soil improvement; soil amelioration
Technical and agricultural term for improving soil quality, structure, or fertility.
In this area, we use compost for soil improvement.
You should consult a soil improvement specialist.
土壌 means 'soil' in a scientific or agricultural context, while 土壌改良 specifically refers to the process of improving it.
改良 is a general term for 'improvement' or 'reform', used in many contexts; 土壌改良 narrows it to soil.
Compound of 土壌 (soil) and 改良 (improvement).