More and bigger plants will also mean even faster exhaustion of micro-nutrients from the soil. Since not all the biomass produced in that soil is being recycled into it - the whole point of agriculture is our removal and use of parts of the plants - then the soil will slowly be exhausted of its non-infinite supply of those nutrients. The future results is food crops that contain less of those micro-nutrients, leaving future generations that consume them with a deficit. We've already seen this effect in the last century or less. A very deliberate effort could be made to restore what is exhausted, but this is COMMERCIAL agriculture FOR PROFIT; money is the ultimate motivation, not long-term soil health or the health of people who eat what grows from it.