Effects of Plant Essential Oils on Soil Microbial Community and Soil Respiration.

Plant essential oils have been known since antiquity to possess notable biological activity, including antibacterial, antifungal and antiviral properties. Several reports have been published in recent years on the antimicrobial activity of some essential oils in the soil. Essential oils for their antimicrobial activities and accordingly direct effect on soil microbial fauna in the soil and physical and chemical nature of the effect on plant productivity has to be evaluated carefully. Achillea millefolium (Y₁), Artemisia dracunculus (Y₂) and Salvia officinalis (Y₃) plant species are well known for their high contents in aromatic compounds, and essential oils. This study focused on the impacts of essential oils of Achillea, Artemisia and Salviaplants on; (a) soil reaction, (b) soil bacteria and fungi population and (c) soil respiration. Soils were collected from the research farm of Ataturk University, Erzurum, Turkey and 0-20 cm depth. We used four different essential oil doses (0, 100, 1000 and 10.000 ppm). Soils were potted and incubated for several weeks and taken soil samples for analysis of bacteria, fungi and soil respiration in different incubation days (0, 15, 30, 45, 60 days).

In this study, we concluded that soil pH level, bacteria populations and soil respiration decreased with increasing essential oil concentration and the lowest pH level has been obtained in 60 days incubation periods, but opposite effect has been observed on fungi populations at the 60 days incubation period. Among different essential oils Y₁ applications has been shown low effect, and Y3 application shown high effect on soil reaction, soil bacteria and fungi populations and soil respiration in the soil.