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In the USA a suggested method for correcting late season K deficiencies in cotton (Gossypium hirsutum L.) is by in-row deep placement of K fertilizer. Experiments were conducted on three Alabama soils (southeastern USA) for 3 years to evaluate cotton response to K fertilizer when surface broadcast with and without in-row subsoiling (to 38 cm depth) or deep placed in the in-row subsoil channel. Potassium was applied at rates ranging from 0 to 84 kg K ha−1. Deep placement was achieved with a fertilizer applicator developed to distribute dry fertilizer at three depths down the back of the subsoil shank. All three soils also had deep placement treatments of 1680 kg ha−1 agricultural limestone with and without 84 kg K ha−1. Soils were an Emory silt loam (fine-silty, siliceous Fluventic Umbric Dystrochrepts), a Norfolk sandy loam (fine-loamy, siliceous Typic Kandiudults), and a Lucedale sandy clay loam (fine-loamy, siliceous Rhodic Paleuduts). All three soils had medium soil test K concentrations in the plow layer and medium or low concentrations of K at greater depths. The Norfolk soil had a well-developed traffic pan and in-row subsoiling increased seed cotton yields by an average of 22% during the 3 years of the study. Cotton responded to K fertilization in 2 out of 3 years at each location (6 out of 9 site-years) regardless of the method of K application. Annual applications of 84 kg K ha−1 increased 3 year average seed cotton yields by 17%, 10% and 19% on the Emory, Norfolk and Lucedale soils, respectively. Deep placement of agricultural limestone with or without K fertilizer for cotton did not increase cotton yields. 相似文献
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Ronan A. Mullins MVB DECVS Carlos Sanchez Villamil DVM Laura E. Selmic BVetMed MPH DACVS-SA DECVS Michael S. Tivers BVSc PhD DECVS J. Brad Case DVM MS DACVS Ameet Singh BSc DVM DVSc DACVS Kelley M. Thieman Mankin DVM MS DACVS Davina M. Anderson MA VetMB PhD DSAS DECVS Robert N. White BSc BVetMed DSAS DECVS SFHEA Kathryn M. Pratschke MVB MVM DECVS Hilde de Rooster DVM MVM PhD DECVS Anne Kummeling DVM PhD DECVS Donald A. Yool BVMS PhD DECVS SFHEA Melanie Olive DVM Jean-Philippe Billet Dr vét DECVS Ines Gordo DVM MS Herve Brissot DV DECVS Cameron Broome BVSc DVCS FANZCVS Barbara M. Kirby DVM MS DACVS DECVS 《Veterinary surgery : VS》2020,49(5):958-970
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Haemophilus parasuis, the bacterium responsible for Gl?sser's disease, is a pathogen of significant concern in modern high-health swine production systems but there is little information regarding the identity or function of its virulence factors. Several important human mucosal pathogens, including the closely related bacterium Haemophilus influenzae, utilize IgA proteases to aid in defeating the host immune response and facilitate disease but it is unknown whether H. parasuis synthesizes any product with IgA protease activity. To investigate potential virulence mechanisms of H. parasuis, we evaluated five strains for their ability to digest purified IgA. Western blotting demonstrated cleavage of swine IgA, but not human IgA1, following incubation with culture supernatants from three strains, two of which are known to cause invasive disease. No genes with homology to the H. influenzae IgA protease genes iga and igaB could be identified in any H. parasuis strain using either PCR or Southern blotting. These results demonstrate that a novel IgA protease produced by some strains of H. parasuis cleaves the swine IgA heavy chain at a site not found in human IgA1. 相似文献
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SUMMARY Thirteen Tammar wallabies (Macropus eugenii) were dosed orally with 500, 1000 or 10 000 oocysts of Toxoplasma gondii, as part of a vaccination trial. Eleven animals died of acute toxoplasmosis 9 to 15 days after challenge. The lesions were similar in all animals, consisting of foci of necrosis and inflammation in the intestines, lymphoid tissue, adrenal cortex, heart, skeletal muscle and brain, and severe generalised pulmonary congestion and oedema. Free and intracellular tachyzoites of Toxoplasma were associated with the lesions. The remaining 2 animals had shown no signs of disease when euthanased four months after challenge. Small, focal, non-suppurative inflammatory lesions were seen in brain, heart and skeletal muscle of these animals and chronic Toxoplasma infection was confirmed by mouse inoculation. 相似文献
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Abstract. Field measurements of cumulative infiltration and of the matric potential prior to infiltration were made with double-ring infiltrometers and tensiometers, respectively, on two sandy loams in north-east Scotland. The time to ponding for constant-rate infiltration was also measured in the same infiltrometers by applying water at a constant rate until ponding commenced. Under the range of initial potentials studied (-2 to - 17 kPa), an exponential relation was adequate to describe the relation between sorptivity and initial matric potential. The time to ponding was also strongly dependent on initial matric potential and increased dramatically as the soil became drier. Measurements of time to ponding were in good agreement with values predicted from the theory of Clothier et al. (1981) using values for sorptivity and the A parameter obtained from the cumulative infiltration experiments. Measurements and predictions clearly showed the importance of the sorptivity versus initial matric potential relation in controlling the time to ponding of such sandy soils. These results have implications for determining the generation of runoff and the establishment of stream flows, as well as determining optimum rates and design of irrigation. 相似文献
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D Pardi E A Hoover S L Quackenbush J I Mullins G N Callahan 《Veterinary immunology and immunopathology》1991,28(3-4):183-200
We used a panel of in vitro assays to investigate the nature of immune dysfunction in cats infected with FeLV-FAIDS, a naturally occurring, molecularly cloned feline leukemia virus (FeLV) isolate which induces a fatal immunodeficiency syndrome in infected cats. During the asymptomatic period preceding immunodeficiency disease, we were unable to detect any deficits in concanavalin A-induced blastogenesis, xenogeneic mixed-lymphocyte reaction assays, stimulation of lymphocytes by soluble protein antigen, and cytotoxic T lymphocyte assays. However, during this period humoral immune responses in the FeLV-FAIDS-infected cats were dramatically impaired. As early as 9 weeks after virus inoculation, the ability to mount either an IgM or IgG response to soluble protein antigens was lost. Neither B cell function, as assessed by lipopolysaccharide-induced blastogenesis or circulating B cell numbers, as assessed by immunofluorescence, differed between infected and control cats. These results suggest that FeLV-FAIDS infection may impair a subpopulation of T helper cells, that provides help for the production of antibody. Consistent with earlier observations of cats naturally infected with FeLV, our results indicate that early impairment of humoral immunity is an important component of the immunodeficiency syndrome induced by FeLV in cats. 相似文献