There is one fundamental rule in nature: Given enough dilution, given enough time, Nature will handle anything. The trick is to know how much dilution and how much time. To some extent, the two factors are interchangeable. Fortunately, humus (that complex mixture of hydrocarbons, carbo-hydrates and proteins with significant colloidal capacity) is a very effective chemical “buffer” which will smooth out release of toxins and nutrients. There is also a biological buffer in that the mycorrhizae can be selective and take what they need (and no more) from an otherwise too high a concentration of a toxin or nutrient in a feedstock (such as compost). These mechanisms add enormously to the safety of recycling to land.
Having said that, like all living mechanisms, don’t push it too far, knowing how far depends on reading the research, using common sense and not rushing the fence – build up slowly and learn to manage the stress in the system.
Also see “How to make on-farm composting work”, by Bill Butterworth, MX Publishing, London 1998,
Bill Butterworth, Land Research Ltd, 6 June 2018