Estimation of aboveground biomass and grain yield of winter wheat using NDVI measurements

Aboveground biomass of wheat is considered as one of the most important crop parameters and correct estimation of aboveground biomass can help improve crop monitoring and grain yield prediction. Remotely sensed vegetation indices such as NDVI (Normalized Difference Vegetation Index) represent one of the most promising tools for application in field phenotyping with potential to provide complex information on different traits of wheat. The objective of this study was to evaluate the potential of different NDVIs derived from field reflectance measurements in identification of a specific growth stage in which proximally or remotely sensed data showed the highest correlation with aboveground biomass and grain yield of 24 winter wheat genotypes. The NDVI was determined using an integrated proximal sensor GreenSeeker (NTech Industries Inc., Ukiah, California, USA) and hyperspectral camera (Ximea Corp., Lakewood, CO USA) at four growth stages of wheat: full flowering, medium milk, early dough and fully ripe. The hyperspectral NDVI indices were calculated from two-band combinations between red (600-700 nm) or far-red (700-750 nm) and near-infrared (756-955 nm) regions. Highly significant correlations were found between different NDVIs and both examined traits at medium milk growth stage, with r values of up to 0.69. The strong positive relationship implies that medium milk stage is optimal for wheat traits assessment in semiarid or similar growing conditions. The overall results indicated that hyperspectral camera provided alternative spectral combinations for different NDVIs which could be successfully used in assessing aboveground biomass and grain yield of a large number of wheat genotypes