Food grade, identity preserved soybean research has been pursued as an opportunity for farmers to capture value-added markets like edamame soybean [Glycine max (L.) Merr]. Research was initiated to evaluate the impact of agronomic decisions on edamame soybean pod yield. Edamame is Japanese for "vegetable green soybean ." Edamame is a common snack food in Japan. Japan and the United States command 88 and 11% of the global edamame demand, respectively (Lin 2001). Edamame can be substituted for peas or lima beans and can be sold fresh or frozen. The frozen market allows greater flexibility in direct or internet-based marketing systems. Quick preparation on the stove top, microwave, or steamer and the health benefits of edamame make it a natural fit into today's fast pace heat-and-eat meals. As a health food, edamame soybean has ranked at the top of the list. Research has reported that edamame had elevated levels of asparagine, alanine, and glutamic acid up to 40 days after flowering compared with grain-type cultivar amino acid levels which decreased 20 to 30 days after flowering (Yanagisawa et al. 1997). Due to the health benefits of vegetable soybean, demand for vegetable green soybean may increase substantially over time.

Supply of edamame soybean has been concentrated in southeast Asia; however, research and breeding programs in Washington (Miles et al. 2000), Colorado (Johnson et al. 1999), Kentucky (Ernst and Woods 2001), Canada (Li 2000) and other parts of the world have been initiated. Several resources on edamame varieties, harvesting & marketing, recipes, seed sources, and educational brochures are available from Washington State University (Miles et al. 2000). However, no resources are available on the influence of agronomic decisions on edamame production in Missouri. The following sections outline a summary of the growing, harvesting, handling, and marketing aspects of edamame soybean.

Growing edamame

Edamame is a specialty soybean and management is necessary to market a high quality directly consumed product. Flavor, sweetness, texture, nutritional value, and visual appearance are key quality components of edamame. Sucrose, glutamic acid, and alanine are important for flavor; sweetness is influenced by the sugar levels in the beans; and harvest timing commonly affects bean texture. Pods should be free from defects, dark green, have light pubescence, and at least two beans. Agronomic practices can have a significant effect on quality assurance for edamame.

Edamame require excellent fertility for quality beans. Edamame cultivars vary in their nodulation (visual observation). Current recommendations call for 50 to 120 lbs of nitrogen per acre (Miles et al. 2000). A split application of 25 lbs of nitrogen plus phosphorus and potassium preemergence followed by a side-dress application of the remaining nitrogen fertilizer six weeks after planting has been recommended (Miles et al. 2000). Nguyen (2001) reported a side-dress application of potassium nitrate was important. Fields that are well-drained allow soils to warm up quickly and reduced the incidence of soybean disease. Seeding rates target 60- to 70,000 plants/acre. Edamame seed may cost up to $22/lb; therefore, yield/plant should be maximized.

Conventional herbicides were used for weed control in 2001. No Roundup Ready® cultivars are available which allows edamame to maintain a non-GMO status for consumers desiring non-GMO soy alternatives. A preemergence followed by a split-postemergence weed management program was successful in the 2001 growing season. A split-postemergence application was used to minimize crop response.

Harvesting edamame

Edamame need to be harvested when the seeds are at the R6 stage of development (green bean stage). Edamame can be harvested by hand or direct harvested using a green bean picker. After hand harvesting research plots, hand harvesting is not an option unless labor is readily available and inexpensive. Green bean harvesters have been utilized for mechanical harvest of edamame.

Handling and processing edamame

Marketable pods have two to three beans and can be separated using mechanical sieves for sorting. Shelled vegetable soybean (maudou) was accomplished with a rubber coated metal roller and corrugated roller which squeezes the pods to remove beans. Pods are frozen and bagged for consumer use. Frozen edamame can be stored for long periods of time. Instant quick freeze (IQF) technology, a combination of carbon dioxide and nitrogen, provides a quality frozen pod. Cave storage in eastern or western Missouri could meet storage demand for edamame.

Marketing edamame

Marketing is important for any crop. Missouri is one of the leading soybean producers in the United States; however, the United States does not ranked as a supplier of edamame in the global market (Lin 2001). Japan and the United States command 88 and 11% of the global edamame demand, respectively (Lin 2001). Edamame can be substituted for peas or lima beans in the diet. Edamame can be marketed in the fresh and frozen markets as edamame in the pod or shelled edamame. Estimated return per acre in Kentucky ranked sweet corn ($135/acre) < pumpkins ($243/acre) < wholesale fresh edamame ($259/acre) < staked tomatoes ($715/acre) < cantaloupe ($1,113/acre) (Ernst and Woods 2001). The fresh market, sold as pods or on the plant, may provide the greatest returns; however, frozen markets seem the most stable and may require less marketing labor.

