Effects of CO2 dissolution on phase distribution and degradation of dimethyl disulfide in soils under grape production.

BACKGROUND

Dimethyl disulfide (DMDS) is a fumigant recently registered in parts of the United States. The fumigant has high pesticidal activity, but does not disperse in soils as well as other fumigants. This study assessed the use of CO2 as a propellant to improve soil dispersion and diffusion by evaluating the partitioning and degradation of DMDS after carbonation in four vineyard soils collected in California.

RESULTS

The soil with the highest organic carbon content (Clarksburg) had the highest soil-water partition coefficient (Kd ) (P < 0.001), which increased after carbonation. However, DMDS sorption decreased in the Mecca and Fowler soils. Henry's law constant (Kh ), which measures a compound's potential for partitioning between air and water, doubled from 0.04 to 0.10 with the addition of CO2 , indicating less DMDS solubility. Carbonation did not negatively affect DMDS's half-lives in the different soils.

CONCLUSION

While trials are needed for validation of field-scale impacts, carbonation had mixed effects on soil partitioning and no discernable impact on degradation, but greatly decreased DMDS water solubility. This indicates that carbonation could improve some facets of DMDS diffusion and dispersion, depending on soil properties (carbon content and moisture), without greatly affecting its other behaviors.