Managing docks

We have a field that has been intensively grazed for 40 years.  We took it over 18 months ago and were going to leave it get to hay stage so that it attracts wildlife but it is covered in docks 2-3 foot high.  We tried to pull them but they are returning with a vengeance.   We want to leave the field chemical free so how should we manage the field so that it becomes more species rich than just docks!  Thanks Naomi. (This query came in by text so the FFN account are sharing it)