Production and stability of ethylene in soil

Summary One of the major factors affecting the production and stability of ethylene (C₂H₄) in soil is its water content. This study was conducted to determine the effect of unsaturated vs. saturated conditions on the production and stability of C₂H₄ in soil. L-Methionine and D-glucose were added alone and in combination at 1.0 and 5.0 g kg^-1 soil, respectively. The addition of l-methionine significantly promoted C₂H₄ production at field capacity to a much greater extent than under waterlogged conditions. Glucose was equally effective under both moisture regimes, while the combined application of both amendments (l-methionine and d-glucose) led to the release of significantly higher amounts of C₂H₄ under saturated conditions. Antibiotic experiments revealed that under aerobic conditions, l-methionine may be more efficiently converted to C₂H₄ by soil fungi, while in glucose-amended soil, both bacteria and fungi are active in generating C₂H₄. C₂H₄ was more stable under saturated conditions. The magnitude of C₂H₄ removal from the headspace after 3 days of incubation under unsaturated conditions (25.7%) was comparable to that after 6 days under saturated conditions (24.1%). The loss of C₂H₄ was approximately 10-fold greater in non-sterilized soil than in sterilized (autoclaved) soil, both maintained at field capacity, indicating that a biotic component has a major influence on C₂H₄ stability. Kinetic analysis revealed that the C₂H₄ loss/degradation in nonautoclaved soil under aerobic conditions followed a firstorder reaction, with a rate constant (k) of 0.115 day^-1 and a half-life (t _1/2) of 6.0 days.