Meeting the needs of a growing population places increasing demands on arable crop production. The challenge now and in the future is to ensure high and stable yields of superior maize genotypes under extreme weather conditions. In the development of agriculture, microbiological preparations are being used to an increasing extent to improve the resistance of crops and reduce the use of chemicals. In contrast to root fertilisation, foliar fertilisation is applied directly to the leaves, so that nutrient supplementation can be applied more effectively at different growth stages of the plant.

The research in this paper was carried out in an experiment at the Látókép Plant Production Experiment Site of the University of Debrecen. The efficiency of natural foliar fertilisers was investigated in the year 2021 under drip irrigation. The maize stand was treated with foliar sprays of Natur Plasma T biostimulant, Natur Active complex foliar fertiliser and Zinc and Sulphur Mono additives at the 7–8-leaf stage. The application of these products allows a rapid and efficient nutrient incorporation during the vegetative or even the generative cycles. During the growing season, the main parameters (SPAD, NDVI) of maize hybrids Ivola (FAO 350) and Mv Marfi (FAO 480) were measured at critical phenophases (12-leaf stage, silking, physiological maturity). In addition to the maize plant phenometry factors, the evolution of several ear parameters was also investigated, taking into account the effect of foliar fertilisation (number of grains, thousand grain weight, ear weight, grain-cob ratio, ear length, ear diameter).

The applied foliar fertiliser treatment resulted in a yield increase of more than half a tonne (0.7 t) for the hybrid Ivola. For the hybrid Mv Marfi, the difference was more significant, with a yield of 15.023 t ha-1 in the control plot, while the treatment resulted in an increase of 13.4% and a yield of 17.041 t ha-1. Foliar fertilisation increased the thousand grain weight of both examined maize genotypes, with a 22.8% increase in the hybrid Ivola (348.5 g), while the hybrid Mv Marfi showed a 6% increase (356.9 g).

Based on the obtained SPAD readings, the two hybrids responded positively to the treatment at all measured developmental stages. The highest value in the treated stand was measured in the hybrid Ivola (62.78 SPAD) at silking. The positive NDVI values obtained during the growing season at the 12-leaf stage, silking and physiological maturation properly reflected the development and health of the hybrids. The treatment improved the condition and biomass production of the maize stand.

The obtained results show that the use of the tested foliar fertilisers improved the endurance of the maize stand and resulted in additional yield increases over and above the primary fertilisation.

Keywords: maize, genotype, foliar fertiliser, irrigation, SPAD, NDVI