Application of vegetation indices for comparative evaluation of soybean field germination

The article examines the correlations between the field germination of soybeans and the values of vegetation indices. Tests on two groups of breeding samples showed that the MCARI and NDVI indices are the most sensitive to field germination indicators. The use of vegetation indices is advisable in years with unstable field germination of soybeans as an indirect method for its assessment.

Introduction. Field germination is estimated by counting the number of germinated plants per unit area. This is expressed as a percentage of the seed sown. This method requires not only certain physical costs but also time. With the development of digital technologies in modern conditions, it is necessary to search for new methods of assessing field germination.

Object. The object of the research is the soybean competitive and preliminary variety testing nurseries and the soybean breeding and collection nursery.

Materials and methods. The research was carried out at the experimental base of the Federal Research Centre for Legumes and Cereals in the Orel region. The planting of the nurseries and the related observations were carried out according to the methods of VIR and State Agricultural Testing. A DJI Matrice 200 v2 unmanned aerial vehicle equipped with a MicaSense Altum multispectral camera was used for multispectral aerial imaging. Six flights during the main growing season. Vegetation indices were calculated: NDVI, NDRE, CLGreen, GNDVI, and MCARI.

 Results and conclusion. Tests on two groups of breeding samples showed that the correlations are stronger, with large differences in the values of field germination of cultivars on plots. The correlation coefficient (r>0.8) for most of the indices reaches its highest value on the 25th day after the appearance of the first shoots. The most sensitive to field germination are the MCARI and NDVI indices, for which the average correlation (r>0.7) remained until the beginning of August (the end of flowering for most cultivars) with average differences in field germination and until the end of August (the beginning of maturation for most soybean cultivars) with high differences in field germination (r>0.5). The use of vegetation indices is advisable in years with unstable field germination of soybeans as an indirect method for its assessment, especially when there are significant differences between the samples studied and when there are a large number of forms studied on extensive and heterogeneous crop areas. It is also relevant for breeding material testing or environmental testing to reduce the amount of groundwork when assessing soybean field germination.

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