Nitrogen Content of Rice Leaves as Predicted by SPAD, NIR, Spectral Reflectance and Leaf Color Charts.
(S04-witt413035-oral)
Authors:
C. Witt* - IRRI, Philippines
J.M.C. Cabrera-Pasuquin - IRRI, Philippines R. Mutters - Univ. of California, Oroville, CA S. Peng - IRRI, Philippines
Abstract:
The accurate estimation of leaf nitrogen (N) content in rice is of equal importance in research and extension. The objective of this study was to compare the accuracy of a chlorophyll meter (SPAD), a Near Infrared Reflectance (NIR) meter, and leaf color charts (LCC) with spectral reflectance (SR) measurements of rice leaves in assessing leaf N. A two-season field experiment in 2001 included 10 modern varieties grown at three N levels. SPAD explained only 40% and NIR only 34% of the
variation in leaf N based on dry weight (Ndw). Both SPAD and NIR explained 79% of the variation in Ndw only after adjusting readings for leaf thickness. Partial Least Squares (PLS) regression was able to account for over 99% of the predictor variation (reflectance) and over 96% of the response variation (leaf N content). Available LCCs differed in their reflectance characterizing the range from light to dark green, and their general SR patterns that characterize the ‘type of green’ of each chart. Regression analysis of leaf SR measurements showed little difference in SR patterns among varieties, sampling days and seasons, so that the ‘type of green’ is largely the same for all varieties. Based on the actual leaf SR measurements, we developed target SR patterns for an ideal LCC prototype. We discuss the relevance of our observations and present a prototype of a refined LCC.
Speaker Information: Christian Witt, IRRI, Philippines, DAPO Box 7777, Metro Manila, ; Phone:
1-650-833-6620, #2648; E-mail: [email protected]
Session Information: Wednesday, November 5, 2003, 1:40 PM-4:30 PM Presentation Start: 1:45 PM