The use of biostimulant as foliar fertiliser is a globally used technique. Nourishment through the leaves is a new technological opportunity of modern crop production which has a direct effect on the physiological processes of the plant. The experiment was established on the experimental site on the campus of the Faculty of Agricultural and Food Sciences and Environmental Management of the University of Debrecen on maize (Zea mays L.) as a test plant. Foliar fertilisation was performed with algae-based biostimulant at the 8-leaf stage. The developments were carried out using two treatment concentrations (0.3 g l-1 and 1 g l-1), applied with 400 l ha-1 water and ethoxylated isodecyl alcohol as adjuvant. During the growing season, the relative water content (RWC) of plants was measured on seven occasions. The proline content of plants and the nitrogen and protein content of maize yield were also measured. Based on the obtained research findings, it was concluded that algae treatment increased the protein content of grain yield by more than 6%. During the growing season, the proline content of the green vegetable parts decreased constantly, although that of the treated plants was higher than the control in the same period. In the initial growing period, the 0.3 g l-1 foliar fertilisation treatment resulted in a higher proline content than the high concentration treatment. As a result of the 0.3 g l-1 foliar fertilisation treatment, yield increased by 10%, while the 1 g l-1 treatment increased yield by 11%.
In conclusion, the use of Nostoc piscinale biostimulant as a foliar fertiliser had a positive effect on yield its protein content. During the growing season, algae treatment increased the proline content of green vegetable parts, which had a favourable effect on the tolerance of maize to drought stress.