Wiktionary
plough back
vb. To reinvest profits into a business
Usage examples of "plough back".
One would take the plough goin' out where his long leg would be downhill, then his brother'd be waitin' for him to plough back the same way.
Everything he uncovered, every advance, every idea he had, he would quietly plough back into his applied studies.
Whoever financed it, indeed, found it so profitable that he was able to plough back profits into the business.
He dare not now plough back into the soft surface snow where Peck had had no time to clear the runway.