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Research Highlights

Research Highlights
Using Best Practices to Create Value with Natto Soybean Production

Seeding rate for natto soybean production is critical to avoiding lodging such as this.

By Barb Baylor Anderson

Opportunities exist for soybean farmers in Wisconsin and other states to service markets for identify-preserved soybeans and earn premiums. One opportunity, natto soybean production, is similar to conventional production, but with a priority focus on seed size and quality. 

To help farmers capitalize on the market, Shawn Conley, Wisconsin soybean and small grains specialist, served as principal investigator on best practices research funded by the Wisconsin Soybean Marketing Board. The project also included John Gaska, University of Wisconsin senior outreach specialist and Tommy Butts, University of Arkansas assistant professor.

“Natto is a traditional Japanese food made from soybeans fermented with a particular bacteria strain,” says Conley. “Natto-type soybeans are usually less than 5.8 millimeters in diameter and have a clear hilum and thin seed coat. These smaller beans are preferred because the required fermentation process for natto can reach the center of the bean easier.”

Research objectives included evaluating the effect of soybean seeding rate with fungicide and insecticide seed treatments on natto soybean stand establishment, growth and yield. Researchers also evaluated foliar fungicide use for disease control on several natto varieties and studied seeding rates on four varieties to assess yield, growth characteristics and seed quality.

Small plots were established during two growing seasons at three Wisconsin locations coming out of corn production. Cultivars chosen for the studies all had desirable seed characteristics and yield potential to be grown in Wisconsin and be marketable in the food-grade sector. 

Planted in 15-inch rows, objectives were repeated each year at each location. The first included seed treatments with five seeding rates ranging from 100,000 to 260,000 seeds per acre with two seed-applied fungicide-insecticide treatments. Two foliar fungicide treatments were applied at the R1 stage on three natto cultivars for objective two, and three seeding rates (180,000, 220,000 and 260,000 seeds per acre) were assessed on four natto and food-grade cultivars to meet objective three. Yield in all studies was adjusted to 13 percent moisture at harvest.

“Variety selection and seeding rate were the most important agronomic and economic considerations,” sums Conley. “Seeding rates above 140,000 seeds per acre resulted in the highest yields and smaller seed sizes. A combination fungicide plus insecticide seed treatment or foliar fungicide had minimal impacts on any of the response variables. Varieties varied in white mold incidence. However, seeding rate did not impact incidence, but increased plant lodging.”

Once harvested, natto seed used for food must be small, clean, free of foreign material and have no mold, smell or off-coloration. Many markets require seed must meet the less than 5.8-millimeter diameter, and Conley confirms the right seeding rate is the pathway to achieve that.

“The decision to grow natto soybeans requires a local market and generally a contract with a buyer. Most contracts include specific variety requirements as well as strict quality grading,” he says. “Agronomically, natto soybeans generally yield less than conventional varieties, but price premiums may offset that in an economic analysis. Ultimately, growers should select high yielding varieties with good seed quality characteristics to succeed in this market.”