

Under solutions, there, is written “compost” and “animal manure”. That’s fertiliser. Import-dependent agriculture is a whole another topic and I didn’t want to get into it, but long story short, no matter how good and natural your soil management is you can’t expect to export nutrients all the time and not develop a shortage. You can pull nitrogen out of the air, that’s nice, but you can’t do that with phosphate and minerals in general. Good news is that good water treatment plants will pull phosphate out of the waste water.
Yep systems that could automatically dose the fertiliser were not yet in widespread use. Farmers don’t want to over-fertilise for the simple reason that fertiliser costs money but before those systems were available it was all too easy to say “fuck it I’ll drown the field so that there’s enough everywhere”.
Not rotating crops seems to be a US thing, farmers over here never stopped doing that. There’s also EU-wide laws about having to either let land fall fallow, or plant cover crops or nitrogen fixers. You can, in principle, plant your nitrogen fixers year after year on one field and your cash crops on another, but only if you’re a complete idiot.