1,720,998 research outputs found
Water management reduces greenhouse gas emissions in a Mediterranean rice paddy field
No full textRice paddy fields are one of the largest anthropogenic sources of methane (CH4), the second most important anthropogenic greenhouse gas (GHG) after carbon dioxide (CO2). For this reason most studies on the GHG budget in these agricultural systems focus on the evaluation of CH4 production. However, these systems also exchange other GHGs with the atmosphere, such as CO2 and nitrous oxide (N2O). To estimate the total global warming potential (GWP) of rice cultivation, a field experiment was carried out in a Mediterranean rice paddy field in the Po Valley (Italy), the largest rice producing region in Europe. For two consecutive years, ecosystem CO2 and CH4 fluxes were assessed using the eddy covariance technique and CH4 and N2O fluxes were measured with closed chambers. The net biome productivity indicated a nearly carbon (C) neutral system in 2009 while it accumulated C in 2010, due to the application of organic fertilizers and the midseason drainage of the otherwise flooded field, the latter having the additional benefit of leading to lower water consumption. The rice paddy field acted as a strong GHG source with a GWP of 1148 g CO(2-)eq m(-2) yr(-1) in 2009 and decreased four-fold in 2010 (289 g CO(2-)eq m(-2) yr(-1)). In both years, the site was a large CH4 source. Differences in the GHG budget between the two years of measurements were mainly caused by the lower CH4 emissions in 2010 (21.0 g CH4 m(-2) compared to 37.4 g CH4 m(-2) in 2009), probably driven by drainage of the otherwise flooded field in the middle of the growing season during 2010 and moderately larger CO2 uptake. The increased N2O fluxes (29%), had a marginal contribution to the GWP. However, midseason drainage, which needs to be evaluated in combination with the concurrent application of organic fertilizers, resulted in small decreases of yield. Our results therefore suggest that an adequate management of the water table level reduces CH4 fluxes and has the potential to decrease the GWP and water losses through evapotranspiration of rice paddy fields, confirming that full GHG budgets should be assessed in combination with yields in order to develop and evaluate effective mitigation strategies. (C) 2016 Elsevier B.V. All rights reserved.FPVI project Nitroeurope-I
Comparison of Aerodynamic, Bowen-Ratio, and Penman-Monteith Methods in Estimating Evapotranspiration of Oil Palm Plantation
Full text linkOil palm is one important agricultural commodity that has high economic value. Oil palm productivity is significantly influenced by its water use (needs). Measurement and estimation of oil palm evapotranspiration is needed for determination of its water needs. Various methods are available and this study compare three methods, consisting of aerodynamic, Bowen-Ratio and Penman-Monteith methods in analyzing water needs/use of oil palms plantation located in PTPN VI Jambi. Peak of evapotranspiration rate occured in the afternoon around 13.00 and 14.00 local time. Bowen-Ratio method has higher estimation value of evapotranspiration than the other two methods. Ratio between evapotranspiration and global radiation of two and ten-years old oil palm plantations remain similar, around 47%. Penman Monteith method has the nearest estimation value to reference method (aerodynamic method) showed by the smallest RMSE value, 0.087 for two years oil palm and 0.157 for ten-years old oil palm
Sensible heat flux of oil palm plantation: Comparing Aerodynamic and Penman-Monteith Methods
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Distribution of invasive plant species in different land-use systems in Sumatera, Indonesia
No full textDisturbances caused by the conversion of rain forests into agricultural systems provide an opportunity for the expansion of Invasive Plant Species (IPS). Bukit Duabelas National Park is one of the few remaining lowland forests in Jambi Province (Sumatera, Indonesia). The surrounding areas up to the national park borders have already been converted into jungle rubber agroforests as well as rubber and oil palm plantations which might lead to an increased spread of IPS into the forest. This study was aimed at compiling a list of IPS and determining their distribution and coverage of IPS in four land use systems (rain forest jungle rubber, rubber and oil palm plantations). Spatial distribution patterns were investigated by creating a horizontal vegetation profile diagram for the permanent plots of the EFForTS project (Ecological and Socioeconomic Functions of Tropical Lowland Rainforest Transformation Systems, http://www.uni-goettingen.de/crc990). The dominance of IPS was determined using Important Value Index. A total of forty IPS were identified across the four land-use systems. The numbers of IPS were the highest in oil palm (28 species) and rubber plantations (27 species), and the lowest in jungle rubber (10 species). IPS were absent in the lowland rain forest. The diversity of IPS was influenced by environmental factors, especially canopy openness. IPS with the highest ground coverage were Dicranopteris linearis and Clidemia hirta. Both of them were found in all three land-use systems outside the rain forest when the forest canopy opens due to illegal logging or other human disturbances. Therefore, reforestation of disturbed areas is recommended to prevent the spread of IPS
Soil moisture determines the effectiveness of two urease inhibitors to decrease N2O emission
No full textAmong the mitigation strategies to prevent nitrogen (N) losses from ureic fertilizers, urease inhibitors (UIs) have been demonstrated to promote high N use efficiency by reducing ammonia (NH3) volatilization. In the last few years, some field experiments have also shown its effectiveness in reducing nitrous oxide (N2O) losses from fertilized soils under conditions of low soil moisture. An incubation experiment was carried out with the aim of assessing the main biotic mechanisms behind N2O emissions once that the UIs N-(n-butyl) thiophosphoric triamid (NBPT) and phenil phosphorodiamidate (PPDA) were applied with Urea (U) under different soil moisture conditions (40, 60 and 80 % water-filled pore space, WFPS). In the same study we tried to analyze to what extent soil WFPS regulates the effect of these inhibitors on N2O emissions. The use of PPDA in our study allowed us to compare the effect of NBPT with that of another commercially available urease inhibitor, aiming to see if the results were inhibitor-specific or not. Based on the results from this experiment, a WFPS (i.e. 60 %) was chosen for a second study (i.e. mesocosm experiment) aiming to assess the efficiency of the UIs to indirectly affect N2O emissions through influencing the pool of soil mineral N. The N2O emissions at 40 % WFPS were almost negligible, being significantly lower from all fertilized treatments than that produced at 60 and 80 % WFPS. When compared to U alone, NBPT+U reduced the N2O emissions at 60 % WFPS but had no effect at 80 % WFPS. The application of PPDA significantly increased the emissions with respect to U at 80 % WFPS whereas no significant effect was found at 60 %. At 80 % WFPS, denitrification was the main source of N2O emissions for all treatments. In the mesocosm study, the application of NBPT+U was an effective strategy to reduce N2O emissions (75 % reduction compared to U alone), due to a lower soil ammonium (NH4+) content induced by the inhibitor. These results suggest that adequate management of the UI NBPT could provide, under certain soil conditions, an opportunity for mitigation of N2O emissions from fertilized soils
Long-term reduced tillage does not enhance crop yield, soil organic carbon stocks or greenhouse gas mitigation under ambient rainfall and rainfall exclusion in a temperate Luvisol
No full texthttp://dx.doi.org/10.13039/501100001659 Deutsche Forschungsgemeinschafthttp://dx.doi.org/10.13039/501100002347 Bundesministerium für Forschung, Technologie und Raumfahr
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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