Oh yeah, just top up the compost every year. Where are you getting that compost from? Wood chips you say? You'd have to denude ten acres of forest to make enough compost to Dowding one acre of field.
He's a soil vampire, sucking in fertility from somewhere else to feed his own garden.
In my parents' farm the compost comes from cleaning up the forest around it (trim branches, vegetation, dying trees, etc) mixed with the chicken and goat manure plus whatever else gets mixed in there (food leftovers, ashes, coffee grounds, etc). Of course it's at a small-ish scale (less than 1 hectare) but my parents definitely don't denude 4 hectares to do so.