2013 Annual Report
1a.Objectives (from AD-416):
1) Replace methyl bromide with an alternative fumigant,
2) Reduce the application rates of pre-plant alternative fumigants through a combination of decreased losses by better retention with low permeability films and enhanced sub-surface dispersion by carbonation of the fumigants, and
3) To ascertain the minimum fumigation rate required to be effective in various soils in multiple states with a variety of crops under different tarping techniques.
1b.Approach (from AD-416):
Three field trials will be conducted to collect field data. Targeted cropping systems are deep-rooted perennial tree/ornamental/grapevine orchards or nurseries. Telone and chloropicrin products will be tested in all trials. The first two years will focus on filed trials to determine effective reduced rates of carbonated fumigants. In the third year, a demonstration trial will illustrate those successful fumigation methods in growers’ fields. Emission loss, fumigant distribution (or concentration change over time in soil profile), and efficacy on nematode, pathogen and weed control will all be determined. The expected outcome is an economically feasible alternative to methyl bromide by increasing use efficiency, reducing chemical input and minimizing detrimental impact on the environment. Documents reimbursable with U of FL. (NIFA). Log 41604.
This project addresses the in-house project (NP 211) Objective 5: Develop various application methods, soil amendments, and physical barriers to reduce the emissions and enhance efficacy of the chemical alternatives to methyl bromide. Pre-plant soil fumigation is often used to suppress pest pressure and establish productive orchards for many perennial crops. Alternative fumigants, such as Telone or 1,3-dichloropropene (1,3-D) and chloropicrin (CP), are often less efficacious in pest control because they do not diffuse as well as methyl bromide in soil. This is especially problematic for deep-rooted tree crops. In addition, emission reduction from soil fumigation is required to meet air quality standards. Low permeability tarps, such as totally impermeable films (TIF), have shown promise in emission reduction because of their effectiveness in retaining fumigants under the tarp, but the effects on improvement of fumigant diffusion into deeper soil were found to be less dramatic than fumigation for annual crops with shallow injection of fumigants. A carbonation technique to improve dispersion of fumigant in soil is investigated in this project. Carbonation refers to the process of dissolving carbon dioxide into the fumigant and using carbon dioxide as a dispersant in a soil application.
In May 2013, a comprehensive field trial was conducted at USDA-ARS San Joaquin Valley Agricultural Sciences Center, Parlier, California, and the trial lasted for five weeks. The trial was designed to evaluate the effects of tarping with TIF and using a carbonation technique in combination with reduced rates on fumigant emission, distribution in soil, and efficacy. A total of 10 treatments in 3 replicates were applied including the non-treated controls (no tarp, standard polyethylene or PE tarp, TIF), fumigated control (full rate, no tarp, regular fumigant), and various combinations of two application rates (full and 2/3) of Telone C35 (a mixture of 1,3-D and CP) with either carbonated or non-carbonated fumigant under different surface sealing methods (none, PE, and TIF). The fumigants were applied via shank-injection to 18 inch depth with shanks spaced 20 inches apart.
Fumigant emissions were measured and fumigant concentrations in the soil profile were monitored for five weeks. Fumigant movement in soil profile under the TIF was monitored by sampling soil gas across the edge of the tarp. To determine the treatment effects on efficacy, bags infested with known levels of nematodes and pathogens were buried prior to fumigant application and retrieved after fumigation to determine viability.
Field sampling continued for five weeks after fumigant and treatment applications. Soil and plastic tarp samples were collected for determining residual fumigants and tarp permeability. Then the tarp was cut for removal in a few days. The pest bags were retrieved from the field for survival count. All samples are currently being processed for laboratory analysis.