Transport and Fate of MethyI Iodide and Its Pest Control in Soils

Lou, Lifang and Ashworth, Daniel and Dungan, R.S. and Xuan, Richeng and Yates, S.R. (2010) Transport and Fate of MethyI Iodide and Its Pest Control in Soils. Environmental Science & Technology. 44(16). 16 July 2010.

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Abstract

For fumigants, information on transport and fate, as well as pest control, is needed to develop management practices with the fewest human and environmental health risks while offering sufficient pest control efficacy. For this purpose, a 2-D soil chamber (60 cm wide, 60 cm long, and 6 cm thick) with a surface-mounted flux chamber was designed to determine volatilization, spatial and temporal distribution of soil gas-phase concentration, degradation and organism survivability after methyl iodide (MeI) fumigation. Three types of pests (barnyardgrass seed [Echinochloa crus-galli], citrus nematode [Tylenchulus semipenetrans], and fungi [Fusarium oxysporum]) were used to give a broad spectrum of pest control information. After MeI fumigation at a rate of 56.43 kg ha-1 for 24 hr, about 25.8 % of MeI was emitted into air, 6.8 % remained in the soil, and 43.6% degraded in the soil (based on the residual iodide concentration). The uncertainty in the measured MeI degradation using iodide concentration was thought to contribute to the unrecovered MeI (about 23%). Based on the spatial and temporal distribution of soil gas-phase concentration, the concentration-time index (CT) and its distribution was quantified. The citrus nematodes were effectively eliminated even at low CT values (< 30 µg hr ml-1) but all Fusarium oxysporum survived at the applied rate. The response of barnyardgrass seeds spatially varied with the concentration-time index (CT) values in the 2-D soil chamber. To fully control barnyardgrass seeds, CT of greater than 300 µg hr ml-1 was required. Using this experimental approach, different fumigant emission reduction strategies can be tested and mathematical models can be verified to determine which strategies produce least emission to atmosphere while maintaining sufficient pest control efficacy.

Item Type:	Article
NWISRL Publication Number:	1369
Subjects:	Soil
Depositing User:	Users 6 not found.
Date Deposited:	02 Sep 2010 22:55
Last Modified:	21 Nov 2010 22:31
Item ID:	1395
URI:	https://eprints.nwisrl.ars.usda.gov/id/eprint/1395