Evaluation of main-crop stubble height on ratoon rice growth and development   总被引：3，自引：0，他引：3  

Dustin L. Harrell  Jason A. Bond  Sterling Blanche 《Field Crops Research》2009

Rice (Oryza sativa L.) ratooning is the production of a second rice crop from the stubble left behind after the main-crop harvest. Lowering the main-crop stubble height by harvesting the main crop at a lower than traditional height is believed to alter growth parameters and increase ratoon yields. The objectives of this study were to evaluate the effect of main-crop stubble height on ratoon grain yield, agronomics, and cumulative/weekly panicle growth parameters (density, point of origin, and weight). Main-crop ‘Cocodrie’ and ‘Trenasse’ rice cultivars were harvested to leave either a 40- or 20-cm stubble height. When the main-crop stubble was harvested at 20 cm, ratoon rice grain yield in 2007 was increased by 375 and 190 kg ha⁻¹ for Cocodrie and Trenasse, respectively. Yield was not improved in 2006 using the low (20 cm) harvest height. The yield advantage in 2007 was associated with the increased weight of the basal panicles when the main crop was harvested at 20 cm. When the main-crop stubble was 20 cm, basal and axial panicle points of origin were numerically similar 5 weeks after main-crop harvest (WAH), while panicles originating from basal nodes were predominant 6 WAH and beyond. In contrast, when the main-crop stubble was 40 cm, approximately 75% of the emerged panicles originated from axial nodes 5 WAH, panicles from both axial and basal points of origin were nearly identical 6 WAH, and basal panicles were dominant thereafter. Results from this study indicate that when the initial stubble height is reduced from 40 to 20 cm the growth of the ratoon crop is altered by shifting panicle point of origin during the early growth period and delaying maturity.  相似文献   

Fish assemblages of perennial floodplain ponds of the Sacramento River, California (USA), with implications for the conservation of native fishes   总被引：3，自引：0，他引：3  

F. Feyrer  T. R. Sommer  S. C. Zeug  G. O'Leary  & W. Harrell 《Fisheries Management and Ecology》2004,11(5):335-344

To assess the likelihood of enhancing native fish populations by means of floodplain restoration projects, habitat characteristics and fish assemblages of seven perennial floodplain ponds in Yolo Bypass, the primary floodplain of the Sacramento River, California (USA), were examined during summer 2001. Although all ponds were eutrophic, based upon high chlorophyll a or dissolved nutrient concentrations, relatively large shallow ponds generally exhibited higher specific conductivity and dissolved phosphorus concentrations than small deep ponds, which exhibited greater water transparency and total dissolved nitrogen concentrations. Using multiple gear types, 13 688 fishes comprising 23 species were collected. All ponds were dominated by alien fishes; only three native species contributing <1% of the total number of individuals and <3% of overall biomass were captured. Fish assemblage structure varied among ponds, notably between engineered vs. natural ponds, and was related to specific conductance, total dissolved solids and water transparency.  相似文献   

Humoral factors important in resistance of salmonid fish to bacterial disease. II. Anti-Vibrio anguillarum activity in mucus and observations on complement     

Lee W. Harrell  Howard M. Etlinger  Harold O. Hodgins 《Aquaculture (Amsterdam, Netherlands)》1976,7(4):363-370

It has been demonstrated that heat-stable (presumably antibody) and heat-labile (presumably complement) components are necessary to prevent the growth of Vibrio anguillarum in in vitro experiments with trout immune serum and mucus. Anti-V. anguillarum agglutinins were found in the body mucus of intraperitoneally immunized rainbow trout (Salmo gairdneri) 3–6 weeks after serum agglutination titers of 131072 or greater were attained. A component of rainbow trout body mucus was found to be indistinguishable from serum immunoglobulin by immunodiffusion and immunoelectrophoresis.  相似文献   

Effect of human interferon on vesicular stomatitis virus released from bovine embryonic kidney cells     

S A Harrell  R K Maheshwari  S B Mohanty  R M Friedman 《American journal of veterinary research》1982,43(4):565-568

Human lymphoblastoid interferon (IFN) had an antiviral activity in bovine embryonic kidney cells that resulted in the release of vesicular stomatitis virus (VSV) particles with decreased infectivity. The inhibition was dose dependent and the cells were highly sensitive to human IFN. Examination of the proteins of VSV released from bovine cells after IFN treatment showed a reduction in the glycoprotein. Electron microscopic studies revealed a large number of VSV particles with characteristic spike-like surface projections released from nontreated cells. There was a reduction in the number of mature virions produced in IFN-treated cells and the virions lacked the characteristic surface projections.  相似文献   

Vertical transmission of channel catfish virus   总被引：3，自引：0，他引：3  

J A Wise  S F Harrell  R L Busch  J A Boyle 《American journal of veterinary research》1988,49(9):1506-1509

Channel catfish broodfish were examined nondestructively for the presence of channel catfish virus (CCV), using a nucleic acid-probing technique. A dot blot assay was tested and shown to be accurate and rapid in the diagnosis of CCV. Two CCV-positive fish were successfully mated, and fertilized eggs were collected. Offspring that hatched were tested and were shown to have CCV. This result indicated vertical transmission of CCV, a herpesvirus.  相似文献   

