Our harvest has begun. This week we collected 1,259 lbs (571 kg) of edamame soybean plants, weighed down with 655 lbs (297 kg) of beans. Soybeans are usually allowed to mature and dry on the plant, then harvested as the dry bean used to make tofu, soy sauce, waxes, artificial plastics, soyfoods, animal feed, and biodiesel. Edamame soybeans are harvested green, like green beans, to be eaten as vegetables.

We harvested our biointensive and market garden plots by hand, and cut the small farm plots with a sickle-bar mower attached to a walk-behind tractor. The picture below shows Tony Silvernail cutting beans in a small farm plot. Sweet potatoes are in the foreground, with corn and sorghum in the background.

We separated the beans from the plants using a simple slotted board design from the Asian Vegetable Research and Development Center. It sped the bean picking process considerably.

We recently had to irrigate for the first time, because we've gone about three weeks without rain, but maintaining the study has taken less time and energy in August than in previous months. Here are the updated charts, showing labor in minutes per square meter and energy in megajoules per square meter since May:

Now that we have collected our first yield data, it is possible to calculate the land, labor, and energy use efficiency for edamame soybeans grown at each of our farm scales. Yields are usually presented as the amount harvested per unit area (e.g. tons/acre, kg/ha). The blue bars on the chart below show the weight of edamame soybeans harvested from each square meter of land, giving a measure of land use efficiency at each of the three farm scales. The maroon bars show yield per megajoule of energy invested, and the yellow bars show yield per minute of labor invested. These measures of energy and labor use efficiency are less typical ways of measuring yield.

The edamame soybean yield suggests that each of the farm scales has a different strength: The biointensive scale was the most energy efficient; the market garden scale made the most efficient us of land; and the small farm scale made the most efficient use of labor.

Michael Bomford provides research and extension services related to organic agriculture and small-scale renewable energy production through Kentucky State University's Land Grant Program. He thanks Tony Silvernail, Brian Geier and John Rodgers for their help with maintaining the organic land at the KSU Research Farm.