Soil properties affect vapor-phase adsorption to regulate dimethyl disulfide diffusion in soil

Area of Science:

• Agricultural Science
• Soil Science
• Environmental Chemistry

Background:

• Dimethyl disulfide (DMDS) is an effective soil fumigant against nematodes and pathogens.
• Inconsistent efficacy of DMDS has been reported, potentially due to variations in soil type affecting its diffusion.
• The impact of soil adsorption on gaseous DMDS diffusion remains poorly understood.

Purpose of the Study:

• To investigate the role and mechanism of soil adsorption in the diffusion of gaseous DMDS.
• To determine how soil properties influence DMDS diffusion and efficacy.

Main Methods:

• Soil column experiments to measure the diffusion rate constant (R_t) of gaseous DMDS.
• Batch-equilibrium headspace method to quantify DMDS adsorption at gas-soil, soil-water, and gas-water interfaces.
• Analysis of adsorption isotherms (Freundlich and Henry).

Main Results:

• DMDS adsorption equilibrium followed Freundlich and Henry isotherms.
• Diffusion rate (R_t) was negatively correlated with the Henry coefficient (K_d).
• K_d was higher in dry soils and correlated with pore size, but in moist soils (3-12% w/w), it correlated with specific surface area (SSA).
• Elevated temperatures increased DMDS diffusion.

Conclusions:

• Soil adsorption significantly impacts DMDS vapor-phase diffusion in soil.
• Soil properties, particularly SSA and moisture content, are critical determinants of DMDS diffusion.
• Optimizing DMDS application (dose, timing) based on soil characteristics and environmental factors is crucial for consistent pest control efficacy.