Effects of the foliar application of humic biostimulant on alfalfa and cucumber – case studies

Abstract The aim of the research was to evaluate the effect of the new humic biostimulants preparation containing fulvic acids on the growth and quality of the yield of alfalfa ( Medicago × varia T. Martyn) and cucumber ( Cucumis sativus L.). In 2025, two experiments were conducted: 1. with alfalfa – a grow room experiment, and 2. with cucumber – a field experiment. Experimental factors: I – biostimulant, II – number of applications (2 and 4 sprays). The concentration of the preparation and the number and timing of treatments are recommended by the manufacturer. Morphometric characteristics (alfalfa), marketable yield (cucumber) and chemical composition (ICP-AES method) were determined in the plant material. Application of tested biostimulant increased the value of morphometric traits of alfalfa: the length of stalks, number of shoots per plant and leaves per shoot, diameter of root collar, weight of shoot and root system per plant, weight of leaves and inflorescence per shoot. It also resulted in an increase of up to 61% in the dry weight of plants compared to the control. Moreover, it increased the concentration of potassium, magnesium, and phosphorus in the dry matter of the plant. Foliar application of the tested biostimulant to cucumbers resulted in a statistically significant increase in fruit yield of gherkin cucumbers by 24% and in total marketable yield by 12.5% compared to the control. No significant changes were observed in the dry matter, protein, phosphorus, potassium, or magnesium content in cucumber fruit. The research conducted is a preliminary step towards expanding the assessment of the effects of fulvic acid use on the characteristics of tested plants under various growing conditions.