Effect of organic biostimulators with Bacillus amyloliquefaciens ssp. plantarum (Former Bacillus subtilis) as the main agent in vegetable cultivation

Abstract

In the last decade, investigations were carried out to analyze the effects of biostimulators (e.g., humate, lactate, Bacillus amyloliquefaciens ssp. plantarum, formerly Bacillus subtilis) in hydroponic systems especially under stress conditions (nutrient deficiency, temperature, salt, and pH stress) on the growth of different vegetables (tomatoes, cucumbers, water spinach, sweet potatoes) in different substrates. Applications of biostimulators are reported to reduce abiotic stress in plants. The physiological effects of these substances, however, are little investigated so far. For biostimulators as K-humate, LACTOFOL, and FZB24®, there were reports about their beneficial effects. Application of different biostimulating substances in diverse combinations, however, could be even more beneficial to plants' growth and development than their separate utilization. Effects of humate, lactate, and Bacillus amyloliquefaciens ssp. plantarum FZB24® as single treatment and as mixture on pH and EC values in substrate culture confirmed this assumption. After application of each biostimulator to the roots, the number of marketable cucumbers was enhanced in total and in relation to the nonmarketable fruits. The application in the root zone had a stronger effect than the application on the leaves and should be preferred. This was also visible under stress condition, e.g., under growing conditions with suboptimal pH value and temperature. In previous experiments, we used therefore a bioactive complex containing K-humate, LACTOFOL, and FZB24® and recorded positive effects on plant growth and yield. If biostimulator mixture (humate, lactate, and Bacillus amyloliquefaciens ssp. plantarum) was applied, no plant growth reduction under pH and temperature stress was determined, in comparison to plants without biostimulator treatments. Results show that there is strong correlation between green biomass of treated plants and their root mass. It can be assumed that the effect of stress reduction by use of this biostimulator mixture is based mainly due to enhancing the root growth.