Plant biostimulants increase nutrient uptake, nutrient efficiency, tolerance to and recovery from abiotic and biotic stress and they improve crop quality. Plant biostimulants can be substances or microorganisms such as humic acids, beneficial elements, nitrogen-fixing bacteria and mycorrhiza. They aren’t fertilizers or pesticides, because they don’t supply plant nutrients or have direct action on pests. Biostimulants also improve soil health by enhancing the development of beneficial soil microorganisms.

The aim of this study was to clarify the different types of biostimulants, the usage and utilization of biostimulants, but also establish the suitability to Finnish climatic conditions, soil types and agricultural crops. The work was made for order from Timo Mäkinen, Naturcom Oy (Ruukki, Finland).

A cultivation test was made for this work. Its aim was to study the impact of five different biostimulant products to the growth of red clover (Trifolium pratense) and timothy-grass (Phleum pratense). Biostimulant products included nitrogen-fixing bacteria, mycorrhiza, a mixture of beneficial microorganisms and sea salt. On one treatment, sea salt and a mixture of beneficial microorganisms were combined.

Based on the cultivation test, the most promising product for both red clover and timothy-grass was the sea salt (SEA-90, SeaArgi, Atlanta, USA). It increased the yield by 5-10 %. It was also effective when combined to beneficial microorganism which alone decreased the yield and condition of the plants.

In the future the cultivation tests should be repeated in a greenhouse scale for more reliable results and to secure the sufficient amount of usable light for plants. After that, a field test should be established in a different soil types and nutrient levels.