Dig (ground) by digging over the lower soil with the topsoil temporarily removed.
〔园艺〕（将表土暂时移开后）深挖
Example sentencesExamples
Stretton set himself to bastard-trench a quarter of an acre, and never having done any serious digging in his life before, he went to work with such fierceness and wasted so much energy that he had no back left, or, rather, he was all back and blisters by three in the afternoon.
The ground should be trenched. or bastard-trenched, at least a fortnight before planting is to take place, and then arched up and trodden very firm.
This is a process known as double-digging or as the gardeners of old called it 'bastard-trenching' - for obvious reasons.
You could have bastard-trenched that manure so it's exactly where you want it.
The bed covered in plastic was "bastard-trenched" in the Autumn in readiness for Pumpkins & Squashes when the time comes.