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91.
Phosphorus nutrition of rice in relation to flooding and temporary loss of soil-water saturation in two lowland soils of Cambodia 总被引:1,自引:1,他引:0
In the rainfed lowlands, temporary loss of soil-water saturation during crop growth is a common factor limiting rice (Oryza
sativa L.) yield but its effects on phosphorus (P) availability are poorly understood. Rice plants were transplanted into
pots containing soils that were either continuously flooded, maintained at field capacity or flooded and then dried to field
capacity for 3 weeks during the vegetative stage. A black clay soil (Kandic Plinthaquult) and a sandy soil (Plinthustalf)
from south-east Cambodia were compared with or without amendments by rice straw and P fertilizer.
Under continuously flooded conditions, the growth of rice was vigorous without straw addition and there was a strong response
of rice growth to the addition of P fertilizer. The soil underwent reduction, which increased pH from 4.2 to 5.5 or 6.0, in
the black clay or sandy soil, respectively. By contrast, a loss of soil-water saturation 3 weeks before panicle initiation
(PI) markedly impaired the growth of rice. This was not through any effect of water stress, and the growth reductions were
not as strong as with continued loss of soil-water saturation from transplanting to PI. Fluctuations in soil pH and Eh corresponded
closely to changes in soil-water regimes. Growth reductions were attributed to reduced shoot P levels resulting from the decline
in P availability during the loss of soil-water saturation. The addition of rice straw stimulated soil reduction and lessened
changes in soil pH and Eh during the loss of soil-water saturation in both soils. Straw addition enhanced P uptake by the
rice plants during loss of soil-water saturation, but its beneficial effects could not be attributed to the direct addition
of P, N or K to the soils. Thus the application of rice straw may be effective in lessening the effects of temporary loss
of soil-water saturation on rice growth in lowland rice soils by minimising the decline in P availability.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
92.
Andy D. Robertson Pete Smith Andy W. Stott Emily L. Clark Niall P. McNamara 《Bioenergy Research》2017,10(1):86-101
The carbon (C) dynamics of a bioenergy system are key to correctly defining its viability as a sustainable alternative to conventional fossil fuel energy sources. Recent studies have quantified the greenhouse gas mitigation potential of these bioenergy crops, often concluding that C sequestration in soils plays a primary role in offsetting emissions through energy generation. Miscanthus is a particularly promising bioenergy crop and research has shown that soil C stocks can increase by more than 2 t C ha?1 yr?1. In this study, we use a stable isotope (13C) technique to trace the inputs and outputs from soils below a commercial Miscanthus plantation in Lincolnshire, UK, over the first 7 years of growth after conversion from a conventional arable crop. Results suggest that an unchanging total topsoil (0–30 cm) C stock is caused by Miscanthus additions displacing older soil organic matter. Further, using a comparison between bare soil plots (no new Miscanthus inputs) and undisturbed Miscanthus controls, soil respiration was seen to be unaffected through priming by fresh inputs or rhizosphere. The temperature sensitivity of old soil C was also seen to be very similar with and without the presence of live root biomass. Total soil respiration from control plots was dominated by Miscanthus-derived emissions with autotrophic respiration alone accounting for ~50 % of CO2. Although total soil C stocks did not change significantly over time, the Miscanthus-derived soil C accumulated at a rate of 860 kg C ha?1 yr?1 over the top 30 cm. Ultimately, the results from this study indicate that soil C stocks below Miscanthus plantations do not necessarily increase during the first 7 years. 相似文献
93.
94.
Impacts of natural factors and farming practices on greenhouse gas emissions in the North China Plain: A meta‐analysis 下载免费PDF全文
Requirements for mitigation of the continued increase in greenhouse gas (GHG ) emissions are much needed for the North China Plain (NCP ). We conducted a meta‐analysis of 76 published studies of 24 sites in the NCP to examine the effects of natural conditions and farming practices on GHG emissions in that region. We found that N2O was the main component of the area‐scaled total GHG balance, and the CH 4 contribution was <5%. Precipitation, temperature, soil pH , and texture had no significant impacts on annual GHG emissions, because of limited variation of these factors in the NCP . The N2O emissions increased exponentially with mineral fertilizer N application rate, with y = 0.2389e0.0058x for wheat season and y = 0.365e0.0071x for maize season. Emission factors were estimated at 0.37% for wheat and 0.90% for maize at conventional fertilizer N application rates. The agronomic optimal N rates (241 and 185 kg N ha?1 for wheat and maize, respectively) exhibited great potential for reducing N2O emissions, by 0.39 (29%) and 1.71 (56%) kg N2O‐N ha?1 season?1 for the wheat and maize seasons, respectively. Mixed application of organic manure with reduced mineral fertilizer N could reduce annual N2O emissions by 16% relative to mineral N application alone while maintaining a high crop yield. Compared with conventional tillage, no‐tillage significantly reduced N2O emissions by ~30% in the wheat season, whereas it increased those emissions by ~10% in the maize season. This may have resulted from the lower soil temperature in winter and increased soil moisture in summer under no‐tillage practice. Straw incorporation significantly increased annual N2O emissions, by 26% relative to straw removal. Our analysis indicates that these farming practices could be further tested to mitigate GHG emission and maintain high crop yields in the NCP . 相似文献
95.
