Enhancing cucumber production through compost and plant growth promoting rhizobacteria in an unheated soil based greenhouse.

The transition toward more sustainable horticultural practices requires approaches that maintain productivity while reducing environmental impact. The use of organic amendments such as compost and plant growth-promoting rhizobacteria (PGPR) offers environmentally friendly strategies to enhance soil health, nutrient availability, and plant resilience. Here, we investigated the effects of different compost doses and PGPR inoculation on plant growth, yield, and fruit quality of greenhouse-grown cucumber, cv. ‘Oscar’. Compost was applied to the upper 10 cm depth of soil at four rates (0 g m−2, 100 g m−2, 200 g m−2, 300 g m−2) and two PGPR strains, Bacillus subtilis and Pseudomonas fluorescens, were applied twice to the root zone. Correlation analysis and Principal Component Analysis were used to evaluate associations between growth parameters, yield, and leaf nutrient status. The interaction between compost and PGPR significantly increased root fresh and dry weight. The most effective treatment—200 g m−2 compost combined with Pseudomonas fluorescens—enhanced marketable yield by 9.3% relative to the untreated control. Yield improvements were closely linked to increased nutrient uptake, particularly magnesium (Mg) and phosphorus (P), as confirmed by PCA. The highest nutrient enrichment was observed with the 300 g m−2 compost + Pseudomonas fluorescens treatment, where Mg and P increased by 13.5% and 27%, respectively, compared to the control. Overall, the combination of compost at 200 g m−2 with Pseudomonas fluorescens represents a practical and sustainable strategy to improve cucumber performance under greenhouse conditions. Future research should assess its effectiveness across diverse soil types, stress conditions, and production systems to optimize long-term implementation.