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soil for horticulture; soil for seed planting
春に用土を入れ替えた。
I swapped out the potting soil in spring.
園芸店は毎季、自家配合の用土をブレンドしている。
The nursery blends its own horticultural soil each season.
祖父は盆栽のために、専用の用土を丁寧に使い分ける。
My grandfather carefully uses a dedicated potting mix for his bonsai.