Abstract
ABSTRACT The objective of this study was to evaluate the water status of maize cultivars through thermal and vegetation indexes generated from multispectral aerial images obtained from an unmanned aerial vehicle (UAV), and correlate them with physiological indicators and soil water contents. The application of three water regimes based on the reference evapotranspiration (ETo) (30%, 90%, and 150% ETo) was evaluated for two maize cultivars (AG-1051 and BRS-Caatingueiro). An UAV was used to acquire thermal and multispectral images. The indexes evaluated were CWSI, CI-G, CI-RE, CIV, NDVI and OSAVI, which were correlated with gas exchange and soil moisture measures. The CWSI present correlation with physiological indicators (stomatal conductance, transpiration, and net CO2 assimilation rate) that can be used to evaluate water status of maize plants. The multispectral vegetation indexes NDVI and OSAVI can replace the CWSI thermal index in water status evaluations for maize plants.
Highlights
Water is an important factor that limits grain yield in maize crops
Maize genotypes selected as tolerant to water stress present lower canopy temperature and higher leaf stomatal conductance (ROMANO et al, 2011; ZIA et al, 2013), indicating that the thermography can be applied to studies on tolerance to water stress (CASARI et al, 2019)
The objective of this study was to evaluate the water status of maize cultivars through thermal and vegetation indexes generated from multispectral aerial images obtained by an unmanned aerial vehicle (UAV), and correlate them with physiological indicators and soil water contents, focused on substitute aerial thermography, which is an expensive method, by multispectral indexes obtained from RGB cameras, which has a lower cost
Summary
Water is an important factor that limits grain yield in maize crops. Maize plants have C4 photosynthetic metabolism, with high efficiency in solar radiation use under adequate soil water availability. The more critical period for water deficit in maize plants is from the pre-flowering to the beginning of grain filling (BERGAMASCHI; MATZENAUER, 2014). The canopy temperature is a water stress indicator in plants, which has been measured using portable thermographic cameras (BIAN et al, 2019; CASARI et al, 2019). Canopy temperature has significant negative correlation with maize yield (ROMANO et al, 2011). Maize genotypes selected as tolerant to water stress present lower canopy temperature and higher leaf stomatal conductance (ROMANO et al, 2011; ZIA et al, 2013), indicating that the thermography can be applied to studies on tolerance to water stress (CASARI et al, 2019)
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