Locally lead promotion and contacts could provide the foundation for successful edamame markets. Kentucky has pioneered "Kentucky edamame" with the efforts of professional marketing experts and grassroots producer-led efforts (Ernst and Woods 2001). Identification of imported edamame markets and distributors may provide the infrastructure for more widespread marketing. Direct marketing through web-based health food resources may provide the greatest returns for producers involved in edamame production.

Objectives:

Research was initiated in the spring of 2001 to evaluate: 1) the effect of plant population on yield of ‘Sapporo Midori' (Table 1), 2) the effect of starter and side-dress fertilizer on yield of ‘White Lion' (Table 2), and 3) yield of seven edamame soybean cultivars (Table 3).

Materials and Methods:

Research was conducted at the University of Missouri Greenley Research Center near Novelty, MO. Soybean were planted in 30 in. wide-rows and plots 10 by 30 ft. on June 20, 2001. The experiment was a randomized complete block design with five replications. The plot area was maintained weed-free throughout the experiment with Outlook applied preemergence followed by a split application of Basagran plus Reflex and Basagran plus Reflex plus Select. Starter fertilizer, 50-100-100, was applied with the planter and a side-dress application of 50-0-50 was applied at the R1 stage of development. Edamame soybean were hand harvested at the R6 stage of development. Pods were sorted by the number of beans/pod, frozen, counted, and weighed. ANOVA was conducted and means were separated using Fisher's Protected LSD (P 0.05).

Results and Discussion:

1) Effect of plant population on yield of ‘Sapporo Midori' pod yield. Marketable pod yield increased as soybean plant population increased in 2001 (Table 1). Since edamame seed was expensive, up to $22/lb, it is essential to determine optimum plant population and the influence of population on marketable pod yield. Pod yield/plant was 25, 19, and 16 for 40,000, 70,000, and 100,000 plants/acre, respectively. Pod yield/plant was maximized at 40,000 plants/acre.

Table 1. The effect of plant population on 'Sapporo Midori' pod yield in 2001.

2) Effect of starter and side-dress fertilizer on yield of 'White Lion'. Inadequate fertility may result in poor pod fill or increase the number of one-seeded edamame pods (Nguyen 2001). Variable nodulation was observed in 2001 (personal observation). However, fertility treatments did not affect pod yield of 'White Lion' (Table 2). Starter fertilizer may suffice.

Table 2. The effect of starter and side-dress fertilizer on 'White Lion' pod yield in 2001.

3) Research in 2001 demonstrated edamame cultivars ranged from 17 to 34 inches tall (data not presented). Pod yield was also variable depending on the variety. Edamame pod yield was 3520 to 7220 lbs/acre in 2001 (Table 3). Pod yield of 'Sayasume' was 3.6 ton/acre and was similar to 'Early Hakucho' and 'Envy' cultivars. 'Envy' had the greatest number of non-marketable pods while other cultivars were similar.

Table 3. Edamame variety pod yield in 2001.

References:

Ernst, M. and T. Woods. 2001. Marketing challenges for emerging crops in Kentucky: vegetable soybeans. pp. 35-38. In: Second Intl.Veg. Soybean Conf. Tacoma, WA. 10-12 August 2001.

Johnson, D. S. Wang, and A. Suzuki. 1999. Edamame: A vegetable soybean for Colorado. pp. 385-387. In: J. Janick (ed.), Perspectives on new crops and new uses. ASHS Press, Alexandria, VA.

Li, T. 2001. Vegetable soybean development in Canada. pp. 83-86. In: Second Intl.Veg. Soybean Conf. Tacoma, WA. 10-12 August 2001.

Lin, C. 2001. Frozen edamame: global market conditions. pp. 93-96. In: Second Intl.Veg. Soybean Conf. Tacoma, WA. 10-12 August 2001.

Miles, C.A., T.A. Lumpkin, and L. Zenz. 2000. Edamame. Pacific Northwest Extension Publication, PNW0525. pp. 8.

Nguyen, V.Q. 2001. Edamame (vegetable green soybean). (http://www.rirdc.gov.au/pub/handbook/edamame.html).