1. Why was black soil brought to Koshien Stadium, which was in a white-soil area?
Koshien Stadium opened on August 1, 1924. The name "Koshien" comes from the year being one of the "Kinoe-Ne" (a specific cycle in the traditional Japanese calendar) years, which occurs once every 60 years [2]. During construction, the most critical consideration was the ground surface.
The Hanshin area is historically known for white sand and green pines. The local soil was pale, making it hard to track a baseball. In baseball, batters and fielders must follow the white ball visually after it leaves the pitcher’s hand. If the background soil is white, the ball blends into the ground [1].
At the time of opening, records indicate that black soil from Kumouchi in Kobe was mixed with red clay from Awaji Island. They tested the stickiness as they laid it down [1]. Later, a person named Masayoshi Ishikawa, who managed the soil, brought earth and sand from many places. He mixed them repeatedly to find a black soil that made the white ball easy to see. For this work, he is sometimes called the "father of Koshien's soil" [3].
Therefore, Koshien’s soil was not dug up from beneath the stadium. It was "created" with the specific goal of visibility. But what is it made of today?
2. Which materials are mixed in Koshien's soil today?
The basic mixture used today consists of "black soil" from Shibushi City in Kagoshima Prefecture and "hill sand" from Joyo City in Kyoto Prefecture [3]. In some years, soil or sand from other regions may be added.
The black soil is actually "Kuroboku" (black earth). It is made mostly of volcanic ash and contains many organic materials from decayed plants. This gives it a dark brown color. It is light and holds water well. On the other hand, hill sand is a bright beige color with good drainage [3]. By mixing black soil that holds water with sand that drains water, they create a surface where the white ball is visible, yet the ground does not become muddy in the rain.
The source of the black soil is not always the same every year. Reports mention using soil from areas such as Nihonbara in Okayama, Suzuka in Mie, Kanoya in Kagoshima, Mieda in Oita, and Daisen in Tottori [2]. The sand has also traveled far. It is said to have come from local beaches, the Seto Inland Sea, and Fujian Province in China before arriving at its current source in Joyo, Kyoto [2].
According to the stadium, the blend of black soil and white sand is adjusted based on the long-term experience and skills of the groundskeepers. It is not mixed strictly according to a fixed chart; rather, it is finished by human eyes and hands [1].
Safety Note: Hill sand is bright beige and drains water well.
3. Why does Koshien change its soil mix for spring and summer?
The ratio of soil to sand changes depending on the season and weather. In spring, there is more rain, so they use more sand to prioritize drainage [4]. In summer, they use more black soil to make the white ball easier to see. The basic ratio for summer is reported as 6 parts soil to 4 parts sand, though this is not a fixed value for all times of the year.
This uses the two properties of the materials directly. More sand means better drainage; more black soil means a darker color. In spring, they prioritize drainage against rain. In summer, they prioritize "seeing the white ball clearly." They adjust the amounts accordingly.
The specific ratio for spring is not clear from public documents. Since the stadium does not officially publish these numbers, it is best to remember only the general direction: "more sand in spring."
4. How does Koshien's soil change after a year of use?
Even if mixed perfectly, the soil separates over a year of use. Fine black soil sinks to the bottom, and sand rises to the top [5]. To fix this, they till the ground to a depth of about 30 cm (about 1 foot) at the start of each new year. During the season, only the top 1–2 cm (less than an inch) is disturbed.
Thirty centimeters is the height of a ruler stood on its end. Considering that they dig up and remix to this depth, it is a massive task.
The soil that disappears is replaced. One report states that more than 2 tons of soil are added each year [3]. In any case, black soil is not something you lay down and forget. It requires yearly maintenance to keep it in good condition.
5. When did players start taking Koshien soil home?
The habit of players from losing teams collecting Koshien soil to take home is a famous scene, but its exact beginning is unclear.
One common theory points to Tetsuharu Kawakami of Kumamoto Technical High School, who was runner-up in the summer of 1937. However, it is also reported that he himself denied starting the trend. Another theory says Kazuo Fukushima from Kokura High School put soil in his pocket during the summer of 1949 [6].
What do newspapers say? One investigation found no reports of losing teams collecting soil until the spring tournament of 1958. A 1968 article in the Asahi Shimbun described it as "commonly seen," and a book from 1987 noted that players had been taking large amounts home for about twenty years [6].
Comparing these dates suggests that it became a common practice between the 1950s and 1960s (Showa 30s to 40s). This conclusion includes some speculation by the researcher.
6. What happened to the Koshien soil that Okinawan high school players took home?
In the summer of 1958, Shuri High School from Okinawa, which was under US administration at the time, appeared in Koshien for the first time. After their game, the players tried to take Koshien soil back with them.
However, they could not bring the soil into Okinawa because of a law called the Plant Protection Act. It is reported that the soil was discarded at sea during quarantine [6].
Knowing that this soil was originally collected from various places and mixed together makes this story even more interesting.
7. How can you enjoy noticing Koshien's soil color and upkeep when watching games?
If you watch a broadcast this year, pay attention to the color of the ground. The darkness of the soil might look different in spring compared to summer.
Another point to watch is the groundskeepers’ techniques during breaks between games. How do they remove water after rain? Where do they repair the surface? A ground where the white ball is visible and play is easy is supported by their experience [1].
In your local area, you might try comparing park soil and sandbox sand when wet and when dry. You can see the difference between soil that holds water and sand that lets water pass through by looking at the color and feeling the texture. Try this in a place where you can wash your hands, and do not put soil in your mouth or lick it.
The stadium’s explanation is found on the official Hanshin Koshien Stadium website under "Koshien Secrets." Look for sections about the soil and compare them with this article.