From our Central Coast Agriculture Highlights newsletter -- October 2001:
 Green fresh vegetable soybeans (often sold as "edamame," the Japanese word for fresh soybeans) are gaining popularity as a vegetable and snack food in many parts of the US. Long an important food in Asian diets, they are consumed boiled as snacks or as part of many dishes and soups. Edamame vegetable soybeans are grown for harvest as fresh green pods, which are then boiled for a short period of time in salted water. They are served warm and shelled from the pod for eating. Vegetable soybeans may offer a promising new crop alternative for one or more areas of California. The selection of the appropriate variety is a key decision for successful edamame production. Soybeans have specific adaptation requirements that are dictated in large part by latitude and temperature regime. They are day length sensitive "short day" plants, which flower when day length reaches a certain length or less. So there are so-called Maturity Groups of soybeans ranging in North America from latitudes in Southern Canada to the Gulf Coast. And in some cases there are day length insensitive varieties available for specific short season growing environments. Field trials have been conducted over the past several years in various parts of the U.S., but these adaptation requirements mean that trials are quite site specific, and it is difficult to make assumptions from the performance of a given variety in another growing area. Vegetable soybeans are a special class of soybeans that have been selected for larger seeds and other desirable eating characteristics. There are not nearly as many commercial cultivars of vegetable soybeans as common grain soybeans, and much less specific information is available about their specific production practices. Seed availability has been a critical limitation for edamame production historically, but several varieties are now offered by seed companies (Table 1). The edamame soybeans are also special among the vegetable soybean group because they have been selected over the years for other specific quality characteristics. The following characteristics are especially valued for Japanese edamame:
We have been evaluating several commercially available varieties in field trials in San Luis Obispo County (Huasna area, Arroyo Grande) during the 2001 growing season. We planted each of the edamame varieties on three planting dates - June 1, June 18, and July 3, 2001. The initial results from those trials are presented in Table 2-5 (the third planting has not yet been harvested). The varieties are commercial varieties currently available from seed sources (Table 1) and a variety from Taiwan, Kaoshiung 1, that comprises much of the edamame production traditionally exported to Japan. The field plots were replicated four times and managed according to standard practices for fresh soybean production. Ten contiguous plants were cut from each plot on their typical harvest date, and the pods were stripped in the packing shed for counting and weighing. A variety was selected for harvest when plants had a maximum number of filled pods, and the first pods were turning to yellow. Some varieties germinated poorly in the second planting date, and measurements were made from less than ten plants and corrected to per plant averages. Only those pods with two or three seeds are considered marketable, and larger pods with fuller seeds are considered higher quality. A common measure used for edamame beyond weight of two- and three-seeded pods is number of pods per 500 gram sample. Common values cited by some sources for number of pods per 500 grams in edamame breeding programs in Asia range from 163 to 209. Thus, fewer pods in a 500 gram sample is considered desirable. All the varieties evaluated in this trial produced acceptable yield and quality. The pod size for these varieties at these planting dates was in the range reported for traditional edamame markets and production areas. Although there were no marked differences between many of the varieties, Sayamasume and Shironomai stood out as varieties with consistently high yields and large pods in both planting dates. Lucky Lion and Early Hakucho also performed well and were among the earlier producing varieties. Plants tended to be smaller in the second planting, but there was no clear trend for yield between the two planting dates. The third planting date will provide additional data that may support a clearer trend. We have reported data previously from experimental edamame lines, indicating the potential for edamame production in coastal California growing areas, but these are the first trials comparing commercially available varieties. If you are already growing vegetable soybeans for edamame, this data may provide some additional information on a promising variety. If you are interested in growing edamame for the first time, this may help decide which varieties to evaluate first. These results provide a basis for some additional decision-making for growing edamame in the area of central, coastal California. Do not make major changes in varieties based on this or any other limited trial data. Use trial data to select promising varieties to incorporate in small plots in your own growing conditions and only make major shifts in varieties or planting dates after your own preliminary trials. Edamame seed requires relatively warm soil to germinate and emerges best when the temperature is above 60°F, and this will largely determine how early to plant. Once emerged, the plant is relatively more tolerant of cooler growing conditions and succession plantings are possible. The latest planting will be determined by the threat of frost or cool night temperatures, depending on the area, which limit normal pod development. Plants should be spaced two to four inches apart in the row and rows approximately 30’ apart, depending upon the configuration of planting and cultivating equipment. For additional specific information on edamame production practices, Washington State University maintains a Website at: http://agsyst.wsu.edu/edamresearch.html or contact this office (805/934-6240). Edamame production trials are ongoing in other parts of California, and additional information on edamame soybean production and post-harvest management will appear here as it becomes available.
Table 2. Total marketable pod yield of nine varieties of edamame from two planting dates. There is no significant difference (P<0.05) between yields of varieties within a planting date followed by the same letter.
Table 3. Two-seed pod yield (g/plant) of nine varieties of edamame from two planting dates. There is no significant difference (P<0.05) between yields of varieties within a planting date followed by the same letter.
Table 4. Three-seed pod yield (g/plant) of nine varieties of edamame from two planting dates. There is no significant difference (P<0.05) between yields of varieties within a planting date followed by the same letter.
Table 5. Number of pods in 500 gram sample of nine varieties of edamame from two planting dates. There is no significant difference (P<0.05) between yields of varieties within a planting date followed by the same letter.
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The Territorial Seed Company P.O. Box 158 Cottage Grove, OR 97424-0061 Tel: 541/942-9547 http://www.territorial-seed.com Snowbrand Seed 7-1 Shinminato Mihama-Ku, Chiba City Ciba 261 JAPAN E-mail: SBS00976@nifty.ne.jp
Additional varieties grown in previous trials, but not evaluated in this field trial, are also available from:
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