Monday, November 5, 2007
51-1

Remote Sensing for Canopy-level Nitrogen and Water Status Detection in Rainfed Wheat.

Glenn Fitzgerald1, Daniel Rodriguez2, Garry O'Leary1, and Robert Belford3. (1) Department of Primary Industries, Private Bag 260, 110 Natimuk Rd., Horsham, 3401, Australia, (2) Department of Primary Industries and Fisheries, 203 Tor St, Toowoomba, 4350, Australia, (3) Curtin University of Technology, Muresk Institute, Private Bag 1, Northam, 6401, Australia

Targeting the right amount of nitrogen (N) at the right location and physiological stage could reduce or at least redistribute N inputs leading to improved N use efficiency on a field scale. This could reduce input costs and lower the risk of off-farm movement of chemicals. Under rainfed conditions, the spatial distribution of N uptake is dependent on soil and plant water status imposed by rainfall patterns. Thus, ideally, N should be applied only to areas with sufficient plant available water. Two remote sensing indices, the Canopy Chlorophyll Content Index (CCCI) and Water Deficit Index (WDI) were used to simultaneously measure N and water stress, respectively, in a three-year (2004-2006) plot-level wheat experiment set up with varying levels of N and water stress near Horsham, Victoria, Australia. These indices are designed to minimize the effect of incomplete ground cover on the measure of the given stress. Ground-based and aerial spectral and thermal infrared sensors and imagers were deployed and extensive plant and soils data were collected to develop relationships between crop response and sensor data to the N and water treatments. Preliminary results show that with ground-based spectral reading, the CCCI consistently estimated canopy N near stem elongation (Zadoks 31) with correlations (r2) ranging between 0.65 and 0.75. The WDI was able to indicate relative water stress differences between rainfed and irrigated plots as well as track changes over time. Future research will endeavour to improve the ability of both indices to detect stress and develop uniform calibrations across locations and seasons.