|Qui, Ruijun -|
Submitted to: Proceedings of International Research Conference on Methyl Bromide Alternatives
Publication Type: Proceedings
Publication Acceptance Date: September 6, 2010
Publication Date: November 1, 2010
Citation: Qui, R., Gao, S. 2010. Effect of soil moisture on emission and behavior of fumigants in different textured soils. Proceedings of International Research Conference on Methyl Bromide Alternatives. p.87-1 - 87-3. Interpretive Summary: Emission reduction from soil fumigation is required to protect air quality in California. Water application is a low-cost strategy for emission control and applicable to a wide range of commodity groups especially for those with low-profit margins. This study determined the effects of increasing soil water content on the emissions and the fate of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) in three different textured (sand, sandy loam, and loam) using soil column tests. Increasing soil water content significantly reduced the emission peak flux, delayed its occurrence time, and reduced total emission losses in the sandy loam and loam soils for both 1,3-D and CP. Emission reduction was found to be minimal in the sandy soil for 1,3-D, while there was some reduction for CP. Higher fumigant concentrations in soil gas-phase were found in high soil water content treatments indicating the ability of moisture to reduce fumigant diffusion to the soil surface. Despite soil texture, air-filled porosity was found to have a close correlation with fumigant emissions. Further field testing can verify the laboratory findings. Increasing soil water content to proper levels can be an easily operated, effective, and low-cost strategy to control fumigant emissions.
Technical Abstract: Stringent environmental regulations are being developed to control fumigant emissions and protect air quality in California. Water application is a low-cost strategy for fumigant emission control and applicable to a wide range of commodity groups especially for those with low-profit margins. Laboratory studies were conducted to determine the effect of soil moisture on the emission and distribution of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) in three different textured soils (Delhi sand, Hanford sandy loam, and Madera loam) using soil column tests. The tested soil moisture levels ranged from 30% to 100% (w/w) of field capacity for sandy loam and loam soils, and from 60% to 200% (w/w) of field capacity for the sandy soil. The increase in soil moisture was found to decrease the emission peak flux and delay its occurrence, particularly in finer textured soils while the reduction in the sandy soil was small. Reduction in cumulative emission loss was not as significant as the reduction in the peak flux. Gaseous fumigant concentrations in the soils were consistently higher in wetter soils than in the drier soils, due to more retention and slower emission rates in the moist soils. A linear relationship was found between the air-filled porosity and emission loss of fumigants, indicating that reducing the air-filled space to a proper level may be a good indicator to ensure emission reduction in different types of soils. Further studies are needed to determine a proper range of soil moisture that reduces fumigant emissions but does not affect fumigant distribution under field conditions to conclude how water management can be carried out to achieve maximum emission reduction and good pest control efficacy.