Start Date: Apr 01, 2012
End Date: Mar 31, 2016
Experiments will be conducted in 12 cm (dia) x 150 cm (long) cylindrical soil columns and will be packed uniformly with a homogeneous mixture of soil with uniform moisture content and bulk density. The soil will be well mixed to ensure that soil properties and soil degradation rates are as uniform as possible. Soil properties will be reported and experiments will be conducted at 25 ± 1 oC. The tops of the columns will be fitted with stainless steel caps that allow for trapping of fumigants emitted from the soil surface. These columns are suitable for the 1-dimensional (vertical) study of fumigant behavior following a broadcast shank injection into ploughed soil. In these experiments, shank injection at about 46 cm depth will be tested by injecting a small volume of fumigant or fumigant formulation into the soil via an injection port. The volume of fumigant will be based on normal field experiment application rates. Immediately following fumigant application, air will be drawn across the soil surface (through the column headspace caps) and the emitted fumigant swept through a sampling system via Teflon tubing. The sampling system will use sorbent tubes (e.g. charcoal or XAD resin) to collect the fumigant vapor. Backup tubes will be installed in case of fumigant breakthrough. Solenoid valves will allow switching between sorbent tubes at regular time intervals and mitigate the need for human intervention. The sampling intervals will be the same for each column and will allow direct comparison between columns. The diffusion of the fumigant within the soil will be determined by periodic soil gas sampling; a small volume (e.g. 500 µL) of gas will be removed from the soil using a gas-tight syringe inserted through sampling ports along the side of the column. The duration of experiments will approximately 10–14 days. The experiments will involve 6 soil columns injected with one of the following fumigant/co-formulation levels. – 1,3-D alone – chloropicrin alone – Telone C17 (83% 1,3-D + 17% chloropicrin) – Telone C35 (65% 1,3-D + 35% chloropicrin) – Pic-Clor 60 (60% chloropicrin + 40% 1,3-D) – Pic-Clor 80 (80% chloropicrin + 20% 1,3-D). The experiment will be replicated 3 times and, for each replication, the columns will be randomly assigned to a treatment. The reported data will include the flux rate with time and will include the means and standard deviations for each treatment, cumulative flux with time (means and standard deviations) and soil gas-phase concentrations (means and standard deviations). The data will be subjected to a statistical analysis (Analysis of Variance) to test if the treatments are significantly different at the 95% probability level.