plough something back in something

Từ điển Oxford Advanced Learner 8th

ˌplough sthˈback (in/into sth) | ˌplough sthback ˈin derived
1. to turn over growing crops, grass, etc. with a ↑plough and mix them into the soil to improve its quality
2. to put money made as profit back into a business in order to improve it
•The money was all ploughed back into the company.
Main entry: ↑plough_derived