Normalized difference vegetation index and fractional green canopy cover under winter rapeseed and safflower crops

Abstract

Purpose. Perform an analytical assessment of the relationship between satellite NDVI and FGCC obtained directly in the field using the Canopeo mobile application to provide models of their possible mutual conversion for winter rapeseed and safflower crops. Methods. Field photography of photographic materials in winter rapeseed and safflower crops during the periods 'beginning of flowering – end of ripening' and '10–12 true leaves – end of ripening', respectively. Processing of photographs in the software product Canopeo to calculate the fractional green canopy cover in the crops (FGCC). Binding, according to geotagging data, of photographic sites to the values of the spatial normalized differentiated vegetation index (NDVI) on the OneSoil AI platform. Statistical processing of the results by the method of polynomial regression, the formation of conversion models between vegetation indices and the assessment of the accuracy of the models by the magnitude of the mean absolute percentage error. Results. It has been established that the studied vegetation indices have a high tightness of non-linear relationship, the developed polynomial curves and models have a high quality of fitting with a determination coefficient of more than 0.90, and also have a sufficient level of accuracy (the calculation error for most models does not exceed 10%). The maximum error (37.88%) was given by the model for converting the fractional green canopy cover area (FGCC) of winter rapeseed into NDVI, which is associated with the characteristics of the leaf apparatus of the crop and distortions in the value of the vegetation index due to the bright yellow color of the crop flowers during its mass blooming. It is promising to develop such models for all major crops cultivated in the South of Ukraine and create a special mobile application for automated conversion between vegetation indices. Conclusions. The results of the study showed a high relationship and the possibility of mutual conversion between the normalized differentiated vegetation index (NDVI), obtained from satellite monitoring data, and the fractional green canopy cover area (FGCC) in winter rapeseed and safflower crops. The development results can be improved by increasing the initial data set and implemented in precision farming systems for scientific, theoretical, and practical purposes.