Hollister, CA, United States
Hollister, CA, United States

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Ashworth D.J.,University of California at Riverside | Ashworth D.J.,U.S. Department of Agriculture | Yates S.R.,U.S. Department of Agriculture | Van Wesenbeeck I.J.,Dow AgroSciences | Stanghellini M.,TriCal Inc.
Journal of Agricultural and Food Chemistry | Year: 2015

Co-formulations of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) are commonly used for preplant fumigation in the production of high-value crops. Various ratios of 1,3-D to CP are available in these co-formulations. Collation of previous field data suggested that when the two fumigants were co-applied, the emissions of CP were significantly lower than when CP was applied singly. However, none of these previous studies had a control treatment with CP applied alone, alongside a treatment where CP was co-applied with 1,3-D under the same climatic and edaphic conditions. This work aimed to address this issue by measuring emission fluxes from soil columns maintained under controlled conditions in which 1,3-D and CP were applied alone and as four commercial co-formulations with various 1,3-D:CP ratios. A strong positive relationship between CP emissions and CP percentage in the formulation was observed. Furthermore, strong positive relationships between CP degradation half-life and CP percentage in the formulation and between CP degradation half-life and total column emissions suggested that the lower emissions were due to faster CP degradation when the CP percentage (and hence initial application mass) in the formulation was low. The presence of 1,3-D did not significantly affect the degradation rate of CP, and, therefore, it is hypothesized that co-application was, in itself, not a significant factor in emission losses from the columns. The findings have implications for the accurate modeling of CP because the effect of initial mass applied on CP degradation rate is not usually considered. © 2014 American Chemical Society.

Gao S.,U.S. Department of Agriculture | Ajwa H.,University of California at Davis | Qin R.,U.S. Department of Agriculture | Qin R.,University of California at Davis | And 2 more authors.
Environmental Science and Technology | Year: 2013

Tarping fumigated fields with low permeability films such as commercial Totally Impermeable Film (TIF) can significantly reduce emissions, but it can also increase fumigant residence time in the soil such that extended tarp-covering durations may be required to address potential exposure risks during tarp-cutting and removal. In an effort to develop safe practices for using TIF, a large field study was conducted in the San Joaquin Valley of California. Comprehensive data on emissions (measured with dynamic flux chambers), fate, and transport of 1,3-dichloropropene and chloropicrin were collected in a 3.3 ha field fumigated with Pic-Clor 60 via broadcast shank application. Low emission flux (below 15 μg m-2 s-1) was observed from the tarped field throughout the tarp-covering period of 16 days with total emission loss of <8% of total applied for both chemicals. Although substantially higher flux was measured at tarp edges (up to 440 μg m-2 s-1), the flux was reduced to below 0.5 μg m -2 s-1 beyond 2 m of tarp edge where total mass loss was estimated to be ≤1% of total applied to the field. Emission flux increased following tarp-cutting, but was much lower compared to 5 or 6 d tarp-covering periods determined in other fields. This study demonstrated the ability of TIF to significantly reduce fumigant emissions with supporting data on fumigant movement in soil. Proper management on use of the tarp, such as extending tarp-covering period, can reduce negative impact on the environment and help maintain the beneficial use of soil fumigants for agricultural productions. © 2012 American Chemical Society.

Browne G.T.,University of California at Davis | Lampinen B.D.,University of California at Davis | Doll D.A.,UCCE Pomology Farm | Upadhyaya S.K.,University of California at Davis | And 12 more authors.
California Agriculture | Year: 2013

As much as one-third of California's almond and stone fruit acreage is infested with potentially debilitating plant parasitic nematodes, and even more of the land is impacted by Prunus replant disease (PRD), a poorly understood soilborne disease complex that suppresses early growth and cumulative yield in replanted almond and peach orchards. Preplant soil fumigation has controlled these key replant problems, but the traditional fumigant of choice, methyl bromide, has been phased out, and other soil fumigants are increasingly regulated and expensive. We tested fumigant and nonfumigant alternatives to methyl bromide in multiple-year replant trials. Costs and benefits were evaluated for alternative fumigants applied by shanks in conventional strip and full-coverage treatments and applied by shanks or drip in novel spot treatments that targeted tree planting sites. Short-term sudangrass rotation and prudent rootstock selection were examined as nonfumigant approaches to managing PRD. Trial results indicated that integrations of the treatments may acceptably control PRD with relatively little soil fumigant.

