U.S.EPA
Methyl Bromide Alternative Case Study
Part of EPA 430-R-97-030, 10 Case Studies, Volume 3
September 1997

Hydroponics and Soilless Cultures on Artificial Substrates as an Alternative to Methyl Bromide Soil Fumigation

The use of hydroponic technology can be a viable alternative to methyl bromide soil fumigation for greenhouse grown tomatoes, strawberries, cucumbers, peppers, eggplants, and some flowers. Hydroponics allows crop culturing without soil fumigation by providing a system where a majority of a plants nutrient needs are met by mixing water soluble nutrients with water, and eliminating requirements for soil. Hydroponic systems that use only a nutrient solution, are categorized as water culture or solution culture, however, if the nutrient solution is used in combination with solid inert matter (i.e., Rockwool, turf stone, clay granules, sawdust, flexible polyurethane foaming blocks, composed hardwood bark, or peat) to physically support root systems and hold the hydroponic solution, it is categorized as a substrate culture or aggregate culture.

If the nutrient solution is recycled, then the system is considered to be a closed hydroponic system. If the solution is discharged after use, it is considered to be an open hydroponic system (Cropking 1996). Hydroponic systems are usually utilized in indoor greenhouses in non-tropical climates, allowing the grower to have control over climate conditions. Specialized hydroponic farming systems in the U.S., Canada, and Europe have demonstrated the technical and economic feasibility of eliminating methyl bromide use in greenhouses and (under certian climate conditions) in open fields (Braun and Supkoff 1994, Anonymous 1992b, Anonymous 1992c).

The advantages of hydroponic or soilless cultures on artificial substrates are: 1) an absence of completing weeds and soilborne pests and toxic residues; 2) water conservation (with recycling systems, hydroponic systems use one tenth the amount of water used in irrigated agriculture); and 3) conditions that can be altered quickly to suit specific crops, various growth stages, and environmental/climate conditions. In addition to nutrients, hydroponics also brings fresh oxygen to the root zone and takes away "off-gases," the waste by-product of the root zone, making it a highly efficient and cost-effective technology (Anonymous 1992a, Cropking 1996). Because nutrients are readily available in hydroponic systems, plants have smaller, more efficient root systems and can spend more energy growing the more valuable above ground stems, foliage, and fruit. Furthermore, growers can space plants closer together, thus producing more agricultural products per a given area, while avoiding competition for scarce nutrients in the rootzone (Hydro Aquatic Technologies 1995, Resh 1993).

All hydroponic systems provide water, nutrients, and oxygen to plants; however, hydroponic systems differ significantly. Several of the many types of hydroponic systems include the following: static air techniques, aeroponic systems, nutrient flow techniques, rockwool slab systems, aquaponic systems, ebb and flow, deep flow techniques, aerated flow techniques, nutrient flow techniques, drip irrigation techniques, root mist techniques, fog feed techniques, subaeration methods, gravity flow feeds, and peat bag culture (Hydro Aquatic Technologies 1996).

Hydroponics in the Netherlands

In 1980, the Netherlands decided to phase-out the use of methyl bromide as a soil fumigant by 1992. The work that was done to achieve this and the alternatives developed provides an important model for phasing out methyl bromide, as well as a number of good alternatives to this pesticide (Anonymous 1992a). The Netherlands was formerly one of Europe's largest users of methyl bromide for soil fumigation. Using this pesticide to control soilborne pests on greenhouse-grown crops such as tomatoes, lettuce, strawberries, cucumbers, sweet peppers, eggplants, as well as nursery crops and cut flowers (only a small amount was used to fumigate soils in field crops). By using alternative cropping methods, such as hydroponics and soilless culture on artificial substrates, growers in the Netherlands have successfully eliminated the risk of infestation by soilborne pests, while increasing crop yield and quality (Methyl Bromide Task Force 1995).

The phase out of methyl bromide allowed the Netherlands to develop greenhouse crop production systems with a number of economic and environmental advantages. For example, both strawberries and cucurbits are successfully grown in greenhouses in the Netherlands using artificial substrates (i.e., peat and Rockwool, respectively) on hanging shelves or on raised shelves outdoors (Sneh et al. 1983, Braun and Supkoff 1994). Planting densities in greenhouses are doubled by hanging each tightly-spaced row from cables attached to winches. Alternating rows are then raised and lowered to gain access for tending or harvesting (Methyl Bromide Task Force 1995, Liebman 1994). The hydroponic solution (nutrient rich water) is pumped to the plants using a regulated trickle/drip irrigation system. The wastewater from the roots is recaptured, sterilized, and reused to reduce environmental waste and contamination, and to conserve water. Growers sterilize the recycled nutrient water by heating it to about 90°C (194°F) (Anonymous 1992b, Anonymous 1992c). Substrates are sterilized for reuse using steam (USDA 1996, Liebman 1994).

Strawberries
There are approximately 2,072 ha of strawberries grown in the Netherlands. In 1993, production of greenhouse strawberries in the Netherlands was approximately 31,000 tonnes, of which almost half (14,000 tonnes) was from greenhouse production. Peat bags are primarily used in the production of greenhouse strawberries and to cultivate new runners. Young plants are exposed to short-day lighting to stimulate bud formation, and are then either placed in greenhouse substrates (or outdoors) to fruit or are stored for up to eight months at -2°C in a dormant state poised for flower development (Methyl Bromide Task Force 1995). In warmer weather, mature plants may produce strawberries within 60 days without the use of methyl bromide or any other soil fumigant (Anonymous 1992b, Anonymous 1992c).

