Crop diversity is great. And you also need lots of organic matter to go on top of the soil: to build life in the soil. that's much better than trying to duct tape the matter with fertilizer.
Crop rotation has been standard practice my entire life. One of the many kickers though is soybeans are the fallback crop for really wet springs. Many crops need to be planted by a certain date or the growing season will be too short. Soybeans can "make up for lost time", so to speak. If your first planting gets flooded, or if it's too wet to get any crop in, you can wait until it's dry and toss in some soy to recoup some of the cost. Thing is soybeans use a lot of nitrogen.
Many years ago one of my neighbours tried not rotating is crops. It worked out okay the first couple of years, but it wasn't long before his yields nosedived and within the five years he was bankrupt.
My family's been farming corn on corn for 20+ years. Started strip-tilling in the 80's High residue fields help trap as much moisture as we can with limited irrigation capacity. Farmers have no choice but to take care of their soils to remain viable. And more than viable, be profitable as there are many people who depend on them both for their livelihoods as well as an ever demanding population with mouths to feed.
