CASE STUDY -- Methyl Bromide Alternative
Greenhouse Systems for the Production of Tobacco Seedlings
The production of tobacco generally involves two steps. Tobacco seedlings are initially grown in either outdoor seedbeds or greenhouses, where they remain for 40 to 60 days until they reach a height of 15-22 centimeters. The seedlings are then transplanted to the field where they complete their growth. Currently in the United States, 50 to 70 percent of tobacco seedlings are produced in greenhouses (Miner 1995, Nesmith 1995, Peedin 1994).
The tobacco industry is rapidly shifting from the outdoor seedbed method, which requires fumigating the soil (often with methyl bromide), to on-farm greenhouses, which use floatation systems and steam-sterilized media instead of methyl bromide fumigation. The shift is occurring primarily because seedlings grown in greenhouses are less labor intensive and therefore can be less costly over the long run (Miner 1995, Nesmith 1995). Nearly 8,300 acres of tobacco were treated with approximately 1,678 metric tons of methyl bromide in 1992 (EPA 1994), about 7.5 percent of the total U.S. methyl bromide consumption. However, the continuation of the shift to greenhouse production of tobacco seedlings can reduce the annual consumption of methyl bromide in the United States. Over the next five years, the shift from outdoor seedbed production of seedlings to greenhouse production is expected to be rapid, reaching approximately 90 percent by the year 2000 (Nesmith 1995).
Greenhouse Seedling Production Systems
There are several types of greenhouse production systems including the direct-seeded float system, the overhead watering system, and the plug and transfer system. The direct-seeded float system, which provides plants with water and nutrients through a waterbed, is the most common system and is used by approximately 80 percent of North Carolina tobacco growers in their greenhouses (Lychak and Brown 1993). Direct-seeded float systems use a variety of commercially prepared and sanitized media. The most commonly used media preparations contain 50 percent peat and 50 percent vermiculite (Peedin 1994); these man-made mixtures are generally sterilized using steam treatments.
Benefits of Greenhouse Systems
- greater uniformity of seedlings and
- reduced labor requirements
Replacing Seedbed Production of Seedlings with Greenhouse Systems
All major tobacco producing states are abandoning the traditional, labor-intensive outdoor seedbed production in favor of greenhouse systems (Miner 1995, Nesmith 1995). North Carolina, with roughly 284,000 acres in production, is the nation's number one tobacco-producing state; in 1994, 54 percent of the state's seedlings were produced in greenhouses, with the majority of greenhouses using the float production method (Peedin 1994). This production method also prevails in Kentucky, the second largest tobacco-producing state. Approximately 70 percent of Kentucky's tobacco seedlings are produced in a greenhouse floatation system using hydroponics and soil-less mixtures (Nesmith 1995).
The percentage of North Carolina tobacco growers switching from outdoor seedbed production to greenhouse production of seedlings has increased three-fold in five years, from 18 percent in 1990 to 54 percent in 1994 (Peedin 1994). University specialists estimate that by the year 2001, 90 percent of outdoor seedbed production requiring methyl bromide will be converted to greenhouse production (Nesmith 1995). Some smaller growers may adopt mini-greenhouses, which have similar per-unit construction costs as larger greenhouse systems, but require significantly reduced capital outlays (Peedin 1994). The remaining 10 percent of tobacco growers currently fumigating their seedbeds with methyl bromide will most likely choose the soil fumigant VapamŽ to control soil-borne diseases and nematodes once methyl bromide is phased out (Nesmith 1995).
Costs and Benefits Associated with Greenhouse Systems
Greenhouse production systems produce tobacco seedlings for transplant that are of greater uniformity at reduced labor costs. Based on final yield, greenhouse production systems result in tobacco seedlings of the same quality as those produced by conventional methods, but with increased uniformity of seedlings and flowers (Lychak and Brown 1993, Smith 1995). A typical 150-foot greenhouse can produce enough seedlings to plant 100 acres of tobacco (Miner 1995). Switching from field production to greenhouse production of transplants results in some difficult to quantify benefits, such as more uniform transplants, and possible savings that offset slight increases in production costs.
Increased cost associated with greenhouse production includes a greater capital investment than that required by conventional growing practices. Greenhouses also require more management than conventional growing systems to be successful (Lychak and Brown 1993). However, greenhouse production reduces labor requirements, primarily for the person pulling up seedlings, boxing them, and transporting them to the field for transplant. Substituting capital costs for labor costs includes difficult to quantify savings such as the costs of housing and administrative management, which results in greater savings than from wages alone (Miner 1995, Smith 1995). Production costs for conventionally grown tobacco seedlings are shown below.
Adjustments in greenhouse size and management may also result in additional savings. For example, as the size of the greenhouse increases, the costs of producing tobacco seedlings decrease (Smith 1995). Different management techniques and machinery can also reduce the difference in cost. Increased seedling production due to improved management practices can reduce the cost per seedling, and the use of a carousel transplanter, by further reducing labor requirements, may lead to additional savings (Lychak and Brown 1993).
Tobacco Seedling Production Costs
Greenhouse Production(without Methyl Bromide)
Cost per seedling: $0.019
Cost per acre seeded (6,000 transplants per acre):$114
Seedbed Production (with Methyl Bromide)
Cost per seedling: $0.017
Cost per acre seeded (6,000 transplants per acre):$100
Sources: Smith 1995, Lychak and Brown 1993.
EPA. 1994. Methyl bromide soil fumigation survey. U.S. Environmental Protection Agency, Office of Pesticide Programs. Washington, DC.
Lychak and Brown. 1993 (November 10). The Cost of Producing Flue-Cured Tobacco Transplants in Greenhouses. Tara Lychak, R.J. Reynolds Research Apprentice and A. Blake Brown, Extension Economist and Assistant Professor, Department of Agricultural and Resource Economics, North Carolina State University. North Carolina.
Miner. 1995 (January 11). Personal communication. Gordon S. Miner, Professor of Soil Fertility, North Carolina State University. North Carolina.
Nesmith. 1995 (January 16). Personal communication. Bill C. Nesmith, Professor of Plant Pathology, University of Kentucky. Kentucky.
Peedin. 1994 (December). Flue-Cured Tobacco. Gerald F. Peedin, et al. North Carolina Cooperative Extension Service, North Carolina State University. North Carolina.
Smith. 1995 (January 30). Personal communication. Professor Smith, Cooperative Extension, North Carolina State University. North Carolina.
Please note that this publication discusses specific proprietary products and pest control methods. Some of these alternatives are now commercially available, while others are in an advanced stage of development. In all cases, the information presented does not constitute a recommendation or an endorsement of these products or methods by the Environmental Protection Agency (EPA) or other involved parties. Neither should the absence of an item or pest control method necessarily be interpreted as EPA disapproval.
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