Effect of cover crop management on soil organic matter   总被引：1，自引：0，他引：1  

Guangwei Ding  Xiaobing Liu  Stephen Herbert  Jeffrey Novak  Dula Amarasiriwardena  Baoshan Xing 《Geoderma》2006,130(3-4):229-239

Characterization of soil organic matter (SOM) is important for determining the overall quality of soils, and cover crop system may change SOM characteristics. The purpose of this study was to examine the effect of cover crops on the chemical and structural composition of SOM. We isolated humic substances (HS) from soils with the following cover crop treatments: (a) vetch (Vicia Villosa Roth.)/rye (Sesale cereale L.), (b) rye alone, and (c) check (no cover crops) that were treated with various nitrogen (N) fertilizer rates. CPMAS-TOSS (cross-polarization magic-angle-spinning and total sideband suppression) ¹³C NMR results indicated that humic acids (HA) from soils under rye only were more aromatic and less aliphatic in character than the other two cover crop systems without fertilizer N treatment. Based on the DRIFT (diffuse reflectance Fourier transform infrared) spectra peak O/R ratios, the intensities of oxygen-containing functional groups to aliphatic and aromatic (referred to as recalcitrant) groups, the highest ratio was found in the HA from the vetch/rye system with fertilizer N. The lowest ratio occurred at the vetch/rye system without fertilizer N treatment. The O/R ratio of fulvic acids (FA) can be ranked as: vetch/rye without fertilizer>vetch/rye with fertilizer>no cover crop without fertilizer>rye alone (with or without fertilizer) soils. Both organic carbon (OC) and light fraction (LF) contents were higher in soils under cover crop treatments with and without fertilizer N than soils with no cover crop. These chemical and spectroscopic data show that cover crops had a profound influence on the SOM and LF characteristics.  相似文献   

Modelling soil temperature in forest clearcuts using climate station data     

R.J. Stathers  T.A. Black  M.D. Novak 《Agricultural and Forest Meteorology》1985,36(2):153-164

A physically based numerical model was developed to estimate the time courses of soil temperature in forest clearcuts from measured solar irradiance, air temperature and wind speed. The model is based upon a finite difference solution of the one-dimensional soil heat flow equation with a surface boundary condition determined from aerodynamic heat transfer and energy balance theory.Modelled soil temperatures were compared with data from two other studies reported in the literature and with temperatures measured in a forest clearcut during 6 and 16 day periods in the summer. The model calculated surface and subsurface soil temperatures accurately over these long intervals. Modelled soil temperatures were relatively insensitive to air temperature, soil thermal properties and the lower boundary soil temperature but quite sensitive to solar irradiance, wind speed and surface roughness.  相似文献   

Intracranial extension of retrobulbar blastomycosis (Blastomyces dermatitidis) in a dog     

Baron ML  Hecht S  Westermeyer HD  Mankin JM  Novak JM  Donnell RL 《Veterinary ophthalmology》2011,14(2):137-141

Blastomycosis (Blastomyces dermatitidis) is a fungal disease that is endemic in the southern United States. This case report illustrates the clinical, MRI and histopathologic findings in a dog with invasion of a retrobulbar blastomycotic lesion into the calvarium. A 5‐year‐old intact female Weimaraner was referred for a 2‐month history of change in behavior and recent onset of visual deficits. Magnetic resonance imaging (MRI) examination revealed a large (5.8 × 2.0 × 2.5 cm) mass extending from the left orbit through a circular defect in the left cranioventral aspect of the calvarium caudally to the level of the pituitary fossa and interthalamic adhesion. The mass was heterogeneously iso‐ to hypointense on T2‐W images, slightly hypointense on T1‐W images, did not attenuate on fluid attenuated inversion recovery (FLAIR) images, and did not show evidence of susceptibility artifact on T2*‐W gradient recalled echo (GRE) images. Vasogenic edema and associated mass effect were noted. The mass showed strong homogeneous contrast enhancement with well‐defined margins and had thickening of the adjacent meninges (dural tail sign). Based on MRI findings a malignant neoplastic process was considered most likely and the patient was placed on oral prednisone to decrease peri‐tumoral inflammation. The dog initially improved but was euthanized 3 weeks later for worsening clinical signs. Histopathologic assessment of the mass revealed marked pyogranulomatous optic neuritis with intralesional fungal yeasts consistent with blastomycosis (Blastomyces dermatitidis). To our knowledge this is the first report of invasion of a retrobulbar blastomycotic lesion into the calvarium in a dog.  相似文献   

Scanning Tunneling Microscopy and Nanolithography on a Conducting Oxide, Rb0.3MoO3     

Garfunkel E  Rudd G  Novak D  Wang S  Ebert G  Greenblatt M  Gustafsson T  Garofalini SH 《Science (New York, N.Y.)》1989,246(4926):99-100

The scanning tunneling microscope has been used to image and modify the surface of a conducting oxide (Rb(0.3)MoO(3))in ambient atmosphere. Individual octahedral MoO(6) units of the oxide can be imaged, and under certain conditions defects can be created in the surface that are stable in air. The ability to produce nanometer-sized structures on the surface of an oxide is demonstrated and discussed with reference to nanolithographic applications.  相似文献   

Food safety program. Endrin monitoring in the Mississippi river     

A F Novak  M R Ramachandra Rao 《Science (New York, N.Y.)》1965,150(704):1732-1733

Twelve successive monthly samplings and analyses of representative fish and shellfish and of mud and water from the lower Mississippi River showed neither a high concentration of endrin nor a time-ordered change in the concentration. The general absence of endrin from the samples indicated no significant contamination.  相似文献   

AN INEXPENSIVE DISPOSABLE FILTER FOR BLOOD AND PLASMA TRANSFUSIONS     

Novak M 《Science (New York, N.Y.)》1943,97(2515):248

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Aggressive and mild Potato virus Y isolates trigger different specific responses in susceptible potato plants     

P. Kogovšek  M. Pompe‐Novak  Š. Baebler  A. Rotter  L. Gow  K. Gruden  G. D. Foster  N. Boonham  M. Ravnikar 《Plant pathology》2010,59(6):1121-1132

Differences in the early responses of two potato cultivars, Igor and Nadine, to two isolates of Potato virus Y (PVY), the aggressive PVY^NTN and the mild PVY^N, were monitored. Microarray and quantitative real‐time PCR analyses were carried out to identify differentially expressed genes after inoculation with each virus isolate. Additionally, symptom severity and development was observed and the amount of virus isolate accumulated in systemically infected leaves was evaluated, where a significantly higher amount of PVY^NTN was detected. Microarray analysis revealed 572, 1288 and 1706 differentially expressed genes at 0·5, 12 and 48 h post‐inoculation, respectively in cv. Igor, with a similar pattern observed in cv. Nadine. Microarray and quantitative real‐time PCR results implied an earlier accumulation of sugars and lower photosynthesis in leaves inoculated with the aggressive isolate than in leaves inoculated with the mild isolate. The PVY^NTN isolate did not activate early differential expression of the Fe‐superoxide dismutase and pectin methylesterase inhibitor (PMEI) genes, indicating a delay in plant response relative to that following PVY^N inoculation. Differences in the expression of the β‐glucanase‐I gene were also observed in early plant responses to inoculation with each virus isolate.  相似文献   

Frequency of occurrence and genetic variability of Grapevine fanleaf virus satellite RNA          下载免费PDF全文

U. Čepin  I. Gutiérrez‐Aguirre  M. Ravnikar  M. Pompe‐Novak 《Plant pathology》2016,65(3):510-520

Little is known about the natural occurrence and genetic variability of nepovirus large satellite RNA (satRNA). This study screened 71 Grapevine fanleaf virus (GFLV) isolates mainly from Slovenia, but also from other countries in Europe and the USA, for the presence of satRNA, using a newly developed RT‐PCR assay. GFLV satRNA (satGFLV) was detected in 72% of naturally GFLV‐infected grapevines analysed, which is the highest frequency of occurrence of satGFLV reported to date. From 39 naturally GFLV‐infected grapevines, 122 satGFLV clones were sequenced and compared to publicly available sequences of satGFLVs and the closely related satRNAs from Arabis mosaic virus (satArMVs). Phylogenetic analyses of these satRNAs revealed that their evolution was driven by substitutions, insertions, deletions, recombinations and reassortments between closely related helper viruses. Phylogenetic relationships of the satGFLVs and satArMVs show their separate and subsequent common evolution. Furthermore, the satGFLVs varied in size and showed higher variability at the amino acid level than at the nucleotide level, just as the 2AHP gene of their helper virus. This study shows that satGFLVs are also similar to their helper virus with respect to their quasispecies nature and their transmission route through anthropogenic exchange of propagation material.  相似文献   

Effect of Glomus mosseae on concentrations of rosmarinic and caffeic acids and essential oil compounds in basil inoculated with Fusarium oxysporum f.sp. basilici     

J.‐P. Toussaint  M. Kraml  M. Nell  S. E. Smith  F. A. Smith  S. Steinkellner  C. Schmiderer  H. Vierheilig  J. Novak 《Plant pathology》2008,57(6):1109-1116

This study investigated the potential of the arbuscular mycorrhizal (AM) fungus Glomus mosseae to protect basil (Ocimum basilicum) against Fusarium oxysporum f.sp. basilici (Fob). It was hypothesised that G. mosseae could confer a bioprotective effect against Fob as a result of increases in leaf rosmarinic (RA) and caffeic acids (CA) or essential oil concentrations. Glomus mosseae conferred a bioprotective effect against Fob by reducing plant mortality to 20% compared to 33% in non‐mycorrhizal (NM) plants. This bioprotective effect was not related to improved phosphorus (P) nutrition, as AM and NM plants treated with Fob had similar shoot P concentrations (6 and 8 mg g^?1 dry weight (DW), respectively). Both AM and NM plants treated with Fob had similar leaf and root RA and CA concentrations. Furthermore, phenolic (40–70 mg CA g^?1 DW) or essential oil concentrations (0·1–0·6 mg g^?1 DW) were not increased in plants treated with the AM fungus and Fob. Therefore, the bioprotective effect conferred by G. mosseae was not a result of increases in the phytochemicals tested in this study. However, under the AM symbiosis, basil plants treated with Fob had lower methyleugenol concentrations in their leaves (0·1 mg g^?1 DW) than NM plants treated with the pathogen (0·6 mg g^?1 DW).  相似文献   

End use performance characterization of unconventional knitted fabrics     

Hafsa Jamshaid  Rajesh Mishra  Jan Novak 《Fibers and Polymers》2015,16(11):2477-2490

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