oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Microbial Community Composition as Affected by Dryland Cropping Systems and Tillage in a Semiarid Sandy Soil  [PDF]
Verónica Acosta-Martínez,Scot E. Dowd,Colin W. Bell,Robert Lascano,Jill D. Booker,Ted M. Zobeck,Dan R. Upchurch
Diversity , 2010, DOI: 10.3390/d2060910
Abstract: This study evaluated microbial communities of soil (0–10 cm) as affected by dryland cropping systems under different tillage practices after 5 years. The soil type was an Olton sandy loam with an average of 16.4% clay, 67.6% sand and 0.65 g kg ?1 of organic matter (OM). The cropping systems evaluated were grain sorghum ( Sorghum bicolor L .)—cotton ( Gossypium hirsutum) (Sr g-Ct), cotton-winter rye ( Secale cereale)-grain sorghum (Ct-Rye-Sr g), and a rotation of forage (f) sorghum ( Sorghum bicolor L. and Sorghum sudanense) with winter rye (Sr f-Rye), which were under no-tillage (nt) and conventional tillage (ct) practices. Soil microbial communities under cotton based cropping systems (Sr g-Ct and Ct-Rye-Sr g) showed lower fungal:bacterial ratios compared to the soil under Sr f-Rye. Soil under Sr f-Rye showed higher population densities of Bacteroidetes and Proteobacteria while lower Actinobacteria compared to Sr g-Ct and Ct-Rye-Sr g. Chloroflexi, Gemmatimonadetes and Verrucomicrobiae were higher in tilled soil compared to the no-tilled plots. Regardless the limited irrigation available to sustain agricultural production within these dryland cropping systems, this study demonstrated that differences in microbial communities are more affected by crop rotation than tillage management history. Although soil fungal diversity was not analyzed in this study, pyrosequencing suggests that tillage practices can affect bacterial phyla distribution in this sandy soil.
Modeling Impacts of Alternative Practices on Net Global Warming Potential and Greenhouse Gas Intensity from Rice–Wheat Annual Rotation in China  [PDF]
Jinyang Wang, Xiaolin Zhang, Yinglie Liu, Xiaojian Pan, Pingli Liu, Zhaozhi Chen, Taiqing Huang, Zhengqin Xiong
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0045668
Abstract: Background Evaluating the net exchange of greenhouse gas (GHG) emissions in conjunction with soil carbon sequestration may give a comprehensive insight on the role of agricultural production in global warming. Materials and Methods Measured data of methane (CH4) and nitrous oxide (N2O) were utilized to test the applicability of the Denitrification and Decomposition (DNDC) model to a winter wheat – single rice rotation system in southern China. Six alternative scenarios were simulated against the baseline scenario to evaluate their long-term (45-year) impacts on net global warming potential (GWP) and greenhouse gas intensity (GHGI). Principal Results The simulated cumulative CH4 emissions fell within the statistical deviation ranges of the field data, with the exception of N2O emissions during rice-growing season and both gases from the control treatment. Sensitivity tests showed that both CH4 and N2O emissions were significantly affected by changes in both environmental factors and management practices. Compared with the baseline scenario, the long-term simulation had the following results: (1) high straw return and manure amendment scenarios greatly increased CH4 emissions, while other scenarios had similar CH4 emissions, (2) high inorganic N fertilizer increased N2O emissions while manure amendment and reduced inorganic N fertilizer scenarios decreased N2O emissions, (3) the mean annual soil organic carbon sequestration rates (SOCSR) under manure amendment, high straw return, and no-tillage scenarios averaged 0.20 t C ha?1 yr?1, being greater than other scenarios, and (4) the reduced inorganic N fertilizer scenario produced the least N loss from the system, while all the scenarios produced comparable grain yields. Conclusions In terms of net GWP and GHGI for the comprehensive assessment of climate change and crop production, reduced inorganic N fertilizer scenario followed by no-tillage scenario would be advocated for this specified cropping system.
