[WorldMaker]

One other big, basic reason from early school Biology you are missing is the Nitrogen Cycle. Earth crops are not particularly efficient at fixating Carbon into biomass and generally need plenty of other mineral inputs such as potassium and phosphorous and zinc and especially Nitrogen. Nitrogen alone is an interesting problematic "inefficiency" because Nitrogen wants to be a gas at Earth pressures/temperatures (like Carbon) and so also needs to be fixated and plants very rarely have evolved that sort of fixation directly, instead relying on "the Nitrogen Cycle" to (eventually) fixate it into soils.

One of the things humanity has done as it has industrialized agriculture (to deal with the time issue of that "eventually") is that it has industrialized "the Nitrogen Cycle" as much as it can, and in so doing added a lot of additional Carbon inefficiencies to how we fixate Nitrogen for use by our crops. Modern crops couldn't grow at the same industrial scales without modern fertilizers, but modern fertilizers generally don't exist without massive carbon subsidies.

https://en.wikipedia.org/wiki/Nitrogen_cycle