Roots and Cultivation Methods of Konjac Tubers
<Table of Contents>
1. Roots of Konjac Tubers
2. Types of Konjac Tubers
3. Cultivation Methods for Konjac Tubers
1. Roots of Konjac Tubers
Konjac is a processed food made from the corm of a plant in the Araceae family called the "konjac tuber" (also known as konjac ball).
The konjac tuber is said to have originated in the Indochina Peninsula, and in that region, it is nicknamed "elephant's foot" due to the shape of the tuber.
Even today, many relatives of the konjac tuber grow wild in Southeast Asia, and there are said to be about 130 species.
Most of these are different varieties from Japanese konjac tubers; they are konjac tubers that do not contain the dietary fiber called konjac mannan, so they do not solidify even when processed and are not suitable for making konjac.
However, recently, countries in Southeast Asia, including China, have also been cultivating them for food for the Japanese market.
It is said that konjac was introduced to Japan from China along with Buddhism around the 6th century as a medicine, but the exact details are unknown.
As a plant, it is believed to have been introduced during the Jomon period along with taro and other crops.
Konjac tubers are propagated from seed tubers (*) just like potatoes, but unlike potatoes, they require 2 to 3 years to grow.
* Seed tubers (taneimo) are tubers that are stored during the winter to be used as seeds for planting in the spring.
First, when seed tubers are planted in the spring, new tubers are formed, from which side buds (suckers) grow, and by autumn, "baby" konjac tubers called kigo are produced.
These kigo are harvested once and replanted the following spring; these are called 1-year-old tubers. Those harvested in the autumn are called 2-year-old tubers, and those planted again the following spring and harvested in the autumn are called 3-year-old tubers.
They grow 5 to 10 times in size from kigo to 1-year-old, and another 5 to 8 times from 2-year-old to 3-year-old, reaching about 30 cm in diameter when they become 3-year-old tubers.
While these 3-year-old tubers are suitable for making konjac, konjac tubers are sensitive to low temperatures and prone to rotting, making them a very difficult crop to store between harvest and the next planting.
2. Types of Konjac Tubers
In Japan, there have long been varieties known as "Zairai-shu" (native species) and "Bitchu-shu".
Because these each had similar characteristics, it was difficult to crossbreed them for improvement. In the Taisho era,by importing a variety called "Shina-shu" from China, they succeeded in creating varieties that were easier to cultivate..
As a result,"Harunakuro","Akagioodama","Miyamasari" were born as improved varieties.
Currently, these three varieties account for over 98% of production.Thus, recently, varieties that are easier to cultivate and have higher productivity have appeared.
3. Cultivation Methods for Konjac Tubers
Laying down straw prevents the soil from drying out and prevents sudden changes in temperature. It also makes it harder for weeds to grow, which helps prevent insects and diseases.
Although konjac tubers have been cultivated for a long time, surprisingly, a stable cultivation method was not established until around 1955.
Konjac tubers are such delicate plants that even a scratch on the leaf can lead to disease, so they do not grow well in strong sunlight, wind, drought, or areas with poor drainage.
Until then, it relied on many years of experience and luck, making it a crop that plagued growers so much that it was even called the "luck tuber."
Because konjac tubers require an average annual temperature of about 13 degrees Celsius, while they can be grown in cold regions, it is difficult for them to grow large, and the northern limit for open-field cultivation is around Miyagi and Yamagata.
In the past, they were grown for home use by ordinary farmers, but since cultivation shifted to a production-oriented focus, they have been grown extensively in the northern Kanto region, including Gunma, Tochigi, and Saitama.
Konjac tubers used as seed tubers require temperature management after harvest. They are dried in the sun for half a day in the field and then thoroughly dried in a well-ventilated, shaded area.
During the winter, they are wrapped individually in newspaper, placed in a well-ventilated basket or similar container, and stored in a place where the minimum temperature does not drop below 13 degrees Celsius.
Source: "Japan Konjac Association" Website
End