Pea Protein as a novel biostimulant: Investigating microbial functions determining cucumber growth enhancement and comparison with commercial products

Abstract

Cucumber (Cucumis sativus) cultivation often faces challenges related to nutrient availability, requiring effective fertilization strategies. Biostimulants are gaining interest as sustainable alternatives to traditional fertilizers. This study evaluated the effects of Pea Protein, insect frass amendments, and commercially available products on cucumber plantlet growth. Two experiments were conducted, assessing shoot and root biomass, leaf and cotyledon area, shoot nutrient composition, microbial abundance, nitrogen fixation potential, and soil enzyme activities. Among treatments, Ecosol and Pea Protein combined with a phosphorus and potassium compensation resulted in the highest plant growth. Differences in shoot nutrient composition, particularly potassium and nitrogen, were observed despite nitrogen inputs being standardized across treatments. Bacterial and fungal abundances did not differ significantly between treatments, and relative nifH gene abundance appeared slightly reduced in Pea Protein-amended soils. A slow-release formulation of Pea Protein (Minigran Pea) appeared to increase both acid and alkaline phosphatase activity, although no statistically significant differences could be observed. These results suggest that Pea Protein’s growth enhancing effect may require nutrient compensation, yet the microbial mechanisms remain unclear. Overall, Pea Protein shows promise for enhancing cucumber growth when combined with sufficient nutrient supplementation, and further studies on microbiome interactions are warranted.