I have very carefully prepared a bed over a couple of years nurturing it with compost, manure, and de-stoning etc. in order to end up with very soft soil that I could use in particular to grow carrots which had always defeated me. All was going well and I sowed my first row 2 weeks ago. However, a few days ago the surface of the soil has developed what I can only describe as a skin. On a trial section, if i use my hands it can rub back into a really good physical structure. But that will of course disturb the sown seeds. Not too sure how to proceed other than to hope the seeds will germinate successfully. Comments most gratefully received.