I wonder if we have studies on loss of elements in farming (for some typical crops such as rice, cassava, sweet potatoes, ...) to understand the 'rate of soil/nutrient depletion' (when crops are sold and removed from the farm.

We should have soil analyses from time to time, some estimates of the reserve of elements on the farm and some estimates of elements removals from the farm. This could be a more rational basis for using organic or inorganic replenishment/improvement.

Commercial farming would of course suffer higher rates of depletion.