Pete Beckman Kamil Iskra Kazutomo Yoshii Susan Coghlan Aroon Nataraj 《Cluster computing》2008,11(1):3-16
We investigate operating system noise, which we identify as one of the main reasons for a lack of synchronicity in parallel
applications. Using a microbenchmark, we measure the noise on several contemporary platforms and find that, even with a general-purpose
operating system, noise can be limited if certain precautions are taken. We then inject artificially generated noise into
a massively parallel system and measure its influence on the performance of collective operations. Our experiments indicate
that on extreme-scale platforms, the performance is correlated with the largest interruption to the application, even if the
probability of such an interruption on a single process is extremely small. We demonstrate that synchronizing the noise can
significantly reduce its negative influence.
相似文献
Aroon NatarajEmail: |
96.
Zhao X Deyanova EG Lubbers LS Zafian P Li JJ Liaw A Song Q Du Y Settlage RE Hickey GJ Yates NA Hendrickson RC 《Journal of proteome research》2008,7(10):4373-4383
Estrogens are a class of steroid hormones that interact with two related but distinct nuclear receptors, estrogen receptor (ER) alpha and beta. To identify potential ER biomarkers, we profiled the rat plasma glycoproteome after treatment with vehicle or 17beta-estradiol (E2) or an ERalpha-selective agonist PPT by differential mass spectrometry. Our comparative proteomic experiment identifies novel E2- and PPT-responsive proteins, such as serine protease inhibitor family members. 相似文献
97.
98.
Kralt D Light B Cheang M MacNair T Wiebe L Limerick B Sarsfield P Hammond G MacDonald K Trepman E Embil JM 《Mycopathologia》2009,167(3):115-124
Background Blastomycosis is an uncommon granulomatous infection caused by the thermally dimorphic fungus Blastomyces dermatitidis. The most frequent clinical infections involve the lung, skin, and bone. Pulmonary manifestations range from asymptomatic
self-limited infection to severe diffuse pneumonia causing respiratory failure.
Objectives To establish the clinical characteristics and outcomes of patients with pulmonary blastomycosis diagnosed at hospitals in
Manitoba and northwestern Ontario, Canada.
Methods A retrospective review of medical records was done for 318 patients with blastomycosis in these regions.
Results The majority of patients were Caucasian (198 (62.5%) patients), male (193 (61%) patients), and residents of Ontario (209 (65.7%)
patients). Most patients were treated in an inpatient hospital ward (266 (84%) patients) and survived (294 (92%) patients).
Pulmonary involvement, either alone or associated with other sites, was present in 296 (93%) of the 318 patients; 22 (7%)
patients had no evidence of pulmonary blastomycosis. The majority of patients had localized lung disease (1–3 quadrants on
chest radiograph involved; 225 (82%) patients). Of 294 (92%) patients requiring hospitalization, 266 (90%) patients received
all inpatient care on a general medical ward; 28 (10%) patients received some care in the intensive care unit (ICU). Factors
associated with ICU admission included diffuse pulmonary disease (four quadrants involved on chest radiograph), diabetes,
and prior use of antimicrobial therapy. Twenty-four (8%) patients died, and multivariate analysis showed that older age and
Aboriginal ethnicity were the significant risk factors for death from blastomycosis.
Conclusion Blastomycosis is a cause of serious, potentially life-threatening pulmonary infection in this geographic region.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
99.
David L. Kimbro Edwin D. Grosholz Adam J. Baukus Nicholas J. Nesbitt Nicole M. Travis Sarikka Attoe Caitlin Coleman-Hulbert 《Oecologia》2009,160(3):563-575
Although invasive species often resemble their native counterparts, differences in their foraging and anti-predator strategies
may disrupt native food webs. In a California estuary, we showed that regions dominated by native crabs and native whelks
have low mortality of native oysters (the basal prey), while regions dominated by invasive crabs and invasive whelks have
high oyster mortality and are consequently losing a biologically diverse habitat. Using field experiments, we demonstrated
that the invasive whelk’s distribution is causally related to a large-scale pattern of oyster mortality. To determine whether
predator–prey interactions between crabs (top predators) and whelks (intermediate consumers) indirectly control the pattern
of oyster mortality, we manipulated the presence and invasion status of the intermediate and top trophic levels in laboratory
mesocosms. Our results show that native crabs indirectly maintain a portion of the estuary’s oyster habitat by both consuming
native whelks (density-mediated trophic cascade) and altering their foraging behavior (trait-mediated trophic cascade). In
contrast, invasive whelks are naive to crab predators and fail to avoid them, thereby inhibiting trait-mediated cascades and
their invasion into areas with native crabs. Similarly, when native crabs are replaced with invasive crabs, the naive foraging
strategy and smaller size of invasive crabs prevents them from efficiently consuming adult whelks, thereby inhibiting strong
density-mediated cascades. Thus, while trophic cascades allow native crabs, whelks, and oysters to locally co-exist, the replacement
of native crabs and whelks by functionally similar invasive species results in severe depletion of native oysters. As coastal
systems become increasingly invaded, the mismatch of evolutionarily based strategies among predators and prey may lead to
further losses of critical habitat that support marine biodiversity and ecosystem function.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
100.