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dc.contributor.authorAdams, Jennifer Anne
dc.date.accessioned2020-05-04T21:59:58Z
dc.date.available2020-05-04T21:59:58Z
dc.date.issued1987
dc.identifier.urihttps://hdl.handle.net/10182/11822
dc.description.abstractMouse-ear hawkweed is a serious weed of grasslands in the South Island high country. This series of studies looked at how total nitrogen content and levels of phenolics, in particular, umbelliferone changed in response to varying combinations of phosphorus and sulphur fertiliser. Nitrate reductase activity of plant parts under varying levels of external nitrate was also assessed. The trial from which samples were collected was set up. by Dr. D. Scott Grasslands Division, DSIR at Mount John in 1982. Twenty seven combinations of phosphorus and sulphur fertiliser and four extra plots with micro-nutrient application were laid down and oversown with a large mixture of legumes, grasses and herbs to assess the effects of fertility on species composition. Visual assessment of the plots showed that mouse-ear could be effectively controlled using oversowing and fertiliser treatments, with different introduced species dominant under different conditions. At low fertiliser inputs Russel lupin performed well, but white clover was the dominant legume at high fertility. Grasses were dominant using the highest fertiliser application ( 100 kg P / 100 kg S applied annually). Most plots were legume dominant. Mouse-ear hawkweed was the dominant species under unfertilised conditions. The Kjeldahl digestion technique was used to determine total nitrogen levels in whole plants and mature leaves of mouse-ear hawkweed. A response surface was fitted which showed a positive linear trend to phosphorus and a quadratic trend in response to sulphur. Phosphorus and sulphur fertiliser were used to encourage legume growth and hence nitrogen fixation. The nitrogen content of mouse-ear thus reflected the level of available nitrogen in the soil, both from nitrogen fixation and nutrient return via sheep used to graze the trial. Total nitrogen content of mature leaves of mouse-ear hawkweed varied between 2 - 3 % depending on the fertiliser regime. Nitrate reductase activity of root, shoot and stolon of mouse-ear hawkweed was measured using an in vivo assay. Root assimilation was most important at low external nitrate concentrations (74 % of total NRA) but stolon and shoot assimilation became more important as external nitrate concentration increased reaching 29 % and 25 % respectively of total NRA at 20 mol m⁻³ nitrate. Phenolic acids have been implicated in allelopathic behaviour exhibited by mouse-ear hawkweed. Paper chromatography techniques were used to show the presence of umbelliferone caffeic acid and chlorogenic acid in samples of mouse-ear leaf tissue collected from the field, but caffeic acid and chlorogenic acid were present only in trace amounts. Varying fertility conditions did not affect the levels of allelochemicals found in mouse-ear leaves. Levels of allelochemicals in glasshouse grown plants were lower than those in the field, suggesting that other environmental factors could be important in controlling their formation.en
dc.format.extent66 pages
dc.language.isoen
dc.publisherLincoln College, University of Canterbury
dc.rights.urihttps://researcharchive.lincoln.ac.nz/page/rights
dc.subjectmouse-ear hawkweeden
dc.subjectgrasslandsen
dc.subjectnitrogen measurementen
dc.subjectfertiliseren
dc.subjectsoil analysisen
dc.titleStudies on Pilosella officinarum Hill (mouse-ear hawkweed) : changes in nitrogen balance and phenolic allelochemical levels under varying soil fertility conditions : a dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Horticultural Science (Honours) at Lincoln Collegeen
dc.typeDissertationen
thesis.degree.grantorUniversity of Canterburyen
thesis.degree.levelOtheren
thesis.degree.nameBachelor of Horticultural Science with Honoursen
lu.thesis.supervisorDaly, G. T.
lu.contributor.unitDepartment of Soil and Physical Sciences
dc.rights.accessRightsDigital thesis can be viewed by current staff and students of Lincoln University only. If you are the author of this item, please contact us if you wish to discuss making the full text publicly available.en
dc.subject.anzsrc0503 Soil Sciencesen
dc.subject.anzsrc0703 Crop and Pasture Productionen
dc.subject.anzsrc070303 Crop and Pasture Biochemistry and Physiologyen


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