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The project dealt with modelling the interaction of nitrogen nutrition and stripe rust (yellow rust) incidence in wheat using spectral reflectance characteristics at different spatial scales as observed by ground based sensors, airborne and satellite data. Experimental plots, with different levels of N application, variety and seed treatment for stripe rust disease, were set up in crop seasons 2006 and 2007. Temporal ground based multispectral data were collected using Crop Circle ACS-210 (Holland Scientific Inc., NE, USA) and the GreenSeeker model 505 (Ntech Industries Inc., CA, USA). Hyperspectral data were collected using USB 2000 (Ocean Optics, FL, USA). This ground based data were analysed in relation to airborne data collected using an airborne multispectral sensor, UNEBiRD (UNE, Armidale). Multispectral and hyperspectral vegetation indices (VIs) derived from the two years of data were analysed in relation to the occurrence of N deficiency, disease incidence, LAI, chlorophyll content, biomass and yield in wheat. Further, applicability of these VI based models at a higher spatial scale was examined employing multispectral (Landsat 5TM ) and hyperspectral (EO1 Hyperion) satellite data acquired over commercial wheat paddocks in northern NSW, Australia. Analysis of agronomic data confirmed the expected outcomes of a positive correlation between N application and yield up to a certain rate of N application, with further addition of N causing yield to plateau or subsequently decrease. This study also confirmed that there was significant positive correlations between N application and stripe rust severity. |
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