Avian community response to vegetation and structural features in grasslands managed with fire and grazing   总被引：1，自引：0，他引：1  

Bryan. R. Coppedge  Samuel. D. Fuhlendorf  Wade. C. Harrell  David. M. Engle 《Biological conservation》2008,141(5):1196-1203

This study examined the importance of natural and manmade structural features on the avian community relative to management-induced vegetation dynamics. The study was conducted within the context of two alternative vegetation management treatments applied to pastures on a tallgrass prairie site in northcentral Oklahoma from 2001 to 2003. The brown-headed cowbird, a brood parasite, and the grasshopper sparrow, a common grassland obligate species, were most abundant in areas managed under a traditional treatment in which entire pastures were annually burned. Conversely, Henslow’s sparrow, a grassland obligate of conservation concern, was completely absent from traditional treatment pastures. Total bird species diversity and grassland obligate richness was highest in the patch-burn treatment, in which only discrete portions of each pasture were burned each year to create a mosaic of vegetation ‘patches’ in various stages of recovery from disturbance. Models of bird abundance reflected not only species-specific vegetation preferences, but also the often negative influence of structural features such as woody edges, roads, and ponds on breeding bird use of grasslands. Our study demonstrated that both disturbance-derived vegetation attributes and structural features contribute to heterogeneity and influence subsequent use by and composition of grassland bird communities.  相似文献   

Use of Civilian Skills in the Army Air Forces     

Harrell TW 《Science (New York, N.Y.)》1947,106(2741):26-28

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Large‐bodied fish migration and residency in a flood basin of the Sacramento River,California, USA     

Ted R. Sommer  William C. Harrell  Frederick Feyrer 《Ecology of Freshwater Fish》2014,23(3):414-423

River–floodplain complexes represent some of the most variable and diverse habitats on earth, yet they are among our planet's most threatened ecosystems. Use of these habitats by large‐bodied fishes is especially poorly understood, particularly in temperate regions. To provide insight into the factors that affect floodplain assemblages and migration, we sampled large‐bodied fishes with a fyke trap for 7 years in the Yolo Bypass, the primary flood basin of the Sacramento River, California. We collected a total of 18,336 individual fish comprised of 27 species, only 41% of which were native. Year‐round resident species white catfish Ameiurus catus, channel catfish Ictalurus punctatus and common carp Cyprinus carpio (all alien species) were the most abundant and comprised 74% of the total catch. Splittail Pogonichthys macrolepidotus (3.8%), white sturgeon Acipenser transmontanus (2.3%) and Sacramento sucker Catostomus occidentalis (1.1%) were the primary native species. We found that seasonal variation in water temperature and flood stage were important factors affecting the fish assemblage structure and the presence of migratory species. American shad Alosa sapidissima, an alien species, showed highest abundance during the early summer upstream migration, when temperatures were warmer. For native species, the abundances of white sturgeon, splittail, Sacramento pikeminnow Ptychocheilus grandis and Sacramento sucker were all highest during flood pulses. While our results suggest that flow alone is not sufficient to control alien species, the strong linkage between native fish migration and flow pulses highlights the importance of river–floodplain connectivity for the conservation of native fishes.  相似文献   

Prevalence and risk factors for hyperinsulinaemia in ponies in Queensland,Australia     

RA Morgan  TW McGowan  CM McGowan 《Australian veterinary journal》2014,92(4):101-106

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Evaluation of red and red-edge reflectance-based vegetation indices for rice biomass and grain yield prediction models in paddy fields     

Yumiko Kanke  Brenda Tubaña  Marilyn Dalen  Dustin Harrell 《Precision Agriculture》2016,17(5):507-530

Remote sensing-based nitrogen (N) management has been evaluated in many crops. The water background and wide range of varieties in rice (Oryza sativa), are unique features that require additional consideration when using sensor technology. The commonly calculated normalized difference vegetation index is of limited use when the crop has reached complete canopy closure. The objective of this research was to evaluate mid-season agronomic parameter and grain yield prediction models along with the effect of water background and of different varieties using a red- and red-edge-based vegetation index. Varieties × N trials were established at the LSU AgCenter Rice Research Station located in Crowley, Louisiana in 2011 and 2012. Canopy spectral reflectance under clear and turbid water, biomass yield, N content, plant coverage, and water depth were collected each week for three consecutive weeks beginning 2 weeks before panicle differentiation. Grain yield was also determined. Water turbidity had an influence on spectral reflectance when canopy coverage was less than 50 %. While water depth influenced red reflectance, this was not carried over when reflectance was transformed to vegetation indices. The red-edge-based vegetation indices, especially those computed by ratio, had stronger relationships with measured agronomic parameters as compared with red-based indices. Furthermore, the effect of variety on the yield prediction model was observed using derivative-based red-edge indices but not with other ratio-based indices. Future researches should focus on developing a generalized yield prediction model using ratio-based red-edge indices across different varieties to extend its applicability in production fields.  相似文献