Gardeners seem to believe that the darker a soil is, the better it is. And that does tend to be true in many cases. But not always.
In my part of the world (Northeastern North America), there is a product widely sold as “black earth” that is very popular with gardeners. It is also very cheap. I’d like to say dirt cheap, but it’s actually cheaper than “dirt” (topsoil). It’s sold by the bagful in garden centers, hardware stores and even supermarkets where people load up their trunks with what they think is top-quality soil at rock-bottom prices. They’re very unlikely to be happy with the results.
Of course, this product isn’t black earth. Black earth (the real stuff) is a type of soil officially called chernozem. It’s very rich in humus, chock full of NPK and ideal for growing most nutrient-dependent plants, including vegetables. It’s usually found in what were originally low-lying, marshy areas, now mostly drained and being used for agriculture. If you really could get your hands on true black earth at a reasonable price, it would be wonderful: pretty much the ideal garden soil!
But the stuff sold as black earth is not chernozem, at least not in the eastern part of the continent (I’m sorry I can’t generalize: the term “black earth” can mean different things in different areas). In fact, it isn’t soil at all, but black peat, a very dark-colored type of peat found at the bottom of sphagnum peat bogs, under the more widely used blond peat (the top layer) used in most quality potting mixes and the somewhat decomposed brown peat moss (middle layer), a lesser quality peat used mostly in soil mixes for outdoor gardens.
Black peat, also called peat humus, is the lowest quality peat. It contains no fiber and, unlike other peats, compacts readily and doesn’t hold nutrients well. It needs to be amended with limestone for most garden uses, as its pH is much too low for most plants. It can be useful for amending clay soils (if you can get it to mix with clay: good luck with that!) and sandy soils, but its effects don’t last. Blond or brown peat are much better choices for this use.
But “black earth” (black peat or peat humus) remains popular in the soil packaging industry … essentially as a colorant. No, packaging people will never say that, but that’s pretty much the case. They know gardeners associate a dark soil color with good quality soils, so … give the people what they want.
The problem is, you never know what you’re getting with a product labeled “black earth.” Hopefully, the manufacturer added some limestone to the product to bring the pH up to an acceptable level and if so, that would be listed on the package. You should never try growing plants in this. Yet the label says “earth” in big letters and many people assume that means they can use it directly from the bag for containers, vegetable gardens, etc. And that will lead to disaster. Very few plants will survive for long in black earth if it’s just limed decomposed peat moss.
Other “black earth” products do contain topsoil and may be labeled “black earth soil”, “black garden soil” or “black earth topsoil.” They’re slightly better, but again, you’d probably be better off with regular topsoil, which is usually amended with higher quality brown peat.
In a nutshell, “black earth,” unless you are certain you are really getting true chernozem (and that may be possible in certain parts of the world) is at best a lower quality product, certainly not the quality product many gardeners think it is. At worst, it’s strictly a soil amendment and not “earth” that you should try growing plants in. Personally, I avoid it like the plague.
But black earth will probably continue to be a big seller because people remain convinced dark soils are the best. But if black earth really were the best product, why is it always the cheapest “soil” on the market? And why is it always on sale?
I know your mama told you this, but it’s worth reminding you from time to time: you get what you pay for!