HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Figures Only Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in Web of Science Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Web of Science (7) Citing Articles via Google Scholar Google Scholar Articles by Zhao, D. Articles by Koti, S. Search for Related Content PubMed Articles by Zhao, D. Articles by Koti, S. Agricola Articles by Zhao, D. Articles by Koti, S. Related Collections Cotton Remote Sensing Nutrient Management

Remote Sensing

Selection of Optimum Reflectance Ratios for Estimating Leaf Nitrogen and Chlorophyll Concentrations of Field-Grown Cotton

^a Dep. of Plant and Soil Sci., Box 9555, Mississippi State Univ., Mississippi State, MS 39762
^b USDA-ARS, Crop Sci. Res. Lab., P.O. Box 5367, Mississippi State, MS 39762

^* Corresponding author (krreddy{at}ra.msstate.edu)

Received for publication January 8, 2004. Leaf N and chlorophyll (Chl) concentrations of cotton (Gossypium hirsutum L.) are important indicators of plant N status. Laboratory determinations of plant tissue N are time consuming and costly. Measurements of leaf reflectance may provide a rapid and accurate means of estimating leaf N and Chl. Studies were conducted to determine the relationships between leaf hyperspectral reflectance (400–2500 nm) and Chl or N concentration in field-grown cotton. One study consisted of four N rates of 0, 56, 112, and 168 kg N ha^–1, and another study consisted of four mepiquat chloride (MC) rates of 0, 0.59, 1.17, and 2.34 L MC ha^–1. Chlorophyll and N concentrations and reflectance of uppermost, fully expanded mainstem leaves were measured throughout the growing seasons. Reflectance at 556 and 710 nm increased significantly as N fertilizer rate decreased. Averaged across years and sampling dates, the percentage increase in reflectance at these two wavelengths was 8, 10, and 19% greater in the 112, 56, and 0 kg N ha^–1 treatments, respectively, compared with the 168 kg N ha^–1 treatment. The effect of MC on leaf reflectance was more complex than the N effect. In both the N and MC studies, a linear relationship was found between leaf N and a simple ratio of leaf reflectance at 517 and 413 nm (R₅₁₇/R₄₁₃) (r² = 0.65–0.78***). Leaf Chl concentration was associated closely with reflectance ratios of either R₇₀₈/R₉₁₅ or R₅₅₁/R₉₁₅ (r² = 0.67–0.76***). Our results suggest leaf reflectance can be used for real-time monitoring of cotton plant N status and N fertilizer management in the field.

Abbreviations: Chl, chlorophyll • DAS, days after sowing • DW, dry weight • FF, first flower • FS, first square • MC, mepiquat chloride • R_i, reflectance at i nanometers • RD, reflectance difference • RS, reflectance sensitivity

This article has been cited by other articles:

				S. Biewer, T. Fricke, and M. Wachendorf Development of Canopy Reflectance Models to Predict Forage Quality of Legume-Grass Mixtures Crop Sci., August 7, 2009; 49(5): 1917 - 1926. [Abstract] [Full Text] [PDF]

				G. A. Blackburn Hyperspectral remote sensing of plant pigments J. Exp. Bot., March 1, 2007; 58(4): 855 - 867. [Abstract] [Full Text] [PDF]

				P. J. Starks, D. Zhao, W. A. Phillips, and S. W. Coleman Development of Canopy Reflectance Algorithms for Real-Time Prediction of Bermudagrass Pasture Biomass and Nutritive Values Crop Sci., February 24, 2006; 46(2): 927 - 934. [Abstract] [Full Text] [PDF]