Suzumaki!

Niigata is famous for rice cropping, especially major rice brand "Koshihikari."
The rice crop starts in spring.
One of the preparatory works for rice planting called "Suzumaki" (or "Sujimaki").
Suzumaki is to sow rice seeds in trays. And then the the trays are placed in a plastic greenhouses.
Depends on areas and varieties, in Niigata, Suzumaki is conducted in early April and transplanting the seedlings into rice fields is done in Japanese spring holidays in early May called " Golden week".