Abstract
Soils generate numerous volatile gases, primarily carbon dioxide (CO₂) and ammonia (NH₃), as byproducts of microbial metabolism, organic matter decomposition, and biochemical processes. CO₂ mainly originates from plant root, microbial, and nematode respiration, while microbial and nematode excretions contribute significantly to NH₃. Elevated CO₂ and NH₃ levels disrupt the host-finding mechanism of plant-parasitic nematodes (PPN) by altering chemical cues from plant roots, reducing invasion and suppressing populations. High concentrations can also directly impair nematode physiology, leading to mortality. This study estimated CO₂ and NH₃ emissions under increasing concentrations of Heterorhabditis indica, an entomopathogenic nematode (EPN) applied in large numbers for pest management. Based on our hypothesis that high EPN concentrations suppress PPN invasion, we introduced varying H. indica levels into airtight pots containing tomato plants in unsterile field soil. Volatiles were collected in vials with boric acid and sodium hydroxide and quantified via titration. Unlike previous protocols, our setup included live plants, improving accuracy by accounting for root exudate influence on rhizosphere activity. This method provides a robust approach to estimating soil volatiles in heterogeneous environments, addressing key challenges in soil ecology. Simulates a natural rhizosphere for studying field-like microbial interactions Estimates CO₂ and NH₃ emissions in soil with H. indica Cost-effective method for measuring CO₂ and NH₃ in a controlled setup with live plants.