Effects of compost application on sunflower (Helianthus annuus L.) yield and some soil enzyme activities in heavy metal-contaminated soils

Heavy metal accumulation in soils causes environmental pollution, negatively affecting soil microbiota and limiting plant growth and development. This study investigated the effects of different compost doses (0, 1.5%, 3%, and 4.5%) on sunflower (Helianthus annuus L.) growth and soil enzyme activities under high heavy metal content soil conditions. The experiment was conducted with three replications, and morphological plant characteristics (plant height, number of nodes, root length, fresh and dry weights), and soil enzyme activities (catalase, urease, dehydrogenase), were analyzed. The results showed that compost applications significantly affected plant growth and soil enzyme activities. The 1.5% compost dose yielded the best results for plant height, root length, and fresh and dry weights, whereas root length, number of nodes, root weights, and catalase and dehydrogenase enzyme activities reached their highest levels at the 4.5% compost dose. These findings suggest that compost can enhance plant growth and improve soil biological activity in heavy metal-contaminated soils. Specifically, the 1.5% compost dose promoted plant growth, while the 4.5% dose increased soil enzyme activities.