While the Sigma lens is certainly known to be a very sharp lens, it won't offer any additional depth of field at the same aperture as any other lens.
The first picture looks like it was sharpened quite a bit in post processing, and to my eye it looks oversharpened. A matter of opinion, of course.
One thing that is a great way to get almost unlimited depth of field is to take 3-5 pictures on a tripod varying the focus from near to far, then focus stack them in Photoshop or another post processing program. This works well with landscapes.
Out of curiosity, what lens are you using now?
I like the composition in your second shot a lot, BTW.