Predicting the global warming potential of agro-ecosystems  [PDF]
S. Lehuger,B. Gabrielle,E. Larmanou,P. Laville
Biogeosciences Discussions , 2007,
Abstract: Nitrous oxide, carbon dioxide and methane are the main biogenic greenhouse gases (GHG) contributing to the global warming potential (GWP) of agro-ecosystems. Evaluating the impact of agriculture on climate thus requires a capacity to predict the net exchanges of these gases in an integrated manner, as related to environmental conditions and crop management. Here, we used two year-round data sets from two intensively-monitored cropping systems in northern France to test the ability of the biophysical crop model CERES-EGC to simulate GHG exchanges at the plot-scale. The experiments involved maize and rapeseed crops on a loam and rendzina soils, respectively. The model was subsequently extrapolated to predict CO2 and N2O fluxes over an entire crop rotation. Indirect emissions (IE) arising from the production of agricultural inputs and from cropping operations were also added to the final GWP. One experimental site (involving a wheat-maize-barley rotation on a loamy soil) was a net source of GHG with a GWP of 350 kg CO2-C eq ha 1 yr 1, of which 75% were due to IE and 25% to direct N2O emissions. The other site (involving an oilseed rape-wheat-barley rotation on a rendzina) was a net sink of GHG for –250 kg CO2-C eq ha 1 yr 1, mainly due to a higher predicted C sequestration potential and C return from crops. Such modelling approach makes it possible to test various agronomic management scenarios, in order to design productive agro-ecosystems with low global warming impact.
Global warming and greenhouse gases  [PDF]
Beli? Dragoljub S.
Facta Universitatis Series : Physics, Chemistry and Technology , 2006, DOI: 10.2298/fupct0601045b
Abstract: Global warming or Climate change refers to long-term fluctuations in temperature, precipitation, wind, and other elements of the Earth's climate system. Natural processes such as solar-irradiance variations, variations in the Earth's orbital parameters, and volcanic activity can produce variations in climate. The climate system can also be influenced by changes in the concentration of various gases in the atmosphere, which affect the Earth's absorption of radiation.
Greenhouse gas emissions from Indian rice fields: calibration and upscaling using the DNDC model  [PDF]
H. Pathak,C. Li,R. Wassmann
Biogeosciences Discussions , 2005,
Abstract: Crop growth simulation models provide a means to quantify the effects of climate, soil and management on crop growth and biogeochemical processes in soil. The Denitrification and Decomposition (DNDC) model was evaluated for its ability to simulate methane (CH4), nitrous oxide (N2O) and carbon dioxide (CO2) emissions from Indian rice fields with various management practices. The model was calibrated and validated for field experiments in New Delhi, India. The observed yield, N uptake and greenhouse gas (GHG) emissions were in good agreement with the values predicted by the model. The model was then applied for estimation of GHG emissions from rice fields in India using a newly compiled soil/climate/land use database. Continuous flooding of rice fields (42.25 million ha) resulted in annual net emissions of 1.07–1.10, 0.038–0.048 and 21.16–60.96 Tg of CH4-C, N2O-N and CO2-C, respectively, with a cumulated global warming potential (GWP) of 130.93–272.83 Tg CO2 equivalent. Intermittent flooding of rice fields reduced annual net emissions to 0.12–0.13 Tg CH4-C and 16.66–48.80 Tg CO2-C while N2O emission increased to 0.056–0.060 Tg N2O-N. The GWP, however, reduced to 91.73–211.80 Tg CO2 equivalent. The study suggests that the model can be applied for studying the GHG related issues in rice cropping systems of India.
Being creative in a greenhouse: art and global warming  [PDF]
Donato Ramani
JCOM : Journal of Science Communication , 2008,
Abstract: The world, all at once, has become a small world. Not only owing to TV, satellites and the Internet that allow us to jump from side to side of our planet in a click. But also owing to a phenomenon that evokes dry lands, devastating rains, tsunamis and hurricanes, torrid summers and melting glaciers: global warming. In the heated argument on this issue with so many people talking, in the past few years also artists have made their rising voice be heard. Artists-popularisers, aware of their role and of the considerable communication potential of the art medium. Because “One salient image, sculpture or event can speak louder than volumes of scientific data”.
CLIMESCO: evolution of cropping systems as affected by climate change
Domenico Ventrella
Italian Journal of Agronomy , 2012, DOI: 10.4081/ija.2012.e1
Abstract: In this number of Italian Journal of Agronomy, seventeen scientific papers are published on the main results of the project CLIMESCO. This project was supported by three Italian Ministries (“Ministero dell'Istruzione, dell'Università e della Ricerca”, “Ministero delle Politiche Agricole Alimentari e Forestali” and “Ministero dell'Ambiente e della tutela del territorio e del Mare”) in the framework of “Fondo Integrativo Speciale Ricerca” (FISR, Special Integrated Research Fund). Most recent studies based on observed data and simulations of future climate conditions showed that the global increase of temperatures is most likely due to the increased concentration of Green House Gases. The effect of warming is unequally distributed around the globe, with some areas more sensitive to climate change than others, as the Mediterranean region. Climate change over this region is shown to be characterized by increasing temperatures and by relatively large changes in the frequency of extreme climatic events for both temperature and rainfall. The agricultural and food systems represent one of the most sensitive and vulnerable sectors of the area....
Growth and productivity of corn as affected by mulching and tillage in Alley cropping systems
Moura, Emanoel Gomes de;Albuquerque, Jonas Mendes;Aguiar, Alana das Chagas Ferreira;
Scientia Agricola , 2008, DOI: 10.1590/S0103-90162008000200014
Abstract: alley cropping has been considered a means of intensifying land use sustainably as an alternative to slash and burn agriculture in tropical regions. an experimental trial was used to evaluating the growth and productivity of corn under alley cropping to test the viability of this system as a sustainable land use practice in an amazonian ultisol. the experimental layout was a completely randomized block design with four replications of six treatments: mulch with 13.4 and 8.9 t ha-1 of pigeon pea, and a control treatment without mulch of pigeon pea, with or without tillage. sustainability of soil and crop were determined from changes on physical properties, such as total porosity, air capacity, available water capacity of the soil, net assimilation rate, crop growth rate, and leaf area index, as well as several productivity parameters, including average weight of ears, weight of 100 grains, and total dry matter. both mulching and tillage increased the air capacity. mulching of tilled areas protects the soil against the rainfall impact and prevented its recompaction. the reduced air capacity of the soil had a negative impact on the net assimilation rate, resulting in lower productivity in the no-mulch and no-till plots, mainly due to the reduction of grain weight.
Effects of long-term cropping on the forms and the availability of micronutrients in dryland soils on the Loess Plateau
黄土高原旱地长期种植作物对土壤微量元素形态和有效性的影响

WEI Xiao-Rong,
魏孝荣

生态学报 , 2005,
Abstract: The low availability of soil micronutrients in dryland of the Loess Plateau cannot meet the need of crop growth and then it has become one of the limiting factors for the agriculture production in this area for many years.The current cropping systems applied in the area may have effects on the availability of soil micronutrients.The long-term field cropping experiment,which composed of fallow(FA),continuous clover cropping(CC),continuous wheat cropping(WC), and clover-legumes rotation(CLR),was initiated in ...
New proofs of the recent climate warming over the Tibetan Plateau as a result of the increasing greenhouse gases emissions
Anmin Duan,Guoxiong Wu,Qiong Zhang,Yimin Liu
Chinese Science Bulletin , 2006, DOI: 10.1007/s11434-006-1396-6
Abstract: A striking climate warming over the Tibetan Plateau during the last decades has been revealed by many studies, but evidence linking it to human activity is insufficient. By using historical observations, here we show that the in situ climate warming is accompanied by a distinct decreasing trend of the diurnal range of surface air temperature. The ERA40 reanalysis further indicates that there seems to be a coherent warming trend near the tropopause but a cooling trend in the lower stratosphere. Moreover, all these features can be reproduced in two coupled climate models forced by observed CO2 concentration of the 20th century but cannot be produced by the fixed external conditions before the industrial revolution. These suggest that the recent climate warming over the Tibetan Plateau primarily results from the increasing anthropogenic greenhouse gases emissions, and impacts of the increased greenhouse gases emissions upon the climate change in the plateau are probably more serious than the rest of the world.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.