Effects of application of plant growth promoters, biological control agents and microbial soil additives on photosynthetic efficiency, canopy vegetation indices and yield of common buckwheat (Fagopyrum esculentum Moench)

ABSTRACT Microbial soil additives and plant biostimulants contain substances and microorganisms that can enhance stress tolerance in plants and increase the yield and quality of the crop. The interest in such inputs for sustainable and agroecological farming systems has led to the development of a range of products. The aim of the study was to determine the effects of some microbial soil additives (MSADs), plant growth promoters (PGPs) and biological control agents (BCAs) on photosynthetic efficiency, canopy vegetation indices and yield of common buckwheat (Fagopyrum esculentum Moench), an under-utilised nutraceutical crop. The study showed that soaking the seeds in the BCAs Pythium oligandrum and Bacillus subtilis, on their own, had significant effects on the yield of the buckwheat. Increases in chlorophyll a fluorescence indices were observed in plants grown from seeds soaked in a solution containing P. oligandrum (ET0/RC) and also in soil treated with the MSAD UG Max (ABS/RC, TR0/RC). Treatment with either of the two MSADs also increased the normalised differential vegetation index (NDVI). Soaking the seeds in PGPs combined with BCAs affected only the chlorophyll a fluorescence parameters, whereas the combined treatment of spraying the plants with PGPs and treating the soil with MSADs affected not only the chlorophyll a fluorescence parameters (FV/FM, ET0/RC, DI0/RC), but also indicated a tendency for a decrease in the leaf area index (LAI) (p = 0.058) and the NDVI (p = 0.186). The correlations between grain yield, chlorophyll a fluorescence parameters and vegetation indices of the canopy were discussed.