The Effect of a Preparation Containing Humic Acids on the Growth, Yield, and Quality of Strawberry Fruits (Fragaria × ananassa (Duchesne ex Weston) Duchesne ex Rozier)

Humic acids are plant biostimulants, which can be used in horticulture as an effective and relatively inexpensive alternative to chemical means of production. The aim of the study was to assess how the fertiliser containing humic acids affected the growth, yield, and quality of strawberry fruits. In 2021, an experiment was conducted on two-year-old strawberry bushes (Fragaria× ananassa (Duchesne ex Weston) Duchesne ex Rozier) of the ‘Rumba’ cultivar growing on a horticultural farm in northern Wielkopolska, Poland. During the growing season, the soil was fertilized by the mineral fertilization and the bushes were sprayed two, three, or four times with the Humi Brown Gold fertiliser containing humic acids. In the experiment, the soil enzymatic activity, biometric parameters of strawberry leaves, fruit yield and fruit quality was assessed. It was determined that, in the experimental treatments where foliar fertilisation had been applied, the activities of proteases and dehydrogenases as well as soil respiration increased by more than double and were significantly higher than in the variants where soil fertilisers had been applied. The strawberry bushes treated with the humic acids fertiliser developed more than 60% larger surface leaves, bloomed more intensively and gave a higher yield. Fruits with significantly higher firmness were harvested from such bushes, with higher weight and extract content than those where the soil fertiliser had been applied. The difference was several tens of percent. This leads to the conclusion that the foliar application of humic acids could be an effective alternative to mineral fertilisation in strawberry plantations.