Doesn't mean what you think it means. Topsoil is not vital for agriculture. The best corn grows on eroded clay hillsides - because it's well-drained. The ferti

Doesn't mean what you think it means. Topsoil is not vital for agriculture. The best corn grows on eroded clay hillsides - because it's well-drained. The fertility of topsoil is largely irrelevant because everybody uses liquid ammonia fertilizer. The midwest is where the glaciers melted, leaving 100+ feet of silt, sand and gravel. A long way to bedrock most places. So what, 1000 years before we have to worry? Sure we should understand it and measure the processes. But let me tell you it's light-years better than when I was a kid, and every field was a mass of ruts and washout. Because farmers over the last half-century were educated. They do contour plowing to avoid fast-moving water after a rain. Now many do no-till planting where the plow never touches the soil, not for years anyway. You want to know where the real erosion is now? Construction sites. They are allowed to suspend the rules about soil conservation entirely.