Tuesday, November 6, 2007 - 3:00 PM
147-3

Spectral and Spatial Response of Nitrogen and Phosphorus Stressed Wheat in Ultraviolet, Visible and Near Infrared Region.

Mohammad Shamim Ansari1, Ken R. Young2, and Marc E. Nicolas2. (1) School of Agriculture and Food Systems, Faculty of Land and Food Resources, The University of Melbourne, Dookie Campus, Dookie, Victoria, 3647, Australia, (2) School of Agriculture & Food Systems, Faculty of Land and Food Resources, The University of Melbourne, Dookie campus, Dookie, Victoria, 3647, Australia

Undersupply of nitrogen (N) and phosphorus (P) leads to loss of plant production whereas an oversupply can lead to runoff from paddock causing downstream eutrophication. Remote sensing technique plays an important role in analyzing plant growth data in a timely fashion, inexpensively and precisely. To determine the spectral response of nutrients in a wheat crop, an experiment was conducted at different levels of N and P, consisting of zero N, zero P, 10% N, 10% P and full nutrient (control) in randomized block design with seven replications. Hyperspectral reflection percentages (200 to 1100 nm at 0.5 nm intervals) were taken using the EPP 2000 fiber optic spectrometer (StellerNet Inc.) at pre-flowering and grain filling stages. Results showed that N and/or P stressed crops could be separated from the full supplied plant nutrient in the ultraviolet (UV), visible and near infrared (NIR) range dependant on plant growth stage. The separation between high N levels (100% N) and low levels (0-10% N) could also be obtained by using the wavelengths of 335- 415 nm (UV to blue), 706 – 934.5 nm (red edge to NIR) at pre-flowering and 355-515.5 nm (UV to blue), 617 – 695 nm (red) and 726 -1075 nm (red edge to NIR) at grain filling. The separation between high P levels (100% P) and low P levels (0- 10% P) could be obtained by using wavelengths of 544 .5 - 612.5 nm (green to red) and 687 - 761.5 nm (red to red edge) at pre-flowering stage and 355 – 521 nm (UV, blue and green), 644 – 692 nm (red) and 716 – 929.5 nm (red edge to NIR) at grain filling stage. Thus, these wavelengths could be useful to derive N and P indices for the spatial and temporal estimation of these nutrients in the plant.