Today, California growers face an increasing number of requirements regarding the preplant application of soil fumigants promulgated by federal, state, and county governments. These requirements are issued as label requirements, use regulations, and county permit conditions. Because of increasing regulation of fumigants, it is unclear that their use as the exclusive means of soil disinfestation will continue to be economically viable, even if they remain technically available for growers to use on some land. Some regulations prohibit fumigant applications entirely, such as buffer zone distance requirements for applications near sensitive sites, such as schools (California Department Pesticide Regulation, 2015a). The efficacy and economic feasibility of a nonfumigant treatment is an important consideration when part of a field cannot be fumigated. Leaving buffer zones untreated reduces yields and provides a reservoir for pests and disease, which can spread into treated areas of the field. Soil disinfestation using steam is one nonchemical alternative that can be used where the preplant application of soil fumigants is prohibited.
Steam has demonstrated efficacy against weed, insect, nematode, and pathogenic pests affecting crops (Fennimore et al., 2014). It has been used for decades as part of greenhouse floriculture production. In addition to its technical efficacy, the application of steam is safer than applications of chemical fumigants for human health, and no buffer zones are required. Thus, even if the majority of a field is treated with a fumigant, steam can increase field-level returns by reducing weed and pest pressure if it is used in the field’s buffer zone.
This analysis evaluates the economic feasibility of steam application as a mean of soil disinfestation before planting for strawberries produced in California’s Central Coast production region. It compares the economic performance of steam to that of CP + 1,3-D and an untreated control. Using results from a separate trial, it compares the economic performance of steam when it is applied alone to when it is paired with soil amendments of MSM and an untreated control.
The economic feasibility of a technology is dependent on the crop or cropping system. One consideration in the production system we examine is that transitioning to alternative crops is challenging. Cropland values are quite high in strawberry production areas on California’s Central Coast compared with cropland values in the Central Valley, and growers who produce strawberries are specialized in berry production (An et al., 2009); berry growers’ desire to control their cropland is a primary driver of cropland values in the region (American Society of Farm Managers and Rural Appraisers-California Chapter, 2015). Thus, identifying technically and economically viable alternatives for preplant soil fumigation in California strawberry production is an urgent task for researchers.
Strawberries are an economically important crop in California. In 2012, the total value of California strawberry production was US$2.1 billion, ranking strawberries sixth among California commodities (California Department of Food and Agriculture, 2013). Strawberry production is a significant user of preplant soil fumigation in California. In 2012, it accounted for 75% of the total use of CP and 24% of the total use of 1,3-D (California Department of Pesticide Regulation, 2015b).
There has been relatively little economic analysis of the use of steam for preplant soil disinfestation in strawberry production. Various steam application technologies have been tested alone or in combination with other soil disinfestation techniques. Samtani et al. (2011) found that steam provided strawberry yields and weed control comparable to CP + 1,3-D but did not evaluate economic feasibility explicitly. Samtani et al. (2012) tested the efficacy of steam in soil pest control and whether soil disinfestation using both steam and solarization affected pest control and yield response, compared with application of these two alternatives individually. Treatments included methyl bromide:chloropicrin, solarization and steam, solarization alone, and steam alone. The treatments of steam alone and the combination of steam and solarization provided the most effective pest control, and had yield effects comparable to methyl bromide:chloropicrin. Regarding economic viability, the authors concluded that net returns from treatments of solarization or steam were lower than those from the methyl bromide:chloropicrin treatment.
Fennimore et al. (2013) evaluated the efficacy of the preplant application of anaerobic soil disinfestation (ASD) and steam with and without a MSM soil amendment for strawberries. Trial results suggested that steam with and without MSM had comparable weed control effects to CP + 1,3-D, whereas ASD was less effective than CP + 1,3-D. Both steam and ASD treatments had yields equivalent to CP + 1,3-D. However, the costs associated with steam application were much higher than those for CP + 1,3-D.
This paper provides an example of the use of economic analysis in multidisciplinary production system research projects. It is now expected by most granting agencies and stakeholders that such projects will include an analysis of economic feasibility of the examined techniques. Studies on alternative soil disinfestation techniques are limited due to costs and time involved in conducting the studies. Thus, policymakers and producers will benefit from researchers extracting as much information as possible from each trial. Growers are also concerned with the reliability of the performance of alternative treatments, which is not captured as part of a standard partial budget analysis.
The structure of the first set of trials we evaluated allowed us to apply techniques commonly used by economists to obtain more information than that provided by a standard partial budget analysis. We used Monte Carlo analyses to enhance the information regarding economic viability that can be obtained from the field trials. We compared the distributions of net returns, defined as total returns minus treatment, weeding, and harvest labor costs, using the observed variability in yield and weeding time across plots for each treatment. Evaluating the distributions provided a fuller picture of the net returns obtained from steam relative to those obtained from a conventional soil fumigant. The study also used sensitivity analysis to consider the effects of changes in the yield distribution, cost of propane, and steam application technology on the relative economic performances of the treatments.
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