RT info:eu-repo/semantics/article T1 Assessment of RGB vegetation indices to estimate chlorophyll content in sugar beet leaves in the final cultivation stage A1 Sánchez Sastre, Luis Fernando A1 Alte da Veiga, Nuno M. S. A1 Ruiz Potosme, Norlan Miguel A1 Carrión Prieto, Paula A1 Marcos Robles, José Luis A1 Navas Gracia, Luis Manuel A1 Martín Ramos, Pablo K1 Beta vulgaris K1 Chlorophyll K1 Clorofila K1 Sugar beet K1 Remolacha azucarera K1 Unmanned aerial vehicles K1 Vehículos aéreos no tripulados AB 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. PB MDPI SN 2624-7402 YR 2020 FD 2020 LK https://uvadoc.uva.es/handle/10324/52598 UL https://uvadoc.uva.es/handle/10324/52598 LA eng NO AgriEngineering, 2020, vol. 2, n. 1, p. 128-149 NO Producción Científica DS UVaDOC RD 19-sep-2024