You haven't given enough information for anyone to be able to give you a good answer to your question. Are you saying that the area has remained barren for a long time without chemicals or routine human intervention? The sides look freshly cut, which makes me think it probably has had recent maintenance. The bare soil looks sandy while the grassy area looks more clayish (from what little I can tell by the picture). Is this the case?

There are many ways an area can be kept free, or relatively free, of vegetation. Most involve routine maintenance (spraying, pulling, edging, etc).

It looks to me like recently laid sod, Though the apparently curved edge is a bit of a mystery.