Abstract
Estimation of chlorophyll content with portable meters is an easy way to quantify crop nitrogen status in sugar beet leaves. In this work, an alternative for chlorophyll content estimation using RGB-only vegetation indices has been explored. In a first step, pictures of spring-sown ‘Fernanda KWS’ variety sugar beet leaves taken with a commercial camera were used to calculate 25 RGB indices reported in the literature and to obtain 9 new indices through principal component analysis (PCA) and stepwise linear regression (SLR) techniques. The performance of the 34 indices was examined in order to evaluate their ability to estimate chlorophyll content and chlorophyll degradation in the leaves under different natural light conditions along 4 days of the canopy senescence period. Two of the new proposed RGB indices were found to improve the already good performance of the indices reported in the literature, particularly for leaves featuring low chlorophyll contents. The 4 best indices were finally tested in field conditions, using unmanned aerial vehicle (UAV)-taken photographs of a sugar beet plot, finding a reasonably good agreement with chlorophyll-meter data for all indices, in particular for I2 and (R−B)/(R+G+B). Consequently, the suggested RGB indices may hold promise for inexpensive chlorophyll estimation in sugar beet leaves during the harvest time, although a direct relationship with nitrogen status still needs to be validated.
Highlights
In sugar beet (Beta vulgaris L.), nitrogen plays a major role in the spreading of leaves to capture sunlight
From the summary of descriptive statistics for the CCM-200 measurements shown in Table 2, one can see how chlorophyll content decreased over time, evidencing chlorophyll deterioration in the leaves as time went by
Thirty-four RGB vegetation indices were evaluated for chlorophyll content estimation in spring-sown sugar beet leaves at the final stage of the cultivation period
Summary
In sugar beet (Beta vulgaris L.), nitrogen plays a major role in the spreading of leaves to capture sunlight It is considered a decisive factor in the growth rate of both leaves and the storage root [1]. The determination of leaf N levels in the last stage of sugar beet’s growth cycle becomes relevant since it has been demonstrated that late N incorporations or releases from the soil decrease sucrose content [7]. Gordo-Ingelmo [2] reported that sugar beet reacts to N fertilization increases with a larger development of leaves and roots, which in turn cause an excessive use of sucrose and an increase of nonsugars This mainly happens in cases of excessive organic fertilization, because part of the N is released belatedly, causing a stop of root ripeness
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
