Ideally, soil disinfection should be done in winter, but I ended up doing it in May. I turned over the entire field to expose the soil to air and loosen the hardened layers. Of course, I removed any stones I found along the way.
May 2021
This is what it looks like now. Soil improvement seems to follow several stages. The ground here used to be very hard, and roots couldn’t grow well. But as I loosened it, roots began to spread, further breaking up the soil and releasing exudates that help form aggregate structures. At the same time, the soft clods and stones buried underground were exposed to rain and wind, gradually breaking down.
The soil on top is from this year, and the one below is from last year. Although the moisture content and magnification differ, it’s clear that the soil has improved significantly.

The myoga (Japanese ginger) sprouted successfully this year too.