deal of effort has been invested to understand the physics of infiltration and to develop quantitative predictors of infiltration dynamics. Jean-Yves Parlange and Wilfried Brutsaert have made seminal contributions, especially in the area of infiltration theory and related analytical solutions to the flow equations. This review retraces the landmark discoveries and the evolution of the conceptual approaches and the mathematical solutions applied to the problem of infiltration into porous media, highlighting the pivotal contributions of Parlange and Brutsaert. A historical retrospective of physical models of infiltration is followed by the presentation of mathematical methods leading to analytical solutions of the flow equations. This review then addresses the time compression approximation developed to estimate infiltration at the transition between preponding and postponding conditions. Finally, the effects of special conditions, such as the presence of air and heterogeneity in soil properties, on infiltration are considered. © 2013. American Geophysical Union. All Rights Reserved. Source


Shoresh M.,Institute of Soil, Water and Environmental Sciences | Harman G.E.,Cornell University | Mastouri F.,Cornell University
Annual Review of Phytopathology | Year: 2010

Biocontrol fungi (BCF) are agents that control plant diseases. These include the well-known Trichoderma spp. and the recently described Sebacinales spp. They have the ability to control numerous foliar, root, and fruit pathogens and even invertebrates such as nematodes. However, this is only a subset of their abilities. We now know that they also have the ability to ameliorate a wide range of abiotic stresses, and some of them can also alleviate physiological stresses such as seed aging. They can also enhance nutrient uptake in plants and can substantially increase nitrogen use efficiency in crops. These abilities may be more important to agriculture than disease control. Some strains also have abilities to improve photosynthetic efficiency and probably respiratory activities of plants. All of these capabilities are a consequence of their abilities to reprogram plant gene expression, probably through activation of a limited number of general plant pathways. © 2010 by Annual Reviews. All rights reserved. Source


Cytryn E.,Institute of Soil, Water and Environmental Sciences
Soil Biology and Biochemistry | Year: 2013

Antibiotic resistance is a global phenomenon with severe epidemiological ramifications. Although the spread of antibiotic resistance is generally associated with selection derived from clinical use of antibiotics, recent studies have indicated that global proliferation of antibiotic resistance is also affiliated with natural environmental reservoirs, which can potentially transfer antibiotic resistance genes to clinically relevant bacteria via drinking water and the food chain. Terrestrial antibiotic resistance reservoirs are traditionally linked to anthropogenic activities such as manure and biosolid application, wastewater irrigation and agricultural application of antibiotic compounds that transmit residual concentrations of antibiotic compounds (that exert selective pressure), antibiotic resistant bacteria and antibiotic resistance genes to the soil. Although some evidence correlates between anthropogenic factors and elevated levels of antibiotic resistance in soil, it is becoming increasingly clear that un-impacted and pristine soils contain highly diverse and abundant levels of antibiotic resistant bacteria, which harbor a wide array of clinically-associated and novel antibiotic resistance genes. This has led to the resistome hypothesis, which speculates that many pathogen-associated antibiotic resistance genes originated in antibiotic-producing soil bacteria and reached pathogens via horizontal gene transfer. This review provides a holistic overview of how external and intrinsic factors influence soil antibiotic resistance. •Antibiotic resistance (AR) is a major health concern.•Anthropogenic activities such as manure amendment can enhance soil AR reservoirs.•Non-impacted soils contain highly diverse collections of AR genes.•Native soil AR genes appear to be the source of many AR genes in pathogens. © 2013 Elsevier Ltd. Source

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