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Title: EFFECT OF SOIL MOISTURE AND IRRIGATION ON PROPARGYL BROMIDE VOLATILIZATION AND MOVEMENT IN SOIL

Author
item ALLAIRE, SUZANNE - UNVERSITE LAVAL, CANADA
item Yates, Scott
item ERNST, FREDERICK - UC RIVERSIDE, CA

Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/5/2003
Publication Date: 5/20/2004
Citation: Allaire, S.E., S.R. Yates and F.F. Ernst. 2004. Effect of soil moisture and irrigation on propargyl bromide volatilization and movement in soil. Vadose Zone J. 3:656-667.

Interpretive Summary: Soil fumigants are used to disinfest soil and control soil-borne pests. Methyl bromide has been one of the primary fumigants used for decades to control nematodes, weeds, and fungi, but will no longer be available due to environmental concerns. This could negatively affect an array of agricultural production systems. This has led to a search for new fumigant chemicals, including propargyl bromide. Before adopting propargyl bromide as a replacement soil fumigant, a better understanding of its behavior in the environment is needed. Information on the fate and transport of propargyl bromide in soil is very limited. Experiments were conducted to investigate the behavior of propargyl bromide in soil and to obtain information on potential fumigant management practices. The objectives of this paper were to study the movement of propargyl bromide in the soil profile under transient conditions, to study the spatial and temporal variability in a bed-furrow system, and to study how irrigation affects propargyl bromide movement in soil. This information will be useful should propargyl bromide be registered for use as a soil fumigant.

Technical Abstract: Propargyl bromide (3BP) is a potential replacement for the soil fumigant methyl bromide. Since little is known about its movement in soil, a study was conducted to compare the volatilization and movement of 3BP in the soil profile for different irrigation treatments. A rectangular soil column was used to simulate a bed-furrow system. The surface of the bed was covered with high-density polyethylene (HDPE) plastic (i.e., a tarp). The furrow was left uncovered. Multiple volatilization chambers were used to measure emissions from the furrows, the slopes of the bed, and the bed. The soil was fumigated by injecting 1.0 ml of 3BP to the center of the column. Three treatments were studied, no irrigation, a single 5-h surface irrigation 24 h after fumigation, and a 2-h daily surface irrigation. Volatilization was about three times greater from non-irrigated soil. Irrigation and higher initial soil moisture content were more effective in controlling 3BP volatilization than the use of a HDPE tarp. Volatilization and degradation were similar for both irrigation treatments, but the 2-h irrigation had the advantage of requiring 1/3 less water. Volatilization rates from the slopes of the bed were lower than from the bed surface. To obtain accurate total mass, volatilization chambers should cover the whole bed-furrow system. Short advective gas and liquid fluxes created by the irrigation had pronounced and prolonged effect on 3BP distribution and degradation. Henry's law could not be used to predict the 3BP distribution pattern in the liquid phase even long after the irrigation ceased.