Comparing Canopy Hyperspectral Reflectance Properties of &amp;lt;i&amp;gt;Palmer amaranth&amp;lt;/i&amp;gt; to Okra and Super-Okra Leaf Cotton

Reginald S Fletcher,Rickie B Turley

doi:10.4236/ajps.2018.913197

Abstract

Palmer amaranth (Amaranthus palmeri S. Wats.) is a major weed problem of cotton (Gossypium hirsutum L.) production systems in the southern United States. Hyperspectral remote sensing has shown promise as a tool for crop weed discrimination, and there is a growing interest in using this technology for identifying weeds in cotton production systems. Information is lacking on differentiating Palmer amaranth from cotton with an okra leaf structure based on canopy hyperspectral reflectance properties. Two greenhouse studies were conducted to compare canopy hyperspectral reflectance profiles of Palmer amaranth to canopy hyperspectral reflectance profiles of okra and super-okra leaf cotton and to identify optimal regions of the electromagnetic spectrum for their discrimination. Ground-based hyperspectral measurements of the plant canopies were obtained with a spectroradiometer (400 - 2350 nm range). Analysis of variance (ANOVA, p ≤ 0.05), Dunnett’s test (p ≤ 0.05), and difference and sensitivity measurements were tabulated to determine the optimal wavebands for Palmer amaranth and cotton discrimination. Results were inconsistent for Palmer amaranth and okra leaf cotton separation. Optimal wavebands for distinguishing Palmer amaranth from super-okra leaf cotton were observed in the shortwave infrared region (2000 nm and 2180 nm) of the optical spectrum. Ground-based and airborne sensors can be tuned into the shortwave infrared bands identified in this study, facilitating application of remote sensing technology for Palmer amaranth discrimination from super-okra leaf cotton and implementation of the technology as a decision support tool in cotton weed management programs.

Highlights

Cotton (Gossypium spp.) is an important crop grown throughout the world
The curves were similar in pattern and were representative of the typical spectral curve for healthy vegetation in that healthy vegetation minimum reflectance occurs in the visible region of the spectrum with a notable increase in the green region of the visible spectrum (500 - 600 nm); a sharp increase in reflectance arises from 600 - 800 nm and plateaus at 900 nm in the near infrared region of the spectrum; and the reflectance decreases in the shortwave infrared region of the spectrum
Palmer amaranth canopy hyperspectral reflectance values were lower than the okra leaf cotton canopy hyperspectral reflectance values in the near infrared region of the spectrum

Summary

Introduction

Cotton (Gossypium spp.) is an important crop grown throughout the world. It is an important source of fiber and is one of the few crops with unique leaf shapes: 1) normal, 2) sub-okra, 3) okra, and 4) super-okra. Leaf shape plays a major role in cotton survival [1]. Advantages and disadvantages have been documented for sub-okra, okra, and super-okra versus normal leaf cotton. A detailed review is provided in [1] and the references therein the differences between normal leaf versus sub-okra, okra, and super-okra leaf cotton types.

Objectives

Methods

Results

Discussion

Conclusion