raised seedbed
Agricultural term for a seedbed built above ground level, often used in rice cultivation or vegetable growing to improve drainage and temperature control.
In rice farming, seedlings are often raised on raised seedbeds.
Raised seedbeds drain well, so they can prevent root rot.
温床 is a hotbed (heated seedbed) or metaphorically a breeding ground, whereas 揚げ床 is simply a physically raised bed without implying heating.
Standard kanji spelling for a raised seedbed, using 揚げ (raised) and 床 (bed/floor).
Alternate spelling using 上げ (raised); less common but still seen.
Abbreviated spelling; rarely used.
Abbreviated spelling; can be confused with 上床 (うわどこ) meaning 'upper floor' or 'top bed'.
Compound of 揚げ (age, 'raising') + 床 (toko/doko, 'bed' or 'floor'). The kanji 揚げ is often used for lifting or raising something, and 床 here refers to a prepared planting area.