subsoil

n.

（土壤的）底土，心土；

1. With ample moisture stored in the subsoil, the crops matured rapidly.
   由于下层土壤湿度大,农作物生长迅速。
2. Earthworms burrow deep into the subsoil.
   蚯蚓深深地钻进底土。

Impact of subsoil water use on wheat yield
Subsoil compaction effects on crops in Punjab, Pakistan:
Simple Method of Modeling PVD-Improved Subsoil
Subsoil compaction by vehicles with high axle load—extent, persistence and crop response
Cationic Surfactant Sorption to a Vermiculitic Subsoil via Hydrophobic Bonding.
Water Infiltration and Redistribution in a Silt Loam Subsoil with Vertical Worm Channels
Poorly crystalline mineral phases protect organic matter in acid subsoil horizons.
Spatial Variability of Saturated Hydraulic Conductivity of the Subsoil of Two Forested Watersheds
Influence of root diameter on the penetration of seminal roots into a compacted subsoil
Acceleration of organic matter decomposition after the input of available substrate in subsoil horizons