Submitted to: Agricultural and Biosystems Engineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/25/2007
Publication Date: 5/25/2007
Citation: Kim, Y., Reid, J. Spectral sensing for plant stress assessment – a review. International Journal of Agricultural and Biosystems Engineering. 7(1):27-41.
Interpretive Summary: Assessment of plant nitrogen (N) has been of interest worldwide to provide growers with site-specific N fertilizer and minimize environmental impact. Plant leaf interaction with radiation is a major influence on the remote sensing signals. It is important to understand the optical characteristics of plant leaves to apply the principle of remote sensing. Most spectral measurements of plant leaves previously reported were made in 500 to 2500 nm portion of the electromagnetic spectrum. It was generally observed that N stressed plant leaves have a reflectance higher in visible and lower in near-infrared waveband than non-stressed leaves. Spectral signature of plant leaves have great potential to characterize the plant features and the spectral reflectance of the plants in visible region (400 – 750 nm) is primarily influenced by the leaf pigment chlorophyll and inversely correlated to leaf chlorophyll content. Several studies indicated a good estimation of leaf N content at 550 nm wavelength. This paper described remote sensing technologies, applications, and factors to be considered. With the progress of remote sensing technology and understanding plant optics, remote sensing is a promising tool to lead precision agriculture in the future.
Technical Abstract: Assessment of nitrogen and chlorophyll content from crop leaves can help growers adjust N fertilizer rates to meet the demands of the crop. Numerous researchers have presented their studies about spectral signature of plant leaves to characterize the plant features. However, interrelational review and summary were limited and a communication gap exists between the plant science and optical engineering. Understanding the mechanism of leaf interaction to electromagnetic radiation and factors affecting spectrophotometric measurements can enhance the foundation of optical remote sensing technologies. This paper provides extensive review of previous works in optical sensing and explains the basics of plant optics, spectral measurements for plant stress, factors that affect sensitivity to spectral analysis, and applications that deploy optical remote sensing technologies.