Biostimulants Increase Soybean Productivity in the Absence and Presence of Water Deficit in Southern Brazil

Biostimulants offer a potentially novel approach for the regulation/modification of physiological processes in plants to stimulate growth, to mitigate stress-induced limitations, and to increase yield. The objective of this work was to evaluate the influence of vegetable biostimulants in soybean crop subjected to different soil water conditions. The experiments were carried out in 2017/2018 and 2018/2019, in a completely randomized design (water deficit, combination of biostimulants, and application time). The combinations of biostimulants and time of application were: no combination (control); foliar application at stage V5; foliar application stages V5 and R1; seed treatment; seed treatment and V5 applications; and seed treatment, V5 and R1 applications. All the biostimulant combinations were moreover subject to either the presence or absence of water stress. Evaluations performed were maximum photochemical efficiency, pods per plant, seeds per pod, thousand grain mass, productivity, and incremental increases in performance of each biostimulant treatment. No differences were observed under water deficit in either season, and the use of biostimulants increased the thousand grain mass and final productivity. After two crop seasons with results in increasing yield, the application of biostimulants is recommended in three stages (TS + V5 + R1) for the best management of soybean crops.