Cucurbits
Approximately 1,020 ha of cucurbits (i.e., cucumbers, eggplant, and melons) are grown in the Netherlands. In the current post methyl bromide period, more than 90 percent of the cucurbits were grown on artificial substrates in temperature controlled greenhouses, while the remainder were grown in steam sterilized soil. The main cucurbit crop is cucumber, of which 484,720 tonnes were produced in greenhouses in 1993. The area used to grow cucumbers has remained constant since 1970, however, the area of crops grown on artificial substrates has increased from 272 ha in 1991 to 935 ha in 1994 (Banks 1993).

Costs

Hydroponics is an economically viable alternative to methyl bromide fumigation for a number of crops, including strawberries and cucumbers (See Table 1a and b). Although materials and total costs are higher for hydroponic systems compared to methyl bromide fumigation, operating costs are generally lower (except for double crops of strawberries) and overall crop yields far exceed those obtained with methyl bromide. In general, strawberry and cucurbit yields using artificial substrates are double those obtained using soil. In fact, production on one greenhouse acre is equivalent to that on 8 to 10 field acres with long term production costs being much lower (Rosselle 1996). Adjusting costs ($/kg yield) to take into account crop yield renders costs comparable to that of methyl bromide fumigation. Furthermore, hydroponic costs are expected to decrease as sales continue to increase and these systems become more commercialized (Rosselle 1996, USDA 1996).

Other economic advantages of hydroponics include a potentially fast and flexible hydroponic cropping period, which allows growers to quickly change production to take advantage of market conditions. Because of the short cropping period (4 months total) and the development of cold storage techniques, growers can increase or decrease production depending on prices, or select alternative crops if crop prices are not favorable. By marketing produce when the prices are at a premium, growers can pay off the initial capital investments in as little as 3 years (Methyl Bromide Task Force 1995, Liebman 1994). In fact, Dutch growers have already reported a 10 to 20 percent increase in cash income with the use of these artificial substrates (USDA 1996, Banks 1993). Lastly, unlike conventional crops, growers also have the option of "double cropping" to produce 2 crops/year from one planting, thereby halving the cost of crop establishment (Banks 1993, Anonymous 1992b, Anonymous 1992c).

Table 1a. Strawberries: Cost of Hydroponics vs. Methyl Bromide as a Preplant Fumigant.



Cost Factors ($/acre/year) Greenhouse

Hydroponic/Artificial Substrate

 Greenhouse

Methyl Bromide

Single Crop Double Crop
Labor/Operating 4,692 15,602 8,455
Materials

(Water/Chemical)

 25,844 28,604 14,553
Total 30,536 44,211 23,008

Yield (kg/acre)

20,235

 36,423 23,008

Adjusted Cost ($/kg)

1.51

 1.21 1.14

Source: Banks 1993.



Table 1b. Cucumbers: Cost of Hydroponics vs. Methyl Bromide as a Preplant Fumigant.



Cost Factors ($/acre/year) Greenhouse

Hydroponic/Artificial Substrate

 Greenhouse

Methyl Bromide

Labor/Operating 11,818 12,696
Materials

(Water/Chemical)

 70,381 18,216
Total 82,199 30,912

Yield (kg/acre)

274,791

 107,650
Adjusted Cost ($/kg) 0.30 0.29

Source: Banks 1993.



References

Anonymous. Into the Sunlight: Exposing Methyl Bromide's Threat to the Ozone Layer; Friends of the Earth: Washington, D.C., 1992a.

Anonymous. "Methyl Bromide". Executive Summary, International Workshops on Alternatives to Methyl Bromide for Soil Fumigation. Rotterdam, The Netherlands, October 1992, and Rome, Italy, October 1992b; p 32.

Anonymous. "Methyl Bromide: Its Atmospheric Science, Technology and Economics"; synthesis report of the Methyl Bromide Interim Scientific Assessment and Methyl Bromide Interim Technology and Economic Assessment, United Nations Environmental Programme, Montreal Protocol Assessment, 1992c.

Banks, J. Agricultural production without methyl bromide - Four Case Studies. CSIRO Division of Entomology and UNEP IE's Ozone Action Programme under the Multilateral Fund, 1993.

Braun, A.L.; Supkoff, D.M. "Options to Methyl Bromide for the Control of Soil-borne Diseases and Pests in California with Reference to the Netherlands"; Pest Management Analysis and Planning Program; State of California, Environmental Protection Agency, Department of Pesticide Regulation, Sacramento, CA, 1994.

Cropking, Seville, OH, unpublished material, 1996.

Hydro Aquatic Technologies, Switzerland, 1995, unpublished material.

Liebman, J. Alternatives to methyl bromide in California strawberry production. The IPM Practitioner 1994, 16(7).

Methyl Bromide Task Force. Alternatives to Methyl Bromide: Research Needs for California; Department of Pesticide Regulation and The California Department of Food and Agriculture: Sacramento, CA, 1995.

Resh. Hydroponic Food Production (fourth edition); Woodbride Press Publishing: Santa Barbara, CA, 1993.

Rosselle, T. Seeing Green Under Glass. The Packer 1996, 103, p. 1A.

Sneh, B.; Katan, J.; Abdul-Razig, A. Chemical control of soil-borne pathogens in tuff medium for strawberry cultivation. Pestic. Sci. 1983, 14, 119-122.

United States Department of Agriculture (USDA). "The Netherlands' Alternatives to Methyl Bromide." Internet: http://www.ars.usda.gov/is/np/mba/oct96/nether.htm, 1996.

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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