There are current problems with wind and water erosion almost everywhere. Here in Minneapolis the Mississippi and Minnesota rivers are both contaminated from the runoff of agricultural land. Any place that is plowed up and does not have crops growing is contributing to soil/water erosion. Without growing plants there the soil and nutrients get washed away. Plants hold the soil down and allow water to soak in.
The benefits of plowing and chemically fertilizing do not outweigh the environmental impact those practices have. We are poisoning and killing the gulf of Mexico (not to mention all the other bodies of water). The dead zone where the Mississippi enters into the gulf is now the size of the state of Conneticut and growing. We either have to eliminate use of chemical fertilizers or figure out a way to use them without poisoning our water.
Below are areas that struggle with or are at risk for erosion. It is not just isolated incidents but widespread problem.
what you are talking about is called eutrophication. it is indeed caused by agricultural runoff but it is not exclusively to blame. poor storm water management and natural phenomena contribute largly. eutrophication or just giant fish kills have been happening long before modern agriculture. i think there are biblical accounts of massive population of fish dieing off. its a natural process to an extent.
what you see in the gulf is however caused by humans almost exclusively. dead zones are somewhat unpredictable with a number of factors converging in order to create a dead zone. this problem is not exlcusive to "chemicals" natural cow shit will cause the same thing. there is a reason pig farms are strictly regulated. pig shit is insanely high in nitrogen. i admit to not being knowledgeable about this particular dead zone, but i can tell you from professional experience( i work with waste water treatment systems) that bad fecal runoff is every bit as bad ecologically as the fertilizer runoff you see today. the problem has to be solved with adequate and appropriate land manage. watersheds need to be protected and even engineered to resist contamination from agricultural runoff. at the same time agricultural runoff needs to be scrutinized and adressed. i think its foolish to think you can eliminate runoff entirely... a single 5 year rainfall event is enough to overwhelm almost every single storm water drainage system designed in most cities. the dead zone in the gulf is not a static body of water it is constantly moving and changing shape and size. a nuber of factors dictate the levels of dissolved oxygen available to fish not just the presence of fertilizer pollutants.
soil erosion happens yes. some farmers in prone areas plant cover plants in between actual money crops just to adress this. this however means that they then need to till under these plants and spray herbicide to keep competetive weeds down.
obviously soil erosion is GREATLY GREATLY influenced by a number of factors...not the lease of which is soil composition itself. its foolish to try and apply one method to solve an entire issue that is so intrinsically complicated.
i do not know alot about natural soil and soil errosion. this is a subject i suspect could take you all the way through grad school. i do not understand why you think modern agriculture and retarding soil errosion are not compatable. what is it exactly that organic methods offer that traditional ones cannot accomplish? planting cover certainly is not one of them.
you say that its not worth it to continue farming with modern agronomic technologies. i say that its entirely impossible to do without them. unless you want to starve an inordinate amount of people, or double the land used for farming.