Ajwa H.,University of California at Davis | Stanghellini M.S.,TriCal Inc. | Gao S.,U.S. Department of Agriculture | Sullivan D.A.,Sullivan Environmental Consulting Inc. | And 3 more authors.
California Agriculture | Year: 2013

With methyl bromide's phase-out, most growers have turned to alternative fumigants, particularly 1,3-dichloropropene (1,3-D) and chloropicrin. These alternatives are tightly regulated because they are classified as toxic air contaminants and volatile organic compounds; the latter combine with other substances to produce ground-level ozone (smog). Two ambient air monitoring studies were conducted to evaluate the potential of totally impermeable film (TIF) to reduce emissions from shank applications of chloropicrin and 1,3-D. In 2009, a study demonstrated that TIF reduced chloropicrin and 1,3-D peak emissions by 45% and 38%, respectively, but TIF did not reduce total emissions when it was cut after 6 days. In 2011, increasing the tarp period from 5 to 10 days decreased chloropicrin and 1,3-D peak emissions by 88% and 78%, and their total emissions by 64% and 43%, respectively. Concurrent dynamic flux chamber results corroborated the ambient air monitoring data. These studies provide regulatory agencies with mitigation measures that should allow continued fumigant use at efficacious application rates.

Udompetaikul V.,King Mongkut's University of Technology Thonburi | Udompetaikul V.,University of California at Davis | Coates R.W.,University of California at Davis | Upadhyaya S.K.,University of California at Davis | And 3 more authors.
California Agriculture | Year: 2013

Our research goal was to use recent advances in global positioning system (GPS) and computer technology to apply just the right amount of fumigant where it is most needed (i.e., in a small target treatment zone in and around each tree replanting site) to control Prunus replant disease (PRD). We developed and confirmed the function of (1) GPS-based software that can be used on cleared orchard land to flexibly plan and map all of an orchard's future tree sites and associated spot fumigation treatment zones and 2) a tractor-based GPS-controlled spot fumigation system to quickly and safely treat the targeted tree site treatment zones. In trials in two almond orchards and one peach orchard, our evaluations of the composite mapping and application system, which examined spatial accuracy of the spot treatments, delivery rate accuracy of the spot treatments, and tree growth responses to the spot treatments, all indicated that GPS spot fumigation has excellent potential to greatly reduce fumigant usage while adequately managing the PRD complex.

Spurlock F.,U.S. Environmental Protection Agency | Johnson B.,U.S. Environmental Protection Agency | Tuli A.,U.S. Environmental Protection Agency | Gao S.,U.S. Department of Agriculture | And 6 more authors.
Vadose Zone Journal | Year: 2013

We evaluated the HYDRUS 2D/3D model for simulating chloropicrin and 1,3-dichloropropene fate and transport in broadcast applications. The calibrated model provided relatively accurate estimates of fumigant soil gas concentrations, and volatilization in two data sets using input data were measured, estimated, or obtained by independent calibration. We evaluated the ability of the HYDRUS 2D/3D model to simulate chloropicrin (CP) and 1,3-dichloropropene (13D) fate, transport, and volatilization. Three fields with similar soil conditions were broadcast fumigated under a totally impermeable film (TIF). One field was used to calibrate HYDRUS by adjusting fumigant degradation rates, soil sorption coefficients, and TIF tarp resistance factors. In comparisons of simulated and measured soil gas concentrations, soil temperature, soil water contents, and inverse-modeled estimates of fumigant volatilization flux, the model accurately simulated the basic individual processes of fumigant partitioning and degradation, heat transport, and soil water dynamics in the calibration field. Subsequent flux simulations of the remaining two fields were performed using only measured, independently estimated or calibrated inputs with no further adjustments. The magnitudes of simulated cumulative fluxes and both pre- and post-tarpcut discrete flux densities were within the estimated range of uncertainty (factor of ~2) of conventional inverse-modeled field-based flux estimates. However, the timing of maximum discrete flux densities was delayed by 1 to 2 d relative to inverse-modeled estimates. While HYDRUS provided reasonably accurate flux estimates, it was also evident that parameterization, particularly for TIF tarp permeability properties, generally requires field-based calibration because of a lack of representative field effective permeability data. © Soil Science Society of America 5585 Guilford Rd., Madison, WI 53711 USA. All rights reserved.

TriCal Inc. | Date: 2016-02-08

Chemicals used in agriculture and horticulture; chemical substances for preserving foodstuffs; fertilizers, fumigants, fungicides and herbicides, agricultural machinery and equipment, irrigation systems, components and supplies, agriculture and horticulture services, including plant grafting; nursery services; soil testing, analysis and consulting; and irrigation system design, installation services.

Trical Inc. | Date: 2016-06-09

Chemicals used in industry, namely, propylene oxide.

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