I happen to think that dirt is important. And that dirt has value. And I think you'd agree that it would be stupid to fill a wheelbarrow with soil from your yard and dump it in the stream that runs through your neighborhood park. Right? But that's what gardeners and farmers do every winter in Maryland and throughout the Chesapeake Bay watershed.
We seem to still be holding onto the "clean fields" farming and gardening aesthetic of 18th century Europe and not paying attention to soil - one of our most important resources......and also happens one of our most serious pollutants when it gets into the water. Here's an example of what a typical garden looks like during the winter, when we receive the bulk of our annual precipitation (and runoff):
Over the next 6 months, somewhere between 50 and 100 pounds of good, nutritive soil is going to wash off of that garden plot and into the nearest street drain, which outfalls into Herring Run in central Baltimore. The easiest and cheapest way to prevent this, which also happens to be the easiest and cheapest way to fertilize your field or garden for next spring, is to plant winter cover, like these Austrian field peas I've started, and the white clover that's just starting to germinate in the first photo in this post.
The field peas store nitrogen underground, and will eventually be tilled into the soil before I plant next summer's garden. In the process, the roots and knotty vegetation will also keep rain from hitting the soil directly and washing it away. Seems like common sense, and yet out of about 40 gardeners at my "City Farm," I haven't seen one other person put down winter cover. That's giving away a lot of soil to an urban stream that doesn't want or need it. I'm doing 4 test plots for cover crops in my garden and I hope that other gardeners pick up on the technique and results next year......what else can I do?
And for the record, winter cover doesn't just have to be composed of plants you don't want to eat. Here's some other residents of my winter garden: